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OBX voice card (with non-custom CEM3310 equivalent circuits)
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author OBX voice card (with non-custom CEM3310 equivalent circuits)
oldcrow
Ever since playing MC's OB-X at AHMW, I got it into my head to try and make one--gotta be cheaper than ebay! This meant making my own voice cards, first in the original form factor to test first on a "host board" to power and provide pots and switches for the voice board under test, then later in an actual OB-X. Since the vintage cards used CEM3310s and discrete everything else, I made the EGs in non-custom form using JH's VC_HADSR as a design reference (it was inspired by the 3310). It works on a breadboard, so they're in the CAD schematic and the "hard" part of the layout is done: the VCOs. I squashed the circuits a bit in order to open up some room on the board as my EGs were going to be a tad larger than a single 16-pin chip; they each use 4 chips, 4 transistors and a handful of passives. Throughhole parts as my eyes have gotten too bad to hand solder SMT very well (but I have a full SMT factory line for that if I ever make more than 8 of these ;)

The CA3080s are replaced by 13700s, which are dual 3080s. I do not bother with the darlington buffers. The CA3086 transistor array is replaced by two LS318s, and those mount over SMT TC resistors (see A3A, A3B in image). I do use some SMT bypass caps as the original board features no bypass caps whatsoever, save for the DC filter caps on the local voltage regulators.

More later. --Crow

Jarno
Looks great!
moogah
This would be a dream come true! The OB-X and Xa have long been my favorite old polys smile
spneca
```````
EMwhite
Same here, I'd be up for 8 or 12 of these if you ever getting around to fab'ing a board.

I bought a OBX voice card off eBay with plans to simply restore and make into a MU module. I can build just fine and move a schematic to breadboard but have zero skills when it comes to working one of those fancy design tools; please let us know how this progresses.
glmodular
I would also be interested in a set of 8! applause

Tony
oldcrow
Layout done. I need to verify the dimensions of the mounting holes and connectors, and I need to create the correct library part for the Molex bottom-entry connectors, but otherwise done. Now to make a breakout board for it. Well, after I sleep. ;)

moogah
nanners

This makes me so happy :0) Any chance you'd be interested in making a version with the 2p/4p switchable filter ala OB-Xa? I would program the everloving shit out of a microcontroller to see a neo-ob become reality!
numan7
MY ASS IS BLEEDING what a wonderfully awesome idea, oldcrow! we're not worthy

;hmm: i think i'd be down for 4.... and would like to mount them behind 5U/motm panels as individual voice-modules, patching a motm 650 as the voice-controller, should you decide to offer these for sale.

Enjoy the show!

cheers
negativspace
That came together quick!
oldcrow
I will experiment with other filters after I verify this standard version works as expected. I left space at the top and right end of the board for extra filter parts, so there can eventually be a 2 pole / 4-pole revision. Programmable switching means I have to find connector pins for the control signal; there are 4 wired but unused "X" signals that were meant for something on the VCOs, probably pitch and pulse width modulation from a 2nd LFO, I might use some of those for extra filter control.

These KK-156 Molex connectors are not my favorite, we used them when I designed factory instrumentation in the 1980s. They had a knack of tarnishing rather badly. The last time I used them was on the original MOTM-480 prototype to make swapping of filter elements quick. I will have to ponder a proper card edge for a future version.

--Crow

moogah wrote:
:nana:

This makes me so happy :0) Any chance you'd be interested in making a version with the 2p/4p switchable filter ala OB-Xa? I would program the everloving shit out of a microcontroller to see a neo-ob become reality!
oldcrow
I will definitely sell the bare boards. I am not building up more boards that have 200 resistors apiece than I absolutely have to. I am in the electronic manufacturing business and can farm out assembly work relatively cheap, however--it is just a matter of logistics as they like to have all the parts sent to them along with the boards. But that is down the road a bit.

--Crow
/**/

numan7 wrote:
:omg: what a wonderfully awesome idea, oldcrow! :hail:

;hmm: i think i'd be down for 4.... and would like to mount them behind 5U/motm panels as individual voice-modules, patching a motm 650 as the voice-controller, should you decide to offer these for sale.

:popcorn:

cheers
oldcrow
Analog is easy. lol No 0.4mm pin pitch SMT here. This took about 15 hours of actual CAD work. --Crow

negativspace wrote:
That came together quick!
aladan
Wow - fantastic!

Even just five or so years ago if you'd told me that people would soon be offering DIY OB-Xs*, 2600s and VCS-3s then I reckon I would have been somewhat skeptical. We really are living in an unbelievable golden age of synth DIY!

So, yeah, count me in for a poly's worth.

Cheers,
A.

* Ok, taking some small liberties here - obviously someone's going to have to design and build processor and other support circuitry to get the complete thing smile
beyourdog
I'm as well amazed by the obstination and talent of the people who deliver such Projects and the quality of the documentation provided, which surpass often the original (For the VCS3 clone for exemple...)
Jarno
oldcrow wrote:
Analog is easy. lol No 0.4mm pin pitch SMT here. This took about 15 hours of actual CAD work. --Crow

negativspace wrote:
That came together quick!


But no 4+ layers to route on either hihi
suitandtieguy
holy shit this is amazing, Mr Crow!
oozitron
I'm amazed at how fast you put this together Scott... it was just a couple weeks ago when MC's OBX was the center of attention (mine at least!) in the library. Call me foolhardy, but I would choose it over any polysynth It's peanut butter jelly time!

I would love to have a 4+ voice OBX. Even if it wasn't programmable.

Drew
doepferiano
please count me in for 4!
EMwhite
Re: being programmable, I'd be thrilled with a set of controls which are hard wired (single Filter Cutoff knob wired through a buffer to all voice cards, for example) and forget about the complexity of patch memory.

I dont have an understanding of the original intent of the project. Was it for voice board replacement of originals for those that have an OBX synth with wonky, or an incomplete set of voice cards, or is it a pure DIY affair to be implemented as each individual sees fit?

If the latter, a missing piece is the voice distribution/dispatch/voice stealing control. I have MidiPal and it works well but as the name implies, it's Midi only. Will be buying the ACXsynth kit from Hexinverter but it will only do 4 with the ability to daisy chain a bit of an unknown at the moment (the code is owned by a bloke in France and my understanding is that the project is held up waiting on some fairly basic additions to key priority.)

I suppose that a large ExpertSleepers compliment for all cv, gate, and envelope duties is a possibility but excessive in terms of cost and complexity in my opinion.

Any ideas?
negativspace
oldcrow wrote:
Analog is easy. lol No 0.4mm pin pitch SMT here. This took about 15 hours of actual CAD work. --Crow


I realize it's not a daunting layout for a seasoned pro... nevertheless, usually things don't materialize here in a matter of hours - even 15 of them.
Isaiah
EMwhite wrote:
Re: being programmable, I'd be thrilled with a set of controls which are hard wired (single Filter Cutoff knob wired through a buffer to all voice cards, for example) and forget about the complexity of patch memory.


+1
Is it as simple as wiring a voltage divider to the same point on all four voices, or will there be a separate control PCB to handle parameter CV distribution?



Quote:
I dont have an understanding of the original intent of the project. Was it for voice board replacement of originals for those that have an OBX synth with wonky, or an incomplete set of voice cards, or is it a pure DIY affair to be implemented as each individual sees fit?


I'm also keen to know this.



Quote:
If the latter, a missing piece is the voice distribution/dispatch/voice stealing control. I have MidiPal and it works well but as the name implies, it's Midi only. Will be buying the ACXsynth kit from Hexinverter but it will only do 4 with the ability to daisy chain a bit of an unknown at the moment (the code is owned by a bloke in France and my understanding is that the project is held up waiting on some fairly basic additions to key priority.)


I was thinking about the ACXsynth/Hexinverter Poly MIDI-CV converter, too.
Four voices polyphony isn't a problem for me.
Isaiah
I'll just leave this here...

http://youtu.be/jAnsJJB6Qws
marvkaye
I'd be in for 2 to 4 as well, depending on final price, if and when this happens. Very nice!!

<marv>
oldcrow
I am doing this because I want the classic Oberheim sound, the one before everything went CEM chips. I started with the voice card because it is the actual synthesizer and I had annotated documents from MC to work from--he corrected drawing errors in the service manual schematics and so on.

The next board to make, for testing a voice card, is a manual patch manager. On it would be a panel control for each parameter, as well as connections for external jacks to provide places to apply signals such as LFOs for pitch and PWM. I would make this manual patch "breakout" board such that it would attach to a front panel say 6U wide and have the voice card plug onto the back. While it is mainly for me to use as a test platform other folks might see it as a module sort of in the original SEM category.

A programmable-preset patch manager would of course use a microcontroller and a host of multiplexed CV storage buffers, provide a local VCLFO and noise source--all the elements the original OBX patch manager did. Of course there is also a panel digitizer to consider, but unlike single-CPU systems where for example the OBX's Z80A ran everything, I can split the workload across "smaller" microcontrollers for each task.

I know that to implement the polyphonic OBX I will also need to build a key assigner. At this point I would revise the voice card to have an actual card edge connector so as to use say a Vector card rack enclosure and rack eight voice cards, patch manager, key assigner, power supply, etc.

It is a lot of work, but nothing so far is that daunting. When I did instrumentation design, I worked with the Z8 microcontroller series extensively and used one to make one of the oldest MIDI retrofits I can think of for the Korg Polysix in 1985. I would keep the patch manager and key assigner as separate boards with their own microcontrollers, having them share a common MIDI interface to pick up MIDI messages and decide which board is supposed to handle it.

This divide and conquer method is, for me, the best way to realize all possible parts of the project.

Crow
/**/

EMwhite wrote:
Re: being programmable, I'd be thrilled with a set of controls which are hard wired (single Filter Cutoff knob wired through a buffer to all voice cards, for example) and forget about the complexity of patch memory.

I dont have an understanding of the original intent of the project. Was it for voice board replacement of originals for those that have an OBX synth with wonky, or an incomplete set of voice cards, or is it a pure DIY affair to be implemented as each individual sees fit?

If the latter, a missing piece is the voice distribution/dispatch/voice stealing control. I have MidiPal and it works well but as the name implies, it's Midi only. Will be buying the ACXsynth kit from Hexinverter but it will only do 4 with the ability to daisy chain a bit of an unknown at the moment (the code is owned by a bloke in France and my understanding is that the project is held up waiting on some fairly basic additions to key priority.)

I suppose that a large ExpertSleepers compliment for all cv, gate, and envelope duties is a possibility but excessive in terms of cost and complexity in my opinion.

Any ideas?
paults
What a modern, fast and cheap MCU might look like:

http://www.mouser.com/ProductDetail/Microchip-Technology/PIC32MX120F03 2B-I-SO/?qs=sGAEpiMZZMto2ohCYbAIUZHpRa%252bOg0TcjsdCGk%252bS8tk%3d
oozitron
Wow... I am looking at the realistic possibility of a DIY 2600 and OBX

As Louis Armstrong said, "What a wonderful world" It's peanut butter jelly time!

Drew
mattrick
awesome sauce applause
oldcrow
Finished my tweaking of the first revision of the board, submitted it for a small batch of boards to build up and test.

Next up is the "host board" I will use to test the voice cards--it will have a panel pot/switch/jack arrangement so I can use it like the SEM.

Crow
/**/
aladan
oldcrow wrote:
Finished my tweaking of the first revision of the board, submitted it for a small batch of boards to build up and test.

Next up is the "host board" I will use to test the voice cards--it will have a panel pot/switch/jack arrangement so I can use it like the SEM.

Crow
/**/
thumbs up thumbs up thumbs up thumbs up
Isaiah
oldcrow
Interesting!
Did you get my PM about GX-1 VCF PCBs?
Peake
oldcrow wrote:
I am doing this because I want the classic Oberheim sound, the one before everything went CEM chips.


Strongly agree with the non-CEM assessment (different likes for different Mikes) but doesn't the 3310 exhibit a linear response for its first 15% of travel/cycle? A nice expo circuit would be perfect here. I know you won't want to change the design but had to say it. I'd love a set of these as well for That early sound (but I'd use different envelope circuits in mine). Regards and best success on this, and thanks to Mike C. for the fixes.

(OB-1 talk earlier in the thread...I agree, the 1 envelopes are extremely fast-sounding, allowing a tiny "TIK" sound at minimum settings, especially nice when modulating. They're VC/memory.)
oldcrow
Hey Mike, long time. This first rev is sort of experimental as I determine the fitness of my CEM3310 workalike to the actual OBX synthesizer voice, among other things. Anything can change. My EGs are exponential response based on JH's inverse-parallel exponential multiplier design, which is--going full circle--based on the multipliers Doug Curtis used. If the first 15% is linear it sounds like a Vbe thing, I will have to run it in a spice model and see.
oldcrow
Host board for the CrowBX voice card. This board has a number of "hard points," meaning certain hole and connector positions cannot move. Since the voice card is designed to fit the original OBX these same hard points are applied to my host board. In order to make the host board with a voice card attached to the back useful beyond the test bench, my goal is to fit the boards onto a 6U x 5U panel with the control complement as shown. At the bottom of the panel, off-board, will be the various jacks for CVs and gate.
The control positions echo the OBX as much as possible; certain things like pitch bend will have to be externally applied as a CV. I will provide for things like OSC 2-only FM so as to get those screaming sync mods.

On-board, I will provide the LFO, a (better than the MM5837) noise source, a single instance of the OBX portamento slew circuit, master tune control and a few option on power supply.

Speaking of power supply, the voice card is made to expect a +/-19V pre-regulated DC supply from the main power board in the original OBX.
The typical modular doesn't provide +/-19V. I will have the option to strap out local regulators and run things from +/-15V, although some small bias changes may be needed in the VCOs--I will determine this when I have hardware to hack on.

Note: I am trying to attach an image, but for some reason it is not uploading. Will attach it when it works again.

Edit: I placed the image at
http://www.oldcrows.net/~oldcrow/synth/crow/crowbx_hostboard.png

More later. --Crow
Peake
Hats off to you, brilliant project.
Macron
Awesome project! we're not worthy we're not worthy we're not worthy
oldcrow
Completed host board layout. About 25 hours of CAD time, except for proofing later today.

Except for restrictions imposed by the voice card (things like cannot split trigger from gate on the stock voice card) I tried to provide all the I/Os I could think of:

*) JP1 - OUTPUT
*) JP2) -EXT AUDIO IN (final volume VCA only) -- this is more for my testing than user utility.

*) JP3/JP4 - external PWMs, provision to normalize with jack switches
*) JP5 - EXT VCF CV, use a foot pedal or voltage.
*) JP6/JP7 - FTA/FTB inouts, this is for the OBX fine tune CVs set by the CPU, I brought them out for testing purposes.

*) JP8 - external FM level , use a foot pedal or other pot, DO NOT USE A CV.

*) JP9 - external pitch bend CV, a switch allows VCO1+2 or VCO2 only. Pitch down is positive CV, pitch up is negative CV.

*) JP10 - GATE
*) JP11 - 1V/OCT "key voltage" input
*) JP12 - external vibrato depth CV. The local triangle LFO is provided here as well. The pads expect a TRS jack with T=triLFO, R=vib rate CV, S=GND.

*) JP13 - external volume CV/pedal
*) JP14 - external LFO rate CV

More later -- Crow
/**/

chipaudette
Grandmaster Crow,

You're making my own Polysix aftertouch/velocity/portamento project look completely amateur (which it is). Sweet sweet work.

You're totally making me itch for one of these things. Do you have any intention of selling PCBs?

Chip
oldcrow
Once I make sure the host board works, and then that a voice card works, I plan to make some bare PC boards for sale. I made the host board to fit along with some 1/4" jacks behind a 6U W x 5U H panel. --Crow

chipaudette wrote:
Grandmaster Crow,

You're totally making me itch for one of these things. Do you have any intention of selling PCBs?

Chip
Peake
"Crowbx"

Mr. Green
Peake
"Crowbx"

Mr. Green
Nordcore
regarding polyphone midi: I did a midi interferace that can do 4 channels cv/gate polyphon..

It´s open source (gpl/CC-sa), but has got a brilliant copy protection: documentation is in german ...

That would be enough for a simple 4 Voice / no patch memory test.

Iˋve also done some programming on the polydac (GPL), which uses the here needed S&H outputs. If S&H Multiplexer for the outs is used (everything else is braindead for 43+ really slow voltage outs), one can take a 16 Bit DAC. There is an affordable one from AD (around 6Eur), but thats not too large smd...

The outputs are static, so the cpu speed is of no concern - if you want to keep the "no software modulation". Than some ATMEGA will do, AND programming can be done in C. (I *can* write assembler, so I know why I would spend 1 Eur more for the next faster / bigger CPU to stay in C.)
For the sake of more fun one might think about some arm with an fpu (might cost about 20$ on a DIP "evaluation" board ... no BGA 256 home soldering ... ). This can do a complete and pretty fast modulation engine (as a matrix 1000 has, but w/o 8bit/60Hz steps)
oldcrow
No turning back now, board orders are in. Now for the (large) parts order...

Crow
/**/
paults
I want one, just to say I have one.
oldcrow
Spent the morning fiddling with Front Panel Designer. Not quite done yet, but getting there...

demian
I just opened this thread for the first time..

wow. I am im.. 8_)
oldenjon
I'm also super excited for this project. Owned an OB-8 for a few years, and often fantasized about owning an OB-Xa or OB-X love Sigh.
oozitron
Thinking about this project occupies much of my time lately. I have been looking for a powerful polysynth that I can afford for a long time. I want this primarily as an instrument to *play* rather than to sequence.

If one was to build *two* complete four-voice CrOwBXies, each with its own 4 note MIDI->CV convertor (which can be had pretty cheap) you would have a lot of flexibility:

* You could run them in "double" mode where you would have four notes of polyphony and 4 VCOs/2 VCFs per note.

* You could run them in "split" mode with 4 voices on upper and 4 voices on lower and different patches on each.

* In "split" mode with the same patch on both upper and lower, you'd effectively have an eight voice (being mindful of the split point). This would allow you to play "Camera Eye" SlayerBadger!


If possible, I'd love to see a preliminary parts list, especially for the common parts. I could get some parts stocked up now to cushion the blow later hihi

Drew
guillaume10
well..!!! I just discover this project..
GREAT!!!!

I am very interrested ... I hope that you will made a full kit for sale...
oldcrow
I do not have time to make full kits. We are talking about many, many, many parts. I will provide bare boards, a parts list, and some construction notes. I *might* make a batch of pre-assembled voice cards, but that is a ways out given I need to assemble and test/debug one card first. My bare boards ship to me on the 28th, so I might see them at the end of the week.

Between the voice card and the host board I will be using to test voice cards, there are about a thousand parts. These will take time to put together. If I can get a reasonable price, say $25/board for a local assembly house to put them together, things get a little easier. But again, that is off a ways.

--Crow
/**/

guillaume10 wrote:
well..!!! I just discover this project..
GREAT!!!!

I am very interrested ... I hope that you will made a full kit for sale...
vtl5c3
This is highly interesting. I'll get at least one board.
home_listening
I've been working on some PCBs for multiplexing signals, will definitely post once I've confirmed it all works. I would consider selling them, but if I don't will happily post the gerbers for people to use.

Still looking like a great project!
guillaume10
Good PCB, good BOM and good construction notes will be really , enough, GREAT....
kynsi
Very cool project. I'm servicing an ob-x at the moment and am curious to see how these boards work in a original one.
Also looking forward to having a test-rig for voicecards!
oldcrow
As parts slowly start to trickle in to build the initial test setup, I had time for the next board, while is a simple one, addresses the basic problem of a tray-mounted voice card in a rack-mounted chassis: the voice card needs to be at a right angle for space efficiency. So, you take a stock voice card, and bolt this to it:



The bottom row of headers are right angle KK156 Molex types, and the upper row are KK156 male pins. Instant right-angle voice card without the need to (as yet) make a different edition of the voice card. This means it can use original OBX cards too. That GG connector must have been some afterthought in the original design as it is off in the middle of nowhere.

In any case, next is a 4-slot voice card carrier board that mounts to the back of my host board assembly (where a single voice card would mount in the test setup), with parameter CVs and logic signals ganged to their cards and the gates, key CVs and audio outs brought out to their own terminals to be wired to a MIDI-CV unit (gate/CV) and a panning mixer (probably on the carrier board) as the original OBX has.

One thing not yet shown is the individual portamento lag circuits per voice. There is a single circuit on the host board for a single voice setup, but for "real" OBX flavor each voice needs its own lag circuit.

But first, I need to build the test rig. That will take a while--lots of parts. Pics of the bare boards when I get them in any day now.

Crow
/**/
woodster
thumbs up
Really good stuff oldcrow.
I find it truly inspiring that there are people out there with not only the knowledge to do projects like this, but also have the skills and desire to complete them to such a high standard.
To then go on and share the fruits of their labour with the wider world is simply philanthropy at it's best.
applause
oldcrow
And just like that--boards. Kuroko approves!

Host board:



Voice card:



Only tiny issue is I forgot to adjust some of the silkscreened text to a vectored font. Easily revised for the "official" board run. Parts fit, holes line up. And the soldering begins...

Crow
/**/
chipaudette
Awesome work! The idea of populating the voice card x8 is making my eyes bug out and my hand shake from imagined fatigue. Wow.

With the picture of the PCB shown against your computer keyboard, the scale of the boards also becomes a lot more clear. These are not small boards. Never having seen a real OBX, I'm amazed at how large the voice card is compared to the per-voice PCB area on, say, a Polysix. Granted the OBX does more with each voice than the single-oscillator single-envelope Polysix, but it's still a pretty stunning difference in area.

What do you think...your OBX voice card is maybe 5x the area compared to the Polysix?

Chip
oldcrow
chipaudette wrote:
What do you think...your OBX voice card is maybe 5x the area compared to the Polysix?

Chip


Well, here: exhibit A. On the left, crOwBX voice card, on the right, the six voices of a Polysix. Tossed some drafting scales in for reference.



In other news, Mouser order arrived, mainly pots and Molex connectors.

--Crow
/**/
oldcrow
chipaudette wrote:
Awesome work! The idea of populating the voice card x8 is making my eyes bug out and my hand shake from imagined fatigue. Wow.

Chip


This is why I will build one, then hire an assembly house for the rest. --Crow
chipaudette
Roughly from your pic:

Polysix: 7 in x 8.5 in = 59.5 in2 for PCB
59.5 in2 / 6 voices => 9.9 in2 per voice

crOwBX: 4.5 in x 10 in = 45 in2 for PCB
single voice => 45 in2 per voice

crOwBx / Polysix = 45 in2 / 9.9 in2 => 4.5x Bigger

So, my ballpark guesstimate of the OBX being 5x bigger was pretty close!

This then prompts other similar questions regarding scaling:

1) Does the heat dissipated by an OBX voice also happen to be 4.5x higher? If so, you gotta be careful about how many you pack together!
2) And how about cost? Does an OBX go for 4.5x more than a Polysix?

I can't speak to the heat dissapation, but a mostly-working Polysix seems to go for $900-$1300 on eBay. Does an OBX go for $4000-$5800? It'd be kinda weird if it worked out that way.

Chip
oldcrow
chipaudette wrote:
This then prompts other similar questions regarding scaling:

1) Does the heat dissipated by an OBX voice also happen to be 4.5x higher? If so, you gotta be careful about how many you pack together!
2) And how about cost? Does an OBX go for 4.5x more than a Polysix?

I can't speak to the heat dissapation, but a mostly-working Polysix seems to go for $900-$1300 on eBay. Does an OBX go for $4000-$5800? It'd be kinda weird if it worked out that way.

Chip


I imagine most of the heat in the OBX was from the Z-80 computer system, which used power-eating 2708-type EPROMs (that need 3 voltages). The voice cards each draw about 50mA per rail at most--each card has local voltage regulators, which on the original voice cards are 78/79L15s (TO-92 pkg), 100mA max. I use TO-220 packaged regulators since I have two non-custom EGs added in place of the CEM3310s. Still, I figure the card will pull about the same 50mA or so.

The MSRP on the 4-voice OBX was $4600, 6-voice was $5000 and 8-voice was I think $5400. MSRP on the Polysix was $2000. Ebay (which I do not consider a valid estimate of an instrument's value) has listed 8-voice OBXs in the past for $4000 to $5000. So MSRP ratio is about 2.5 to 1, ebay ratio about 4 to 1 at a guess.

Crow
/**/
EMwhite
oldcrow wrote:
chipaudette wrote:
Awesome work! The idea of populating the voice card x8 is making my eyes bug out and my hand shake from imagined fatigue. Wow.

Chip


This is why I will build one, then hire an assembly house for the rest. --Crow


I'm actually looking forward to the build. Am sure 1/2 way through I'll wonder what I got myself into but if I do it factory style and knock of a little each night, I figure in 2 weeks, I'll be playing the monster!
oozitron
If I get tired of soldering CrOwBX boards, I'll just put on Moving Pictures for some inspiration :-)

This is the coolest thread on the entire internet...

Drew
chipaudette
oldcrow wrote:

The MSRP on the 4-voice OBX was $4600, 6-voice was $5000 and 8-voice was I think $5400. MSRP on the Polysix was $2000. Ebay (which I do not consider a valid estimate of an instrument's value) has listed 8-voice OBXs in the past for $4000 to $5000. So MSRP ratio is about 2.5 to 1, ebay ratio about 4 to 1 at a guess.

Crow
/**/


Assuming your MSRP for the OBX is from the 1979 (its first year, according to vintagesynth), and assuming that the MSRP for the Polysix is from 1981 (its first year, according to vintagesynth), there's some inflation to take into account since that was a really bad time for that sort of thing.

From the US Federal reserve (http://www.minneapolisfed.org/index.cfm?): 1$ of goods or services in 1979 would cost $1.25 in 1981. That same dollar of goods or services from 1979 would require $3.22 in 2013.

I was going to use this data to make an argument that the cost ratio, even in MSRP, is higher than the 2.5 value stated above due to the difference in dollar value between 1979 and 1981. But, then I stopped myself because, in looking at that 2013 value, I'm able to really get a perspective on how expensive these synths really were back then:

6-Voice OBX: $5000 in 1979 becomes $16,000 in 2013. WOW!
6-voice Polysix: $2000 in 1981 becomes $5100 in 2013. Still WOW!

That's A LOT of money.

Can you even spend $16,000 on a keyboard-format (not modular) synth in 2013? Yes, I know of Schmidt, but has he produced more than the single unit that appears at trade shows? Are there any other $16K new synths out there?

Also, even the $5K Polysix price is killing me. And it was considered a "budget" synth. At (the equivalent of) $5000!?!? That doesn't feel "budget" to me. Is there any synth out there produced in moderate volumes that costs this much today? Even DSI's latest monster synth is looking like it'll be ~$3K.

Wow. I'm floored.

Chip
boops
Wow !!!! chapeau bas Monsieur eek!
Isaiah
oozitron wrote:
If I get tired of soldering CrOwBX boards, I'll just put on Moving Pictures for some inspiration :-)


Rockin' Banana!
oldcrow
Hm, I gaffed the audio connector on the host board--misaligned to the voice card. A minor issue that I am fixing now for the "real" boards. It won't prevent this first revision from being put together, that connection will just have to use an inline connector on some short wires. The connector alignment on the voice card is correct which is more important as it has to fit in an OBX.

Crow
/**/
The Real MC
Howdy, been following this thread and decided to join the community of wigglers (things that sound dirty but aren't...).

Seems I have been a bad influence. Nice work, Scott.
EMwhite
The Real MC wrote:
Howdy, been following this thread and decided to join the community of wigglers (things that sound dirty but aren't...).

Seems I have been a bad influence. Nice work, Scott.


Are you the Real MC from Painted Post something or other, with an equipment list that includes a tractor and a gaggle of alpaca (or something like that).

If so, welcome... if not... also welcome!
oldcrow
Well, after 25 years, I've finally used the last resistor in the last bag of the pile of resistors I bought from Stackpole when they vendored at the Dayton Hamvention in 1988. The resistors with the green body here and there are Stackpole ones.

Huge resistor order just now placed with Digikey. If you squint you can see some of the surfacemounted caps and the two 3300ppm resistors.

And the soldering continues...

--Crow
/**/

The Real MC
EMwhite wrote:
Are you the Real MC from Painted Post something or other, with an equipment list that includes a tractor and a gaggle of alpaca (or something like that).

If so, welcome... if not... also welcome!


That would be me 8_)
oldcrow
For those brave souls who intend to build one or more parts of this project and wish to get a head start on acquiring the needed parts inventory, this URL has basic files like parts overlays and parts lists:

http://www.cs80.com/crowbx/

Please note this is for the "prototype" rev. 1 board set. There will be minor changes for rev2 but 99% of these parts lists will be the same.

I just today ordered the rev1 front panel from Schaeffer. And the soldering continues...

Crow
/**/
Peake
The Real MC wrote:
Howdy, been following this thread and decided to join the community of wigglers (things that sound dirty but aren't...).

Seems I have been a bad influence. Nice work, Scott.


Moar bad influence please SlayerBadger!

Welcome to Muff's!
Peake
"For JH"

SlayerBadger! SlayerBadger! SlayerBadger!
EMwhite
Quick question for Old Crow;

'ad a butchers at your BOMs and wondered what the total cost would be for 8 * voice cards + the host board parts. I'm not pushing for a price on boards, just interested in cost of parts at this point 8_) And a + or - $50 estimate is fine, just looking for a ball park so I can start to set $$ aside.

And, a question: I don't see any microcontrollers or CPUs on the host board, and I like that (ALOT). Can you confirm that this beast will 'just' be all knobby/button-ey, no code, memory, etc.?

Thank you!
kynsi
The host board contains a PIC...
The Real MC
There is no PIC for system control. I helped with schematic peer review on the host board.

The host board is pure CV control from knobs. No microcontroller, no code, no memory, no patch storage.
Nordcore
w/o controller it would never get polyphonic.
Minimum controller needs 8 CV outputs for the pitch + 8 gates, everything else might be controlled by pots and/or external CV inputs.

The control board in the obx contains the modulation sources:
- one LFO (tri, square, S&H)
- pitch-wheel
which are routed to the modulation destinations:
- pitch
- filter pitch
It contains the noise source.
All of this can be replaced by simple inputs, where you just patch a modulation from some modules and adjust the mod amount with a pot.

The control board contains the CV generation for the autotune. This could either be a battery of 16 trim pots - or you rely on properly calibrated voice boards an just ground that signal.
So all of this can be done in "simple" analogue just with pots - the only thing you loose is patch storage.

Whats left is the "glide" circuitry. This applies an adjustable slope to each of the eight note pitches. Than the generation of the eight note pitches themselves, and the eight gate signals.
This could be done by a very simple midi to cv converter:



P.S.: the software for a similar design is already done (only 4ch but with some more bells 'n whistles, see my avatar picture... )
oldcrow
You are probably looking at about US$1000 in parts for 8 voice boards and 1 host board. This does not include the bare boards or a front panel.
I ordered $620 in parts this week, but I had some parts on hand already.

There is one PIC part on the host board for the noise generator. Specifically, this noise source: http://www.electricdruid.net/index.php?page=projects.noisegen

Everything else is analog save for a 4011 gate chip used to select if a VCO is muted or set to a waveform.

Crow
/**/

EMwhite wrote:
Quick question for Old Crow;

'ad a butchers at your BOMs and wondered what the total cost would be for 8 * voice cards + the host board parts. I'm not pushing for a price on boards, just interested in cost of parts at this point 8_) And a + or - $50 estimate is fine, just looking for a ball park so I can start to set $$ aside.

And, a question: I don't see any microcontrollers or CPUs on the host board, and I like that (ALOT). Can you confirm that this beast will 'just' be all knobby/button-ey, no code, memory, etc.?

Thank you!
oldcrow
My initial "rev1/prototype" setup is designed to operate as a 4-voice system, with an externally-provided MIDI to CV/gate unit (I have an MOTM-650 for this). At the moment, I am only setting it up to test a single voice.

After that test phase concludes, I will be making a "slot adapter" (see the L-shaped board farther down this thread) and a 4-card carrier board. The carrier board bolts onto the back of the host board where a single voice card can currently mount, and by using the slot adapters 4 voice cards can mount to the carrier. The carrier board will have the four glide/portamento slew circuits as well as a panning mixer and volume VCAs similar to the original OBX. There will need to exist a breakout panel for the 4x CV and 4x gate inputs, as well as the left, mono and right audio outputs. I may try to incorporate the host board's local porta/glide circuit and volume VCA, but it depends on how much cross-wiring this entails. The host board was originally meant to test single voice cards after all. ;)

Crow
/**/
home_listening
Thanks for all the updates, following keenly.

The BOM is handy too, cheers.

keep up the good work!
oldcrow
I update the BOM pdfs as I find errata (wrong resistor values, swapped reference designators, etc) so check it every few days ;) --Crow

home_listening wrote:

The BOM is handy too, cheers.
oozitron
Is there any reason to use 5% resistors (as indicated in the BOM) instead of 1% everywhere?

Will 5% resistors add to the (slight) note-to-note differences (imperfections) in tone that make older synths sound better?

Or is that a silly question meh

Drew (who has a lot of the required resistors, but they're all 1%)
oozitron
CS80 Website note:

The links to the two BOM files are backwards. Figured it out after spending several minutes wondering why the Voice board needed 21 pots!

Dang this is exciting screaming goo yo

Drew
oldcrow
Oops, fixed. Thanks SlayerBadger!

oozitron wrote:
CS80 Website note:

The links to the two BOM files are backwards. Figured it out after spending several minutes wondering why the Voice board needed 21 pots!

Dang this is exciting screaming goo yo

Drew
oldcrow
It won't make a difference worth noting. I just use 5% because they're cheaper. --Crow

oozitron wrote:
Is there any reason to use 5% resistors (as indicated in the BOM) instead of 1% everywhere?
The Real MC
BTW if you want the "Tom Sawyer" rezz, that sound requires at least four voices in unison. You won't get that sound with just one voicecard.

A big part of that sound is the inherent filter scale error and EG timing tolerances between the voicecards. The filter scale doesn't match between voicecards due to the cheap expo converter in the filter cutoff CV summing circuit. Slight EG timing differences between voicecards due to tolerances in 3310s and/or Cx charge caps also add to tracking error.

The service manual also says that filter tracking is linear only within a three octave range - exceed that range and there is no guarantee that tracking will match between voicecards. This is not hard to do with EG filter modulation, which certainly is what the "Tom Sawyer" rezz is doing.

So because the filters between voicecards aren't tracking in scale, this creates a rather unique flanging effect that is the soul of that rezz sound. It took some fiddling around trying to get "that sound", but once I hit the UNISON button it was WHOOAAAHHH! I tried the same effect on my Memorymoog and Andromeda, but the tracking is "too perfect". Well!

AFAIK, Scott has retained the cheap expo converter at my urging. This is one of those circuits where imperfections can be a good thing.

The later Oberheims got more accurate tracking with the move to CEM3320s and software envelopes. Whether that is a positive improvement is highly debatible...
The Real MC
This is the guilty party that inspired Scott's project. Restoring one of these is no walk in the park!
EMwhite
The tolerances (read, varied tolerances) is presumably what gave it that great sound. Hard to mimic in a VST but these guys tried: http://www.sonicprojects.ch/obx/separatevoicedesign.html

I was so intrigued that I actually dumped the $150 or whatever it was to buy it, painstakingly fought with Wine an an ASIO drive to run under xwindows on my MacPro and succeeded. How does it sound? Well, it sound good to me but surely not the same.

The 'better' versions of OPX like Pro and Pro II have fancier modulation and other features like up to 12 voices and built in effects but I don't like it.

Funny thing... I'm such a snob that I won't use a period inaccurate version of a virtual synth's representation of an actual synth and certainly won't use it's digital reverb hihi

Really looking fwd to this build but I think I said that already. By the way, I was in touch with Olivier @ Mutable and was told that MIDIpal will do > 4 voices, in fact, it will do 16 voices worth of Note distribution. It will even 'wrap' so if your starting channel is 10, it will go 10,11,12,13,14,15,16,1. Not sure that any of the Midi->CV converters will do this but the thought (my evil plan) is either to pickup a second MOTM-650, or to build two quad ACXSynth interfaces.
oldcrow
Giant bag of resistors arrived. Now I have to go to Target and get a couple Stanley Sortmasters as I am out of bin box space. Guinness ftw!
aladan
oldcrow wrote:
Giant bag of resistors arrived. Now I have to go to Target and get a couple Stanley Sortmasters as I am out of bin box space. Guinness ftw!


I've started using these:

http://www.cheapaschips.com.au/estore/style/ha6095.aspx
http://www.cheapaschips.com.au/estore/style/ha6094.aspx

Life is so much easier with storage drawers thumbs up
oldcrow
Oh I have plenty of drawers, never mind I have this thing:

http://www.uline.com/Product/ProductDetailRootItem.Aspx?modelnumber=H- 1428

I just find these days I like to organize things by project, and the Stanley Sortmaster is great for this, given they can be locked shut and toted around. USD$9 at Target. Just came back with two. 8_)

http://www.stanleytools.com/default.asp?CATEGORY=ZAG+ORGANIZERS&TYPE=P RODUCT&PARTNUMBER=014026R&SDesc=Stanley%26%23174%3B+SortMaster+Organiz er

Crow
/**/

aladan wrote:
I've started using these:

http://www.cheapaschips.com.au/estore/style/ha6095.aspx
http://www.cheapaschips.com.au/estore/style/ha6094.aspx

Life is so much easier with storage drawers thumbs up
Nordcore
EMwhite wrote:
Not sure that any of the Midi->CV converters will do this but the thought (my evil plan) is either to pickup a second MOTM-650, or to build two quad ACXSynth interfaces.

If there are about ten people wanting one, I could make an pcb for this: https://www.muffwiggler.com/forum/viewtopic.php?t=83363&start=78
(Size 50x100mm (2" x 4" ), pcb picture is just a draft. )
As said, firmware for four channels *does* run, and changing that to 8 is easily done. (It was written with flexible channel numbers in mind. )
There is an boot loader /flasher for the atmel, so the firmware is field up-gradable. (Computer with capability of sending midi sys-ex required. )
Costs would be round about 15€, including programmed atmel (first programming had to be done with a hardware programmer) and world wide shipping (registered mail).
mOBiTh
I'm definitely in for building an 8 voice and midi-cv converter for it.


I wonder what 16 voices would sound like hmmm.....

hihi
demian
It sounds better.
oldenjon
hyper
EMwhite
Nordcore wrote:
If there are about ten people wanting one, I could make an pcb for this: https://www.muffwiggler.com/forum/viewtopic.php?t=83363&start=78
(Size 50x100mm (2" x 4" ), pcb picture is just a draft. )


I'd be interested in seeing a list of 'features'/capabilities and certainly would want the 8-voice version. Is this based on a piece of code that you already have tested and running? (may take two as I have a separate SEM 4-voice project that I'm cobbling together).

Tell me more...
Isaiah
oldcrow
Apologies if I'm asking something obvious, but is there a 2-/4-pole switch for the VCF, or did you decide not to implement that?
The Real MC
*raises hand for eight voices plus MIDI->CV converter*
mOBiTh
also one other little question!

will the glide be polyphonic and nicely mismatched between voices for monstrous glides (like my ob-xa)??? hihi

(seems the late ob-xa's had two modes - one accurate, one inaccurate, and also semitone-quantised glide on/off - these features would be awesome)
negativspace
Nothing intelligent to add, but still watching and still highly interested in the outcome! w00t
EMwhite
There's nothing stopping you (us) from taking care of this 'outside' of the box? If you have the Midi->CV priority set such that each voice is assigned starting with the low note on voice 1 then a C Major triad played on octave 3 will do a poly glide up to octave 6; the only requirement is the voice allocation is retained so there is no crossing?

I think asking the controller board to do this (intelligent voice allocation) is the difficult part since it's 100% analog with the exception of the PIC for noise, so we have read.

I'm torn between JUST asking for 8 voice cards and a controller that will let me program the built in features of the board and perform the most basic of analog functions across all of the voices from a central panel, and wanting a FULL function-for-function OBX which will obviously necessitate a much more complex microcontroller, code base, with presets, etc. etc.

Just thinking out loud, assuming the rudiments of cross modulation, waveform selection, central envelope setting were taken care of, I'd rather have this sooner rather than later. Maybe that is the intent of version 1.

Is it too much to ask for extensibility of the voice card (either a provision for daughter card headers in the ares that are likely to be extended later or enough room on the board for major modification).

Just talking here... as a typical user, I'm interested in features; as s develop and Product Manager in real life, I'm wary of scope creep and a project that rolls on for ages that will never make it to 'market'...
oldcrow
This initial version is the stock OBX voice, which has the 2-pole lowpass only. But, this is just the beginning. ;) --Crow

Isaiah wrote:
oldcrow
Apologies if I'm asking something obvious, but is there a 2-/4-pole switch for the VCF, or did you decide not to implement that?
oldcrow
The host board supports one voice without the as-yet-to-be-made "carrier board" and slot adapter boards. The host board has one analog portamento/glide circuit as per the original OBX. Now, when the carrier board is made, it will allow up to 4 voice cards. The carrier board will have 4 OBX glide circuits in the path of each pitch CV, the slew rate of which will still be set by the host board portamento control, and the corresponding unmatched fine tracking that describes part of "the OBX sound" will exist. (Note: this will require a small bit of hacking on the host board to bypass the local glide circuit and provide the control voltage for glide to the carrier board, but nothing major). Remember, the original intent of the host board was to just test voice boards. It is flexible enough to provide the control harness for more than one voice for everything that is not gate/pitch CV, but I am making it more for utility than performance. Not that it won't work fine as a "finished instrument," just making sure it is known that it is first a test platform, and second a finished synthesizer.

Now as for firmware-programmed glides, I'll leave that to the folks who are making poly CV/gate devices. Guinness ftw!

--Crow
/**/

mOBiTh wrote:
also one other little question!

will the glide be polyphonic and nicely mismatched between voices for monstrous glides (like my ob-xa)??? hihi
mOBiTh
excellent excellent 8_) 8_) 8_)
oldcrow
While on the subject, I am not yet making an 8-voice carrier board because 1) it might exceed the power budget of the 40mil power traces on the host board and 2) the carrier board cannot be any larger than the host board, which is 10.25" W x 5.5" H (260mm x 140mm). I prefer a minimum slot-to-slot card spacing of 0.750", and 8 cards would need 5.25" just for the slot rows. Additionally, there still needs to be space for the now-eight glide circuits and eight-voice stereo panning mixer/volume VCAs, nevermind header pads for things like the pitches and gates, fine tune CVs and provision for the auto-tune *hardware* -- someone that is not me gets to write the auto-tune routine. I can program, but my language is assembly and my CPUs are the 12-and-16-series PICs, Z8, Z-80 and the 68000 wink

Right now I just want to get voice card/host board #001 to work. SlayerBadger!

--Crow
/**/
mOBiTh
good plan. i'm going to stop making unwieldy suggestions! hihi
aladan
OK, just assume I'll take one/N of basically everything this thread ends up making - CV monosynth/polysynth with the lot/you name it It's motherfucking bacon yo thumbs up
oldcrow
Resistors, diodes, power supply parts installed on both boards, and an overnight host board voltage test before the rest of the parts go in. I set the bench supply to trip at 20mA, so no chance of fireworks. Quiescent current draw is as you can see 2 to 3mA, mostly from the temporary power status LEDs (the panel ones are 3mm). More fun later. --Crow

Nordcore
EMwhite wrote:
If you have the Midi->CV priority set such that each voice is assigned starting with the low note on voice 1 then a C Major triad played on octave 3 will do a poly glide up to octave 6; the only requirement is the voice allocation is retained so there is no crossing?


In my interface the voice allocation is simple "steal oldest note".
Never thought of adding extra delay to get some chords together and to assign the notes than...
Without delay midi is strictly serial, so there is always only one note at a time coming in - and that is immediately assigned to the voice that is "the most unused", either the oldest "off-note" (if there are any "off" voices left over) or the oldest "on-note", if all are in use.

Useful options starts with unisono modes:
Duosone, assign two voices to each incoming note (add some pitch offset to each).
Can be extended to a variable number of voices, especially interesting with a mode I saw on the Jupiter 4: Keep number of voices constant. So if you play one note at a time it plays 4 voices unisono. If you play two notes each note gets two voices and so on.
This keeps the sound equally "full", independent of the number of played notes.
EMwhite
Oh, sorry, didn't mean 'delay'. No analysis or re-ordering necessary.

I believe the premise is that if you play a chord that is less than the total number of voices (so no stealing necessary in this scenario) it would act accordingly:

When in this mode (Poly glide) and no notes pressed, place the firstnote on the lowest numbered voice (v1), next note on the next numbered voice (v2) and so on.

Any subsequent key pressed gets assigned likewise.

Then upon release of ALL keys, the same occurs, first note on lowest voice, etc.

The result is that if you are 'careful' when you play, you get (the example above) C-E-G play in octave 3 in that order gets assigned to v1, v2, v3 respectively. Release and play the another triad with similar interval elsewhere on keyboard. Simple example is C-E-G in octave 5. Provided that you depress C and then E and then G (and quickly), the glide will traverse the same distance and therefore be pleasing to the ear.

Should the 2nd chord be G, the C below it, then E, then the low C will need to glide to G, E will glide to C and G will glide to E. That is the 'crossing' I speak of. With a really fast glide, I'm not sure you would be troubled by it if it was in the mix but the grand sweeping and resonant somewhat slower glide sounds best when done in this fashion.

Now I'm writing all off this without ever owning an OBX or a true analog poly synth (my Matrix 6 doesn't count) that has Poly glide. But I do have a MOTM-650 and that is how the Poly 2 w/Portamento works. It's very very nice!

As OldCrow said, he'll leave this bit to the next layer up! Even the most rudimentary voice allocation algorithm requires a cpu and some code but I don't have to tell you that, looks like you've been working on this for a while already and I'm looking fwd to seeing if an 8 voice version of your board will integrate well, Poly Glide or not.
keninverse
oldcrow wrote:
Stanley Sortmaster is great for this, given they can be locked shut and toted around. USD$9 at Target. Just came back with two. 8_)

http://www.stanleytools.com/default.asp?CATEGORY=ZAG+ORGANIZERS&TYPE=P RODUCT&PARTNUMBER=014026R&SDesc=Stanley%26%23174%3B+SortMaster+Organiz er

Crow
/**/


Hah! This is exactly what I use for resistors. I put them in 4mil baggies and place in order of total resistance. This way I can sit in front of a TV watch some Nova and stuff boards. I love the portability aspect of this method. I find placing resistors a bit daunting.
The Real MC
Scott, study the OB-X voicecard motherboard design. A MB is a four voice carrier like you are proposing. To add another four voices, connector "J" connects the L/R and autotune busses.

You're not thinking of piggybacking the four voice carrier to the hostboard and front panel? Four of those voicecards is a bit of weight.

The 2nd version service manual describes how autotune works, but the schematic is so convoluted that it doesn't make immediate sense.
I re-wrote the autotune schematic and the description from the manual. Will scan you a copy.

The OB-X has one of the fastest autotunes on the planet. They accomplish that by setting each VCO frequency to a very high frequency square wave and reading the period of each VCO with a counter. By using high frequencies the autotune cycle is very fast. But autotune does not compensate for scale errors so it is imperative that scale (v/oct) and high freq track trimpots are calibrated properly ESP high freq track.

Firmware wise it is probably just a successive approximation algorithm to optimize the autotune CVs with expected autotune period. If the autotune fails after six tries then it disables that voice.
The Real MC
Scott not only replicated the quirky glide circuit, but he also replicated the low fidelity VCAs that is a big part of the OB-X sound Rockin' Banana!
gigasturtz
Let me see if I have this correct:
The current host board/iteration of this project will facilitate 4 single voice boards, with a break out containing the 4 cv and gate inputs?

This project is fantastic. Count me as interested for sure. It's motherfucking bacon yo

So much awesome DIY on this forum these days.
paults
Board is sucking 1W without any ICs. That's cookin'!
oldcrow
Yeah my carrier is just a more compact version with everything brought to headers. I plan to use some sort of support frame for the installed cards.

--Crow
/**/

The Real MC wrote:
Scott, study the OB-X voicecard motherboard design. A MB is a four voice carrier like you are proposing. To add another four voices, connector "J" connects the L/R and autotune busses.

You're not thinking of piggybacking the four voice carrier to the hostboard and front panel? Four of those voicecards is a bit of weight.
oldcrow
There is a a small cheapie shunt regulator for the -10V used by the 405x chips, it is most of the current draw you see there. This bench supply needs a mA current scale as below 50mA the reading is not quite accurate.

Voltages look good on all supply pin/pads, so now it is time to assemble the rest of the host board by circuit section. LFO first. I have to wait for my front panel to arrive before I can attach the switches, however. --Crow

paults wrote:
Board is sucking 1W without any ICs. That's cookin'!
oldcrow
Note to self: put an LFO rate LED on host board rev2. d'oh!
Isaiah
oldcrow wrote:
This initial version is the stock OBX voice, which has the 2-pole lowpass only. But, this is just the beginning. wink --Crow

Isaiah wrote:
oldcrow
Apologies if I'm asking something obvious, but is there a 2-/4-pole switch for the VCF, or did you decide not to implement that?


Ok, thanks.
Hope you manage to add a 4-pole VCF with a 2-pole output that still sounds like the OB-X filter.
It doesn't bother me one bit whether it sounds like an OB-X or OB-Xa hihi
I wouldn't be able to tell the difference, I'm sure!
I only mention it because you said the boards were designed as replacements for originals.

I must admit, this project has me really torn.
I'd love to build a 4-voice OB-X and this project looks incredible.
But, I have an SEM which is my "go-to" synth voice and I'm worried they might sound too similar.
Any thoughts on this, anyone?
EMwhite
You'll miss high pass and therefore band pass, the ability to detune alternating voices (without a screw driver hihi), decoupled LFOs.

But you'll gain a common, more capable LFO and the long list of 'poly' flavored benefits but its probably worth mentioning that the filter design of Tom's original OBX voice cards had the basic capability for the other (read, other than low pass) filter modes; but it was missing some circuitry that might possibly be added. Whether or not OldCrow's project will ever tackle this addition on a later release can only be spoken to by the man. Maybe v4 in 2015?
Nordcore
EMwhite wrote:
When in this mode (Poly glide) and no notes pressed, place the firstnote on the lowest numbered voice (v1), next note on the next numbered voice (v2) and so on.


That should be no problem.
It will often cut the release phase of a sound, playing a line "not legato" will sound like played on a monophonic synthesizer.
Playing legato will use (just) two voices.
Looks useful, as the release sounds won't build up too much whilst you play notes, but is still there on rests.
chipaudette
In case anyone isn't familiar with the importance of not-perfect glide...you might be interested to check out this post:

http://synthhacker.blogspot.com/2013/04/portamento-voice-spreading-fro m-monopoly.html

Prior to this post, I added an Arduino to my Korg Polysix to generate all the pitch CV's. Once I did this, I could easily add glide (portamento) to my synth via software. The demo happens to show unison mode, but each voice gets its own glide calculations.

At first, I used the same glide parameters for generating the Pitch CV for each voice. That ended up with a "perfect" glide where the pitch sliding was in perfect sync between the voices. That was so boring.

Because I own a Mono/Poly, where I noticed that the glide was different for each of the four voices, I went back to my Polysix software and gave each voice its own glide rate. BINGO! Now it sounds so much better.

I think that this is a similar effect that we're discussing here for the OB-X. Making the glide rates different for each voice is SOOO important to giving it that engaging sound. As noted earlier, though, it doesn't necessarily need to be done in hardware...doing it in software is pretty good, too...and is certainly better than having no glide at all!

Chip
Nordcore
The obx glide is in a feedback loop with a current source - so it's linear not 1/e^x. (Of course both can be done in software. )

... which leads to the more general question:
what to do in software, what in hardware. The original control board has a *very* limited analogue modulation engine, and it is pretty slow. So I see no reason to keep that analogue. Better use the board space for some filters after the S&H stages, so any of the CVs could be used for modulation.
The Real MC
Isaiah wrote:
But, I have an SEM which is my "go-to" synth voice and I'm worried they might sound too similar.
Any thoughts on this, anyone?


Monophonic, yes there will be overlap soundwise with the LP filter.

Polyphonic, the CrOwBX is the way to go. Way more convenient using ganged CVs on all parameters as opposed to setting individual SEMs.

The SEM voice in a polyphonic format is a thing to behold...

EMwhite wrote:
Whether or not OldCrow's project will ever tackle this addition [HP/BP/Notch] on a later release can only be spoken to by the man. Maybe v4 in 2015?


I am planning a modification to my OB-X for exactly that, plus other bonuses like voice modulation like the SEM. All without changing the OS, all programmable. I plan on forwarding that to Scott when I get it working.
Isaiah
EMwhite & The Real MC
Thanks for the feedback guys.
I should clarify, I only have one SEM and I certainly don't have the funds to buy more!
Obviously, the SEM is monophonic (I don't multi-track it) and the CrOwBX will be Polyphonic, and I'd use them for monophonic and polyphonic duties respectively.

I should probably rephrase my question:
How does a single OB-X voice compare to an SEM, sonically?
I doubt I'd ever program similar patches on the two units (what works well monophonic use, might sound awful for polyphonic use, and vice versa), but would the two together sound TOO "Oberheim-y" (for better or worse)?
I'm not sure I've explained myself very well...
Hopefully, you'll understand what I mean and be able to attempt an objective answer hihi
Thanks!
The Real MC
I don't own a SEM and can't make sonic comparisons to my OB-X.

Schematic wise, they are very close. Same VCO circuits, same VCA. OB-X VCF is little different because of VC'd resonance. That's in the feedback path and any change in sound is hard to avoid there. Either SEM or OB-X VCF has its thorns - OB-X will sound slightly different, while SEM isn't 100% programmable.

Many people who have owned both claim that the VCF sonic difference is insignificant. I know three very experienced owners from that group whose opinion I trust, and two of them are members here - hopefully they will chime in.
oldcrow
Shipping notification on my front panel, probably here by the 14th. Also, finally after more effort than it should have taken I got my old PIC programmer to work on my CAD system and programmed the noise generator PICs. Still more soldering... --Crow
Peake
If this can be modded to add SEM-style HP/Notch/BP functions, it's mega-win and I'd be all over it.
oldcrow
VCLFO works. S/H testing next as that uses the PIC noise generator and I need to see what tweaks to the amplifier gain are needed from my design estimates. Host board assembly almost finished.
oldcrow
Host board just about done. Switches and LEDs have to wait for the front panel as they cannot be soldered until they are lined up with their panel holes. So far it all checks out.

Note: the green screwdriver is the Xcelite R3322. The most useful tool ever made. SlayerBadger!

--Crow

mOBiTh
I'm still thinking 12 or 16 voices hihi

can't wait to build this monster
EMwhite
This is the best thread on Muffs... I get so excited to see a new post, a picture of progress on the build or board detail that I haven't seen before. it's like Christmas in June. Talk about Gear porn...
Peake
oldcrow wrote:
Note: the green screwdriver is the Xcelite R3322. The most useful tool ever made. SlayerBadger!

--Crow


How very odd that I've got one right here wink
oldcrow
Let's hear it for Digikey...lol Guinness ftw! Guinness ftw! Guinness ftw!

dougt
Heh, guess they don't know their resistor color codes over there...
The Real MC
oldcrow wrote:
Let's hear it for Digikey...lol Guinness ftw! Guinness ftw! Guinness ftw!


d'oh!

Well, THAT'S very reassuring. So now I have to check component values for large BOM orders for EIGHT voicecards dizzy

I thought you were sourcing from Mouser...?!?
The Real MC
oldcrow wrote:
Note: the green screwdriver is the Xcelite R3322. The most useful tool ever made. SlayerBadger!


Dad had many of those for his model train layout, never got around to getting one. They are good tools.
oozitron
[quote="oldcrow"]Let's hear it for Digikey...lol Guinness ftw! Guinness ftw! Guinness ftw!

I wouldn't worry about it. If everything's too precise it'll sound too sterile, like an OB-8 or an Xpander.

Drew
glmodular
oldcrow wrote:
Let's hear it for Digikey...lol Guinness ftw! Guinness ftw! Guinness ftw!


Yep, I've had some head scratching shipments from them. Not too long ago I ordered 100 of these:



But I only get 30 of them in the bag...along with 70 of these (in prepack bags):



The worst part is that these were in a _heat sealed_ and properly labeled bag! MY ASS IS BLEEDING Not the typical - someone grabbed the wrong thing and stuffed it in the box - type of error that I normally see.

They fixed the goof and let me keep the parts.

So does anyone need some really nice gold plated 22-24 awg molex female crimp pins? I'm probably never going to use them.

Molex P/N: 16-02-0104

70 available! hihi

Tony
oldcrow
I source from more than one place. Digikey is a 1-day ground delivery to me, so it gets a lot of business.

There were, by the way, two 330K resistors in that bag. I am guessing the warehouse bin was reloaded with the wrong value when it got low on stock, and the sorting robot does not actually use machine vision or anything to proof the value. I have an old habit of unconsciously naming each value in my head as I prepare them for soldering, which is how I caught that inventory error. They've shipped me (hopefully) the proper resistors already. --Crow

The Real MC wrote:
I thought you were sourcing from Mouser...?!?
oozitron
glmodular wrote:

Yep, I've had some head scratching shipments from them. Not too long ago I ordered 100 of these:




Isn't the the engine block from a 1961 John Deere tractor?

Drew
oldcrow
Found one small circuit mistake on the rev1 host board, I got the +/- pins on one op-amp section reversed which went unnoticed in the schematic layout. Rather than hack the board traces I just doctored another op-amp to swap the pins. Voice board assembly continues...

The Real MC
oldcrow wrote:
Found one small circuit mistake on the rev1 host board, I got the +/- pins on one op-amp section reversed which went unnoticed in the schematic layout. Rather than hack the board traces I just doctored another op-amp to swap the pins. Voice board assembly continues...



Aren't those resistors supposed to be 330K? Haha!
oldcrow
Between soldering sessions I work out the remaining boards that will enable building the 4 voice system. Since the carrier board does not have a lot of room for electronic parts I decided to put the individual portamento circuits on the slot adapter boards. The adapter also has the audio panner front end for one voice.

Isaiah
oldcrow
So a 4-voice unit will have the following:
*1 Control board
*1 Carrier board
*4 Voice boards

Right?
Or is your current Control board just for the purpose of testing the voice board?
I'm just wondering whether the control layout will be fixed. I suppose the pots and switches could be connected to the Control board with flying wires...
oldcrow
There are ten boards overall for 4 voices:

1 host (control) board
1 carrier board
4 slot adapter boards
4 voice boards

The slot adapters turn the voice boards into right-angle mount units vs. the tray method Oberheim used. The voice cards mate to the slot adapters, then the voiceboards+slot adapters plug into the carrier board. The carrier board bolts to the back of the host board where a single voice card goes for testing. There are a few resistors to remove and others to add to allow the host board to control a few items not already on the harness, such as parallel portamento circuits and the carrier board left/right volume VCAs. You of course need an external 4-channel MIDICV unit to actually sound the voices.

The control layout is fixed for this iteration of the project, but you can make your own panel and as you say using flying wires to mount controls and jacks wherever you like. I do not plan to make another host board (yet) as I have enough to do just to make this thing work at all. screaming goo yo

Isaiah wrote:
oldcrow
So a 4-voice unit will have the following:
*1 Control board
*1 Carrier board
*4 Voice boards

Right?
Or is your current Control board just for the purpose of testing the voice board?
I'm just wondering whether the control layout will be fixed. I suppose the pots and switches could be connected to the Control board with flying wires...
oldcrow
Some examples of how I did plug in boards with host/carrier boards:

The only remaining panel from my 7-panel (6 operator panels, 1 common parameters panel) DX7 programming console that I built in 1987. It was built into a studio desk that I (sadly) sold long, long ago. I did build a spare operator panel, which you can see here. This was all hand-taped using Bishop Graphics pre-cut stencils, trace tape and vellum on a light table. 100% old school. SlayerBadger! The cards use 22-pin MTA156 card edge fingers that plug into framed bus connectors. Back then making 2-sided boards by hand was not trivial so I did it all single-sided which is why you see piles of wiring.



Here is the first MOTM-480 ever made: my original prototype from 2001. I wanted to experiment with different kinds of OTA cells so I split the topology of the filters up across several boards: two exponential converters, two 12dB state-variable filters and dual negative feedback OTA cells. These all plug into the carrier board which handled the power and final audio output circuits.



The crOwBX setup tries to improve on this design method by using Molex connectors in the original dimensions dictated by a stock OBX voice card. Fully assembled the only wiring is from the jack headers to the front panel.

Storm has passed, time to solder...

--Crow
/**/
oldcrow
Carrier board layout finished, except for some silkscreen clean up. Has the mute-able master volume VCAs, headers for the fine-tune CVs, the left, mono, and right audio outputs and a 34-pin IDC header for the gates and CVs. 2-pin headers will also fit there. I put a main DC power header on this board too, mainly so I can test it by itself but it serves as an alternate power supply connection.

I re-purposed a couple of the voice board connector signals (does not affect the voice boards) mainly to get the portamento CV harnessed to all voices and the mute and left right audio busses off the slot adapters and into the volume VCAs.

Assembly of this one is a little tricky: the amplifier parts need to mount as close to the board as possible as there is only 1/4" clearance from the bottom edge of a fitted slot adapter card to the carrier board. DIP chips are about the tallest things permitted. The headers are all mounted in known spaces where there is clearance.

The board is shown upside-down wrt mounting to a host board, the "bottom" row of headers are what attach to the top row on the host board.

This is the final board in this iteration of the project.

Late night soldering time. SlayerBadger!

Isaiah
oldcrow
Thanks for explaining.
So, the voice boards will sit perpendicular to the front panel?
How deep do you think a 4-voice unit will be?

Been toying with the idea of building a 4-voice CrOwBX keyboard, you see...
I suppose the voice boards could be connected with headers on ribbon cable, right?

I'm amazed by how quickly you've managed to pull this project together! Rockin' Banana!
The Real MC
This. Is. Too. Cool.
home_listening
Hi Crow,

I'm hard of sight, is there enough clearance to socket the ICs on the control board?

Thanks
oldcrow
I am using 1/2" (12.70mm) standoffs between the front panel and the host board, this is enough room to use IC sockets. The tallest item that just fits are the multiturn trimpots. --Crow

home_listening wrote:
Hi Crow,

I'm hard of sight, is there enough clearance to socket the ICs on the control board?

Thanks
oldcrow
Yes, the voice boards will extend horizontally behind the host board and carrier board (see my MOTM-480 prototype image a few posts down). Admittedly not the ideal configuration as I will have to devise some sort of support frame to hold the cards steady at their back edge: they are heavy enough, especially with the required slot adapters, to droop if no anchoring is provided. Still, given that I am making a 4 voice system run off what is supposed to be a test platform, not every aspect of the design is ideal.

My estimate, as measured from the back of the front panel to the edge of a carrier-mounted voice card, is about 7" (~180mm). I will know more when I get it fully assembled. I do not even have the slot adapter or carrier boards ordered yet--trying to finish up the basic 1-voice prototype for testing first.

Ribbon cables for most signals would be okay I guess, though the power rails should be 16AWG wire at least.

Crow
/**/

Isaiah wrote:
oldcrow
Thanks for explaining.
So, the voice boards will sit perpendicular to the front panel?
How deep do you think a 4-voice unit will be?

Been toying with the idea of building a 4-voice CrOwBX keyboard, you see...
I suppose the voice boards could be connected with headers on ribbon cable, right?

I'm amazed by how quickly you've managed to pull this project together! :bananaguitar:
oldcrow
Envelope generators work, though I need to tweak some resistor values to get the time rates where I want them. You know you need a break when you spend 15 minutes trying to figure out why the ADSR CVs aren't showing up and eventually realize you didn't install the header for those on the host board yet. very frustrating
oldcrow
Voice card mounted to host board example. Using 3/16" (4.75mm) nylon spacers between the boards. This image was taken earlier today when I only had one EG populated for testing. Panel arrives tomorrow, so this weekend will be final assembly for the prototype 1-voice system. SlayerBadger!

mOBiTh
oldcrow wrote:
Voice card mounted to host board example. Using 3/16" (4.75mm) nylon spacers between the boards. This image was taken earlier today when I only had one EG populated for testing. Panel arrives tomorrow, so this weekend will be final assembly for the prototype 1-voice system. SlayerBadger!



this project is relentlessly amazing!

when do you sleep exactly??
oldcrow
CrOwBX: the Road Ahead

As the prototype system nears completion, and some space of time will lapse before I have the boards on hand to build the 4-voice expansion, I find time to consider future enhancements to the machine.

The first one is patch storage capability. It think what I would do here is split the microcontroller tasks across several PICs (or Atmels, or whatever). I would make a board that goes on the back of the host board that does nothing but digitize the control signals and remember them in a "small" patch setting EEROM, say 512 patches worth. Now, this board will not have the CV S/H amplifier arrays and digital latches. Instead it will transmit patch data either by sending it from the host/digitizer or by having the next board request it over the data link.

This next board, which would mount in its own enclosure along with the 4 or 8 voice boards, slot adapters and carrier board, would be the CV and switch signal recovery system. This board would have the local LFO and whatnot that formerly occupied the host board along with the microcontroller, DACs, S/H amps and so on. This board would talk to the host/digitizer and request as well as accept new patch setting information, store it in its own "local" EEROM mirroring the digitzer's, and go about setting the voices.

The point of this split system is that you can program patches, then disconnect the host and let the synthesizer run from its local patch store. Provide a few user controls to recall setting, sync to the host, accept MIDI patch setting commands, and so on.

My voice cards probably will not need auto-tuning, but I want to try something there anyway: an auto-tune microcontroller on each voice card. Let that microcontroller mute the card, lock out all CVs except its own, select the VCO to listen to, set a reference CV, time the period of the waveform, and tweak the fine tune CV until it either tunes up or fails after a number of tries. There are spare I/O pins on the voice card, I would use 2: request tuning and tuning status.

Anyway, this stuff is way, way down the road but it illustrates the path I would take after the all-manual 4-voice system is in the books.

And now, soldering... SlayerBadger!

--Crow
/**/
oldcrow
My office is in my house, so I have flexible hours. Guinness ftw!

Generally, 3AM to 9AM is my downtime, except when school is in session then it is 1AM to 7AM. I design in the daytime, solder at night, unless it is a project with 2,000 parts. You know, like this one. Guinness ftw!

mOBiTh wrote:
this project is relentlessly amazing!

when do you sleep exactly??
mOBiTh
oldcrow wrote:
My office is in my house, so I have flexible hours. Guinness ftw!

Generally, 3AM to 9AM is my downtime, except when school is in session then it is 1AM to 7AM. I design in the daytime, solder at night, unless it is a project with 2,000 parts. You know, like this one. Guinness ftw!

mOBiTh wrote:
this project is relentlessly amazing!

when do you sleep exactly??


i love soldering on nightshifts - very therapeutic and the time flies by. this week i've made 7 modules, one of which was a klee so i'm feeling quite pleased with myself. trying to learn stuff during the night appears to be vaguely impossible however...


anyway, as for the patch memory: I reckon having gone to all this trouble to make such a mega synth, a bit more work to do the patch memory seems like a no-brainer. i wish i could contribute more than pure lust!
EMwhite
(without auto-tune question)

Would tuning [without the aid of the circuit you described above] be generally stable? Say, as stable as an SEM or 4 or 8 of them next to each other. Meaning, once each was in tune, you might expect them to stay in tune across 4 or 5 octaves.

Of course, fine tuning is likely an onboard pot, not a knob you can reach out and tweak but just wondering.

(4v vs 8v question)

What is stopping a near-term iteration of this from supporting 8 Voices? Is it just the possible power issues you mention above and the carriage issues which concern physicals and how to mount it all?

Thank you...
Isaiah
oldcrow
Is it going to be possible to build a 4-voice without all the digital stuff (presets, auto-tune etc)?
I realise the noise source is generated on a PIC hihi
It's not digi-phobia, just my awareness of features I would likely never use.
The Real MC
Considering that my restored OB-X has fresh caps, new CMOS, new buffers, and new trimpots throughout, the voicecards still need the periodic autotune. The drift isn't terrible, no worse than my Memorymoog (which is hot-rodded for better tuning).
oldcrow
Panel arrived today. SlayerBadger! SlayerBadger! SlayerBadger!

oldcrow
Yes, the 4-voice setup is nearly all pure analog. The presets and whatnot are just considerations for where I might go down the road, but the goal of this edition of the project is a fully-manual 4-voice system.

As regards tuning, I imagine my exponential multipliers are better than what Oberheim had to use, so staying in tune is less of an issue than it was back then. The original voice boards had 741-type op-amps for the CV summing and servo amplifiers, and both VCOs shared an LM3086 transistor array for the expo pairs. I use LT1013 precison DC opamps for the summing and servo amps and LS318s for the expo pairs. It works for my VCO153s quite well, so I anticipate no issues here. --Crow

Isaiah wrote:
oldcrow
Is it going to be possible to build a 4-voice without all the digital stuff (presets, auto-tune etc)?
I realise the noise source is generated on a PIC :hihi:
It's not digi-phobia, just my awareness of features I would likely never use.
The Real MC
Description of OB-X autotune for embedded system

oldcrow
So Digikey sends me a shipment to replace the bag of 47K resistors that were supposed to be 330K resistors. I open the box and inside is 500 pieces of 33K. Not 330K, but 33K. Five hundred.

I spent 20 minutes on the phone to their customer service not because I was mad, but there is something wrong in their logistics system that needed fixing. The CS rep and I tracked it down as not only did they have a bin mismatch error, but the correction to the original sales order was marked with an incorrect substitution order number, and I got someone else's 33K parts.

All fixed now. Maybe.

I do use a lot of 33K (and 47K) in circuits, but this will last me a while. Guinness ftw!

--Crow
/**/
oozitron
Maybe you can sell partial kits.

A partial kit consisting of all the 33k resistors you'll need hihi

Drew (salivating like rabid dog over all this...)
glmodular
Quote:
All fixed now. Maybe.


Maybe you need to order a couple of those cheapie BK scopes and see if they will mistakenly throw in a LeCroy! You're batting pretty high right now! hihi

Tony
paults
Quote:
Description of OB-X autotune for embedded system


All of that mess inside a $2 PIC It's peanut butter jelly time!
mOBiTh
could use a little FPGA for everthing! memory, control, autotune, midi, the lot hihi
paults
My very first real EE job out of school was at Data General (made minicomputers....oh forget that!). Any rate, I soon noticed all the pullup resistors were 9.1K.

In fact, I looked at a few boards and saw NO 10K resistors, or even 1K (they were all 910 ohms).

I asked the head engineer. He grinned and said that this was an inside joke that started like 10 years ago to see if the parts ordering folks would notice (but why should they, they were just data entry people with zero technical training, they could be buying peanut butter or nuclear weapons for all they cared). Also, it was to see if their arch-rival Digital Equipment would be silly enough to copy that, because, as he put it "Who in their right mind would do this?".

So, for several year I went along with this but decided it was sort of silly in a nerd way.

Makes you wonder if the 910 ohm resistor (a standard, 5% value) is the most unused part in history.
oldcrow
While tweaking the envelope generators at one point I had max. time rates around 12 minutes. Maybe I will build a "super long-throw EG/VLFO" at some point so you can have for example this really slow undulating filter in a music track. I'll give you this, JH's multiplier design can hold times for, well, ever.

--Crow
/**/
Peake
Thank you for fixing Digikey.
oldcrow
Old Crow's tempco resistor thermal bond in 3 easy steps:

1) Get some thermal goop
2) Apply a bit of thermal goop to tempco resistors (see red circles)
3) Install LS318s. Solder a pin from the top then flip the board over for the rest.

oldcrow
Fully assembled voice card mounted to host board. It still needs some calibration, but it works. I will create a few audio examples once it is tuned up and mounted to the front panel...which is awaiting some fastener hardware from Amazon.

The two boards together draw 120mA on each rail at 19V, so power consumption is somewhere around 5 watts. This will increase slightly when I add in the power LEDs, but not by more than 10 to 12mA.

Note: I triggered the EGs and got this nice, fat BOOOOOONGNNGNGNG with that glassy resonance that is typical of the OBX, so at least I am on the right track. SlayerBadger!

More later. --Crow

/**/
mOBiTh
phwoar 8_)

i cannot wait to hear this thing!

5W sounds fairly warm - are we going to be roughly multiplying this by the number of voice cards we have??
oldcrow
mOBiTh wrote:
5W sounds fairly warm - are we going to be roughly multiplying this by the number of voice cards we have??


The host board is 55mA at +19V and -19V, so thats ~2.1W. Then, each voice board (65mA per rail) is about 2.5W. My standard parts CEM3310 equivalent EGs add about 30mA to whatever the original power budget was, which is why I bumped the voltage regulators up to the 500mA types vs. the original 100mA types.

I project the power budget of a 4-voice system to be:

1x host + 4x voice + 4x slot adapter + 1x carrier.

55mA + (4*65mA) + (4*10mA) + 20mA = 375mA per rail

At 19V this is a little over 7 watts per rail, so 14W overall. This is pretty low power for that many devices. Each board has its own local regulation, so some power (not much) is lost as heat, but nothing is too hot to touch. The temperature of the regulators of the voice board were about 100F / 38C after hours of sitting on the bench running. The board gets slightly warm, but I expected that.

--Crow
/**/
mOBiTh
Yeh not bad not bad.

For comparison, my 8 voice OB-Xa is rated at 40W (no idea what the actual current draw is though - haven't measured it)
ian-c
just had a tip off on this project. looks great, can't wait to hear what it sounds like.
oldcrow
The road toward rev2.

Rev1 is of course where I proof the design concepts and tweak out the bugs. And there are a few I've fixed so far. The biggest one is I will need to buffer all the host board panel controls that do not already have buffering (op-amp mixers, followers, etc) so that the source and load impedances for more than one voice board do not throw off the parameter values. The result is the ADSR controls, LFO rate, VCO mod depth, PW depth and portamento controls need to have voltage followers added. That's 3 more TL074s on an already-crowded board. Packed boards are one of my specialties though, so I will have it done in a day or two. Guinness ftw!

The voice board only has one potential issue: I need to add an op-amp for the sustain CV as each EG should have a buffer local to the voice card so that more than one voice card connected to the buffers-S/H amps of whatever manual or presettable parameter control for sustain doesn't start to exhibit loading issues. I don't think they will now, but I will go ahead and provide for the possibility. The time rates have local buffering.

Anyway, just a couple of the fun things I am contending with at the moment. --Crow

Isaiah
I'm so looking forward to this project.
I've been listening to lots of OB-X demos (OB-Xa and OB-8, too).
From what I can tell, the OB-X sounds more pleasant than the later models.

I asked previously if a 2-/4-pole switch could be implemented, thinking that a choice of slopes would expand the timbral palette.
But really, it sounds glorious with just the 2-pole! "If it ain't broke... " etc etc.

I'm certainly getting ahead of myself (again?! meh sad banana ), but I think my plan thus far is a 4-voice keyboard.
Voice cards laid out in much the same way as the OB-x, connected with ribbon cables.
Panel controls connected to control board via flying wired.
Should be easy enough to solder headers/pins in place of the pots and switches.

Keep up the great work, Scott! thumbs up
Isaiah
oldcrow
Do the VCOs respond to their Frequency controls in a continuous manner (like the SEM, for example), or in a stepped manner like the original OB-X?
I just wondered whether this was accomplished with hardware or software (both in your version, and the original).
kynsi
is there a possibility to mount multi-turn trimmers?
looks fantastic btw!
The Real MC
CrOwBX with hostboard frequency control is continuous like the SEM. Since CV from the hostboard is direct to the voicecard and there is no micro sitting between them, there is no stepping.

Once you put a micro and patch recall in there, all bets are off.

Looking forward to audio samples of CrOwBX nanners
Isaiah
The Real MC
Thanks for the information, I thought as much.
Probably not a bad idea to panel-mount fine tune trim pots (one per VCO) then.
I think this is what kynsi was asking about. It would just be a case of running cables from the trim pot to the PCB.
oldcrow
Well, the main thing here is for a 2/4 pole select there first needs to exist 2 more poles of filter. MC is working that out as I have enough stuff to do right now. screaming goo yo

Isaiah wrote:
I asked previously if a 2-/4-pole switch could be implemented, thinking that a choice of slopes would expand the timbral palette.
But really, it sounds glorious with just the 2-pole! "If it ain't broke... " etc etc.
oldcrow
To fine tune the VCOs there are two fine tune headers. These were originally used by the auto-tune capability of the old Z-80 computer system but for our purposes it is just a pair of extra CV inputs scaled to about a semitone of adjustment. You can also apply a tuning CV to the OSC1/OSC2 FM inputs. These inputs are scaled to 1V/Octave as is the "main" 1V/Oct input, which is the one that has a portamento lag circuit in series.

In a 4-voice system, I have made the eight fine tune A/B headers available on the carrier board for those who want to tinker with auto-tune or otherwise provide a row of fine tune panel controls.

--Crow

kynsi wrote:
is there a possibility to mount multi-turn trimmers?
looks fantastic btw!
The Real MC
Isaiah wrote:
I asked previously if a 2-/4-pole switch could be implemented, thinking that a choice of slopes would expand the timbral palette.


The OBX voicecard doesn't have a 4-pole filter, only 2-pole. Yes it's a multimode 2-pole LP/HP/BP/notch filter but multimode doesn't mean 4-pole. 4-pole filters were not introduced until the OBXa, and they weren't multimode. Putting a 4-pole filter on the OBX voicecard are require more components on an already crowded board.

Quote:
But really, it sounds glorious with just the 2-pole! "If it ain't broke... " etc etc.


Oh believe me the OBX 2-pole filter is VERY useful.

Most OBXa owners feel that the 4-pole filter mode doesn't sound that great and doesn't sound like the Moog 4-pole ladder filter. There isn't much overlap filterwise between my OBX and Memorymoog, but the 4-pole on the OBXa does not make it sound like a Moog.

JLCooper made a modification back in the OBX days that added a 4-pole to the OBX, it was switched in using the little-used HALF NOISE button. That modification used the now-obsolete CEM3320.

I think the best approach is the OB1 which offered 2 and 4 pole filters, the latter implemented by cascading two 2-pole filters. The OB1 filters weren't multimode but they were close to the SEM.

And then there is the crowd that wants HP/BP/Notch modes brought out, ... all real cool possibilities, but implementing multimode and 4-pole would mean it would no longer be a direct replacement for OBX voicecards. There isn't much room for all the support circuitry, and there aren't enough spare control lines on the headers.

I am currently working on an OBX modification to bring out multimode HP/BP/Notch on the OBX voicecard. My approach is a subboard for each voicecard on the OBX, with a global logic switching board controlling the subboards. My modification would also bring in EG-VCF routing to VCO2 Pitch (like OBXa) and EG-VCF routing to VCOx PW. I use these modulations on my Memorymoog and A6 for fat brasses, punchy transients on strings and percussion, and hard sync sweeps.

All done using certain little-used button combinations on the front panel (IE who uses HALF NOISE with either VCO?) with zero changes to firmware. I haven't explored adding a four pole filter because the two pole was so good and I really wanted to bring back some SEM features that were missing on the OBX.
Isaiah
The Real MC
Sorry, I really should try expressing myself clearly some time! hihi
I was aware that the OB-X VCF is 2-pole (like the SEM), but earlier in the thread I asked if it was a possibility that the 2-/4-pole switch (and of course, the VCF necessary to support it) of the OB-Xa might be implemented on future voice boards.
What I was saying earlier today was that after lots of listening to the OB-X (admittedly online), it sounds fantastic with just the 2-pole VCF.
As I said above - "If it ain't broke, don't fix it!" Rockin' Banana!
In summary - I'm not fussed about the 4-pole at all. The 2-pole sounds wonderful!

Personally, I think I'll be pretty happy with just the LPF, but I'm very curious to hear how the BPF mode sounds on the OB-X.

I didn't realise the OB-1 VCF was actually two in series.
Just assumed it was a 4-pole with a tapped 2-pole output.
oldcrow
Courtesy of glmodular, crOwBX in an OBX.

glmodular
nanners

Tony
The Real MC
Who knew a bare board could sound so good. STUFF THAT THING nanners
Isaiah
"Listen... Just listen. The sustain, listen to it."
"I'm not hearing anything."
"Well you would though, if it wasn't a blank circuit board..."
aladan
John Cage mod? razz
oldcrow
Final assembly progress.

Here is the non-linear potentiometer fix: add an antilog curve to the pot with some resistors, in this case 33K--you know, those resistors I got 500 of from Digikey trying to send me 330K twice. 12 pots needed the adjustment: ADSR (filter), ADSR (amp), LFO rate, freq mod depth, PW mod depth and portamento.



More info on tweaking pots for non-linear curves, worth reading: http://www.geofex.com/article_folders/potsecrets/potscret.htm

Next, the 17 switches and 4 LEDs are placed in their positions and the panel carefully placed over them playing a sort of odd Jenga-type game where you get them all to find their panel holes without letting anything fall off the board. Hand-tighten the bushing nuts, anchor the board to the 1/2" panel standoffs, nudge the PC pins of the switches from the solder side of the host board until they're lined up decently, and solder them all in. Let the LEDs drop into their panel holes then solder those too. Unbolt everything, and you get something like this:



Now to check the board stackup with the voice card. Bolt it all back down, add the spacers and screws for the voice card:



From the side you can check to make sure nothing got squashed or shorted:



(The yellow wire is because I gaffed the audio connector position on the host board, it just goes around the boards and a molex pin is used to plug into the audio connector on the voice board. Also, the fuzzy purple board is my work-in-progress on my MOTM-480 Mark II.) Guinness ftw!

And now, the one thing left is to install and wire the jacks and utility attenuator pots:



Getting close to being able to actually play something and record it. SlayerBadger! SlayerBadger! SlayerBadger!

--Crow
/**/
oldcrow
Oh yeah, got the rev2 host board rework done too. Added 3x TL074 for 12 CV buffers--no more non-linear foolishness. Rockin' Banana!

home_listening
Well were ten pages into this thread and no one has asked yet, so I'll bite. Crow, is is possible to get a rough idea (I know its early) of the cost of the PCbs, maybe the cost of a 4 voice set?

Any rough idea would be great, as I'm currently buried by a few audio projects, and a small mountain of serge panels, the looming 2600 project and other things at the moment. Will def need to actively set money aside for this one!

God this corner of the world is going off at the moment! w00t w00t w00t
glmodular
Quote:
STUFF THAT THING


LOL! I think Scott will have completed a full 8 voice by the time I get around to being able to stuff a single board. Dead Banana

Tony
The Real MC
oldcrow wrote:
Getting close to being able to actually play something and record it. SlayerBadger! SlayerBadger! SlayerBadger!


Some audio samples of my unit for inspiration (dry, zero effects!)
oozitron
While you're listening to MC, you can play "Where's the OBX?"

(sort of like "Where's Waldo" but more fun)



Drew
Isaiah
home_listening wrote:
Well were ten pages into this thread and no one has asked yet, so I'll bite. Crow, is is possible to get a rough idea (I know its early) of the cost of the PCbs, maybe the cost of a 4 voice set?

Any rough idea would be great, as I'm currently buried by a few audio projects, and a small mountain of serge panels, the looming 2600 project and other things at the moment. Will def need to actively set money aside for this one!

God this corner of the world is going off at the moment! w00t w00t w00t


+1
In a very similar position and would like to start budgeting.

Also, the crOwBX runs on +/-19V, right?
Are the transformers with the necessary ratings easily available? What about for Europeans (230V AC)?


The Real MC
Thanks for sharing your great demo!
Must admit, I've been listening to Moving Pictures, Signals and Grace Under Pressure a lot recently and it's actually got nothing to do with this project haha!
EMwhite
That pic is from the inside of Moving Pictures. I remember getting the album through one of those "11 records for a penny" deals (RCA record club?) when I was in High School. Love it. Gary Weinrib rules...
oldcrow
My educated guess is that a complete 10 bare board set for a 4 voice system will be around USD$200.00 before considering bulk purchases and such.

The breakdown would be something like

4 voice boards $80 ($25ea if bought individually)
4 slot adapters $50 ($15 each)
1 host board $25
1 carrier board $20

That's USD$175, but I figure if 1) sold as a complete set and 2) at least 25 sets can be "guaranteed sells" the price will be about this much.

The other bulk purchase option I will probably offer is a set of 4 or 8 voice boards. This is more for OBX owners. I would also make tray boards, but that means I need to take dimensions and such from a vintage tray board, etc. I figure a 4 voice set would be $80 and an 8 voice set $150. Tray board unsure, it is not a small board and places charge by the copper weight. I'll have to get a quote.

Pre-assembled boards is "whole 'nother" can of worms. At a guess, a single assembled voice card would be like $250. I will have to consult my usual assembly shop to see what that actual costs will be.

My 5 rev1 host and 5 rev1 voice boards cost me $435 shipped, btw. Low quantity is not cost effective.

--Crow
/**/

home_listening wrote:
Well were ten pages into this thread and no one has asked yet, so I'll bite. Crow, is is possible to get a rough idea (I know its early) of the cost of the PCbs, maybe the cost of a 4 voice set?
oldcrow
I've wired enough jacks to properly calibrate the voice board. All functions are working, if a bit out of tune. Just now got VCO1 tracking adjusted. Now for VCO2. SlayerBadger! SlayerBadger! SlayerBadger!

Edit: VCO2 now tracking. Service manual needs to mention the VCOs are stretch-tuned (summing amp slightly greater gain than unity). very frustrating
glmodular
Quote:
My 5 rev1 host and 5 rev1 voice boards cost me $435 shipped, btw. Low quantity is not cost effective.


Hey it beats the going rate for a real OB-X though! Dead Banana

Tony
home_listening
Thanks for getting back to me, all sounds very reasonable

SlayerBadger! SlayerBadger! SlayerBadger!
Isaiah
oldcrow
Can't wait to hear it! Rockin' Banana!

What sort of transformer are you using for the PSU?
Is there an equivalent available for Europeans (230V AC)?
oldcrow
At the moment I am using my bench power supply,



I need to get a power supply going for the crOwBX before I can use it in the studio as I don't really want to lug this thing down there. I can probably tweak a Power One HAA15-0.8-AG which is a +/- 15V supply (that can also do 230VAC input) to provide +/-19V. I'll have to try it on one I have here. It will probably require I take it apart and change a couple resistors. It mainly depends on what the unregulated DC from the bridge can provide.

My assembled single-voice system uses 130mA per rail. a 4-voice system will use an estimated 400mA per rail.

Crow
/**/

Isaiah wrote:
oldcrow
What sort of transformer are you using for the PSU?
Is there an equivalent available for Europeans (230V AC)?
The Real MC
oldcrow wrote:
The other bulk purchase option I will probably offer is a set of 4 or 8 voice boards. This is more for OBX owners. I would also make tray boards, but that means I need to take dimensions and such from a vintage tray board, etc. I figure a 4 voice set would be $80 and an 8 voice set $150. Tray board unsure, it is not a small board and places charge by the copper weight. I'll have to get a quote.


Keep in mind that the tray board (voicecard motherboard) for voices 5-8 is stuffed with only the audio and autotune buss summing resistors, and pan pots. No active components or their circuits. Connector "J" connects the busses for voices 5-6 to voices 1-4.

If OB-X owners who only have four voices want to expand to another four voices to a full eight voice then they will also need the metal support tray, wiring harnesses, three standoffs with hinged mountings, and three fixed standoffs.
The Real MC
Standoffs for voice 5-8 are 1-1/2" on a stock OB-X. Everyone knows that heat rises and that accumulated heat throws analog VCOs out of tune. The OB-X has no fan for ventilating heat. There is a large aluminum wall separating the keyboard and voicecards that also supports the front edge of the panel. That wall combined with the 1-1/2" standoffs combined with a solid metal tray for the upper voices (Oberheim failed to put vent holes in the metal tray!) creates a near closed box that restricts passive airflow and traps heat in the lower voices. There is little room at the rear of the OB-X for heat to escape. This is why OB-X has a reputation for tuning drift.

This is also why calibration is more difficult on the lower voices - if you raise the upper voice tray to calibrate the lower voices, you have released all that trapped heat. Remember that VCOs need 10-15 minutes to stabilize to ambient temperature when you turn it on? When you release all that trapped heat you STILL need to wait that long before calibrating! If you do not allow this and attempt to calibrate too soon, your calibration will be off when you close the upper voice tray back down and have re-created the heat trap.

And to make calibration matters worse, the VCF expo converter has zero temperature compensation thus raising/lowering the upper tray makes VCF calibration an effort with the heat differences!

I opted for 2" standoffs because 1) room for voicecard subboards in planned modification and 2) better ventilation for lower voices which lets them breathe. I confirmed that there is ample clearance for all components with 2" standoffs.

The later OB-Xa and OB-8 replaced the wall separating the keyboard and voicecards with a pair of standoffs. This allowed air to circulate and they are easier to calibrate than the OB-X.
Isaiah
oldcrow
Hope the Power One supply can be modded.
What are the options if that doesn't work?

The Real MC
Very informative posts, thanks for sharing.

Making mental notes on ventilation holes, and voice card mounting rails with fixed & hinged standoffs.
oldcrow
Well, making a DC power supply is not hard as it is what, seven parts? Fuse, switch, transformer, bridge, two filter capacitors and a piece of perf board (or a tie-point strip). The transformer would be something like a Talema 70053K, their catalog is http://media.digikey.com/pdf/Data%20Sheets/Talema/TransformerCatalog.p df

This is just one example, many other choices are out there.

Crow
/**/

Isaiah wrote:
oldcrow
Hope the Power One supply can be modded.
What are the options if that doesn't work?
oldcrow
Yep, that hardware is not my problem. 8_)

Oh yeah, Digikey replacement order of the replacement order arrived. Actual 330K resistors. I checked both the color code and the measured value. Cannot be too careful these days. --Crow

The Real MC wrote:
If OB-X owners who only have four voices want to expand to another four voices to a full eight voice then they will also need the metal support tray, wiring harnesses, three standoffs with hinged mountings, and three fixed standoffs.
oldcrow
Like the Persian rugs of old, where a flaw in the pattern was purposely introduced so as not to attain perfection and offend the karma of the cosmos, I managed to get the octave select switch reversed. Hardly an issue as this is a rev1 host board thing and only five rev1s will ever exist. d'oh!
mOBiTh
i still have a little chuckle every time I look at my xbase 09 for similar reasons hihi
gdavis
Holy moley, I just came across this project and am amazed. I wanted something like a OBX or Jupiter 8 but didn't want to pay 5-8k for one, so I also started my own project. Not necessarily a drop in replacement like this project but roughly the same functionality. I'm kind of embarrased now after seeing how quickly and cleanly this project is coming together (and apparently with ease) compared to my effort woah I've gone mostly SMT and so far the voice board looks like it's still going to be a fair bit larger than the OBX board.

May I ask where you're having the boards done? Price seems to be about half of what I could find.
PF
Ohh man, this is a great time for DIY. I realy hope you will be selling sets of pcb's. we're not worthy
oldcrow
You should be able to put two voice cards worth of OBX on the that board size in 0805 SMT. SlayerBadger! I might make an SMT version eventually, but that is well after all the 4-voice stuff is finished. I want to bring the 4-voice system to Knobcon in October, which, while still months away, will be here fast enough and waiting til the 11th hour is not very fun.

I get my boards for production quantities from pcbcart.

Crow
/**/
[/i]
gdavis wrote:
I've gone mostly SMT and so far the voice board looks like it's still going to be a fair bit larger than the OBX board.

May I ask where you're having the boards done? Price seems to be about half of what I could find.
mOBiTh
i can smell 'audio demo' surely hihi
oldcrow
That will happen soon, I just need the power supply I ordered to arrive so I can hack it to do +/-19V. The supplies for my modular cabinets are installed and calibrated for the modular and I am not about to muck with those. hihi

This break gives me time to finish assembly of the MOTM-480 Mark II prototype anyway. As well as get some modules shipped to customers.

Crow
/**/

mOBiTh wrote:
i can smell 'audio demo' surely hihi
paults
Quote:
This break gives me time to finish assembly of the MOTM-480 Mark II prototype


THIS
EMwhite
Hmmm; re: power supply. Does one of the boards carry a +15/-15 to 19V converter? (please... eek!)
glmodular
EMwhite wrote:
Hmmm; re: power supply. Does one of the boards carry a +15/-15 to 19V converter? (please... eek!)


hmmm..... Not that I am aware of.

Tony
oldcrow
The OBX voice card and tray system runs from a main power supply that supplies +/-19V among other things. All the voice boards and tray boards have local regulators to obtain +/-15V from a +/-19V input. I can make a small dual voltage DC supply board too, but it won't be mounted on the panel or carrier--too big and too heavy. It would have to be in whatever cabinet/box you'd have the synthesizer mounted.

One thing I have not tried and might work is not using local +/-15V regulators (jumpers where they'd normally be) and directly running the system from a +/-15V supply. The only question would be how the VCOs behave as Oberheim buffers the sawtooth across a pair of FETs at +19/-15V, probably so the ramp does not flatten at +15V before or when it resets.

Crow
/**/

EMwhite wrote:
Hmmm; re: power supply. Does one of the boards carry a +15/-15 to 19V converter? (please... :eek:)
home_listening
No need to be afraid of PSU's, Lm317/337 make things real easy. I just put them together on stripboard most of the time, but you can use something like this to make it easier:

http://www.ebay.com/itm/LM317-LM337-Servo-Power-Supply-Board-PCB-/2211 31787283

(not a plug, just googled 317/337 pcbs)
oozitron
I hope everyone is spreading the word about this project.

More orders will help lower costs This is fun! and spread happiness love

Drew
ChrisWareham
Hi folks,

Absolutely amazed at what some of the board members here are accomplishing. I would love to get another four voices into my OB-X, as it's currently a four voice (early model from 1979 with the less elegant logo than than the later ones).

However, as a couple of posts have mentioned this kind of expansion would require a card tray for voices 5 to 8 - so is anyone up for creating one?

Regards,

Chris
glmodular
Quote:
However, as a couple of posts have mentioned this kind of expansion would require a card tray for voices 5 to 8 - so is anyone up for creating one?


I could possibly make a run of them if there is enough interest.

Tony
PWM
Nooo!! Stop spamming all this must-builds! smile
Please consider a bro's cash flow..
oldcrow
Got a ship notification on my Power One HAA15-0.8-A which I will turn into a +/-19V supply for the modular cabinet. Then I can record some demo sounds into Ableton.

Since I will be on vacation in mid-July, I will be ordering the four board sets just before I leave so they'll arrive just after I return.

In the meantime, I've been working on the MOTM-480 MkII, which is nearly finished. I will also be building one more rev1 CrowBX board set to test using a +/-15V supply and no onboard +/-15V voltage regulators. I will probably have to tweak something in the VCOs as a result.

Crow
/**/
EMwhite
Nah... drop the MOTM-480... just work on the crOwBX hihi

Please do document your mod'ing of the HAA15-0.8-A so that others can adopt.
paults
Quote:
Nah... drop the MOTM-480... just work on the crOwBX


NOT HELPING! angry very frustrating cry Dead Banana
negativspace
Hell, I want both. Keep it up! hihi
gwaidan
Looks great!
keithwin
Wait! What! I'm in!!
Rex Coil 7
2 days ago my wife and I were marvelling at member "zthee's" ARP 2600 resurrection (the "Two Thousand Six Hundred" .. aka "TTSH"). I was mumbing about how it would be so cool to have my modular "Moog" (Dot Com system), one of Zthee's TTSH "Arps" .. and now if only someone would make an OBX to replace my OPXPRoII vst, I'd have "The Big Three" of the 1970s.

And today I trip and fall over THIS!

I AM SO FEKKING IN!!

I do NOT have the money, but I will get it. If I must eat Ramen for the next year, mow lawns to pay my ongoing Dr. bills, I will get in on this setup.

Are you kiddin me? A totally rebuildable, and totally serviceable OBX?!?!? An OBX that can be kept alive? An OBX that will last me at least as long as my Dot Com, and my 1962 Hammond A102, and the TTSH that I will someday own? No proprietary surface mount mass produced made-for-the-mainstream "cost effiecient" plastic chassis'd shitbox of a crap-assed synth version of the mighty mighty OBX?

I can already hear "Subdivisions" flowing out of my speakers ....

Goddammit Old Crow ... you better stay healthy on us and get these out! We don't need you catching some fekked up crap or getting hit by a bus or something!

As I've been saying for about a year, we are truly living in The Golden Age of Audio Electronics .... suck it up! Some of us strut around saying how we lived during the 1970s when synths were so cool. Think of the current ~now~ generation .. think of THEIR bragging rights! They get to say...

"back in MY day it was the Golden Age of synths! We had more synth stuff available to us than ever in the entire history of music made with electricity was there a more versatile and boundless catalogue of different synthesizers and audio processors of all kinds, including amplfiers, stompboxes, synths, guitars, basses, and even speaker cabinets. There was never a greater time to own some of the best gear ever made!"

What a fantastic time to be into music!

(Thanks Crow for your ambition and willingness to create something so wonderful. My sincerest appreciations.)

It's peanut butter jelly time!
Rex Coil 7
The Real MC wrote:
BTW if you want the "Tom Sawyer" rezz, that sound requires at least four voices in unison. You won't get that sound with just one voicecard.

A big part of that sound is the inherent filter scale error and EG timing tolerances between the voicecards. The filter scale doesn't match between voicecards due to the cheap expo converter in the filter cutoff CV summing circuit. Slight EG timing differences between voicecards due to tolerances in 3310s and/or Cx charge caps also add to tracking error.

The service manual also says that filter tracking is linear only within a three octave range - exceed that range and there is no guarantee that tracking will match between voicecards. This is not hard to do with EG filter modulation, which certainly is what the "Tom Sawyer" rezz is doing.

So because the filters between voicecards aren't tracking in scale, this creates a rather unique flanging effect that is the soul of that rezz sound. It took some fiddling around trying to get "that sound", but once I hit the UNISON button it was WHOOAAAHHH! I tried the same effect on my Memorymoog and Andromeda, but the tracking is "too perfect". Well!

AFAIK, Scott has retained the cheap expo converter at my urging. This is one of those circuits where imperfections can be a good thing.

The later Oberheims got more accurate tracking with the move to CEM3320s and software envelopes. Whether that is a positive improvement is highly debatible...
Gotta agree here. This same ~imperfection~ is what attracted me to the OPX VST synth ... they went to great pains to offer little trim pots to knock things out of whack and make the various vcfs and vcos move at their own rates and trackings. If the OPX were "snap your fingers and magically made as hardware" it would be one of the best analogue synths made. Simply because you have total control over how ~fuddup~ it can be made to work.

Going back to whatever page I was on .... It's peanut butter jelly time!
oozitron
oozitron wrote:
I hope everyone is spreading the word about this project.

More orders will help lower costs This is fun! and spread happiness love



Hee hee... I knew posting a link to the crOwBX in the 2600 Clone thread would reel in some more fish hihi

Drew
Rex Coil 7
oozitron wrote:
oozitron wrote:
I hope everyone is spreading the word about this project.

More orders will help lower costs This is fun! and spread happiness love



Hee hee... I knew posting a link to the crOwBX in the 2600 Clone thread would reel in some more fish hihi

Drew
Hook, line, and sinker!
Rex Coil 7
I've just finished page 8. I sit here with my mouth open .... my self esteem slowly tailspinning in a downward spiral like a WWII fighter plane with it's tail section shot to pieces.

I think about how I brim with pride after I ~ahem~ "invent" a single opamp overdrive circuit and have it made up at express pcb. The stack of six dozen boards shows up, and I build a few little OD modules. I sit back and gloat over how bitchen I am and what a friggin genius I must be to be able to create such a wonder with a 12th grade education and a D+ average at a public school in the late 70s. I'm just secretely glad the damned thing worked at all.

Then, fade to present, realtime moment as I read this thread and see what REAL talent produces. As I read the correspondence between real engineers with solid knowledge of how to manipulate electrons to do their bidding at light speed using little tiny components, some tin/lead, a little thermal-spoo, and dense grey matter.

Reality sets in, and I realize I am a roadie among rock stars.

You guys (you know ~who~ I am addressing here, you know who you are) ... your ability that you wield so nonchalantly ... you men are amazingly able. I'm just damned glad that people like yourselves are interested in making the things that I find desireable. You're making available something I've wanted to possess but do not have the skill to produce. And I thank you for applying your wonderful skills to that end. Your efforts make my life just that much finer.

Rex shutting up in 3... 2.. 1.

(white noise floods the room).
mikecameron
Rex, you had me at proprietary surface mount mass produced made-for-the-mainstream "cost effiecient" plastic chassis'd shitbox of a crap-assed synth...

Exciting times indeed!
oldcrow
No need to get depressed. It is less about talent and more about tenacity. The fact that you sat down and made something, then made a lot of them-that is far more important that whatever intrinsic design skill one may have. I know a number of "armchair" engineers that simply cannot manufacture to save their lives. Their territory ends the moment something leaps off the design paper and onto the factory floor. I am sort of the reverse case: I am a decent engineer I suppose, but a really, really good toolmaker. SlayerBadger!

75% of the OBX voice card I made is Tom Oberheim's circuits. The primary change I made was constructing standard EGs in place of the CEM3310s and scaling them to act like CEM3310s. Even this was a fairly standard circuit. I changed a few other things mainly because I wanted better exponential converters for the VCOs than the crummy LM3046 and using LM13700s in place of CA3080Es.

The host board is mostly my design, which is why it has more bugs in it. hihi

In any case, just make stuff--that's the key. --Crow Guinness ftw! Guinness ftw!

Rex Coil 7 wrote:
I've just finished page 8. I sit here with my mouth open .... my self esteem slowly tailspinning in a downward spiral like a WWII fighter plane with it's tail section shot to pieces.
Rex Coil 7
Thanks Crow. smile I can be a bit dramatic sometimes (naw ... really? meh ya don't say!) ... suffice it to say this is a great project and I admire your skills.

Keep on keepin on mangs.

applause
glmodular
Just started building the voice card I have...

So many resistors! Dead Banana

So many different values! MY ASS IS BLEEDING

My next parts order is going to be like 10 pages long! very frustrating

Tony
Rex Coil 7
glmodular wrote:
Just started building the voice card I have...

So many resistors! Dead Banana

So many different values! MY ASS IS BLEEDING

My next parts order is going to be like 10 pages long! very frustrating

Tony
Wait .. somewhere along the line I must have missed something. Are the voice cards available now?
glmodular
No, not yet.

I'm assisting Crow in making sure that the voice cards are compatible with existing OB-X's.

If you look a few pages back, the picture of the OB-X with the new voice card in it is mine.

Tony
Rex Coil 7
glmodular wrote:
No, not yet.

I'm assisting Crow in making sure that the voice cards are compatible with existing OB-X's.

If you look a few pages back, the picture of the OB-X with the new voice card in it is mine.

Tony
Ah! Very well. Like I said, I obviously missed something. smile
oldcrow
No, there are five rev1 voice boards, Tony has one. I am sending one to MC. I will build the last two for my multi-voice testing. Rev1 is the prototype phase. The production boards will be rev2. I plan to order the boards at the end of next week just before my trip so they will be here when I return.

Crow
/**/

Rex Coil 7 wrote:
Wait .. somewhere along the line I must have missed something. Are the voice cards available now?
ttown23
Put me down for 4 please Guinness ftw!

I'm salivating to get these!!!

... now if I could only get the upper tray board too very frustrating
Rex Coil 7
ttown23 wrote:
Put me down for 4 please Guinness ftw!

I'm salivating to get these!!!

... now if I could only get the upper tray board too very frustrating
I'm good for four once a working proto is posted. After I complete a working unit myself, then I'll be good for a four additional voice boards.

It's a money thing .. more like lack of money thing. I want to finsh my Moog system, and also have a DIY 2600 and a DIY OBX, then I'll have The Big 3 From The 70s.

I'm not totally sure about this but nearly anything from the 80s that was of notariety was digital. Almost everything that I can think of that left any kind of a dent in the 1980s were digitals, except for the Korg Mono/Poly, oh and I guess those early Korg PS(units). From that short list I can probably make at least 90% of them in highly convincing ways with the three synths I will then have on line. I mean I may need a Korg filter, or I may need a Roland VCO or Roland VCF. I mean there may have been one or two timer here or there, but nothing I can think of that is worthy of a collection, right?

After that ... It's All About Teh Digi, Mangs! ........

TEH DIGI:
PCM - PM - FM - WAVESAMPLING - WAVESEQUENCING - VA - MODELING - SAMPLERS. You'll noticed I said "wavesampling" and "samplers". I kinda think of "wavesampling" as something you might do with an EMU EMULATOR or a Kurzweil k2500 or some such kybd type synth. And "SAMPLERS" which are more like your DJ type sound creations. Another thread in another universe.

This post does nothing but verify my desire to construct one of these Oberheim systems. With that as well as the other two I'll have the Big 70. Add in a few operators (Yamaha) , a few PCM generators (Korg) and a couple of sampler VSTs (Korg, Roland) and a sortof generalized VA synth and you get yourself the two Big Era synth setups! After creating The Big Three of The 70s, pretty much all of the heavy lifting is done!

Glad to see it moving forward.
moog55
Quote:


Hee hee... I knew posting a link to the crOwBX in the 2600 Clone thread would reel in some more fish hihi

Drew



i have been fished in from the TTSH thread lol lol
oldcrow
Still waiting on the power supply I ordered through Amazon Prime. Touching up rev2 boards for submitting on Saturday. More later.
alexdsteak
Like others, I have been away for a "short" while from MW and what I see here now? A rebuild of an Oberheim classic.

First of all congratulations to oldcrow for making all this, again proof that
in 99% of the situations will is power.

Then I have to say that I am definitely hooked and not afraid of spending
months soldering boards.. I am already doing it for the SynthaSystem
clone, I can consider it a good exercise smile

Now it is just a matter of waiting for oldcrow to tell us that the boards are
ready and we'll flood him with pieces smile

A.
oldcrow
I've posted updated bom lists at http://www.cs80.com/crowbx/

This is for rev2 boards. I have all the gerber files packed up to submit for manufacture tomorrow. I will provide the slot adapter and carrier board boms over the next couple of weeks.

As for audio samples, I am still waiting on the PS from Amazon. angry I will probably just cancel that order and get one from Digikey or Mouser.

More later,

Crow
/**/
EMwhite
Hello all.

I'm working up an alternate panel in FPD to suit my personal needs for crOwBX but had a few quick questions about functionality. I'm likely not going to order it until I get the control board; despite intentionally NOT altering any of the hole placement, I still want to make sure that I'm dead on before ordering.

- How do the Sine, Square, S+H switches operate since they are all toggle switches (and not cpu controlled momentary switches with LEDs). I suppose the question here is, what if S/H and SINE are both "ON". Does one override? or are spring loaded toggles used?

Are there any other conditions elsewhere in the panel where switches were originally mutually exclusive and due to physical switching setup, an exception condition (speaking from a software point of view) will force one to take priority?

- Are switch positions for LFO waveforms really Square, Sine, S/H or is it like the OBX panel with Sine first, then Square?

- Certain elements of the panel design (Gate / Pitch CV) are applicable to the Single Voice design; In a Poly setup, how should these connections be used? (or will all wiring be done behind the panel).

- Is there a Unison switch/function? (if so, I suppose the Mono input in the question above is applicable?) or is it up to the next layer upstream to handle sending the same pitch to all voice boards (there was some talk about distribution of voices needing to be done via a higher layer).

- Finally, can somebody tell me the difference between the OSC 2 Frequency and the OSC 2 Detune?

Thank you...
oldcrow
I use an on-off-on 3-position switch here to encode two logic signals, LW1 and LW2, which select the LFO waveform from the analog switches. I had to change the order of the waveforms to keep it simple. The only switch set that uses logic assistance is the OSC 1 & 2 off/on (OSC2 full/off/half is also a on-off-on switch.):



As for pitch/CV, the host panel pitch/CV is for one card, you use alternate resistor pads on the host board for poly voice use, which changes a few things such as routing the portamento CV to the carrier board and allowing the mute function to apply to the carrier board final VCAs. The pitch & CV for multiple voices then comes from a header on the carrier board. Sustain is up to the MIDI to CV/gate unit. I provide 4 gate inputs and 4 pitch CV inputs--the rest is on the MIDI end. I do diode-OR the gates back to the host board to light the LED SlayerBadger!

OSC2 frequency spans several octaves; in the original OBX I believe this was quantized to octaves, my control can set it anywhere. OSC2 detune is a fine tune, maybe +/- half a semitone.

Crow
/**/

EMwhite wrote:

- How do the Sine, Square, S+H switches operate since they are all toggle switches (and not cpu controlled momentary switches with LEDs). I suppose the question here is, what if S/H and SINE are both "ON". Does one override? or are spring loaded toggles used?

Are there any other conditions elsewhere in the panel where switches were originally mutually exclusive and due to physical switching setup, an exception condition (speaking from a software point of view) will force one to take priority?

- Are switch positions for LFO waveforms really Square, Sine, S/H or is it like the OBX panel with Sine first, then Square?

- Certain elements of the panel design (Gate / Pitch CV) are applicable to the Single Voice design; In a Poly setup, how should these connections be used? (or will all wiring be done behind the panel).

- Is there a Unison switch/function? (if so, I suppose the Mono input in the question above is applicable?) or is it up to the next layer upstream to handle sending the same pitch to all voice boards (there was some talk about distribution of voices needing to be done via a higher layer).

- Finally, can somebody tell me the difference between the OSC 2 Frequency and the OSC 2 Detune?

Thank you...
The Real MC
OSC 2 Frequency is the "coarse" control with a four octave range; Detune is the "fine" control for OSC 2 with +/- 5 or 6 semitones.
EMwhite
Perfect. Thanks for the explanation.

I've re-layed the panel so that it looks more like the original OB-X; not done yet but here is an updated view.

Not sure there is going to be room, but my plan is to move the lower portion of the controls via headers to flying wires and to position to the space currently occupying attenuators. (I have plenty of those elsewhere in my rig : )

Likewise, I'd like to bring the individual voice board LEDs to the panel (see the 3mm LEDs in red). Will try to squeeze 8 of them to the bottom left (next to 1V/Oct. notation) if it fits, ultimately.

This is all draft and to be honest, I haven't flown it by Scott yet, he may hate it; but he was kind enough to give me his FPD so I will certainly be doing this for my own use and wanted to share.
oozitron
The LEDs on each side of the "O" make kind of an anti-umlaut

thumbs up

Drew
EMwhite
Here is my latest mock up of Scott's original FPD.

And now for some more questions : )

Do the Vol, Mod, Vib pedals provide a reference voltage (5v) on the ring of the jack?

Is the bend switch 1.5 steps (3 half steps) or two full steps or am I reading that incorrectly?

Is Mute meant to be a toggle switch? (up is muted?)

Is the output stage a single (mono) VCA attenuated by the volume control or is there circuitry behind that allows for panning per voice. Didn't know if this aspect was roll your own or if you have the panning circuitry and stereo output on the host board but not represented on the panel (maybe v3?)

Confirm that the lower half (below the line) is free area (no board beneath); if so, I'd like to have an actualy 3/4" knob on mine for Volume control and perhaps a push button toggle for Mute. I suppose that section might be up to the builder?

And thank you very much!

(below; an adaptation of Crow's original panel adapted to accommodate my grand plans including a genuine SEM/OB vintage knob for the volume control depicted below hihi)

The Real MC
EMwhite wrote:
Here is my latest mock up of Scott's original FPD.


I like that design, esp using the original outline font of the "OBX" logo!

Quote:
Do the Vol, Mod, Vib pedals provide a reference voltage (5v) on the ring of the jack?


No they don't. Not hard to route it but I would include a 100ohm resistor in series to limit short circuit current in case one inserts a TS plug and the ring on the jack shorts to ground.

Quote:
Is the bend switch 1.5 steps (3 half steps) or two full steps or am I reading that incorrectly?


No - they refer to VCOs. "1+2" means pitch bend is routed to both VCO1 and VCO2, "2" means pitch bend routed to VCO2 only (awesome when hard sync is used).

Quote:
Is Mute meant to be a toggle switch? (up is muted?)


Meant to be toggle, not sure which position it is active. When the terminals are shorted, the output is muted.

Quote:
Is the output stage a single (mono) VCA attenuated by the volume control or is there circuitry behind that allows for panning per voice. Didn't know if this aspect was roll your own or if you have the panning circuitry and stereo output on the host board but not represented on the panel (maybe v3?)


The output stage is a single VCA attenuated by volume control CV.

Since the host board is designed for a single voicecard, panning circuitry wasn't included. Maybe for a future multiple voicecard hostboard, I'm not going to read the mind of Crow or make any promises.

Quote:
Confirm that the lower half (below the line) is free area (no board beneath); if so, I'd like to have an actualy 3/4" knob on mine for Volume control and perhaps a push button toggle for Mute. I suppose that section might be up to the builder?


Free area below the line, so the builder is free to their whims smile
oldcrow
All boards are ordered. That was a chunk of change. I expect them in the week of July 22. I will have to build up a full rev2 to check out before placing bare boards on the shopify site, as well as record some audio from the single voice rev1 once I get home. I hope my power supply is there waiting. SlayerBadger!

For EMWhite,

MC answered most of those, the only remark I have is if you are using my host board it is 10.25" x 5.5" and the octave switch, LEDs, volume pot, pitchbend switch and mute switch mount directly from the board to the panel like the voice controls up top. They don't strictly have to be mounted this way, but just remember there is a 1/2" height restriction between the host board and panel across that 10.25" x 5.5" area.



--Crow
/**/
EMwhite
oldcrow wrote:
f...there is a 1/2" height restriction between the host board and panel across that 10.25" x 5.5" area.


Ah.. thanks. The MTA connectors that I have piles of ARE 1/2" and that leaves no buffer for safety or the header so I'll have to do something else. I'd hate to hack up such a nice board with hard soldered wires but I"ll figure something out.

Yes, MC did answer them thanks for that.

Assume that you'll be selling it as a full board set with the programmed PIC as one setup (as well as individual voice cards, I presume).

You made a comment some time ago about not having enough copper (trace width) to drive more than 4 boards? I think that was the comment. Were you talking about powering individual voice boards from a central point (your .156 MTA) or were you talking about the leads that go to each of the voice card connectors for control signals, or maybe even op amp output?
oldcrow
I designed it so that MTA connectors attach from the back of the board, so those should not be an issue. A voice card or carrier board (for 4 voice cards) is 10x4.313" and when adjusted for the mounting clearance at the edges, the lower edge of the host board is about 1.25" with no height restriction on the back--this is where all the headers go. Well, except for the FTA/B headers at the top, but those aren't really used; I just brought them out for test purposes.

Folks who buy a host board will have the option to include a pre-programmed PIC for a small extra cost.

The MTA156 power header on the host board is meant to power only the host with one voice card attached. It can "probably" power a 4-voice system just fine, but I didn't originally design it for that--although in rev2 I beefed up the power traces a bit. To power a 2-4 voice setup I provide another MTA156 on the carrier board with power traces big enough to power everything. There will be two power options, provided I can get the 2nd option to work (not yet tested): +/-19V and +/-15V. +/-15V will do away with all the local voltage regulators and run everything from a regulated +/-15V supply. I still have to test this and make a possible adjustment as the VCOs use the +19V rail in their FET buffer tree and changing that to 15V will probably require a bias adjustment.

--Crow
/**/

EMwhite wrote:
Ah.. thanks. The MTA connectors that I have piles of ARE 1/2" and that leaves no buffer for safety or the header so I'll have to do something else. I'd hate to hack up such a nice board with hard soldered wires but I"ll figure something out.

Yes, MC did answer them thanks for that.

Assume that you'll be selling it as a full board set with the programmed PIC as one setup (as well as individual voice cards, I presume).

You made a comment some time ago about not having enough copper (trace width) to drive more than 4 boards? I think that was the comment. Were you talking about powering individual voice boards from a central point (your .156 MTA) or were you talking about the leads that go to each of the voice card connectors for control signals, or maybe even op amp output?
oldcrow
Oops, unsure what caused the double-post. hmmm.....
The Real MC
<python>

"The BBC would like to apologize for the constant repetition"

</python>
The Real MC
<python>

"The BBC would like to apologize for the constant repetition"

</python>
EMwhite
It's been quiet and I just had some time to re-read the entire thread, look at board diagrams, etc. so I figured I'd hit you guys up with a few more questions.

But first an opinion: If it can easily be worked out (swapping of some of the components to adjust bias, etc) I think that +/- 15V is desirable for most of us over 18V as many of use already have it.

Question: Do you rectify the base voltage down for the PIC or is there a requirement for 5V or 3.3V required?

Question: about feeding voices and the carrier board, which somehow I didn't read about until just now:

Looks like the 34 pin header carries CV and Gate for the four voices and it looks like you have a set of separate connectors for fine-tuning should an auto-tune circuit be added at a later date (or manual micro tuning should somebody desire wiring something up per voce).

About audio output... you have a single 13700 on here and some notes (above) about L, Mono, R outputs. If I've read this right, where are the controls for panning per voice? Voice cards are mono, right, so it's here somewhere, per voice? I see a dist trim L and R 100k trim pots does one apply to voices 1 & 3 and the other to 2 & 4 or is this for future expansion and only partially implemented?

Is the portamento circuitry now per voice? Looks like it's on voice card adapter boards (and I suppose already ordered with the lot you just pushed through?) in which case the host board portamento is simply unused or we'll need to disable in some way?

Finally, do you anticipate the full set being on offer by the end of this month? (just want to make sure I plan out consecutive days of eating Ramen Noodles for lunch so that I can buy a set before they vanish).

Thank you!
oldcrow
EMwhite wrote:

But first an opinion: If it can easily be worked out (swapping of some of the components to adjust bias, etc) I think that +/- 15V is desirable for most of us over 18V as many of use already have it.


Well, the voice cards are meant for an actual OBX, which uses +/-19V. I have not built more than one voice card and host panel as of yet (and those are rev1), but I see no reason the entire n-voice system cannot run from +/-15V by strapping out the regulators on each board--except the 5V regulator on the host board. There is a VCO FET buffer that floats to 19V that I will have to see what tweaks are needed for 15V. This is the only real item I have not examined yet and will do so once the rev2 stuff is in.

EMwhite wrote:

Question: Do you rectify the base voltage down for the PIC or is there a requirement for 5V or 3.3V required?


For the PIC (and other host board circuits that use 5V) there is a local 5V regulator for this on the host board. This regulator stays there whether or not the system is rigged for +-/15V or +/-19V.

EMwhite wrote:

Question: about feeding voices and the carrier board, which somehow I didn't read about until just now:

Looks like the 34 pin header carries CV and Gate for the four voices and it looks like you have a set of separate connectors for fine-tuning should an auto-tune circuit be added at a later date (or manual micro tuning should somebody desire wiring something up per voce).

About audio output... you have a single 13700 on here and some notes (above) about L, Mono, R outputs. If I've read this right, where are the controls for panning per voice? Voice cards are mono, right, so it's here somewhere, per voice? I see a dist trim L and R 100k trim pots does one apply to voices 1 & 3 and the other to 2 & 4 or is this for future expansion and only partially implemented?

Is the portamento circuitry now per voice? Looks like it's on voice card adapter boards (and I suppose already ordered with the lot you just pushed through?) in which case the host board portamento is simply unused or we'll need to disable in some way?

Finally, do you anticipate the full set being on offer by the end of this month? (just want to make sure I plan out consecutive days of eating Ramen Noodles for lunch so that I can buy a set before they vanish).

Thank you!


The audio outputs on the carrier board replace any audio path on the host board. The host board volume VCA is for a single directly-mounted voice card only. When you build a host panel intended for >1 voice use, you leave certain resistors off and install others to change the host control functionality slightly.

These changes are:

Disabling the host board's portamento lag circuit and routing the CV to control portamento to the "Key CV" header pin of the host board. The attached carrier board provides this CV to each lag circuit on the slot adapter boards, which then pass the processed key CV to the attached voice card.

The audio mute switch is routed to use the audio output pin (from a single voice card) as a master mute control to the carrier board. The volume CV is likewise routed to the carrier board. The local (host) volume VCA is not used in this case.

Voice panning is done by a trimpot on the slot adapter card as this was the easiest place to provide it in the circuit path. One trimpot per slot adapter. The actual final volume VCA pair is on the carrier board, which is why you get L/R outputs.

There are individual portamento lag circuits per voice because that is how it was done in the OBX, and it is a major factor in the OBX poly-glide sound. When a host board is configured for n-voice operation, the local (host) lag circuit is not used.

Board sets will be available sometime in August as they do not arrive at my shop until July 25th, and I need to proof the carrier and slot adapter builds.

Hope this clarifies things. --Crow

/**/
EMwhite
It does (clarify), thanks as always.

So nothing stopping me from wiring flying-wire panel mounted pots (as depicted above) of appropriate value vs. board mounted.

Use case (for me) is that I have a sequencer running one voice at center pan, while an arpeggiator runs a three voice that I wish to pan 15% left, 15% right and center. Obviously, a pain in the arse to tweak board mounted pots for each patch.

The only other thing I'll bother you about for now as I've done alot of this as of late, is to ask what is 'stopping me' from bolting up, via frankenstein wiring, two carrier boards (for 8 voices). Aside from the physical challenges, is it an issue of being able to drive x8 without droop?

To Isaiah (not sure I saw this was answered), it's a beast, the depth of the voiceboard + an inch deep by the height of the panel you see. Granted, the lower portion of the panel (jack field) is not as deep, but the thing will be massive, and for good reason. What a lovely compilation of discreet components.

As an aside, have a look at the L-1 Vocoder for a BIG / heavy / deep DIY project. This beats it by 4x or 5x.
oldcrow
The original OBX uses panning trimmers on the tray boards; I just put them where they logically fit in my configuration. 50K panel pots should work fine, though you might want to use shielded wires for the CW & CCW leads with the shield braids going from slot adapter W (ground) to panel pot W.

As far as 8 voices go, two 4-voice trays is how the OBX does it, so the same concept with two 4-voice carrier boards applies. You would need some sort of split wire harness but nothing overly complicated. Note that only one carrier board would need to have the volume VCAs, I provide mix buss inputs to connect 2 carrier board L/R panning audio signals together.

--Crow
/**/

EMwhite wrote:
It does (clarify), thanks as always.

So nothing stopping me from wiring flying-wire panel mounted pots (as depicted above) of appropriate value vs. board mounted.

Use case (for me) is that I have a sequencer running one voice at center pan, while an arpeggiator runs a three voice that I wish to pan 15% left, 15% right and center. Obviously, a pain in the arse to tweak board mounted pots for each patch.

The only other thing I'll bother you about for now as I've done alot of this as of late, is to ask what is 'stopping me' from bolting up, via frankenstein wiring, two carrier boards (for 8 voices). Aside from the physical challenges, is it an issue of being able to drive x8 without droop?
Rex Coil 7
Imagine the project threads comong about around here soon. You guys are amazingly talented.
EMwhite
Something to dream about. A reworked panel with an 'xPander' 2 space panel; Unfortunately, the physicals of the OBX Voice card are too long to fit sandwhich style with a 2 space panel so a -V E R Y- deep carrier will need to be fashioned; picture a pot bracket type ('L' shaped sheet metal) which screws to the panel with four screws and protrudes depth wise.

Going to be ugly from behind (but beauty in the eye of the beholder, right?) but the front is all you'll see;

There will likely be interfacing concerns relating to integration with the first four voices; it would be swell if this could be accomplished without too much change in the host board design. I'm fairly certainly there will need to be a separate power source but I'll leave the smart guys to point that out.

TO BE CLEAR, I'm just a guy sitting behind Front Panel Express, I have no boards yet, no schematics, etc; just asking a bunch of [sometimes] dumb questions here and getting some really good answers; time will tell if this is possible near term or if it will need to wait for v3 of the host board and carrier system.

But I think it's a dream of many here to have an 8 voice as depicted (or something close to it) in 8 spaces of MOTM. So why not dream ...

oozitron
My plan is to build a desktop case for this and have the controls right in front of me when I play. Set it on top of my MIDI keyboard, which will be the Wavestation.

Considering putting the jacks across the top of the controls so the cables can lay down the backside were they are out of the way.

Drew
Isaiah
EMwhite
Good work on those panel designs, Mike!

I'm trying hard not to think about this project too much. It's far too easy to day dream about it.
But, my initial thoughts are a 4-voice keyboard, with the voice cards laid flat, side by side like the OB-X.
Then mount the control board on hinged stand-offs. Connect the panel-mounted components to the control board via flying wires and headers ( Dead Banana ).
All jacks on the rear of the instrument (1/4" for audio and pedal connections, banana for CV).
MIDI-CV and voice allocation handled by the Hex-Inverter circuit.

Or, maybe keyboard-less in a briefcase (probably have to mount the four voice cards flat, side by side parallel behind the control board.

Hmmm... I'm day dreaming again! help
Isaiah
Also, though it would require adding an extra three switches (to allow the same functionality as a 3-position switch), I'm thinking of using Moog-like rocker switches.
The Octave shift would be replaced with a 3-position rotary switch.
EMwhite
It would be cool to have (possibly) the more often used jacks on 'top' of the module/desktop and the CV/Gate jacks in the back as it will be most likely that you will (I sure would) want CV and Gate plugged up all the time. Have a look at the SEM Pro; like that but bigger. Maybe Mini's or Banana if that is your bag.

Oozitron's msg above is making me think that a desktop box might be better for me than the MOTM style panel. This synth is going to deserve it's own enclosure and dedicated power supply but still will want to play with modular.

I have the Hexinverter Midi2CV also; I really dig his stuff would like the flexibility to do 3 voices or 6 voices, etc. So for me, MidiPal from Mutable will sit between the keyboard and and crOwBX. The classic Oberheim didn't have any notion of keyboard velocity or aftertouch but I'm going to see if my MOTM-650 can be used in creative ways before buying a 2nd Hexinverter unit.

Either way, I can't wait to get my hands on these boards; likely going to do the builds in pairs of voices simply because I won't have the cash to finance $2k worth of components in one go.
sicpaul
great project!
seems to be the time to proclaim my interest in a 4 voice pcb set.
oldcrow
After 2,817 miles of travel (4532 km for the rest of the world), I am home from family vacation. Boards ship to me this coming week. Will work out the remaining bills of materials over the next few days. --Crow

/**/
spneca
I'm also in for a full 4 voice set of boards.
oldcrow
My power supply finally got here. I will be modifying it this weekend for +/- 19V. Then I can operate the rev1 crowbx in the studio and record some test audio.

Also, my ship notification for 25kg of bare PC boards arrived, so I expect I'll have a big box of rev2 boards tomorrow.

More later,

Crow
/**/
Rex Coil 7
oldcrow wrote:
After 2,817 miles of travel ....
Holiday road in the Family Truckster ...... smile
Rex Coil 7
(oldcrow) It still blows my mind that you do stuff like this for enjoyment ... I mean this is like what you do for fun!

It would take me 3 years or more to get something like this worked out. I just stand in the shadows and watch in awe of this project.

Go man, go!
oldcrow
Off-topic but possibly still interesting note: since Fermilab is about 30 minutes from here and they're in the final day of moving a huge superconducting electromagnet called the muon g-2 from Brookhaven lab in New York to Fermilab in Batavia, IL, I decided to drive over and get a pic of the thing which is currently parked on 5 flatbeds sitting in the north entry of Morton Arboretum. It will take them about 18 months to get it installed and cooled to 4 degrees Kelvin, but then the fun begins. http://muon-g-2.fnal.gov/index.shtml

EMwhite
What ever happened to BNL? When I was in High School, I had an account on their Ultrix system. For a "National Lab", security in those days was loose enough to allow a 15 year old to have access to their VAX PDP 11/780.

During college, a friend of mine co-op'd there via RIT. I only went there once for a tour. Is it shut down now? (I think they are famous for leaking radioactive material into the Long Island ground water) d'oh!
Peake
I'm in for four voice boards and all supporting PCBs. Want to build eight; will see. Bravo!
oldcrow
50lbs of boards arrived in two boxes today. Soldering time: I need to construct enough of a rev2 to verify it is all working and ready to sell as bare board sets.
mckenic
applause

Enjoy sir! Very exciting times!
negativspace
w00t
home_listening
Well I'll also put up my hand for a complete four voice set at this point.

Yay! w00t
oldcrow
One note: when I deem boards are ready to sell, I'll update my shopify site with them. That is how to buy them--the site does the bookkeeping for me and makes it much easier for me to concentrate on delivery. --Crow
Isaiah
oldcrow
Do you plan to keep these PCBs in stock regularly?
I'm trying to budget for several projects at once, you see, and the last thing I want is a stack of circuit boards and no money for components to populate them!
mOBiTh
likewise...

also, when can we hear audio demos? hihi

(or did I miss them?)
home_listening
Sounds good Crow, I understand orders on a forum can quickly get messy.

Any chance you can provide us with a link to that page?

Cheers
oozitron
Isaiah wrote:
oldcrow
Do you plan to keep these PCBs in stock regularly?
I'm trying to budget for several projects at once, you see, and the last thing I want is a stack of circuit boards and no money for components to populate them!


I can relate to this cry

There's the crOwBX, the 2600 and my partly-finished Hexinverter 909 drum machine (that I've already got started).

Come to think of it, when I get these three projects done I can probably get rid of everything else This is fun!

Drew
oldcrow
Isaiah wrote:
oldcrow
Do you plan to keep these PCBs in stock regularly?


I plan to restock boards as needed. The first order of the boards is always the most involved, after that it is a bit easier to deal with.
oozitron
Maybe we should organize a group buy of the LS318 ?

Drew
home_listening
oozitron wrote:

Come to think of it, when I get these three projects done I can probably get rid of everything else This is fun!

Drew


Including all of your friends for a while!
oldcrow
Just so folks understand the scope of what they'll be getting themselves into if they elect to build a 4-voice crOwBX:


negativspace
I intend to savor every minute of it.
mOBiTh
8_) 8_) 8_) 8_)
aladan
oldcrow wrote:
Just so folks understand the scope of what they'll be getting themselves into if they elect to build a 4-voice crOwBX:




BRING IT ON! thumbs up
decaying.sine
You call that a knife. That's not a knife.
oozitron
I thought it was just gonna be 4 ASIC chips to solder in hmmm.....

Perfect project for a long winter.

Drew
Peake
Yeah, "your point is..?" wink

SlayerBadger!
paults
You are not scaring them...you are encouraging them.
GrantB
So double that for an 8 voice right?
oldcrow
paults wrote:
You are not scaring them...you are encouraging them.


Not trying to scare anyone, just showing the actual task at hand. Guinness ftw!

I have part of a host board assembled so far.
oldcrow
GrantB wrote:
So double that for an 8 voice right?


An eight voice system would need a carrier board designed to split the control harness with a second carrier board. I have not done this yet. Alternatively you can construct a splitter cable harness to connect one host board to two carriers. At this point the assembly is far too heavy for mounting to the back of the host board/front panel and will need its own chassis.

Down the road I will make a voice card that is better optimized for a modern 8-voice configuration. The rev1 and 2 are meant to fit in a vintage OBX--this host+carrier+slot adapters setup I've devised is just an extension of the way I planned to test voice cards. The "side benefit" is it is a 4-voice synth. SlayerBadger!
GrantB
Thanks for clarifying that. I was half curious and half riffing on the "that's all?" joke.

I would very much like to build an 8 voice some day though, backlog notwithstanding. Amazing work!
mOBiTh
The hardest thing is going to be deciding how many voices to build!!

And affording it...
Sir Ruff
Just joining this fray (after reading through all 31 pages!)

Amazing stuff.
wrath257
Just a quick question about hooking up the lone voice card to other sources, what sort of control voltage ranges would I be looking at? 1v/oct, or something different?

Thanks for any responses
oldcrow
wrath257 wrote:
Just a quick question about hooking up the lone voice card to other sources, what sort of control voltage ranges would I be looking at? 1v/oct, or something different?


All parameter control voltages are 0 to 5V. The pitch CVs are all scaled to 1V/octave for VCOs and VCF. The (linear) resonance CV is reversed: 5V is minimum, 0V is maximum resonance. The remaining CVs are linear but the response of the envelope generator curves are exponential. Switch controls are 0V/5V. The voice card uses a +/-19V supply as per the original OBX chassis power scheme. It can probably run on +/-15V by strapping out the local voltage regulators but I have not tested this yet as the +19V is also used as a FET buffer voltage rail and changing it to +15V might involve a few part value tweaks. --Crow
confinedscommute
Yeah this is pretty amazing...wow
EMwhite
Putting the final touches on my panel; have a few questions:

1. I see you have noted that you used 1/2" stand-offs for panel to Host board, therefore tolerance (distance) of switches etc are approximately this distance. Question is, based on the 5.5" height measurement of Host board, what is the distance from center of LFO LED to edge of Host board; looks as if .5" will do it? (will need to move a few of my jacks around as they are 3/4" not counting lugs!)

2. Jack question, what is the diff between "LFO OUT" and "LFO TRI". Is 'OUT' set by toggle and TRI always ummm.... sine? or is it an actual Triangle?

3. Mute question; I think I saw this answer somewhere above, but it's meant to be a state switch (on/off) and not a latch momentary type of circuit?

4. Is PWM1 and PWM2 actually the PWM of Oscillator 1 and 2 or is it just two different jacks which are additive and attached to both OSCs?

5. Likewise, are OSC1 and OSC2 FM per Osc. and can you confirm that if so, is OSC2 FM also 1V per octave as noted for OSC1 on your panel?

6. How did that power supply work out? If it's affordable (<$100), maybe just let us know what you bought, what additional circuitry was required if any, and call it a day. An investment of the $1500-$2k for these parts, panel, boards is certainly deserving of it's own PS hihi

Thanks.
oldcrow
See remarks inline:

EMwhite wrote:
Putting the final touches on my panel; have a few questions:

1. I see you have noted that you used 1/2" stand-offs for panel to Host board, therefore tolerance (distance) of switches etc are approximately this distance. Question is, based on the 5.5" height measurement of Host board, what is the distance from center of LFO LED to edge of Host board; looks as if .5" will do it? (will need to move a few of my jacks around as they are 3/4" not counting lugs!)


You must mean the gate LED, there is no LFO LED although you can hang an LED on the LFO output easily enough. That LED's center mark is 0.4750" from the board edge.

EMwhite wrote:
2. Jack question, what is the diff between "LFO OUT" and "LFO TRI". Is 'OUT' set by toggle and TRI always ummm.... sine? or is it an actual Triangle?


LFO OUT is an output I provided for modular use, the waveform it provides follows the wave select toggle. LFO TRI is a triangle-only output that in an OBX is routed to the mod wheel. I provide it here for mod pedal, Yamaha breath controller, etc. The TRI signal is on the "external vibrato depth" header for this reason. It is a triangle waveform; there are no OTAs or diode blocks bending it into a sine shape.

EMwhite wrote:
3. Mute question; I think I saw this answer somewhere above, but it's meant to be a state switch (on/off) and not a latch momentary type of circuit?


OBX mute is under CPU control, mainly to mute the system while it auto-tunes. I provide it here as a manual switch. Note: in the 4-voice assembly the mute switch mutes with the switch bat to the left, in a single voice system that is not using a card carrier, the mute is enabled with the switch bat to the right.

EMwhite wrote:
4. Is PWM1 and PWM2 actually the PWM of Oscillator 1 and 2 or is it just two different jacks which are additive and attached to both OSCs?


I normal PWM2 to PWM1 with the jack switch on the host board: use PWM1 jack only, it will modulate both. Of course you can wire it without the switch involved.

EMwhite wrote:
5. Likewise, are OSC1 and OSC2 FM per Osc. and can you confirm that if so, is OSC2 FM also 1V per octave as noted for OSC1 on your panel?


The osc FM inputs are separate. But as with the PWM you can wire the jack switch if you wish.

EMwhite wrote:
6. How did that power supply work out? If it's affordable (<$100), maybe just let us know what you bought, what additional circuitry was required if any, and call it a day. An investment of the $1500-$2k for these parts, panel, boards is certainly deserving of it's own PS :hihi:


The HAA15-0.8-AG is $63.xx at Digikey. You have to change 2 resistors and adjust the trimmers for +/-19V. It then becomes a 600mA per rail supply, which a fully-populated crOwBX will load to about 450mA/rail.

Crow
/**/
oldcrow
Here is how the carrier board and slot adapter look. The carrier board will mount on the back of the host board using 1/2" pillars. The circuit toward the
left on the top view (left image) is the stereo final volume VCAs.



The slot adapters will total four altogether and plug into the carrier board at each slot row. Voice cards attach to the slot adapters. Due to the tight space constraints
I decided on in order to make the full assembly as compact as possible, note that most electronic components mount to the bottom side. On the left tail of the board
is the audio panning trimpot, and on the mid-right is the portamento circuit for that voice.



More later. --Crow
Isaiah
Rockin' Banana!
home_listening
Looking great! Guinness ftw! hyper
numan7
SlayerBadger! screaming goo yo w00t Guinness ftw!

cheers
The Real MC
Ordered LS318s today for the voicecard. Was actually painless. Have piles of resistors, caps, ICs, and other stuff coming from Digikey. I hope the resistors aren't all 330k.

You must get the 330pf mica caps from Jameco. Digikey does not stock a suitable cap. They have to be the CD4 series that are HF silver mica with low ESR.

Scott's BOM on his website has some errors, I sent him the corrections.

This will be my first DIY project with SMT components...
The Real MC
Just found this german MIDI-CV four voice converter, looks sweet

http://marienbergdevices.de/modular/uebersicht/midi-converter/

parquix
Is there sound demo out there? Can't wait to hear it!
oldcrow
parquix wrote:
Is there sound demo out there? Can't wait to hear it!


Getting to that as soon as I can, right now I am trying to build and test a full rev2 4-voice system in time for a conference. --Crow
oldcrow
Slowly the master vision takes shape: here is a nearly-finished host board with a fully-populated carrier board mounted to it, and the carrier board loaded with a slot adapter and attached crowbx voice board.



More later,

Crow
/**/
mOBiTh
this things is madness - i reckon it deserves a glass case! 8_)
oozitron
Maybe a laser-cut plexiglass case like the Ambika?

It's a little bit bigger than the Ambika tho... meh

Drew
EMwhite
By the time you get done soldering [EDIT] ~2,100 components you are going to want to mount it on a pedestal in the middle of your room with spot lights shining on it from every angle as if it was sold by Swarovski.

Looking at Crow's partial build is starting to make me nervous (board weight perspective. So maybe a plexi case with slots grooved on each side wouldn't be a bad idea. I may work something up with a base footprint that rests nicely on my Kurzweil.

Btw: my panel is finished and on it's way to me, should arrive Friday. If the holes don't line up, it will be relegated to control my multi-voice SEMs project hihi. Couldn't resist taking advantage of that 20% off special. Will see hmmm.....
negativspace
1200... I routinely do that in a day or two of building Manhattan Analog modules. Sounds fun!
mOBiTh
i can't stand perspex cases, yuk, they're so bendy (especially on one this big!) and cheap feeling, and the edges feel horrible Dead Banana

Think I'm gonna go wood and metal with plenty of ventilation It's peanut butter jelly time!
oldcrow
EMwhite wrote:
Looking at Crow's partial build is starting to make me nervous (board weight perspective).


When it is finished I will have a support system in place to hold the voice cards. I originally wanted to install them vertically, but they're too long to fit in a 5U height. So, I will use between-board nylon spacers and an edge frame. --Crow
The Real MC
Verified large shipment of components from Digikey from my BOM, and all is correct!!
The Real MC
oldcrow wrote:
Slowly the master vision takes shape: here is a nearly-finished host board with a fully-populated carrier board mounted to it, and the carrier board loaded with a slot adapter and attached crowbx voice board.



More later,

Crow
/**/


That is (going to be) one seriously dense module!
gslug
That is one seriously impressive piece of gear! The TSSH is what finally persuaded me to join the forum, but I'll have to get one of these too...
suitandtieguy
this is exciting!
mikecameron
Just added the rev1 single voice and rev. 2 4-voice crOwBX to the gear list for Knobcon. Looking forward to getting my eyes and ears on this thing oldcrow!
oldcrow
Due to the dense packing of boards, I knew there would be a few "interesting" mounting requirements for the larger components in the "regulator" corner of the voice and slot adapter boards. It turns out voice boards #2 and #4 along with slot adapters #1 and #3 will use a capacitor mounting scheme like this. Perhaps in a future rev I'll go to SMT electrolytics.

Voice board, the slot card is shown positioned closer than the actual mounting dimension to verify the clearances.



Slot adapter capacitor and 78/79L15Z regulator detail. Also note the close trimming of the KK156 male headers needed on slot adapters #1 and #3.




Almost done with first of four rev2 voice boards...
negativspace
Mouser stocks a pretty good array of through-hole aluminum organic polymer caps, it might be worth a browse through their catalog. I've used some 100uF that are only 5mm high or so and would probably work here.
oldcrow
negativspace wrote:
Mouser stocks a pretty good array of through-hole aluminum organic polymer caps, it might be worth a browse through their catalog. I've used some 100uF that are only 5mm high or so and would probably work here.


Yep, I'll have a look at other cap case types. I'm just using what I have here already for these proof of concept builds. --Crow
The Real MC
Axial caps may be another solution
oldcrow
My Haribo "Gold-Bears" sample packet arrived today. It came with this complimentary front panel! SlayerBadger! SlayerBadger! SlayerBadger!

mikecameron
"REV 2 Knobcon Edition"

applause
baylortrewerton
oldcrow wrote:
parquix wrote:
Is there sound demo out there? Can't wait to hear it!


Getting to that as soon as I can, right now I am trying to build and test a full rev2 4-voice system in time for a conference. --Crow


Does this mean you're going to be at Knobcon? I was on the fence before, but now....
negativspace
Those panels they send with the gummi bears rock.
oldcrow
baylortrewerton wrote:
Does this mean you're going to be at Knobcon? I was on the fence before, but now....


Yes. I would have gone last year if I'd known about it: the place is 20 minutes from my house. Guinness ftw! Guinness ftw!
oldcrow
One rev2 voice board done, three to go... SlayerBadger!

paults
Over 65 trimmers??!? sad banana Dead Banana
oldcrow
paults wrote:
Over 65 trimmers??!? sad banana Dead Banana


Err...yes? screaming goo yo Cmon its not like it is a rev2 Prophet-5. Or a CS-80. Guinness ftw!
paults
CS-80 is like 270 total, as I recall. So 64 is 'better'. SlayerBadger!
The Real MC
oldcrow wrote:
One rev2 voice board done, three to go... SlayerBadger!



thumbs up

Looking forward to assembling mine... the OB-X is sitting in the auditorium at work, ready to pull off "Birdland" today.
chrissugar
Congratulations Oldcrow, fantastic project. I have an OB8 and would love to add the OBX sound to my setup (even a monophonic OBX).

I didn't read the whole thread so sorry if it was already answered. What is the estimated price for one voice board PCB and for one control board PCB ?
Any idea when will this project be available?

chrissugar
EMwhite
When I was a kid, I got Ice Skates for Christmas. I laced them up and skated around the living room imagining that I was on ice except it was the 1" shag carpet. My parents were not pleased.

This arrived today so of course, I had to round up some spare switches, jacks and a volume pot (not to mention my lone Oberheim knob) and put it all together to see how it will one day look.

And then I promptly put my family on notice, not to expect to see me much between the date that the boards arrive and ... well, they will know when they hear the beast!

Only thing missing... hihi hint, hint hihi

kbo
please count me for a full 4 voices pcbs

Amazing project we're not worthy SlayerBadger!
RussiaZero23
Are any of the PCB or face plates ready to buy.


I am ready to make an 8 voice to go with my 8 voice OB-Xa.
oldcrow
2 voice boards done, 2 to go. SlayerBadger! SlayerBadger!

oldcrow
RussiaZero23 wrote:
Are any of the PCB or face plates ready to buy.


I will be adding the boards to my sales portal once I have the 4-voice system fully assembled/calibrated and a few audio demos recorded.
I am working against a presentation deadline (Knobcon) and once I am prepared for that, I'll get the sales part of the project online.

Crow
/**/
Microscopial
damn I dont know how i missed this one as I love soldering (find it very relaxing, But ill be in for four boards and controller board please indeey applause applause applause applause applause applause applause applause applause applause applause applause
Microscopial
hey crow how much did the faceplate cost you
applause
EMwhite
Panels of this size and complexity are not cheap on an individual basis.

Mine (based on OldCrow's FPD) cost $155 and I was fortunate, timing wise to use a 20% discount so it came to approx. $128 shipped.

You can save $30-$40 by dropping the white infill and if you don't card much about aesthetics, you can drop the fancy HPGL logo art.

And obviously, if you don't plan to integrate into a modular, or plan on a custom case, the panel can be made more simple or smaller from a height perspective. Look closely at the Host board pcb and you will notice that all of the jacks beneath the octave and pitch bend switches are panel mounted and may be mounted on a generic panel if only CV pitch/gate and audio out is required.

I may build the next rev in a desktop case with an embedded midi->CV interface like the HexInverter quad interface (eg the only outward facing ports will be Midi) and possibly add one of the Doepfer midi cc to cv interfaces hard wired to various modulation sources.
mOBiTh
incidentally, my gut feeling is that the hex interface won't be much use for this as it will always play the same voice first (when playing more than one voice - this I think will sound shit from the stereo pan point of view) instead of the round robin approach of the oberheim control circuits (assuming my ob-xa is typical)

should be easy enough to program an arduino to do what is required though
EMwhite
Good point there! I picked up a set of boards and panel from Hex but have yet to build it.

I was planning on using a MI MidiPal for the round robin initially but it sounds like as a long term solution that will need to stay. My MOTM 650 can do it all but I'm not thrilled with dedicating it to the crOwBx because I use it for general modular duties and don't have the dough (nor are they very available) for another.

Otherwise, anything you can come up with will be of interest especially if it will do up to 6 or 8 voices.
oldcrow
Three voice boards done, one to go... SlayerBadger! SlayerBadger! SlayerBadger!

mOBiTh
w00t hihi
robotmakers
Just wondering out loud - wouldn't this have been the perfect application for an SMT design that could be blasted out cheaply and automatically? Virtually all buyers are going to need multiple identical copies making it appear highly likely that several dozen could be sold, potentially triggering economies of scale. Wondering if the price would be more or less than the sum of the through-hole parts and board, even ignoring the cost of labor.

Best wishes,
Roger
Microscopial
But but but. I like soldering Isn't the point of being in the DIY section. smile
mOBiTh
robotmakers wrote:
Just wondering out loud - wouldn't this have been the perfect application for an SMT design that could be blasted out cheaply and automatically? Virtually all buyers are going to need multiple identical copies making it appear highly likely that several dozen could be sold, potentially triggering economies of scale. Wondering if the price would be more or less than the sum of the through-hole parts and board, even ignoring the cost of labor.

Best wishes,
Roger


I reckon doing that much smt would be outside of most peoples comfort zone - it definitely would be for me - sounds stressful!

These boards are designed to drop straight in instead of the original oberheim voices so there was no desire to pursue smt/compactness...
Peake
5% resistors! You're a madman! Stop him!
robotmakers
mOBiTh wrote:


I reckon doing that much smt would be outside of most peoples comfort zone - it definitely would be for me - sounds stressful!

These boards are designed to drop straight in instead of the original oberheim voices so there was no desire to pursue smt/compactness...


My point is that a robot far away could do all the SMT placing and soldering, painlessly, in no time, and without error.

Best regards,
Roger (too lazy to do this much soldering)
EMwhite
I suppose if this was made for profit, he could have them fabbed and from what I've read, he has access to such outfits and experience but that's no fun for any of us hihi plus a major hassle building up arsenal of amd parts and dealing with headaches.

So instead it's all old school as original and a great, accessible project for anybody that needs one voice board or a one voice behind a panel or two-four voice or whatever will come next. And on that note it will shortly be mutha f'ing bacon yo and Guinness time not to mention thumbs up time and hammer time.
oldcrow
robotmakers wrote:
Just wondering out loud - wouldn't this have been the perfect application for an SMT design that could be blasted out cheaply and automatically? Virtually all buyers are going to need multiple identical copies making it appear highly likely that several dozen could be sold, potentially triggering economies of scale. Wondering if the price would be more or less than the sum of the through-hole parts and board, even ignoring the cost of labor.


If I do a rev3, it will be mostly SMT. I have an SMT assembly line, but it is busy most times with contract work. Loading the feeders for a crowbx voice board would be a true soul-killing procedure, taking several days of preparation before debugging the build flow, etc. (If I am ever mad at someone and they work for me, I will make them load feeders. twisted)

I like using SMT parts, and I've gotten good at mounting them by hand, but it is hard on my eyes. For a DIY board set like this, I went with (mostly) through-hole parts because it makes the project more accessible to folks. I'll go full SMT on something like my master plan: a CS-80 M board replacement. Guinness ftw!
mOBiTh
robotmakers wrote:


Best regards,
Roger (too lazy to do this much soldering)


You can always just pay me to solder them for you hihi
oldcrow
EMwhite wrote:
I suppose if this was made for profit, he could have them fabbed and from what I've read, he has access to such outfits and experience but that's no fun for any of us hihi


The origin of this project is I played MC's OBX, and wanted that sound for myself. For things I make just for myself, I usually don't do an SMT board because programming the L60 for a run of 4 boards isn't worth the time investment, never mind holding up assembly of stuff I get paid for. eek! Thus, like the original OBX voice board, mine is made in the same form factor using mostly through hole parts. The capacitors and two 3300ppm 1K resistors that are SMT are used because 1) the original OBX voice board had no decoupling capacitors (which is kind of a bad design decision, particularly when 78xx/79xx regulators are involved) and when I add decoupling I use SMT because they are easy to work into the design. 2) Temperature compensating resistors in SMT format are easy to use as you just mount the transistor packages over the resistors.

So, everyone benefits from this being a DIYable project because I originally did the design work for myself and a small set of boards, and not tooled for some medium-scale run of like 1,000 SMT boards. SlayerBadger!
mOBiTh
it'll sound better with through hole parts anyway. obviously hihi
negativspace
Plugging 4 pre-finished boards into a pre-finished carrier board hardly feels like DIY anyway, right?
mOBiTh
negativspace wrote:
Plugging 4 pre-finished boards into a pre-finished carrier board hardly feels like DIY anyway, right?


exactly sad banana
oldcrow
Ran out of 220-Ohm resistors. Transplanted a few from some KLM-367A boards (Polysix patch manager pcb), which were made when the OBX was relatively new. Nothing like vintage parts for vintage synths. Guinness ftw!

This last voice card is probably going to exhaust a number of values in my bins, some of which I've had for more than 25 years.

--Crow
/**/
robotmakers
negativspace wrote:
Plugging 4 pre-finished boards into a pre-finished carrier board hardly feels like DIY anyway, right?

Well, here's my take on modulars - many of us are some combination of the following:

(1) Synth museum curators - whose desire is to own the most rare, the most desirable, perhaps the newest, or perhaps just the most

(2) Electronics craftsmen - DIY constructors of the most unique, the most customized and the most arcane, sometimes as a creative expression in and of itself

(3) Musicians - actually creating music or whatever it is you call that noise, using the required tools for that job

These days, I'm less #2 than you guys, fwiw.

In other news, CDM reports on Scott's OBX project:Wonders of DIY Synths

Cheers,
Roger
The Real MC
Decoupling caps in SMT format is much better also because if their inherent lower ESR.
spneca
Already sold out???
sonicwarrior
oldcrow wrote:
Ran out of 220-Ohm resistors.


The funny thing is: I have tons of them. Guess I have to build this, too. help
oldcrow
spneca wrote:
Already sold out???


No, I have just not enabled the inventory for it yet. --Crow
gdavis
0805 SMT aint that bad once you get the hang of it, this is an eye saver though:
Dude163
Hmm so is this for just replacement boards? or can I build a full synth out of all this? I tried reading the whole thread, but my iphone sucks for that
oozitron
1) OBX compatible voice cards.

2) Host board with front panel controls and slots for up to 4 voice cards

3) Approx one million parts hihi

So it's an OBX in a box, just no programmer.

OBX = awesome = Scott (Crow)

Drew
oozitron
1) OBX compatible voice cards.

2) Host board with front panel controls and slots for up to 4 voice cards

3) Approx one million parts hihi

So it's an OBX in a box, just no programmer.

OBX = awesome = Scott (Crow)

Drew
mOBiTh
it was worth the double post to be fair hihi
EMwhite
(Looking at my Gucci its about that time... )

I think we will be getting some audio from the beast shortly...

Hey OldCrow, how difficult is the calibration routine? How much of it can be done by ear and with a simple voltmeter; which critical adjustments require a scope?
The Real MC
Probably the only reason to use a scope is calibrating PW to 50%, but if you've heard enough square waves you can do it by ear.

Range, scale, high freq of VCOs can be done against a digital source. Filter range/scale by ear, VCA by ear. Not sure if the 3310 discrete replacement has any trims.

Since it's a clone of the OB-X voice card, the service manual calibration procedure applies.
oldcrow
For the most part you can follow the service manual adjustment procedure for each card. I calibrated the rev1 using a reference VCO (MOTM-300) and my ears. The only extra steps are the six trimmers I use in the envelope generators to set as close a response to a 3310 as possible. Each EG has a sustain level trim and two rate trims, one for attack time and one for decay/release times.

I will be finishing the 4-voice overall assembly this weekend. Then comes calibration, wiring up the jacks, and putting everything into the rack frame I will be using to host all the gear I am bringing to Knobcon. Once it is all in the frame, I'll do some audio demo recordings.

Actual sales and shipping of the bare boards will be after Knobcon as this prep work is taking up all of my spare time.

--Crow
/**/
dougt
Do you think the new EGs can be matched close enough to the original cards in an OB-X? Have you finished assembling your board and installed it in an OB-X yet MC?
The Real MC
I had a really busy month and have a couple of bench projects to finish, but building the crOwBX is high on the list and it is definitely headed for my OBX. Still waiting for a couple of backordered parts from Digikey, got everything else including the LS318s.
oldcrow
Last voice card completed. One slot adapter left to assemble then the calibration fun begins. Guinness ftw!

The Real MC
oldcrow wrote:
Last voice card completed. One slot adapter left to assemble then the calibration fun begins. Guinness ftw!


Mental note that rev3 of voicecards should have trimpots located on top edge for easy accessibility, 3, 2, 1...
EMwhite
I have an autotune question; been a while since we discussed this so how 'bout it?

Does the original OBX always stay in tune, meaning that you can demand that it autotune from the moment you start it up (no warm up period) and provided that you ask it to recalibrate every so often, it can adapt to changes in temperature, etc?

Just curious, and curious about how the lack of autotune here in rev. 2 will be a pain in the arse, or just a nuisance.

And if I have this right, the provision for autotune is already in place (on voice cards) and it's really just that the hostboard needs to be expanded in order to support; likely the job of a atmega or something similar at some point down the road.

I think I read somewhere that the expectation is that tuning will be reasonable within a 4-5 octave range due to the fact that the design is revamped somewhat and that all components will be of same vintage.

Help us better understand this. Thank you.
oldcrow
EMwhite wrote:
I have an autotune question; been a while since we discussed this so how 'bout it?

Just curious, and curious about how the lack of autotune here in rev. 2 will be a pain in the arse, or just a nuisance.

And if I have this right, the provision for autotune is already in place (on voice cards) and it's really just that the hostboard needs to be expanded in order to support; likely the job of a atmega or something similar at some point down the road.

I think I read somewhere that the expectation is that tuning will be reasonable within a 4-5 octave range due to the fact that the design is revamped somewhat and that all components will be of same vintage.

Help us better understand this. Thank you.


The OBX question I'll leave for MC or Tony.

CrowBX boards have much-improved exponential converters that employ log-conformal matched pairs and precision DC servo amplifiers, so the VCOs will stay in tune a lot better.

That being said, things can go out of tune slightly between voices as they're all their own circuits, but I have not yet encountered a real problem with tuning unless I try to span something like 11 octaves. At that point it begins to be things like dielectric absorption in the timing capacitors that the high-frequency tracking trimmers can't quite compensate for.

Being a functional work-alike to a vintage OBX voice card, a CrowBX card has the two fine tune signals available on a connector. I am working on an autotune PIC circuit that in this case would be placed on the slot adapter for rev2 boards on on the voice card itself for rev3. (And also a 1U module for modulars). I am applying the same "interpolated linearizing table" concept I use in linearizing thermocouples for PID controllers here.
Note that this autotune stuff is down the road a bit as I just now have one rev2 four-voice built except for final card-mounting into the panel and some jack wiring, and after Knobcon I can open the order page for them--that will keep me busy for a while. screaming goo yo screaming goo yo
The Real MC
EMwhite wrote:
Does the original OBX always stay in tune, meaning that you can demand that it autotune from the moment you start it up (no warm up period) and provided that you ask it to recalibrate every so often, it can adapt to changes in temperature, etc?


Given that my OBX has new trimpots and CMOS/buffers, it fires up cold in tune - and my Memorymoog and Minimoog can't do that. I impulsively hit autotune after playing a few notes and notice little difference. There is inevitable temperature drift during warmup but a lot less than my Memorymoog or Minimoog. I used the OBX at a two hour show a couple of weeks ago and only recall hitting autotune once or twice.

The key to reliable autotune is careful calibration of the high frequency trimpots, because the autotune procedure jacks the VCOs into dog whistle territory.

Quote:
I think I read somewhere that the expectation is that tuning will be reasonable within a 4-5 octave range due to the fact that the design is revamped somewhat and that all components will be of same vintage.


The 4-5 octave range is in the VCF keyboard tracking, not the VCOs. The OBX VCOs have a 12 octave range - 5 in the keyboard, 4 in VCO front panel tuning, 3 in LH octave switch - which I have exploited with little trouble in tuning.

The range limit in the VCF tracking is a product of the SEM SVF design. I'll happily deal with that thorn for its great sound.
oldcrow
For those interested, here is how to modify a Power One HAA15-0.8-A power supply to output +/-19V:

You solder a 10K 1% resistor across R20 and another 10K 1% resistor across R28. Then adjust the trimmers for +19.00V (trimmer R21) and -19.00V (trimmer R26). You do not need to disassemble anything. (see image, below)

The supply will nominally provide +/-19V at 600mA per rail. Take care not to accidentally wire +/-15V modules to it!

--Crow

oldcrow
The Old Crow and the Sea (of jacks) SlayerBadger! SlayerBadger!

oldcrow
Somehow I missed this in the rev1 bug check, but I have the OSC1 and OSC2 FM enable switches cross-wired. (OSC1 enable goes to OSC2, etc.) This is a host board bug, not a voice card bug.

It can be remedied without trace cuts, it just needs a couple of creatively-mounted resistors. screaming goo yo




I have calibrated two voices, on to the next... Guinness ftw! SlayerBadger!
oldcrow
Slightly more than four months after I started this project, I can finally say I am....DONE! Guinness ftw! Guinness ftw! Guinness ftw! Guinness ftw! Guinness ftw!

I am not quite finished fine-calibrating a few things here and there, but the 4-voice crOwBX is finally completed. I recorded this rough test using a tiny little Korg nanokey to fire MIDI notes out of Ableton through a Lexicon Lambda module into my MOTM-650 MIDI-CV unit and thus into the crOwBX. The (mono) output is captured back through the Lambda into Ableton to render this short wav file. No extra effects or VSTs were used. More later.

http://www.cs80.com/crowbx/CrowBX_1st_test.wav

/**/

--Crow SlayerBadger! SlayerBadger! SlayerBadger! SlayerBadger! SlayerBadger! SlayerBadger!
/**/
mikecameron
Wow. This is incredbile. Congratulations Crow! applause
oldcrow
There are only two digital parts in this entire rig: a quad NAND gate to assist in the VCO waveform select/off modes and a PIC to generate the white noise in place of the ancient MM5837. The PIC runs Tom Wiltshire's program: http://www.electricdruid.net/index.php?page=projects.noisegen

Using just tuned filters, it makes this sort of wind effect:

http://www.cs80.com/crowbx/CrowBX_Noise_Test.wav

Using it with the LFO for clocked S/H effect:

http://www.cs80.com/crowbx/CrowBX_SH_Test.wav



Rockin' Banana! Rockin' Banana! Rockin' Banana!
kroffe
Awesome project and well executed Old Crow!
Congrats on being done. smile
oldcrow
More detail images:

All VCO scale and offset trimmers are accessible. Things tend to stay pretty stable but as there is no autotune (yet), the occasional tweak may be needed.



In an effort to keep things as temperature stable as possible, all the voltage regulators are at the other end of the board from the VCOs. The trimmers visible here are the panning pots for each voice--there are left and right audio outputs in addition to the mono output.



And with that, to bed. More fun tomorrow! SlayerBadger! SlayerBadger! SlayerBadger!

--Crow
/**/
Isaiah
applause Rockin' Banana!
2thick4uni
Brilliant job, well done!

we're not worthy we're not worthy we're not worthy


Please can you build us that 8 voice CS80 clone now? lol


Rockin' Banana! Rockin' Banana! Rockin' Banana! Rockin' Banana! Rockin' Banana! Rockin' Banana!
The Real MC
Those samples sound REALLY good applause thumbs up
mOBiTh
we're not worthy screaming goo yo hihi
spneca
Wow! Unbelievable work! Sounds amazing. Thank you so much for doing this. Can't wait to build one.
mckenic
SHIT!

I dont now exactly what I was expecting but those demos sound AMAZING!

thumbs up
robotmakers
Congratulations on a true tour de force. Just amazing.

Sincerely,
Roger
spneca
Oops. Delayed double post.
oldcrow
A unison filter sweep. SlayerBadger! screaming goo yo SlayerBadger! screaming goo yo w00t w00t w00t

http://www.cs80.com/crowbx/Unison_Sweep.wav

I am getting the rev1 single-voice crOwBX ready for Knobcon at the moment... Guinness ftw! Guinness ftw! Guinness ftw!
oldcrow
A demo of the OBX portamento circuits, which "by design" have different lag rates due to component tolerances. So instead of all voices arriving on pitch simultaneously, you get this distribution of lag rates that are part of "the OBX sound."

http://www.cs80.com/crowbx/Porta_Unison_Sweep.wav

--Crow
/**/
oldcrow
2thick4uni wrote:
Please can you build us that 8 voice CS80 clone now? lol


My "master plan" is to build the CS(R)-80: a rackmount CS-80. This is why I've determined the individual discrete circuits over the years and turned them into things like the CS VCO, MOTM-480, and so on. Even so, the sound of the CS-80 has as much to do with the performance controls as it does the sound engine, so I need to research a good external MIDI keyboard that can do things like poly AT in order for it to be a true CSR-80. But this is all down the road...

--Crow
/**/
oldcrow
Another info tidbit: the overall supply current for the 4-voice crOwBX is 420mA at +19V and 380mA at -19V, which is well within the HAA15-0.8-A's capability after modification to provide +/-19V.



--Crow
/**/
Chok
Great work, Scott

I am interested in your design of VC envelopes . Would you share plans? They remind me a design of Scott Gamble ( EFM)?
I have the same project to redo voice cards of Cs 60/80 and the monophonic prototype is functional. The most difficult rest to make, to draw the PCB of voice cards...not too big...
oldcrow
Chok wrote:
Great work, Scott

I am interested in your design of VC envelopes . Would you share plans? They remind me a design of Scott Gamble ( EFM)? I have the same project to redo voice cards of Cs 60/80 and the monophonic prototype is functional. The most difficult rest to make, to draw the PCB of voice cards...not too big...


The CSR-80 is my next project, a culmination of all the CS designs I did in discrete form over the past dozen years (which is why I did them, really) SlayerBadger! My ADSR as used on the crowbx voice boards uses JH's inverse-parallel expo multiplier pairs along with the standard-issue 4052 and (CMOS) 555. I posted that schematic elsewhere on muff's, one moment...here it is, https://www.muffwiggler.com/forum/viewtopic.php?t=83193

I need to update that schematic a bit as I changed some resistor values.

--Crow
/**/
Chok
Thanks Scott, but your link is broken cry
oldcrow
Chok wrote:
Thanks Scott, but your link is broken :cry:


Try it again, it was missing a '?' --Crow
Chok
Thanks.... applause

For the CSR, this schematics is ok for EG VCF (IG00152 clone): CS EGVCF clone
2thick4uni
oldcrow wrote:
2thick4uni wrote:
Please can you build us that 8 voice CS80 clone now? lol


My "master plan" is to build the CS(R)-80: a rackmount CS-80. This is why I've determined the individual discrete circuits over the years and turned them into things like the CS VCO, MOTM-480, and so on. Even so, the sound of the CS-80 has as much to do with the performance controls as it does the sound engine, so I need to research a good external MIDI keyboard that can do things like poly AT in order for it to be a true CSR-80. But this is all down the road...

--Crow
/**/


Wow, that would be even more awesome than your already awesome CrOwBX!

we're not worthy we're not worthy we're not worthy

Soon have clones of your OBX and CS-80 along with Zthee's Arp 2600 to build. We are about to enter a golden age of SDIY

nanners nanners nanners nanners nanners
aladan
2thick4uni wrote:
Soon have clones of your OBX and CS-80 along with Zthee's Arp 2600 to build. We are about to enter a golden age of SDIY


Too true.

But you forgot to mention the Putney (available). And there are modular-format near-complete clone-alikes of the majority of the functionality of the MS-10/20 (available), System-100m (available) and System-700 (in progress) as well. I thought I wouldn't be able to afford to own a Putney, CS-80 or a System-700 given their rarity and high prices these days, but now...!

Next up: complete GX-1? ;-)
The Real MC
oldcrow wrote:
Even so, the sound of the CS-80 has as much to do with the performance controls as it does the sound engine, so I need to research a good external MIDI keyboard that can do things like poly AT in order for it to be a true CSR-80. But this is all down the road...


I have yet to find a better polyAT controller than my Kurzweil MIDIBoard. Very few controllers made today implement polyAT, there's the $$$$ VAX77 and some new 25 note controller.

Perhaps in a future AHMW gathering I'll bring my MIDIBoard...
dougt
The Rhodes Chroma with the now available Polypressure kit installed is the best PolyAT keybed I've used. Expensive too but you get an amazing synth with it.
mOBiTh
oldcrow wrote:
A demo of the OBX portamento circuits, which "by design" have different lag rates due to component tolerances. So instead of all voices arriving on pitch simultaneously, you get this distribution of lag rates that are part of "the OBX sound."

http://www.cs80.com/crowbx/Porta_Unison_Sweep.wav

--Crow
/**/


Sounding great for sure - this 'behaviour' is identical to my OBXa with some voices arriving rather quickly and some taking much longer, so good result here for sure!

The overall sound though seems quite different to my OBXa - more precise/less fuzzy maybe? Hmmn I need to compare them side by side for sure but this sounds more modern, what do you think? Is that a feature of new components perhaps?

How do you think it sounds compared to your original OBX?
The Real MC
mOBiTh wrote:
The overall sound though seems quite different to my OBXa - more precise/less fuzzy maybe? Hmmn I need to compare them side by side for sure but this sounds more modern, what do you think? Is that a feature of new components perhaps?


OBXa is going to sound different from OBX. OBXa filter is the CEM3320, OBX filter is discrete. That's the main contributor to the difference in sound between the two. The resonance of the OBX filter is very unique.

This is a pretty discrete circuit which follows the original almost completely. The biggest impact on sound comes from the old cheap-and-dirty CA3080 OTAs used in the VCF and VCA. 3080s aren't available anymore but one 13700 OTA cell without the output buffer or linearizing diodes is the same as the 3080, and that's how Scott configured it. You can get vintage sound from modern components if you know how to do it.

Quote:
How do you think it sounds compared to your original OBX?


It has that colorful alien resonance (especially in filter sweeps), that discrete girth and bite (especially in unison), that subtle distortion in the voice VCA and voice summers which is a classic Oberheim trait, string sound is pretty close. There is more to compare but very promising. I'm sure we'll hear more after Knobcon (wish I could be there). I'll have to get my CrOwBX voicecard assembled and try it in my OBX.
oldcrow
mOBiTh wrote:
How do you think it sounds compared to your original OBX?


I do not have an OBX--which is why I made one. SlayerBadger!

I spent a lot of time working on the distortion profile, I even emailed Tom Oberheim to ask about his method of using a biased diode bridge to perform linearization of the OTA inputs (to which he did reply, btw). I provide the option to try using the 13600's internal linearizing diodes but I've not tried it yet: you remove all the 1N4148s around the volume VCA(s) and install the 15K resistors that bias the internal networks. I'll try this on the single voice system at some point.

The filter I paid strict attention to as well: getting that particular pole spread was critical in my view, and Oberheim's method of using matched OTAs was simplified by the fact the dual OTA packages are intrinsically matched. Read the 13600 designer's notes for more info, http://www.idea2ic.com/LM13700.html

--Crow
/**/
oldcrow
Off to Knobcon 2013's Friday evening events... w00t Guinness ftw! screaming goo yo SlayerBadger! It's peanut butter jelly time!
oldcrow
Home from Knobcon, had a blast. Now, recovery mode. Tomorrow I will set up board ordering, but for now, Dead Banana
oldcrow
12:01AM here in Chicago, and...

screaming goo yo screaming goo yo screaming goo yo screaming goo yo The time has come: bare board sets are now for sale screaming goo yo screaming goo yo screaming goo yo screaming goo yo

I am giving Wigglers the leg up here as this link is not on the crOwBX site just yet: go to http://www.cs80.com/crowbx/orderinfo.html

You will see three order links for single voice, four voice and individual voice board sets. Wigglers will probably want one of the first two as "voice boards only" is primarily intended for OBX owners.

The moment I sell out of any variant I will order more boards, so lead times are minimal. The typical restocking cycle is ten business days: you will not be left out. SlayerBadger!

Enjoy and SlayerBadger! screaming goo yo w00t Guinness ftw! Rockin' Banana!

Crow
/**/
aladan
oldcrow wrote:
12:01AM here in Chicago, and...

screaming goo yo screaming goo yo screaming goo yo screaming goo yo The time has come: bare board sets are now for sale screaming goo yo screaming goo yo screaming goo yo screaming goo yo

I am giving Wigglers the leg up here as this link is not on the crOwBX site just yet: go to http://www.cs80.com/crowbx/orderinfo.html

You will see three order links for single voice, four voice and individual voice board sets. Wigglers will probably want one of the first two as "voice boards only" is primarily intended for OBX owners.

The moment I sell out of any variant I will order more boards, so lead times are minimal. The typical restocking cycle is ten business days: you will not be left out. SlayerBadger!

Enjoy and SlayerBadger! screaming goo yo w00t Guinness ftw! Rockin' Banana!

Crow
/**/



Yes! But no...

"There was a problem communicating with PayPal. Please try again.
(request_id: 0e8b07e13600ca021b37e277f6fa64a1)"

sad banana
oldcrow
aladan wrote:
Yes! But no...

"There was a problem communicating with PayPal. Please try again.
(request_id: 0e8b07e13600ca021b37e277f6fa64a1)"

:sadbanana:


Must be on Paypal's end. --Crow

/**/
aladan
oldcrow wrote:
aladan wrote:
Yes! But no...

"There was a problem communicating with PayPal. Please try again.
(request_id: 0e8b07e13600ca021b37e277f6fa64a1)"

sad banana


Must be on Paypal's end. --Crow

/**/


Indeed... I tried again on a different computer and it went through, so now I am all crOwBX'd up! :-)
home_listening
Ordered a 4 voice set!
magman
I have now officially changed status from a lurker and careful observer to a future owner. Guinness ftw!

It actually took me over 10 minutes from spotting the news on the forum that boards were available to getting my order in. I'm really disappointed with myself that I took that long (too much prevarication again hmmm..... )

Are we likely to have a separate build thread, or are we going to keep it all in this thread?

Regards

Magman
aladan
magman wrote:
It actually took me over 10 minutes from spotting the news on the forum that boards were available to getting my order in.


At $175 + shipping for a 4-voice PCB set this is a no-brainer, even with the crappy Aussie dollar, the huge inventory of parts and the hours of soldering! Going rate for the original is around $5k + the cost of maintaining a museum piece...

Who is going to do a panel run?

Cheers,
A.
Jarno
Fantastic work oldcrow! This wasn't really on the radar as much as the ARP project by Zthee, but it is very appealing indeed. Making the full four voice version is a monumental amount of soldering, I reckon!
Think I'll stick to ordering a single voice version for now!

Where can I find the .fpd file? I've been looking but other than layouts and BOM's, and the example audio files, can't seem to find the frontpanel artwork.
oldcrow
Jarno wrote:
Think I'll stick to ordering a single voice version for now!

Where can I find the .fpd file? I've been looking but other than layouts and BOM's, and the example audio files, can't seem to find the frontpanel artwork.


Hi, and thanks. SlayerBadger! The single voice version is the basis for expanding to more voices as it is. If you want to expand it later, you add anywhere from two to eight additional boards and do a little reconfig on the host board.

I have not yet uploaded the .fpd, but I will do that later today.

Cheers,

Crow
/**/
spneca
Just ordered a 4 voice set, as well.

Crow:
Any idea when you will have the programmed Noise PICs in stock?
mOBiTh
yeh a panel run would be ace!!

I'm in but the greedy half of my brain (clearly it's way more than half) would like 8 voices - will this throw a spanner in the works re front panels? maybe two x four voices would be a more sensible option?

maybe being less greedy would be a more sensible option too? hmmm.....
Sir Ruff
Was really chuffed that I could try out the CrowBx in person at Knobcon (half the reason I went actually)--Scott, the only downside was the small speakers! But that was perhaps for the better, or you might have destroyed the place. It sounded fantastic.

The question now is: who will do front panels, and who will solder this monster for me?! lol
michaelvertex
Fantastic! I owned an OB-X for a few years and the demos sounded spot on

Congratulations applause
negativspace
4-voice sets were gone so I ordered a single. I'll expand later. Looking forward to it! nanners
numan7
oldcrow wrote:
Jarno wrote:
Think I'll stick to ordering a single voice version for now!

Where can I find the .fpd file? I've been looking but other than layouts and BOM's, and the example audio files, can't seem to find the frontpanel artwork.


Hi, and thanks. SlayerBadger! The single voice version is the basis for expanding to more voices as it is. If you want to expand it later, you add anywhere from two to eight additional boards and do a little reconfig on the host board.

I have not yet uploaded the .fpd, but I will do that later today.

Cheers,

Crow
/**/


hmmm..... i just ordered a single voice system + 3 voice cards (and a pic chip) a second ago... will it be possibe for me to purchase the {carrier board + slot adaptors} set for the 4 voice system separately once you have made more, master Crow?

cheers
oldcrow
numan7 wrote:

hmmm..... i just ordered a single voice system + 3 voice cards (and a pic chip) a second ago... will it be possibe for me to purchase the {carrier board + slot adaptors} set for the 4 voice system separately once you have made more, master Crow?

cheers


I may have enough extra slot adapter boards (that is the one I am low on) to enable you to do this, I will know more once I finish parceling out the boards into their shipping bins per customer. --Crow

/**/
oldcrow
I have ordered more slot adapter boards to arrive next week, then four-voice board sets will be back in stock. --Crow

/**/
apoisontree
This is amazing oldcrow! applause

I think I will start building a one voice set and see how it goes, if I do well I'll expand or build a separate 4-voice set. Will you add some noise generator PIC to the shop soon? I'd like to order one with the single voice PCB set.
Thanks.
numan7
hmmm..... i was able to purchase a noise generator PIC from the online store yesterday, apoisontree.

did you try clicking the 'crowbx synth' link from the cs80.com main page (that is where i found them - not on the ordering info page)?

cheers
apoisontree
Today it's sold out.
oldcrow
I'm ordering more PICs today, figure to have them Thursday. --Crow
randel
FYI -

JLM Audio has a 1 Ampere dual rail power supply kit that may appropriate for the +/-19v needed for this project.

http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=11

I've used this in the past with a suitable toroidal transformer for a preamp project.

For those contemplating multiple voice cards, this might be an alternative worth investigating, especially since it can be modded for 1.5A per rail.

Happy building!
spneca
I tried ordering the PDIP LS318s and they said they are out of stock and due to an almost complete lack of demand for thethat version, they have stopped making it. The representative I spoke to suggested that I use the TO-78 version (metal can) and configure the leads to fit in the holes.

Will this cause any problems? I know the height parts can be is somewhat limited in a 4 voice system.

Did anybody have success in getting the PDIP version?
sonicwarrior
spneca wrote:
I tried ordering the PDIP LS318s and they said they are out of stock and due to an almost complete lack of demand for thethat version, they have stopped making it.


Sucks. Did Linear Systems say this?
spneca
sonicwarrior wrote:
spneca wrote:
I tried ordering the PDIP LS318s and they said they are out of stock and due to an almost complete lack of demand for thethat version, they have stopped making it.


Sucks. Did Linear Systems say this?


Yes. Did you grab the PDIPs while they still had them?

EDIT: I see you are in Germany. You probably did not call them.
mOBiTh
oldcrow I forgot to order noise PICs. will you be able to supply me the firmware to blow my own or shall I put in another order?!

d'oh!
sonicwarrior
spneca wrote:
Yes. Did you grab the PDIPs while they still had them?


I made a 250+ group buy. If I had known this before I would have bought at least 300. d'oh!
Isaiah
Sorry, I know I asked this before, but I can't remember the answer and browsing on a phone isn't ideal for searching:
What are the dimensions of the control board and the voice board?
I can't afford a 4-voice any time soon, so I'm wondering if I could fit a single voice in a 7 x 17 x 3" Bud box.
The Real MC
spneca wrote:
I tried ordering the PDIP LS318s and they said they are out of stock and due to an almost complete lack of demand for thethat version, they have stopped making it. The representative I spoke to suggested that I use the TO-78 version (metal can) and configure the leads to fit in the holes.

Will this cause any problems? I know the height parts can be is somewhat limited in a 4 voice system.

Did anybody have success in getting the PDIP version?


I bought twenty back in August, planning for eight voice cards plus spares. They were RoHS non-compliant parts that can't be fitted in mass products, ask if they still have any of those. I paid about $5.30 each.

Somewhere early in the thread Crow said you could substitute one of the MAT ICs for the LS318.
edit: from voicecard BOM "Can also use MAT-02, SSM2210, LM394"
oldcrow
mOBiTh wrote:
oldcrow I forgot to order noise PICs. will you be able to supply me the firmware to blow my own or shall I put in another order?!

:doh:


I will put the firmware file up on the crowbx site. --Crow

/**/
mOBiTh
oldcrow wrote:
mOBiTh wrote:
oldcrow I forgot to order noise PICs. will you be able to supply me the firmware to blow my own or shall I put in another order?!

d'oh!


I will put the firmware file up on the crowbx site. --Crow

/**/


cool nice one smile
Jarno
Crow, it isn't very obvious, but are the boards for a single board set rev1 or rev2? Is rev2 just for repairing originals (in which case they are more separate partnumbers rather than versions, sorry engineer speaking hihi ).
oldcrow
spneca wrote:
I tried ordering the PDIP LS318s and they said they are out of stock and due to an almost complete lack of demand for thethat version, they have stopped making it. The representative I spoke to suggested that I use the TO-78 version (metal can) and configure the leads to fit in the holes.

Will this cause any problems? I know the height parts can be is somewhat limited in a 4 voice system.

Did anybody have success in getting the PDIP version?


I called Linear Systems today and yes, they're not packaging any more LS318s in PDIP because "no one buys them." very frustrating

You will be able to use the LS318 in the TO-78 package, it will just require some leadforming and mounting of the part such that the base of the package is resting on the tempco resistor. The overall height will still leave sufficient space between boards (4 voice). I have ordered samples from them to do this on a voice card so as to document the procedure.

I will also look into making a DIP adapter with a pre-soldered LS318 and tempco resistor to offer on the crowbx site.

I find it funny a TO-78 package is still made but a PDIP is not. Must be all the legacy military hardware out there. angry

--Crow
/**/
The Real MC
oldcrow wrote:
I called Linear Systems today and yes, they're not packaging any more LS318s in PDIP because "no one buys them." very frustrating


Guess we're "nobodies", huh? very frustrating very frustrating very frustrating

Quote:
I find it funny a TO-78 package is still made but a PDIP is not. Must be all the legacy military hardware out there. angry


hmmm..... Either that or the medical devices which use a lot of nonlinear processing, but just hmmm.....
jarvis
Isaiah wrote:
Sorry, I know I asked this before, but I can't remember the answer and browsing on a phone isn't ideal for searching:
What are the dimensions of the control board and the voice board?
I can't afford a 4-voice any time soon, so I'm wondering if I could fit a single voice in a 7 x 17 x 3" Bud box.


Based on the PCB renders:
host board is ~ 10.25" x 5.5"
voice board is ~ 10" x 4.3"

So it seems like there's a good chance a single voice would fit in that BUD box. I plan on doing a single voice like that myself Guinness ftw!
oldcrow
Isaiah wrote:
Sorry, I know I asked this before, but I can't remember the answer and browsing on a phone isn't ideal for searching:
What are the dimensions of the control board and the voice board?
I can't afford a 4-voice any time soon, so I'm wondering if I could fit a single voice in a 7 x 17 x 3" Bud box.


The host board is 10.25" x 5.5" and the voice board is 10" x 4.3125"

The stacking height for a single voice is about 1.5" measured from the back of my front panel, which takes the standoff height of 0.5" into account.

The stacking height for my 4-voice is 6.25" from the back of the panel.

--Crow
/**/
Isaiah
jarvis & oldcrow
Thanks (again d'oh!) for the information!

That leaves plenty of room on the panel, and behind it, to space the controls out a bit and connect them to the PCB with flying wires and headers.

I already have a SEM, but I'm excited about building a mono CrOwBX.
Their similarities and differences should work together wonderfully!
oldcrow
Jarno wrote:
Crow, it isn't very obvious, but are the boards for a single board set rev1 or rev2? Is rev2 just for repairing originals (in which case they are more separate partnumbers rather than versions, sorry engineer speaking :hihi: ).


Host and voice boards being sold are rev2. Carrier and slot adapters are rev1.
I gave different SKUs to the board sets to mark their use, but a rev2 voice board is the same for OBX repair as for crOwBX builds.
Jarno
thumbs up
sonicwarrior
oldcrow wrote:
I called Linear Systems today and yes, they're not packaging any more LS318s in PDIP because "no one buys them."


Is that also true for the LS358 which looks pretty similar spec-wise?
sonicwarrior
oldcrow wrote:
I will also look into making a DIP adapter with a pre-soldered LS318 and tempco resistor to offer on the crowbx site.


Is it possible to offer the footprint for the SOIC version on board as an alternative in a board revision?
randel
Is it possible to post the BOM for each board as a .xls file?

With so many parts, I'm bound to make a copy/paste error...

Thanks!
The Real MC
sonicwarrior wrote:
oldcrow wrote:
I called Linear Systems today and yes, they're not packaging any more LS318s in PDIP because "no one buys them."


Is that also true for the LS358 which looks pretty similar spec-wise?


LS318 is NPN, LS358 is PNP. Not compatible.

randel wrote:
Is it possible to post the BOM for each board as a .xls file?

With so many parts, I'm bound to make a copy/paste error...


The BOM manager on Digikey has an option to export to CSV so I have a CSV for the voicecard but not the other boards.
sonicwarrior
The Real MC wrote:
LS318 is NPN, LS358 is PNP. Not compatible.


Damn, I compared every spec on both datasheets and didn't see the obvious. d'oh! hihi
negativspace
sonicwarrior wrote:
Is it possible to offer the footprint for the SOIC version on board as an alternative in a board revision?


That would be great, SOIC is really pretty easy to hand-solder. However... there are lots of different DIP-adapters out there for SOIC parts. Might as well just pick up a few of those and make your own.
oldcrow
Yes, I plan to add SOIC-8 on the next step revision, but that is some time off yet. --Crow

sonicwarrior wrote:
oldcrow wrote:
I will also look into making a DIP adapter with a pre-soldered LS318 and tempco resistor to offer on the crowbx site.


Is it possible to offer the footprint for the SOIC version on board as an alternative in a board revision?
oldcrow
Digikey parts arrive Friday, so I'll have noise PICs shortly thereafter. Probably get the LS318s in the TO-78 case the same day. --Crow
aladan
oldcrow wrote:
Digikey parts arrive Friday, so I'll have noise PICs shortly thereafter. Probably get the LS318s in the TO-78 case the same day. --Crow


Hi Scott,

If my board set hasn't been posted off yet, could you hold off so I can get a noise PIC and some LS318s included in the order?

Thanks,
A.
oldcrow
aladan wrote:


Hi Scott,

If my board set hasn't been posted off yet, could you hold off so I can get a noise PIC and some LS318s included in the order?

Thanks,
A.


Sure, though I am not selling LS318s, these are samples to check the fit of the TO-78 package. I will look into stocking them if they work out as expected, however. --Crow

/**/
randel
Is there a reason that these caps are sourced at JAMECO? Is there something special about them?

I see that they're both in the filter - are the original parts dipped silver mica?

I'm putting together a BOM sourced from Mouser, and was wondering if any other 330pF 500V mica parts would work as well, but obviously I don't want to mess with the Obie filter mojo.

Thanks!
oldcrow
This is what the original OBX voice card used. I have other capacitor types to try, but given the distinct sound of the OBX filter, I try to change things as little as possible. I figure 330pF mica in higher DC ratings will work fine.

--Crow
/**/

randel wrote:
Is there a reason that these caps are sourced at JAMECO? Is there something special about them?

I see that they're both in the filter - are the original parts dipped silver mica?

I'm putting together a BOM sourced from Mouser, and was wondering if any other 330pF 500V mica parts would work as well, but obviously I don't want to mess with the Obie filter mojo.

Thanks!
oldcrow
I have noise generator PICs in stock once again. Only one is needed whether building a 1-voice or 4-voice. For those with PICs and a programmer, the hex file is posted at http://www.cs80.com/crowbx/

Link to PIC catalog entry,

http://cs80-com.myshopify.com/collections/crowbx-analog-music-synthesi zer/products/crowbx-noise-generator-pic


--Crow
/**/
oldcrow
I received my LS318 samples in the TO-78 metal can package today. It takes a little lead-forming work with the needle-nosed pliers but they will fit fine:



I will order some LS318 TO-78s to stock, estimate they will be $5 each.

Of course, you can just match up some 2N3904s and do this, too. It won't be quite as good as the 318, but 3904s (and 3906s) these days seem to match well when randomly selected.



--Crow
/**/
mono-poly
Are the pcb sets for a 4 voice gonna get restocked?
oldcrow
mono-poly wrote:
Are the pcb sets for a 4 voice gonna get restocked?


Yes, I am out of slot adapters at the moment but they're on order to arrive around Oct 1st. 4 of the 10 boards for a 4-voice are slot adapters.

--Crow
/**/
sonicwarrior
oldcrow wrote:
I received my LS318 samples in the TO-78 metal can package today.


I guess the TO-71 metal can is too high? They are a bit cheaper.
mOBiTh
is it one or two LS318s per voice board?
Nordcore
mOBiTh wrote:
is it one or two LS318s per voice board?
Two. (One per VCO)
mOBiTh
cheers - this is now obvious to a my post-coffee brain hihi
Chok
A friend ordered me of what to build a voice complete of the clone OBX....

I did not find on your site plans and procedure of calibration. Are they in another place?

Thank you

Cordialy
jarvis
Does anyone have any recommendations for a smaller power supply for those of us just doing a single voice & host board? I'm planning to make a relatively compact desktop module and trying to cram a Power One supply in there will just make the case deeper or wider and add a bit of extra unused panel space, and making it an external supply seems unnecessarily bulky (and kind of overkill).
2thick4uni
jarvis wrote:
Does anyone have any recommendations for a smaller power supply for those of us just doing a single voice & host board? I'm planning to make a relatively compact desktop module and trying to cram a Power One supply in there will just make the case deeper or wider and add a bit of extra unused panel space, and making it an external supply seems unnecessarily bulky (and kind of overkill).


How about one of these:

http://www.ebay.co.uk/itm/161055218987?ssPageName=STRK:MEWNX:IT&_trksi d=p3984.m1439.l2649

along with a mains transformer with 0-24V, 0-24V or 24-0-24v secondary
randel
I think that R39 and R40 on the voice card should be Digikey 820KQBK-ND, not 829KQBK-ND, as indicated in the BOM.

Also, Yaego does not appear to manufacture the 56K 1% resistor specified for R142, R143, R168 and R169. I plan to substitute a 56.2K 1% replacement, which carries the Digikey part 56.2KXBK-ND.
The Real MC
randel wrote:
I think that R39 and R40 on the voice card should be Digikey 820KQBK-ND, not 829KQBK-ND, as indicated in the BOM.

Also, Yaego does not appear to manufacture the 56K 1% resistor specified for R142, R143, R168 and R169. I plan to substitute a 56.2K 1% replacement, which carries the Digikey part 56.2KXBK-ND.


That is correct...
oldcrow
So noted, thanks for the heads up. I'll update the BoM. I think my bag of 56K resistors came from Mouser some time ago, I'll check. 56.2K is fine though. --Crow

randel wrote:
I think that R39 and R40 on the voice card should be Digikey 820KQBK-ND, not 829KQBK-ND, as indicated in the BOM.

Also, Yaego does not appear to manufacture the 56K 1% resistor specified for R142, R143, R168 and R169. I plan to substitute a 56.2K 1% replacement, which carries the Digikey part 56.2KXBK-ND.
oldcrow
This is UK week for shipping orders. There is more paperwork involved but everyone in the UK who ordered boards should get a ship notification email over the next several days.

Continental Europe is next week. Trying to be as quick as I can while still being careful. SlayerBadger!

--Crow
/**/
negativspace
Boards arrived, let the fun begin! It's going to hard to leave this in the backlog while I finish the stuff I'm on the hook for already. hihi
mOBiTh
this is great news - nightshifts approaching - hoping to get the slave labour done then!
oldcrow
I made a quick site page about using the LS318 TO-78 package:

http://www.cs80.com/crowbx/ls318.html

I will be ordering an initial 100 pieces to offer at US$5 each. (My cost is $4.54 ea) I am not looking to profit on the transistors--I just want folks to be able to get them. screaming goo yo More later.

--Crow
/**/
oldcrow
Taking a break from order packing, I decided to try and solve the LS318 "problem":



1) Use a PDIP LS318, MAT02, LM394, SSM2210, R28 is your tempco.

2) Use a TO-78 (or TO-71) LS318, etc: DIP pads B1 abd B2, octagonal inset pads, CC1, CC2, E1 and E2 and your choice of R28 or R28A: SMT or through-hole using the DIP pads 4 and 5.

3) Use an SOIC-8 LS318, SSM2212, etc. and R28A (SMT or TH).

4) Use a couple 2N3904s and a TH tempco.

I think that covers most of the combinations. I consider the 2SA798/2SC1583 "retired" so no 5-pin pad row. SlayerBadger!

--Crow
/**/
EMwhite
I read the page you referenced above, thanks for putting that together; quick question though.

regarding the (NLA) IC making contact with the tempco resistor (with thermal goo, I presume); are you saying that the bottom of the TO-78 ought to make contact with the tempco also (is that physically possible) or did I read that the PCB traces are common so the ambient temperature of the embedded transistors will radiate via copper traces sufficiently?

[please correct me]

And thank you (rec'd my order today)
oldcrow
Ideally you want a physical contact between the can and the resistor, but the resistor has conductive edges and so touching the can to it is not a good idea. The way the leads emerge from the bottom prevent the part from fully seating to the board--this is more by the package design than anything. T-series packages usually have a little ceramic pillar embedded in the epoxy known as the "seating pin" but the LS318s do not seem to have these. The next best thing is that I placed the pads of the DIP and resistor close together so the heat coupling is achieved off the transistor die through the leads into the ground plane--same with the resistor. I've used my ambient oven to test this, works fine. SlayerBadger!

Let the soldering commence! screaming goo yo screaming goo yo screaming goo yo

--Crow
/**/

EMwhite wrote:
I read the page you referenced above, thanks for putting that together; quick question though.

regarding the (NLA) IC making contact with the tempco resistor (with thermal goo, I presume); are you saying that the bottom of the TO-78 ought to make contact with the tempco also (is that physically possible) or did I read that the PCB traces are common so the ambient temperature of the embedded transistors will radiate via copper traces sufficiently?

[please correct me]

And thank you (rec'd my order today)
jaidee
Scott, will you be posting configuration information (what to do with all those trimmers)?
oldcrow
Yes, as soon as I finish writing it. Guinness ftw! I will also be adding pictorial build guide pages to the crowbx site as time permits. --Crow

jaidee wrote:
Scott, will you be posting configuration information (what to do with all those trimmers)?
oldcrow
Update: all domestic (US) orders are sent out. UK shipments start tomorrow (9/25/13). --Crow

/**/
mOBiTh
A quick note about midi interfaces - I've been testing the rpocc firmware for the MIDI2CV hexinverter interface tonight and it does the correct type of sequential voice assignment necessary for the crOwBX - and it's cheap!

w00t
randel
I've ordered the parts for 12 voice cards and 12 slot adapters.

My soldering iron will keep me warm in the long nights ahead!
mOBiTh
randel wrote:
I've ordered the parts for 12 voice cards and 12 slot adapters.

My soldering iron will keep me warm in the long nights ahead!


w00t
home_listening
A voice for every finger, thumb, nose and tongue.

Massive respect, you MUST post pictures!

randel wrote:
I've ordered the parts for 12 voice cards and 12 slot adapters.

My soldering iron will keep me warm in the long nights ahead!
mOBiTh
Anyone figured out a rough component cost for a four voice build yet please?
magman
I've got a couple of orders on the go for Mouser and Digikey at the moment which come to just a little over £200 so far.

I do have quite a few parts in stock though (most of the resistors, capacitors, transistors and IC's), plus you would also need to order some LS318's, so I would estimate about another £60-70 on top of this, so say £270 or approx. $400 for a complete parts set for a four voice.

A lot of the cost is in the connectors and pots (preset and front panel) for this project, not surprising really when you look at the complexity.

Regards

Magman
The Real MC
home_listening wrote:
A voice for every finger, thumb, nose and tongue.


Unless you're female, you forgot one digit hihi
EMwhite
Somebody indicated approx $180, not including LS318, connectors or fancy capacitors so figure $200 per voice card + a rounded $200 for the board set and PIC plus $150 for a panel + a wild guess for components for carrier, card adapters (4) and host board which has tons of switches and pots and you are looking at $1500+.

But don't quote me (as I have done with the $180-$200 per voice board above hihi)

Looked at another way:



... or about 1/3rd the cost of a 6 voice OBX that doesn't work!
oldcrow
I am including my FPE front panels and panel hardware in this, but to make the rev1 (single voice) and rev2 four voice it was about USD$1,500.00

Not exactly cheap, but still a fraction of the price I was seeing for OBXes. screaming goo yo

--Crow
/**/

mOBiTh wrote:
Anyone figured out a rough component cost for a four voice build yet please?
skee
Minisonic 3? All that's missing is a ring modulator.
The Real MC
EMwhite wrote:
... or about 1/3rd the cost of a 6 voice OBX that doesn't work!


I paid $1200 for my basketcase four voice OB-X and never saw any lower than that. And I've been watching for ten years.

I turned down a basketcase eight voice OB-X that had been stored in a shed where rodents had made a nest. The dealkiller was the stain of rodent urine on the circuit boards - besides being unsalvageable that urine is a serious toxin.

Seeing the $$$ into four assembled CrOwBX voicecards, it's not hard to fathom why a new OB-X 8 voice listed for $5995 - in 1979 dollars eek!
mOBiTh
I got my 8-voice ob-xa for £300. Actually I swapped it for something I got for free. Ok I'm showing off now hihi w00t

I think I'm gonna have to do this a voice at a time lol
oldcrow
I never had any Oberheim gear until I made it myself. SlayerBadger! SlayerBadger! SlayerBadger!

I do have three CS-80s, bought for $1K, $1.5K and $3.5K in between 2001 and 2003. The "expensive" one was near mint and is the one in my studio. The other two have lived a bit of a rougher life by they mostly work.

CS-80 voice cards are on the slate--something I've planned on doing for like a dozen years now. Guinness ftw! Guinness ftw! Guinness ftw!

--Crow
/**/
mOBiTh
oldcrow wrote:
I never had any Oberheim gear until I made it myself. SlayerBadger! SlayerBadger! SlayerBadger!

I do have three CS-80s, bought for $1K, $1.5K and $3.5K in between 2001 and 2003. The "expensive" one was near mint and is the one in my studio. The other two have lived a bit of a rougher life by they mostly work.

CS-80 voice cards are on the slate--something I've planned on doing for like a dozen years now. Guinness ftw! Guinness ftw! Guinness ftw!

--Crow
/**/


I'm definitely in for the CS-80 project too hihi hihi

Mate, any chance of some more 4-voice audio demos by the way? Would love to hear some.

Also, what's the latest thinking on cases? 8_)
oldcrow
Thus ends UK shipping week. Guinness ftw! Guinness ftw! Guinness ftw! All the UK orders should have received a shipping notification. There is one order outstanding from Ireland I need to process. I will do that next week along with the Australian orders.

--Crow
/**/
oldcrow
Got my board shipping notification for the slot adapter re-order, should be able to restock 4-voice board sets next week. SlayerBadger! SlayerBadger! SlayerBadger!
mOBiTh
w00t
randel
It starts...

78 of the 312 voice card surface mount capacitors are now soldered in. Those things are pretty small, but I found that the beer helps.

home_listening
Oh good, I guess that means whiskey and red wine will put me in gold star mode I guess.

hihi hihi hihi
2thick4uni
randel wrote:
It starts...

78 of the 312 voice card surface mount capacitors are now soldered in. Those things are pretty small, but I found that the beer helps.



Yikes! I think I'll have to invest in a $50k Pick and place machine and reflow oven before I buy my boards...... Dead Banana






.
robotmakers
2thick4uni wrote:
randel wrote:
It starts...

78 of the 312 voice card surface mount capacitors are now soldered in. Those things are pretty small, but I found that the beer helps.



Yikes! I think I'll have to invest in a $50k Pick and place machine and reflow oven before I buy my boards...... Dead Banana


Oldcrow HAS an SMT assembly line! He's either the ultimate sadist or Santa depending on your point of view!

Cheers,
Roger
oldcrow
robotmakers wrote:
Oldcrow HAS an SMT assembly line! He's either the ultimate sadist or Santa depending on your point of view!

Cheers,
Roger


The thing is, my SMT line is constantly busy. It is not a trivial task to unload the deck and reset it for a different task, such as placing these capacitors, especially when the boards are not in a panel array. Now, this does not mean I will not try to do an SMT run at some point, it is just not in the cards at the moment.

--Crow
/**/
mOBiTh
only a mere 104 SMT caps for me then? should be quite good at them by the end of this project lol
spneca
mOBiTh wrote:
only a mere 104 SMT caps for me then? should be quite good at them by the end of this project lol


That's just the voice cards! There are additional SMT caps on host board, the carrier board and slot adaptors.
oldcrow
This is Australia and Netherlands shipping week, with one order to France and one to Ireland thrown in. Slot adapters arrive Wednesday, and I will restock 4-voice board sets at that time.

--Crow
/**/
mOBiTh
spneca wrote:
mOBiTh wrote:
only a mere 104 SMT caps for me then? should be quite good at them by the end of this project lol


That's just the voice cards! There are additional SMT caps on host board, the carrier board and slot adaptors.


hopefully less than another 104 right? hihi Dead Banana

we have those nice chunky lit magnifier things at work - think i'll be using those 8_)
mattrick
oldcrow wrote:
Slot adapters arrive Wednesday, and I will restock 4-voice board sets at that time.


w00t woohoo!
paults
Meh...the last cell phone I designed has 614 capacitors in it.
oldcrow
Once you get the knack of working with SMT parts, you tend to find out they are faster to solder. I've gotten it to around 5 or 6 (2-pin) parts installed a minute; lots of time is saved by not having to bend, form or trim leads. SOICs are similarly easy. It only gets tough when the parts go leadless or have a tiny pin pitch...or both. A DAC chip I want to use in a project comes in the MSOP-10 package only. This is when I use a stencil and reflow oven. SlayerBadger!

--Crow
/**/

spneca wrote:
mOBiTh wrote:
only a mere 104 SMT caps for me then? should be quite good at them by the end of this project lol


That's just the voice cards! There are additional SMT caps on host board, the carrier board and slot adaptors.
mOBiTh
paults wrote:
Meh...the last cell phone I designed has 614 capacitors in it.


did you solder them all by hand? MY ASS IS BLEEDING
LED-man
oldcrow
where can we download the schematic of this boards ?
its important to have this for the building and troubleshooting of the voicecards.
if needed place a link on the first site on this thread.

thanks
Rex Coil 7
I saw some videos on You Tube about manually soldering rather large SMT ICs (roughly 2" x 2") that were totally surrounded by pins at pretty tight pitch dimensions. They used a resin pen to "wet" the pins and pads, then tacked down the IC at 2 corners, and then they just dragged the soldering pen across the connection pins as if they were drawing a line with an ink pen. When done properly the solder only adhered to the pins and their associated pads on the PCB. It looks all easy, that is until the camera zooms out and a perspective is gained of just how small and tight everything is! It's pretty amazing, especially watching them train the young Asian (dare I say "women"?) to master the skill.

I have enough "fun" populating a 1.125" x 5" PCB with "only" 50+ components, 5 pots, 3 footswitches, and a few toggles (roughly 200 solder joints). You guys are so far out of my league that I just sit and read this thread with my mouth hanging open.

oldcrow wrote:
Once you get the knack of working with SMT parts, you tend to find out they are faster to solder. I've gotten it to around 5 or 6 (2-pin) parts installed a minute; lots of time is saved by not having to bend, form or trim leads. SOICs are similarly easy. It only gets tough when the parts go leadless or have a tiny pin pitch...or both. A DAC chip I want to use in a project comes in the MSOP-10 package only. This is when I use a stencil and reflow oven. SlayerBadger!

--Crow
/**/

spneca wrote:
mOBiTh wrote:
only a mere 104 SMT caps for me then? should be quite good at them by the end of this project lol


That's just the voice cards! There are additional SMT caps on host board, the carrier board and slot adaptors.
oldcrow
I am working on the remainder of the build docs which include schematics. They will be posted on the crowbx site once completed. --Crow
/**/

LED-man wrote:
oldcrow
where can we download the schematic of this boards ?
its important to have this for the building and troubleshooting of the voicecards.
if needed place a link on the first site on this thread.

thanks
oldcrow
Slot adapters are here a day early; I have stocked some 4-voice board sets. I am starting to run out of voice boards next, so get em while the gettin's good. SlayerBadger! SlayerBadger! SlayerBadger!

http://cs80-com.myshopify.com/collections/crowbx-analog-music-synthesi zer
moogasm
I totally agree. A good magnifier and tweezers makes all the difference. I normally tack a tiny bit of solder on one of pads before laying down the part. I have started to layout single-sided boards with DIPs on top and 0805 SMT on the bottom and it is amazing how more circuitry can fit in the same area.


Quote:
Once you get the knack of working with SMT parts, you tend to find out they are faster to solder. I've gotten it to around 5 or 6 (2-pin) parts installed a minute; lots of time is saved by not having to bend, form or trim leads. SOICs are similarly easy. It only gets tough when the parts go leadless or have a tiny pin pitch...or both. A DAC chip I want to use in a project comes in the MSOP-10 package only. This is when I use a stencil and reflow oven. SlayerBadger!

--Crow
randel
I found that the tricky bit of soldering the SMT capacitors to the voice card is not the actual soldering, but rather the location of each of the 26 pad pairs.

I'd count to count to 26 when I pre-tinned a pad, again when I placed a part, and again when I soldered the second leg.

Inevitably, I'd only count to 25 at some step along the way, and would have to discover what I'd forgotten; which took a fair amount of time.

At voice card 4 I made a simple paper template with masks for each of the pad pairs. This sped things up tremendously, and allowed me to simply verify each connection.

I'd recommend this to anyone building more that 1 voice.





2thick4uni
randel wrote:
I found that the tricky bit of soldering the SMT capacitors to the voice card is not the actual soldering, but rather the location of each of the 26 pad pairs.

I'd count to count to 26 when I pre-tinned a pad, again when I placed a part, and again when I soldered the second leg.

Inevitably, I'd only count to 25 at some step along the way, and would have to discover what I'd forgotten; which took a fair amount of time.

At voice card 4 I made a simple paper template with masks for each of the pad pairs. This sped things up tremendously, and allowed me to simply verify each connection.

I'd recommend this to anyone building more that 1 voice.







If you kept them as little flaps it would make a great advent calendar hihi

Even has an extra flap for Boxing day too!!


BSF This is a great idea, I'll be doing this when I've saved up enough for my boards and start populating them. How about making it a pdf so can be posted as a template?


.
The Real MC
Good idea Randel
randel
Oldcrow-

First, let me congratulate you on an extraordinary project. The more I explore the inner workings of the OB-X, the more I appreciate what you have done to bring your design to fruition.

My ambitious plan is to replicate the rest of the OB-X controller board using a modern microcontroller and components, and implement robust MIDI, with CC control over as many parameters as practical.

I've been sketching a 10 bit DAC and S/H board that I intend to interface, and I'm trying to pin down the number of channels needed.

The original OB-X uses 2 channels of S/H per voice for FT (Fine tune?). You've mentioned that your voice cards stay in calibration very well.

Would you comment on how FT is implemented in your Host board, and if you think autotuning may be unnecessary? I'd rather not add all of those channels of S/H and lines of code if they are not needed.

Thanks!
EMwhite
Super-matched vs. Ultra-matched question:

Absence of LS318 in PDIP and new options for same IC in different packaging as you've documented; thank you for that.

But on the BOM, you also mention MAT-02, SSM2210, or LM394. What's the difference between these and how will it change the tonal quality or stability? (and what did Tom's team use, btw?)

Thank you
The Real MC
randel wrote:
The original OB-X uses 2 channels of S/H per voice for FT (Fine tune?). You've mentioned that your voice cards stay in calibration very well.

Would you comment on how FT is implemented in your Host board, and if you think autotuning may be unnecessary? I'd rather not add all of those channels of S/H and lines of code if they are not needed.


Probably won't need autotune with a single voicecard, "may not" need it with four voicecards.

I say "may not" because heat is the critical variable. Accumulated heat over time throws off the tuning. More than four voicecards in close proximity raises that risk and autotune becomes a necessity. The more voicecards you have, the more supply current you draw and more heat is generated from the power supply. Eight or twelve voicecards in close proximity increases the heat accumulation. Stuff all that in a small closed cabinet and you're asking for tuning trouble.

The early polyphonics were in big cases for a reason.

Good ventilation is the key, best option is passive (no noisy fans). Everybody knows that heat rises. The CrOwBX carrier board holds four voicecards, so allow generous spacing between carrier boards for eight/twelve voice polysystems. Orient the voicecards on end so heat can passively ventilate (IE heat rises). Don't stack multiple carrier boards, this traps the heat below and allows it to accumulate. Use a power supply with generous headroom in the current capability to minimize heat.

Whenever possible put ventilation vents in top and bottom of the cabinet, otherwise front and rear vents - or the ends - are next best choice. You want airflow free of restrictions.

Heat accumulation has been the achilles heel of many polysynths. It almost doomed the Prophet-5. It originally started life as a Prophet-10 with two sets of five-voice circuit boards stacked, and the accumulated heat and near zero vents resulted in severe tuning problems. OB-X has near zero vents and it has been known that eight or six voice configurations are harder to keep in tune than four voice configurations (because the voicecard motherboard trapped accumulated heat in the voicecard below it). CS-80s suffer from inadequate ventilation. The Memorymoog has a fan and it still has trouble staying in tune.

EMwhite wrote:
Super-matched vs. Ultra-matched question:

Absence of LS318 in PDIP and new options for same IC in different packaging as you've documented; thank you for that.

But on the BOM, you also mention MAT-02, SSM2210, or LM394. What's the difference between these and how will it change the tonal quality or stability? (and what did Tom's team use, btw?)


The OB-X used the CA3086. The CA3086 and CA3046 (and second source LM3046 and LM3086) were the best available techology back in the 1970s. There's a Signetics direct replacement that had the edge specwise but it has long been out of production. The CA3086 has looser specs than the CA3046, and neither are as tightly matched as MAT02/SSM2210/LM394/LS318. Only the LM3046 is available albiet in SMT or SOIC package not DIP.

The modern matched pairs will hold tuning far better. They are not used in the audio path so they have no impact on tonal quality.

Specwise there isn't much difference. The difference may be the pinout and may not be a pin-for-pin substitute for the LS318.
EMwhite
Thanks (MC) for the explanation.

So what to do? What are you doing? Or are you one of the lucky ones with LS318 PDIPs in secret reserve.

OldCrow's new design adapts well to various types of packages but of course, I have Rev2 boards so, not an option and I'd hate to have less than optimal results and hate more to [poorly] wireform the TO package AND have no thermal contact aside from the leads, as documented.

Somebody who knows better, please tell me that I am sweating a minor detail and I'll go away (and start soldering). I'm somewhat paralyzed at the moment. If you (anybody) could recommend that the TO is better than a rigged SMD, that would be helpful. I placed an order for qty. 20 with a UK based reseller but I expect to hear tomorrow morning that it's really, truly, NLA. [you know the feeling when you goto RadioShack desperate for an opamp that you know they carry to find the bin empty, then rummage through adjacent bins hoping somebody picked one up and changed their mind? That's what I'm doing right now]

... and Thank you...
oldcrow
There is no fine tune implementation. screaming goo yo The only thing I do is provide headers to wire FTA/FTB to whatever you like--trimpots, an S/H, etc. but autotune is not strictly needed as the expo front end is pretty much a direct copy of the one I use in the CS VCO module and is very stable. I also provide FTA/FTB headers on the carrier board for experimentation/another VCO mod CV input. I've not bothered to put anything on them for either my single voice and my four voice. If there was one tweak to make, it would be to make R1 to R4 100K 0.1% resistors on each voice card as I've noticed a little voice to voice scaling offset from the 1% ones. --Crow

randel wrote:
Oldcrow-

The original OB-X uses 2 channels of S/H per voice for FT (Fine tune?). You've mentioned that your voice cards stay in calibration very well.

Would you comment on how FT is implemented in your Host board, and if you think autotuning may be unnecessary? I'd rather not add all of those channels of S/H and lines of code if they are not needed.

Thanks!
The Real MC
EMwhite wrote:
Or are you one of the lucky ones with LS318 PDIPs in secret reserve


I was one of the lucky ones, bought enough for ten voicecards. I didn't know that was an obsolete part at the time.
oldcrow
You will be fine with the TO-78. The 3300ppm resistor is of such little mass it quickly takes on the ambient temperature of its surroundings. Since the dual transistor and the tempco are both 1) connected to the ground plane and 2) to each other, the thermal equalization is very even.

Other alternatives would be soic8 packaged dual transistors and something like http://www.uctronics.com/pcs-sop8-so8-soic8-sot-to-dip8-adapter-pcb-co nvertor-p-242.html

EMwhite wrote:
Thanks (MC) for the explanation.

OldCrow's new design adapts well to various types of packages but of course, I have Rev2 boards so, not an option and I'd hate to have less than optimal results and hate more to [poorly] wireform the TO package AND have no thermal contact aside from the leads, as documented.

Somebody who knows better, please tell me that I am sweating a minor detail and I'll go away (and start soldering). I'm somewhat paralyzed at the moment. If you (anybody) could recommend that the TO is better than a rigged SMD, that would be helpful.
Nordcore
As I'm planing my midi-cv interface for the host board with 4 voices (will plug in the 34Pin connector on the card frame carrier): is there a schematic of the host board?
ATM its not really obvious, what connector is a CV input, and what for an external potentiometer.

What I guess:
JP16,JP17; FM OSC1, FM OSC2 - extra inputs to the CV summing node for VCO1F, VCO2F modulation line
JP14; EXT LFOCV - extra input for LFO frequency control
JP12; EX VIB DEP - external pot = modulation lever pot. LFO triangle to pitch of both VCOs
JP8; EFM LVL - pot to ground, reduces FM mod level.
JP3, Jp4; EXT PW1, EXT PW2 - extra inputs to summing node, going to pw1, pw2 control lines
JP13; EXT VOL - pot to ground, volume pedal
JP5; EXT VCF CV - VCFM bus line to voices (pot input, but can be used as CV in)
JP9; EXT BEND; CV input, assigned through 2/1+2 switch to VCO1 or VCO1+2 summing modulation nodes

What could be useful?

Pitch bender: calibrated cv from interface, controlled by midi pitch bender. +/- 1V to JP9. Narrow/width switch done by some CC. There is a registered parameter (#1) for this, but I guess few controller keyboards do support this in a useful fashion.

Filter frequency: the pedal input has some build in offset: no pedal is 10k||( 100k/ (4 or 8)) to ground and 47k to +15V. (Around 2V)
Max voltage is around 4V, min is zero. So a 0..5V CV with 2.5V offset should work ok, giving 5 Octaves control range.
This might be assigned to CC 74, pitch bend or modulation wheel.

Modulation "wheel": there is no CV input to control the "LFO-Tri to pitch" amount. In the OBX that is done directly by the vibrato lever pot. So this would need an extra VCA. Im very unsure about this, for me the original configuration is not *that* useful. (I've never made much use of the vibrato wheel. )

Expression/Volume: as is, this is another pot input, but here are two ways to avoid an extra VCA to control this. (Either let the D/A converter work multiplying or put its CV out to the "upper" side of the vol pot on the host board. )
But I see little use in this. If you need it live: plug in the pedal, if you need automation: just do it in the DAW after recording.
mOBiTh
my boards have arrived! my god they're heavy hihi

MY ASS IS BLEEDING
mOBiTh
oh wow - digikey's ordering system is super annoying! angry

I've just lost my whole BOM twice in a row - once it wasn't updating past about 30 items and the second I tried to name it and it disappeared!

Guh.

So I want to do a single Vox BOM and then order 4 of them, and tweak up the quantities to hit price breaks - is that even possible?
The Real MC
mOBiTh wrote:
So I want to do a single Vox BOM and then order 4 of them, and tweak up the quantities to hit price breaks - is that even possible?


Sure, that's what it's designed for. I have a BOM in Digikey, it should be public under "analoguediehard"
mOBiTh
The Real MC wrote:
mOBiTh wrote:
So I want to do a single Vox BOM and then order 4 of them, and tweak up the quantities to hit price breaks - is that even possible?


Sure, that's what it's designed for. I have a BOM in Digikey, it should be public under "analoguediehard"


ah I see, it's because I'm not registered enough to do anything - have to wait 24 hrs. weird...
mOBiTh
The Real MC wrote:
mOBiTh wrote:
So I want to do a single Vox BOM and then order 4 of them, and tweak up the quantities to hit price breaks - is that even possible?


Sure, that's what it's designed for. I have a BOM in Digikey, it should be public under "analoguediehard"



I must be really stupid cos I can't see how I can view or load other people's BOMs.

I can't even name my own although it says I'm fully registered now...

Edit: The nice lady at DK fixed my account issues. BOMs are entered and ready for checking and ordering tomorrow w00t
oldcrow
Ran out of stock on voice cards this time. I will order more next week. --Crow
mOBiTh
oldcrow wrote:
Ran out of stock on voice cards this time. I will order more next week. --Crow


Sounds like it's going well!!

Quick question - are these pots suitable instead of the plastic bourns ones:

http://www.taydaelectronics.com/potentiometer-variable-resistors/rotar y-potentiometer/linear/100k-ohm-linear-taper-potentiometer-round-shaft -pcb-9mm.html

I have these on my L1 stuff and they're nice - I need easy to read knobs cos I can't see those little plastic ones in low light!

Also, if anyone knows the switch equivalent that is the flatted paddle type instead of the round baton type that would be great 8_)

Like this but through hole:

http://media.digikey.com/photos/Carling%20Technologies%20Photos/2M1-SP 1-T6-B1-M1QE,%202M1-SP3-T6-B1-M1QE,%202M1-SP2-T6-B1-M1QE.jpg
oldcrow
Should work fine as it is a 9mm type. --Crow

mOBiTh wrote:
Quick question - are these pots suitable instead of the plastic bourns ones:

http://www.taydaelectronics.com/potentiometer-variable-resistors/rotar y-potentiometer/linear/100k-ohm-linear-taper-potentiometer-round-shaft -pcb-9mm.html

I have these on my L1 stuff and they're nice - I need easy to read knobs cos I can't see those little plastic ones in low light!

Also, if anyone knows the switch equivalent that is the flatted paddle type instead of the round baton type that would be great 8_)

Like this but through hole:

http://media.digikey.com/photos/Carling%20Technologies%20Photos/2M1-SP 1-T6-B1-M1QE,%202M1-SP3-T6-B1-M1QE,%202M1-SP2-T6-B1-M1QE.jpg
The Real MC
oldcrow wrote:
Ran out of stock on voice cards this time. I will order more next week. --Crow


Sounds like a good problem to have.
mOBiTh
oldcrow wrote:
Should work fine as it is a 9mm type. --Crow

mOBiTh wrote:
Quick question - are these pots suitable instead of the plastic bourns ones:

http://www.taydaelectronics.com/potentiometer-variable-resistors/rotar y-potentiometer/linear/100k-ohm-linear-taper-potentiometer-round-shaft -pcb-9mm.html


Good stuff, cheers! smile
magman
With the PCB's and most of the components landing at chez Magman in the last week, of course I couldn't hold off diving right into the build. So far I've got the Carrier Board, one Slot Adaptor and one Voice Board mostly built (some parts still to order), so I thought I'd pass on a few pointers and hints from my build so far.

I actually built a Slot Adaptor first for some unknown reason, but this has worked out quite well. No major issues with this board, but I now that I've built a Voice Board as well, I can see what Oldcrow means about the tight spacing. I've found some alternate electrolytics that I'm going to try for the 10uF and 100uF caps which are a lot shorter than the standard caps, I'll report back when I get these to see if they make the spacing any easier.

For the Carrier Board, don't do what I did and try to use sockets for the chips. There isn't enough space when the Slot Adaptors plug in for a socketed chip. I very carefully desoldered the sockets and everything looks OK now (fortunately I have a good Weller desolderer station).

Another hint is to use a Slot Adaptor to line up the Molex headers. I soldered one pin on each of the two 3 pin headers at each end of the line of connectors then plugged the remaining connectors into the Slot Adaptors then plugged the Adaptor into the requisite 3 pin headers. There was a slight bow on my Carrier Board PCB, so with the connectors aligned in the Slot Adaptor it was easy to solder one pin on each connector to pull things back into alignment.

One final hint on the Carrier Board, the Molex connectors really grip well, so you may need a small lever to separate the Slot Adaptor from the Carrier Board. Choose something relatively smooth or with a padded end if you don't want the scratches I've already made in my boards.

Finally on the Voice Board so far. A few of the resistor values in the BOM are struck through, as if they have been changed. For some this is correct, but R124, R122 and R127 are actually the correct values.

The only other issue I've had so far is with some of the presets. T7 and T8 are shown as 3296Z type, but these are side adjustment types with the adjustment screw pointing into the centre of the board with the current layout (Oldcrow may be able to turn this pot around for a future revision, if in-situ adjustment is preferable with a multi voice stack). I used a 3296Y type that I had in stock instead. Next, I found the spacing too tight for three presets, T8, R176 and R177 to use the specified 3362R type pots, I again used 3296Y type pots.

Given the tight spacing from the 100uF caps on the Voice Board and the preset on the Slot Adaptor, I may try the alternate caps I've found on the Voice Board as well, to see if this gives a slightly more relaxed fit.

That's it for now, more news soon. Time for bed.

Regards

Magman
peteforrest
I'm embarrassed to say this is the first time I heard of this excellent project.
The OB-X is such a sweet sounding beautiful poly... great to see the design getting some new life.
The Real MC
Welcome to MW, Peter!
dougt
Anyone tested one yet in an actual OB-X? MC?
randel
I had the strangest dream last night...

The Real MC
dougt wrote:
Anyone tested one yet in an actual OB-X? MC?


Still waiting for backordered parts
LED-man
randel wrote:
I had the strangest dream last night...

https://www.muffwiggler.com/forum/userpix/3920_obxpander2_1.jpg


A nice long dream.
Only a single voice card fit in this size/high.
oldcrow
LED-man wrote:
Only a single voice card fit in this size/high.


crOwBX/OBX cards mount horizontally: it takes a slot adapter to make them a vertical plugin. The carrier board just needs to be more like the ones the OBX uses. --Crow
EMwhite
LED-man wrote:
randel wrote:
I had the strangest dream last night...

https://www.muffwiggler.com/forum/userpix/3920_obxpander2_1.jpg


A nice long dream.
Only a single voice card fit in this size/high.


Maybe in his dream (or maybe sleepwalking and operating a 3-d rendering application stooper) he planned on having 8 voice cards side by side? But probably not hihi

Looks nice though, for about a minute I thought about scrapping the panel I had made over a month ago and doing a desktop instead. Then I remembered that I spent $150 on it and have $0 for parts still eek!
Jarno
Don't recall seeing a picture of this, but is this how the four voice PCB structure looks?
oldcrow
The carrier mounts to the back of the host, and the slot+voice cards plug into the carrier:



Jarno wrote:
Don't recall seeing a picture of this, but is this how the four voice PCB structure looks?
Jarno
Right, thanks!
Corrected picture:


Initially I thought of making the (desktop) enclosure suitable for expansion, but if it is this deep I'll make a shallow one for the single voice.
mOBiTh
Hey crow/guys

Is there a definitive list of height restricted components please?

ICs mainly - are there any I can't socket? I don't mind caps but I hate desoldering ICs so I'd like to get this right first time!! hihi

Unfortunately I won't have my slotting sockets till last so I can't check spacing and clearance easily...
magman
The only board I have had any issues with for sockets is the Carrier board, as the Slot Adaptors don't leave enough space for sockets when they are fully inserted onto the Carrier Board plugs.

All of the other boards use the taller presets, which set the height limits for each of these boards, so an IC plus socket should come to a similar height as these presets (though this depends on the height of the socket used, I have used turned pin sockets, so this won't be an issue methinks).

I also decided not to use a socket for the LS318's, so there is direct contact with the Tempco (with a little thermal grease to be extra sure).

Hope this helps,

Magman
dougt
The Real MC wrote:
dougt wrote:
Anyone tested one yet in an actual OB-X? MC?


Still waiting for backordered parts


Which ones are those?
mOBiTh
magman wrote:
The only board I have had any issues with for sockets is the Carrier board, as the Slot Adaptors don't leave enough space for sockets when they are fully inserted onto the Carrier Board plugs.

All of the other boards use the taller presets, which set the height limits for each of these boards, so an IC plus socket should come to a similar height as these presets (though this depends on the height of the socket used, I have used turned pin sockets, so this won't be an issue methinks).

I also decided not to use a socket for the LS318's, so there is direct contact with the Tempco (with a little thermal grease to be extra sure).

Hope this helps,

Magman


Thanks mate - very helpful 8_)
oldcrow
Hey folks, for the remainder of 2013 I plan to order enough voice boards to make 15 more 4-voice board sets and 10 more single voice board sets. After that it will be a break until sometime after January 1st for a board re-order. I will announce on here when I am restocked for the final run of 2013.

--Crow
/**/
mOBiTh
mr crow

how critical are the tant cap values?

i have a whole load of tants but not 6u8 I think (although I could probably bodge a couple of smaller ones in parallel but that might be ugly)

what are they doing exactly in the circuit exactly?
mOBiTh
also I noticed you're using IC holders for 13600/13700s but not the TL072s

I didn't bother with the TL072s but is there more of a reason to bother with the other ICs?

I'm always curious about overheating ICs and semiconductors. Typically I'll just solder a couple of legs of each IC at a time and wait 10-15 secs. no idea which ICs are more sensitive to heat than others, if at all?
Nordcore
There is no problem with soldering ICs.
At least I never killed an IC with the soldering iron. (Or the cheap unregulated hot air gun to get out these damned 100+ pin smd parts... )
mOBiTh
Nordcore wrote:
There is no problem with soldering ICs.
At least I never killed an IC with the soldering iron. (Or the cheap unregulated hot air gun to get out these damned 100+ pin smd parts... )


haha yeh true - I'll definitely stop worrying about it, unless I feel like trying different ICs in the future. will probably socket the matched transistors.

cheers m
home_listening
Received my package here in Australia! So much PCB...
oldcrow
This week will see the final orders from the initial crOwBX board batches going out: 4 orders to Germany, 2 to US customers and 1 more to the UK.
After orders are sorted, I will be ordering enough voice boards to cover about 12 more 4-voice board sets. As I said a few posts down, when that voice card re-order arrives, they will be the final board sets available in 2013 as the November-January span is a busy one for me.

I will of course have new stock after the first of the year. I will note here when I have the 2013 year-end close-out board sets back in stock.

--Crow
/**/
negativspace
Can I put my name in now for one more voice card set? I've only accumulated 3 of them so far. (I keep catching the tail end of your stock.)

I'd hate to be stuck with a 3-voice... Dead Banana
oldcrow
Er, one voice board and slot adapter? Not sure what you want, exactly. I'll go look at the order history. Guinness ftw!

negativspace wrote:
Can I put my name in now for one more voice card set? I've only accumulated 3 of them so far. (I keep catching the tail end of your stock.)

I'd hate to be stuck with a 3-voice... Dead Banana
negativspace
Yeah, I just need one more voice card + slot adapter. I got the full 1-voice kit on your first run and 2 extra voice/adapter sets on the second run, but of course I'll still need 1 more for a full 4-voice build.

screaming goo yo screaming goo yo
apoisontree
Just received the PCBs. Will you put the schematics and calibration procedure info on your website soon?

That will be quite useful for debugging etc. (and, let's not fool ourselves, in my case, that will be a necessity).
Thanks.

Alex.
Isaiah
apoisontree
Tarkovsky's Stalker? thumbs up
randel
I have an OB-X on my bench, and I've been measuring actual voltages of the instrument in anticipation of a successful build of my crOwBX system. I've noticed a few unexpected things:

1. On the OB-X Control Board, in the S/H circuits, there are unity gain op amps immediately downstream of the Mux chips - A68 for instance. Several of these op amps feed inputs to the voice card directly - FSUS, ASUS, RES and VCFM, for instance.

In each of these cases, the voltage on the input side of the op amp ranges from 0 - 5 volts, and the output ranges from 0 - 5.27 volts, which strikes me as odd for unity gain.

Does the crOwBX host card generate 0 - 5 volts for these signals? If not, do you think the extra 5% voltage contributes to the sound of the instrument? Is there another explanation for the discrepancy?

2. The OB-X gate voltage is 10 volts as specified, and measures a little higher on mine. On the OB-X processor board, A40 is responsible for the gate signals, outputs 5 volts, and appears to be connected directly to the voice cards via the mother board. How does this signal get to 10 volts? Does the crOwBX voice card require a 10 volt gate signal?

Thanks!
apoisontree
@ Isaiah: what else? we're not worthy
thumbs up
randel
I'd like to modify several of the voice cards in the original OB-X to include the gate LED found in the later versions.

Does anyone have the schematic to the newer version voice card?

Or the schematic to the crOwBX voice card? Mr. Green

Does the LED driver look like the one for the OB-Xa?



Thanks!
oldcrow
Schematics in .pdf format are now uplosded to
http://www.cs80.com/crowbx/schempdf/

I am in the process of writing out the calibration procedure, based on the relevant portions of the OB-X service manual.

--Crow
/**/

apoisontree wrote:
Just received the PCBs. Will you put the schematics and calibration procedure info on your website soon?

That will be quite useful for debugging etc. (and, let's not fool ourselves, in my case, that will be a necessity).
Thanks.

Alex.
oldcrow
The LED circuit is pretty much the same as the OB-Xa's. I just use a 33K where the OBXa uses a 47K, which makes no real difference. For the super cheap version, just use a high efficiency LED--one of those that has full brightness at 1mA--and something like a 10K resistor to the gate signal.

--Crow
/**/

randel wrote:
I'd like to modify several of the voice cards in the original OB-X to include the gate LED found in the later versions.

Does anyone have the schematic to the newer version voice card?

Or the schematic to the crOwBX voice card? :mrgreen:

Does the LED driver look like the one for the OB-Xa?



Thanks!
apoisontree
Thanks Scott!
oldcrow
Inline responses below --Crow

randel wrote:
I have an OB-X on my bench, and I've been measuring actual voltages of the instrument in anticipation of a successful build of my crOwBX system. I've noticed a few unexpected things:

1. On the OB-X Control Board, in the S/H circuits, there are unity gain op amps immediately downstream of the Mux chips - A68 for instance. Several of these op amps feed inputs to the voice card directly - FSUS, ASUS, RES and VCFM, for instance.


Right, these are the S/H amplifiers that store the CVs as written by the host CPU (Z80) as it demultiplexes everything off the DAC and 4051s.

randel wrote:
In each of these cases, the voltage on the input side of the op amp ranges from 0 - 5 volts, and the output ranges from 0 - 5.27 volts, which strikes me as odd for unity gain.

Does the crOwBX host card generate 0 - 5 volts for these signals? If not, do you think the extra 5% voltage contributes to the sound of the instrument? Is there another explanation for the discrepancy?


If you look at the OB-X control board schematic you'll notice the power supply for the 4051s, on both the digitizing/panel pot circuits and the voltage storage array circuits, use a 5.6v positive rail. This extra bit of headroom is to account for (and avoid) "endpoint squashing" as a mux channel approaches 5 volts full-scale off the parameter DAC. If Oberheim had used rail-to-rail analog switches, things like the DG508A. etc. then the extra bit of digitizer supply voltage wouldn't be needed. But as he used cheap 405x series parts, which while extremely useful even today, have rail conditions--see the data sheets.

Now, I do not need to do this as I am not using a CPU on the host board for CV distribution through analog switches, so I just use 5 volts. If you plan to do some kind of CPU-controlled voltage store for CVs then whether you need to goose the demux switches with a bit of extra voltage is up to you. SlayerBadger!

randel wrote:
2. The OB-X gate voltage is 10 volts as specified, and measures a little higher on mine. On the OB-X processor board, A40 is responsible for the gate signals, outputs 5 volts, and appears to be connected directly to the voice cards via the mother board. How does this signal get to 10 volts? Does the crOwBX voice card require a 10 volt gate signal?


The OB-X (and crOwBX) gate inputs can use any positive-going gate from about 2v to 15v, the input circuit is made to handle this large span in the case of the cr)wBX. I'd have to check the CEM3310 datasheet to see what the tolerance is for its gate pin.
Nordcore
Quote:
just use a high efficiency LED-
Or use a cheap blue LED as "really high eff". There are even 3mm tinted opaque ones from Kingsbright: L-934MBDL (The cheap ones from Reichelt are pretty the same, at half the cost... )
These work well as status lights with 22k or 33k.
The Real MC
randel wrote:
1. On the OB-X Control Board, in the S/H circuits, there are unity gain op amps immediately downstream of the Mux chips - A68 for instance. Several of these op amps feed inputs to the voice card directly - FSUS, ASUS, RES and VCFM, for instance.

In each of these cases, the voltage on the input side of the op amp ranges from 0 - 5 volts, and the output ranges from 0 - 5.27 volts, which strikes me as odd for unity gain.


Actually the front panel pots have a rail of (+)5.6v and the DAC can generate above this. It has to because the LM311 comparator (A36) has to be able to detect max pot level.

Quote:
Does the crOwBX host card generate 0 - 5 volts for these signals? If not, do you think the extra 5% voltage contributes to the sound of the instrument? Is there another explanation for the discrepancy?


Yup, the host board pots are on a (+)5V rail. Will half a volt change the sound? Not likely, although the resonance CV is reverse polarity and is maximum at ZERO volts. (+)5V CV gives minimum resonance, will another half volt matter? Highly doubt it given the non-linear behavior of CV to resonance. And the host board includes the correct scaling of the EG CVs to emulate the original.

Quote:
2. The OB-X gate voltage is 10 volts as specified, and measures a little higher on mine. On the OB-X processor board, A40 is responsible for the gate signals, outputs 5 volts, and appears to be connected directly to the voice cards via the mother board. How does this signal get to 10 volts? Does the crOwBX voice card require a 10 volt gate signal?


If you are measuring GATE1 (or the rear panel TRIGGER OUT jack) then it will measure about ten volts because of the buffer circuit for external interfacing on the rear panel jacks. The other GATE signals do not have buffers and will be 5 volts.
The Real MC
oldcrow wrote:
randel wrote:
In each of these cases, the voltage on the input side of the op amp ranges from 0 - 5 volts, and the output ranges from 0 - 5.27 volts, which strikes me as odd for unity gain.

Does the crOwBX host card generate 0 - 5 volts for these signals? If not, do you think the extra 5% voltage contributes to the sound of the instrument? Is there another explanation for the discrepancy?


If you look at the OB-X control board schematic you'll notice the power supply for the 4051s, on both the digitizing/panel pot circuits and the voltage storage array circuits, use a 5.6v positive rail. This extra bit of headroom is to account for (and avoid) "endpoint squashing" as a mux channel approaches 5 volts full-scale off the parameter DAC. If Oberheim had used rail-to-rail analog switches, things like the DG508A. etc. then the extra bit of digitizer supply voltage wouldn't be needed. But as he used cheap 405x series parts, which while extremely useful even today, have rail conditions--see the data sheets.


The 405x switches in the OB-X have a design limitation based on power rails which is why the (+)5.6V rail was supposed to prevent "endpoint squashing". Unfortunately, the OB-X also has a design error that is the reason why so many show up for sale in non-working condition.

These conditions don't exist in the CrOwBX system BTW.
randel
oldcrow wrote:


If you plan to do some kind of CPU-controlled voltage store for CVs then whether you need to goose the demux switches with a bit of extra voltage is up to you. SlayerBadger!



Fascinating.

Thank you for the information, and for posting the schematics. I'm now inclined to use a handful of octal DACs to provide the required voltages, and forget about the 5.6v nonsense!

-Randel
mOBiTh
Hey this smt soldering is a lot of fun - I'm hooked!

It's quite tricky doing it left-handed with chopsticks though, I'm gonna buy some tweezers for the next project.

just waiting for molex connectors (£100??? Argh...) and pots to arrive and then all I'm lacking is a PSU for testing.

so about these psu requirements - why do we need +/-19V exactly?

is +/-18V not enough and +/-20V too much or is there some leeway here? Or are we just aiming for as original spec as possible?

I'm assuming the VRegs are not up to too much voltage and too little causes them headroom (I've forgotten the real term) issues? Any way, would love to know a bit more!

I reckon I'm 75% built It's peanut butter jelly time!

Edit: Ok I re-skimmed the thread, so I can see that not having 19V will affect the bias of the oscillator? I'm still curious to know what would happen if we fed +/-20V or even 24V into it?

Edit more: Gonna check out what I can find lying around - if I can find an LM317/337 based supply I'm guessing it should be pretty easy to modify for 19V assuming it's manly enough. tonights little project...
Tescot
applause
Chok
Thanks Apoisontree 8_) and Thanks Scott for documentation and all things for this big project applause

It is Christmas prematurely and I am going to follow the other cloning with interest, that of the best synthesizer of the world...

mangros
mOBiTh wrote:
just waiting for molex connectors (£100??? Argh...)


woah *gulp*

At least I won't have any trouble hitting the free shipping threshold then...
Chok
I am not going to use connectors Molex but rather to cable boards in wired with potentiometers Alpha separated and new design of face before to make a desktop... meh
oldcrow
mOBiTh wrote:
Just waiting for molex connectors (£100??? Argh...) and pots to arrive and then all I'm lacking is a PSU for testing.

so about these psu requirements - why do we need +/-19V exactly?

is +/-18V not enough and +/-20V too much or is there some leeway here? Or are we just aiming for as original spec as possible?

I'm assuming the VRegs are not up to too much voltage and too little causes them headroom (I've forgotten the real term) issues? Any way, would love to know a bit more!


I imagine 18V is fine, the 4-volt overhead is probably a safety margin to allow for voltage droop on long runs of supply rails as well as dealing with the fan-out of the supply into all those local regulators. If you use "low dropout" regulators that have something like 1.2V overhead, you could probably run it even lower.

One note is the FET buffers on each VCO are tied to the +19V rail, probably to assure the ramp does not flatten as it nears +15V. I have not experimented with lower supply rails yet--I am experimenting with other things at the moment. SlayerBadger!

mOBiTh wrote:
Edit: Ok I re-skimmed the thread, so I can see that not having 19V will affect the bias of the oscillator? I'm still curious to know what would happen if we fed +/-20V or even 24V into it?

Edit more: Gonna check out what I can find lying around - if I can find an LM317/337 based supply I'm guessing it should be pretty easy to modify for 19V assuming it's manly enough. tonights little project...


24V is not a good idea as you would then have the vregs holding back 9 volts and trying to dissipate the extra heat. At that point you would need heatsinks on all of them.

I was going to make a +/-19V supply board using LM3x7 parts at some point as a 4-voice system uses less than 500mA per rail.

--Crow
/**/
oldcrow
mOBiTh wrote:
Hey this smt soldering is a lot of fun - I'm hooked!

just waiting for molex connectors (£100??? Argh...) and pots to arrive and then all I'm lacking is a PSU for testing.


I tried to keep the SMT work as minimal as possible. I just prefer SMT caps as you can put them in close for the ideal bypass spec. Lower ESR, too.

If I had my preference the boards would not have used KK156 series Molex connectors, but as I wanted voice cards to drop into a vintage OB-X I didn't have much choice. They're still better than the connector system a Voyetra-8 uses, however. The only thing that had a flakier connector profile was an old computer kit called the Heathkit H8.

--Crow
/**/
EMwhite
oldcrow wrote:
They're still better than the connector system a Voyetra-8 uses, however. The only thing that had a flakier connector profile was an old computer kit called the Heathkit H8.

--Crow
/**/


No, the worst connectors of all times were used by Gottlieb [Pinball] on the System 1 and Sys80 machines in the late 70s and early 80s.

The fact that there was always batter acid leaking in the general area was a double-bonus but synths suffer from this as well.

mOBiTh
Thanks for the extra info crow!

Ideally I'll find something suitable for testing and then build my own ideal one - I really should buy a nice triple bench supply but I'm not flush enough at the moment.

Those connectors look horrid!!
magman
I found out this evening that an Oakley PSU PCB can be adjusted to 19V quite easily. Coupled with a Yamaha PA30 power supply lump, this should provide plenty of power for a CrOwBX, which is quite good as I had one built already, in the 5U case I was already planning to use. This route also means I don't have to spend time sorting out mains connections inside the case.

I'm also going to connect a CGS66 PSU board onto the other output from the Oakley board to give me a 15V power supply in the same case, for a MIDI interface and one or two other modules. The CGS66 is ideal as it includes a distribution board and it is an easy mod to feed it with a DC supply rather than its normal AC supply.
With a PSU sorted! I can start to get into testing mode. nanners

That can wait till the morning though. Time for bed methinks.

Regards

Magman
thebot
magman wrote:
I found out this evening that an Oakley PSU PCB can be adjusted to 19V quite easily. Coupled with a Yamaha PA30 power supply lump, this should provide plenty of power for a CrOwBX, which is quite good as I had one built already, in the 5U case I was already planning to use. This route also means I don't have to spend time sorting out mains connections inside the case.

I'm also going to connect a CGS66 PSU board onto the other output from the Oakley board to give me a 15V power supply in the same case, for a MIDI interface and one or two other modules. The CGS66 is ideal as it includes a distribution board and it is an easy mod to feed it with a DC supply rather than its normal AC supply.
With a PSU sorted! I can start to get into testing mode. nanners

That can wait till the morning though. Time for bed methinks.

Regards

Magman


Excellent! I thought that might be possible but hadn't got round to reading the user guide again for the Oakley PSU, that's taken a big worry out of this project for me. Guess I'll be ordering some PCBs when they come up then!
mOBiTh
dear mr crow

thank you for including a revA vox board in with my three revB boards just to freak me out at 4am the other morning hihi

this project has definitely kept my brain ticking on my week of nights...

so is there anything I need to be aware of with this revA board other than the errata? I've put in all the same components (ish - some vox boards have more 5% resistors than others, and some different brand ICs) where possible but I believe this board has a few less components overall, is that right? i could well be imagining things, I can hardly see anymore after squinting at those silkscreens all week... Dead Banana

what's the typical lead time on front panels people? still never ordered an fpd one...
mOBiTh
Also I noticed an error on the BOM for the host board - a couple of values were swapped in the pdf compared to the board. I've been a dummy and left my docs at work (not back there for a couple of weeks) but I went with the values on the silkscreen in preference to those in the pdf. Not sure if this was a good tactic or not?!

When I've had some sleep I'd try to figure out which pair are swapped. Anyone else notice it? My brain may be lying to me of course...
magman
I've had a chat with Oldcrow about some of these values already, so here's a copy of this info.

I expect these will make it into revisions of the BOM when he has a bit of time, but I bet he's very busy with other aspects of the documentation (I hope so anyway, as I'm getting very close to testing time nanners ), along with plenty of RL issues.

Quote:
oldcrow wrote:
Heya, sorry for the reply delay, was out of town. See inline comments. --Crow

magman wrote:
Hi Scott,

First, R23 is shown on the BOM as 4K7, but the silkscreen on the PCB shows a value of 33K - what is the correct value for this resistor? If the PCB is correct, then the BOM quantities for these values will need to be adjusted.


The proper value is 4K7. 33K was for single voice kits, but 4-voice needs a lower value.

magman wrote:
Next, R2 and R6 have swapped values from the BOM and what is shown on the PCB silkscreen - can you confirm which value is correct?


R2 is 100K, R6 is 4K87.

magman wrote:
R11 is shown on the BOM as both 1K and 100K. The silkscreen shows the value as 1K, so I have assumed this is the correct value. If this assumption is correct, then the BOM quantity for the 100K value should be reduced to 40.


R11 is 1K. I will adjust the 100K qty.

magman wrote:
Now onto the BOM issues.

C40, C45 and C46 are shown in the list of SMD caps, but they are actually through hole Poly caps, so should've listed separately. C45 should also be in itallics, as it is not needed for a 4 voice.

Next for the resistors, which mainly have quantity issues.

1K - 11 (shown as 7)
10K - 8 (shown as 10)
20K - 1 (shown as 3)
47K - 9 ( shown as 8)


So noted. Will update things here, thanks.

magman wrote:
Lastly, I have a question about some of the presets. I don't think a 3362 type preset will actually fit for R52, as the adjacent components are too close. R83 might fit as a 3362 type, but I suspect it may be tight. I would suggest that 3296Z type pots be used for all presets, at least then adjustments can be made with a front panel installed.


Yeah those should be 3296Z types. I use 3296 on my own host boards.


Regards

Magman
3vcos
HI Michael,

Can you post a link to your BOM or perhaps post an excel file to the the forum? i"m a registered user at Digi and I've spent about an hour on the phone with them. They can seem to find your BOM. :-(



The Real MC wrote:
mOBiTh wrote:
So I want to do a single Vox BOM and then order 4 of them, and tweak up the quantities to hit price breaks - is that even possible?


Sure, that's what it's designed for. I have a BOM in Digikey, it should be public under "analoguediehard"
The Real MC
I put the CSV file here

http://www.retrosynth.com/~analoguediehard/studio/keyboards/oberheim_o bx/crowbx-voice-bom-digikey.csv

It was exported from the digikey BOM manager, it should import right back in. This BOM is only the voicecard, have not ordered for the hostboard yet.

3vcos wrote:
HI Michael,

Can you post a link to your BOM or perhaps post an excel file to the the forum? i"m a registered user at Digi and I've spent about an hour on the phone with them. They can seem to find your BOM. :-(



The Real MC wrote:
mOBiTh wrote:
So I want to do a single Vox BOM and then order 4 of them, and tweak up the quantities to hit price breaks - is that even possible?


Sure, that's what it's designed for. I have a BOM in Digikey, it should be public under "analoguediehard"
oldcrow
Wow, and here I tried to not send out any rev A boards. (There are only 5 of them). It will work fine, they only real differences are the correction shown in the errata and note there are no sustain level trim adjustment trimmers, so you will have to use a fixed resistor around 39K in each case.

--Crow
/**/

mOBiTh wrote:
dear mr crow

thank you for including a revA vox board in with my three revB boards just to freak me out at 4am the other morning hihi
3vcos
Woo Hoo! Thanks MC.

Just wanted to say, it's really nice to be able to put a price on components before you decide to pull the plug on a DIY project. This is a big help.

The Real MC wrote:
I put the CSV file here

http://www.retrosynth.com/~analoguediehard/studio/keyboards/oberheim_o bx/crowbx-voice-bom-digikey.csv

It was exported from the digikey BOM manager, it should import right back in. This BOM is only the voicecard, have not ordered for the hostboard yet.

3vcos wrote:
HI Michael,

Can you post a link to your BOM or perhaps post an excel file to the the forum? i"m a registered user at Digi and I've spent about an hour on the phone with them. They can seem to find your BOM. :-(



The Real MC wrote:
mOBiTh wrote:
So I want to do a single Vox BOM and then order 4 of them, and tweak up the quantities to hit price breaks - is that even possible?


Sure, that's what it's designed for. I have a BOM in Digikey, it should be public under "analoguediehard"
mOBiTh
I had so much 'fun' with the digikey ordering system, I just can't wait to use them again. Even the delivery by UPS was an utter fail...
mOBiTh
oldcrow wrote:
Wow, and here I tried to not send out any rev A boards. (There are only 5 of them). It will work fine, they only real differences are the correction shown in the errata and note there are no sustain level trim adjustment trimmers, so you will have to use a fixed resistor around 39K in each case.

--Crow
/**/

mOBiTh wrote:
dear mr crow

thank you for including a revA vox board in with my three revB boards just to freak me out at 4am the other morning hihi


Haha cool, limited edition hihi

might come back to you later on that when I have the boards in front of me again.


Also thanks Magman smile probably should have reread the thread before commencing as I forgot about the trimmer thing. Will order some replacements today
randel
mOBiTh wrote:
Hey this smt soldering is a lot of fun - I'm hooked!

It's quite tricky doing it left-handed with chopsticks though, I'm gonna buy some tweezers for the next project.



Don't forget to purchase a few extra tempco resistors - one sideways squeeze with the tweezers, and they fly across the room, never to be seen again...
mOBiTh
magman wrote:

Lastly, I have a question about some of the presets. I don't think a 3362 type preset will actually fit for R52, as the adjacent components are too close. R83 might fit as a 3362 type, but I suspect it may be tight. I would suggest that 3296Z type pots be used for all presets, at least then adjustments can be made with a front panel installed.


I can confirm that the 3362 types *will* fit under the following circumstances!

R83: Solder the adjacent 100K 1% after you've fitted the pot - the former will be offset slightly.

R52: If you're making a 4voice with carrier board, most the adjacent components will not be fitted (if I read the BOM correctly!) notably the TL072 that would otherwise be in the way. So this pot type will only need revising if you're making a single voice carrier-free version

M
mOBiTh
randel wrote:
mOBiTh wrote:
Hey this smt soldering is a lot of fun - I'm hooked!

It's quite tricky doing it left-handed with chopsticks though, I'm gonna buy some tweezers for the next project.



Don't forget to purchase a few extra tempco resistors - one sideways squeeze with the tweezers, and they fly across the room, never to be seen again...


oops hihi

I've used up all my spare 100n and 1n caps on some other boards that had 2.5mm spaced holes for TH ceramics. The SMTs fit on there perfectly and it looks rather neat!
mOBiTh
mr crow

one other thing

I noticed IC11 on the host board is pointing in the opposite direction to the others. Just checking this is intentional and not a silkscreen error please?

Cheers 8_)
oldcrow
The chip position is indeed reversed and should be installed that way. Quad op-amps have their power pins on the wrong sides. very frustrating

mOBiTh wrote:
mr crow

one other thing

I noticed IC11 on the host board is pointing in the opposite direction to the others. Just checking this is intentional and not a silkscreen error please?

Cheers 8_)
mOBiTh
oldcrow wrote:
The chip position is indeed reversed and should be installed that way. Quad op-amps have their power pins on the wrong sides. very frustrating

mOBiTh wrote:
mr crow

one other thing

I noticed IC11 on the host board is pointing in the opposite direction to the others. Just checking this is intentional and not a silkscreen error please?

Cheers 8_)


hihi good news cos I already soldered it in! hihi
oldcrow
Hi folks, I have ordered more rev2 voice boards to arrive on or near November 12th. I will stock single voice and four voice bare board sets on the sales site at that time. As I noted a while back, these will be the final board sets offered this year. I will try to get orders out before the thanksgiving holiday week, but as November/December are busy for me some orders may be delayed as I may or may not be in town to fill them as fast as I'd like. I'll have more on this year-end run when the boards arrive.

--Crow
/**/
ttown23
oldcrow wrote:
Hi folks, I have ordered more rev2 voice boards to arrive on or near November 12th. I will stock single voice and four voice bare board sets on the sales site at that time. As I noted a while back, these will be the final board sets offered this year. I will try to get orders out before the thanksgiving holiday week, but as November/December are busy for me some orders may be delayed as I may or may not be in town to fill them as fast as I'd like. I'll have more on this year-end run when the boards arrive.

--Crow
/**/


So should those of us who already posted up their orders also order on your online site?

Thanks!
oldcrow
Well, the sales portal is the only way to actually order as it does all my bookkeeping. Posting an order here isn't really an order though it does help me estimate the number of boards to stock. --Crow

ttown23 wrote:
So should those of us who already posted up their orders also order on your online site?
mOBiTh




getting there! I'm only waiting for pots and PSU now I think. havent soldered in the transistors, filmcaps, trimpots and a few other easy bits - reckon the worst is over.

haven't ordered a faceplate yet so not sure when I'll be able to test with switches in place. might solder them in on little easy-to-remove wires for testing. reasonable idea?

this thing is actually smaller than I thought it would be - I thought it might be shoe box sized but it's more lunch box sized (assuming you're reasonably hungry). It's gonna be an awesome chunk of synth... hihi
EMwhite
mOBiTh wrote:

getting there! I'm only waiting for pots and PSU now I think. havent soldered in the transistors, filmcaps, trimpots and a few other easy bits - reckon the worst is over.

haven't ordered a faceplate yet so not sure when I'll be able to test with switches in place. might solder them in on little easy-to-remove wires for testing. reasonable idea?

this thing is actually smaller than I thought it would be - I thought it might be shoe box sized but it's more lunch box sized (assuming you're reasonably hungry). It's gonna be an awesome chunk of synth... hihi


If you have not yet ordered, Stacy (HexInverter) is coordinating a group buy for switches this month so you can save 25 bucks or so (if you typically go for quality, which you should) Every bit helps!
mOBiTh
Cheers I'm sorted for switches because I had 11 of them already.

I tend to use the flatted paddle type, not entirely sure how they'll look for the horizontal switches but find out soon!

Incidentally the board spacing I measured yesterday to be 23.5mm between the two centre voice cards, and 17.5mm between the outer pairs. mr Crow might be able to confirm this? spacers will be nice to have once the build is complete but in the mean time those molex connectors feel pretty solid. £100 solid in fact... Dead Banana

more to come soon I hope!
mOBiTh
Alrighty then, various people are asking about a cost break-down so here are some approximate figures for the uk:

Note: I had a fair amount in stock already: More than half of the resistors, all the electrolytics and tants, all the TL07x's and mux/logic ICs, 11/15 of the switches, so I may well have made a £100 'saving' here

Digikey order - £245 including VAT, and all charges.

Mouser order - £110 inclusive (I only ordered molex connectors and a couple of other cheap bits that I missed off the digikey order)

RS order - £10 for remaining four toggle switches

Tayda - £20 (for metal alpha 9mm pots - cheap! but god knows when they'll arrive...)

Mouser #2 - £55 for PSU and a couple of other bits

FPD Panel - looks like it'll be about £115 roughly using the base config from old crow. Haven't ordered mine as I need to tweak the lettering placement.

I make that £555 + £125 (PCBs) + £100 (Stuff) = £780 (incl VAT)

Time wise I've spent around 25-30 hours actually building and ordering so far roughly, and quite a lot more thinking about it hihi

Hope that's useful to people.
mangros
My boards arrived... all very big and exciting smile

I'm planning parts orders now, so that's a useful breakdown. I'm wavering between 'sod it, just buy everything off the BOM' and trying to cut costs.

Tayda stuff usually takes about a fortnight for me.
mOBiTh
cool, worth ordering a few extras here and there - see notes above.

i ordered with digikey first and then mopped up with mouser later - you won't need both at the same time.

anyway today i've found removing the voice cards from the carrier EXTREMELY difficult, whereas yesterday they came apart easily.

I'm actually amazed I only broke one component (100R res, argh my last one) getting them apart - it was ridiculous. I have no real idea why it was so tricky, but I'm not reassembling mine now until everything is ready for testing.

Unfortunately this makes swiss cheese of my calibration plan. I was hoping to put each voice card in one at a time and calibrate as I go. Not sure I can do this now without having to remove them again, as they only go in happily as pairs and they don't come out happily at all!

mr crow, what's your plan on calibrating multiple voices?
oldcrow
mOBiTh wrote:
mr crow, what's your plan on calibrating multiple voices?


I plug one voice card/slot adapter onto the carrier/host at a time going from back to front and calibrate each one before adding the next. Span and zero of the VCOs can be done from the side with all card installed, as can the pan trim for each voice.
magman
Getting close now. All parts now delivered, most of the components stuffed and I've just finished making a paper face front panel.



Power supplies are now built and tested as well.



Time to get down to some serious testing. It's peanut butter jelly time!

I've also got a Hexinverter MIDI module part built. I should hopefully get this built tomorrow as well.

Magman
krisp14u
magman wrote:




Time to get down to some serious testing. It's peanut butter jelly time!

I've also got a Hexinverter MIDI module part built. I should hopefully get this built tomorrow as well.


hope your bringing this on Sunday Mike
magman
krisp14u wrote:

hope your bringing this on Sunday Mike

It will be at the meet as a bit of Synth porn as a minimum, but ideally it will be making some music. It just depends if I have enough time left.

Anyway, time for bed as I'm getting a bit too tired for detailed work

Magman
mangros
Moneyspinner idea #1:

Use these and cut off the clip with a Dremel or something. I've measured them and they're very close to the headers from the BOM.
At Tayda vs Mouser prices, that's a saving of about £40!


Moneyspinner idea #2:

Using the same type of part for the 90degree connection. They grip reasonably tight and effectively do the job of the sideways connector and the header. The saving would be about £18. This is a lot more dodgy, but might suffice for testing:



I can't see a reliable way of replacing the vertical sockets (without permanent wiring) so I'm going to take the £40 hit on those.
oldcrow
With all orders now shipped until voice boards arrive in mid-November, I have time to actually write up the calibration docs. A fair bit of it follows the OBX service manual's calibration notes, but the EGs and octave ranging will have their own procedures. Nothing is very complicated: most trimmer settings are set once and forget, only the span and zero (scale and init freq) for each VCO may need the occasional adjustment. Mine have not as of yet. SlayerBadger!

Mid-November is the last chance this year to order crOwBX bare board sets. I will not have my next sets of boards in stock until Feb. 2014 at the earliest as the holiday season will be in full swing, never mind Chinese new year which pretty much shuts down China industry for 2 weeks.

--Crow
/**/
magman
That's just about perfect timing oldcrow, applause as I finished building my system on Sunday. nanners

I've been studying the service manual for the OBX I found on the net and the procedure doesn't sound too bad, I just need to have another battle with the Molex connectors to remove some of the voice cards, then I will be ready for alignment exercise (though it will be a day or two until work and other RL issues give me the time to do this).

I've also spotted a couple more small build issues that I will report back on when I have the time.

Regards

Magman
kynsi
Some small hostboard rev 2 BOM-notes as I build:

D12 is missing
Quantity of 1K 5% resistors should be 11
C40, C45 and C46 are through-hole caps, not SMD.

Also an overlay pdf with text-component numbers would be nice. I've spent some time finding the place for a component.

thumbs up
Paradigm X
mOBiTh wrote:
it's more lunch box sized (assuming you're reasonably hungry).


Best description ever lol thumbs up It's motherfucking bacon yo
randel
492 of the 2,412 Voice Card resistors are currently soldered in place - woo hoo!
kynsi
kynsi wrote:
Some small hostboard rev 2 BOM-notes as I build:

D12 is missing
Quantity of 1K 5% resistors should be 11
C40, C45 and C46 are through-hole caps, not SMD.

Also an overlay pdf with text-component numbers would be nice. I've spent some time finding the place for a component.

thumbs up


Doh! Just saw the post from oct 20.. Strange, thought I did a search. Anyway, moving on..
magman
As promised, here's a couple more pointers from my build so far.

On the Host Board R2 and R6 have the right values in the BOM and circuit diagram, but the part numbers are incorrect on the PCB silkscreen. Use the vales as shown on the silkscreen and ignore the part numbers for these parts. I swapped them at first, following the part numbers instead and had to change them back when the Filter ADSR Decay output was giving the wrong output voltage on the connections to the Voice cards. Luckily, I tested all of these voltages before plugging in the Voice Cards.

On the Slot Adaptors, I would recommend installing the pan trimmers at an angle for Board 2 as well as for Boards 1 and 3, as mentioned in the BOM. I actually ripped one of the 100uF caps off the board 3 adaptor with the pan trimmer on board 2 when installing it, due to the close spacing of boards 2 and 3.

Last but no means least, you really need to apply some force to unplug the Slot Adaptors from the Carrier Board. The best way I found was to use a wooden pencil as a fulcrum and also to protect the Carrier Board, then used a broad flat bladed screwdriver to carefully lever up the Slot Adaptor using the gaps between the connectors. This saves a lot of scratches and dents in the edges of cards and it worked for me (and you may as well avoid the dents and scratches I made whilst figuring this out).

Regards

Magman
kynsi
magman wrote:
Quote:
Next, R2 and R6 have swapped values from the BOM and what is shown on the PCB silkscreen - can you confirm which value is correct?


R2 is 100K, R6 is 4K87.


OK, this is confusing. If I trace the circuitboard, R2 on the silkscreen goes to pin 8 and 9 of IC21. Looking at the schematics its value should be 4K87 so the silkscreen is actualy correct, except that designators R2 and R6 are swapped. This is correct, right?

Edit: yes!
kynsi
Doh! d'oh! You were ahead of me..
magman
kynsi wrote:
Doh! d'oh! You were ahead of me..

For the best jokes, timing is everything. hihi

Magman
EMwhite
I don't have any build news, like I just completed soldering 800 components (I wish) but I did reach a major milestone in procuring components. LS318 PDIP. 20 of them!!! applause

I didn't want to post anything until they were actually in my hands but a fellow wiggler in the UK procured from the same outfit and got theirs a while ago.



Here they are, lovely ladies in a row. If you NEED, hurry and contact http://www.micross.com/ They stockpiled 200 on my recommendation as I was going to organize a group-buy but just don't have the money considering everything that is going on.

But I just checked and they have a 2-3 day lead time (vs. the 3-4 week lead time when I ordered).
mono-poly
oldcrow any updates when you'll have 4 voice sets avaible?
ttown23
oldcrow wrote:


Mid-November is the last chance this year to order crOwBX bare board sets. I will not have my next sets of boards in stock until Feb. 2014 at the earliest as the holiday season will be in full swing, never mind Chinese new year which pretty much shuts down China industry for 2 weeks.

--Crow
/**/


Is this also true for the rev.2 expansion board sets? I just tried your site but it said 'sold out'.

Thanks!
oldcrow
Anything that uses a rev. 2 voice board is out of stock until mid-November when the final 60 boards arrive. For that, there will be 9 four-voice sets and something like 7 single-voice sets. That is it for 2013. There will be spare carrier and voice bare boards for sale as well at that time.

Just a general reminder, saying something like "put me down for 4 boards" here on Muff's is not equivalent to ordering from the sales site. Shopify does all the bookkeeping for me so in order to get boards, you must go there. SlayerBadger! SlayerBadger!

(There being http://cs80-com.myshopify.com/collections/crowbx-analog-music-synthesi zer ) Guinness ftw!

--Crow
/**/

ttown23 wrote:
Is this also true for the rev.2 expansion board sets? I just tried your site but it said 'sold out'.

Thanks!
kynsi
Aaarrgh… Finished the hostboard and want to test some original OBX cards, but IC3 is missing.. Why? It's not on the BOM! very frustrating
ttown23
oldcrow wrote:
Anything that uses a rev. 2 voice board is out of stock until mid-November when the final 60 boards arrive. For that, there will be 9 four-voice sets and something like 7 single-voice sets. That is it for 2013. There will be spare carrier and voice bare boards for sale as well at that time.

Just a general reminder, saying something like "put me down for 4 boards" here on Muff's is not equivalent to ordering from the sales site. Shopify does all the bookkeeping for me so in order to get boards, you must go there. SlayerBadger! SlayerBadger!

(There being http://cs80-com.myshopify.com/collections/crowbx-analog-music-synthesi zer ) Guinness ftw!

--Crow
/**/

ttown23 wrote:
Is this also true for the rev.2 expansion board sets? I just tried your site but it said 'sold out'.

Thanks!


OK, I'll check your sales site come mid-November...!

Thanks!
numan7
will there be an item to purchase on the website for the additional parts needed to make a 4 voice system from a 1 voice system and 3 cards?

cheers
oldcrow
Well, futz. Do not know how I missed that one. confused I must have cut that line item in an edit. The good news is you can go to a Radio Shack and get that part. --Crow

kynsi wrote:
Aaarrgh… Finished the hostboard and want to test some original OBX cards, but IC3 is missing.. Why? It's not on the BOM! very frustrating
oldcrow
Eventually, yes. I will offer the individual bare boards as well as "1 voice to 4 voice upgrade" board sets. Not until probably Feb. 2014, however.

I will have some extra carrier boards on hand that can be purchased individually, those will be placed on the sales site around November 13th as I am out for most of a week from Nov. 7th to the 12 at a west-coast conference. --Crow

numan7 wrote:
will there be an item to purchase on the website for the additional parts needed to make a 4 voice system from a 1 voice system and 3 cards?

cheers
kynsi
It's alive!
Luckily I managed to desolder a 4011 from a telefunken m15 card. Stores are closed here in NL till monday and I'm not that patient.. hehe.

Here's a sample with original OBX-card. Very nice!

Thanks Oldcrow!!
filterstein
oldcrow wrote:
Well, futz. Do not know how I missed that one. confused I must have cut that line item in an edit. The good news is you can go to a Radio Shack and get that part. --Crow

kynsi wrote:
Aaarrgh… Finished the hostboard and want to test some original OBX cards, but IC3 is missing.. Why? It's not on the BOM! very frustrating


Radioshack...
They are not around here anymore since the mid 90's eek!
kynsi
Small question: is it also possible to use the 12F675 pic as a noise source (with electric druid code)? A should we only use the PIC12C508A with your source?
oldcrow
I believe Tom's original code was for an F675, so: yes! SlayerBadger!

See http://www.electricdruid.net/index.php?page=projects.noisegen

--Crow
/**/

kynsi wrote:
Small question: is it also possible to use the 12F675 pic as a noise source (with electric druid code)? A should we only use the PIC12C508A with your source?
kynsi
Sweet. Because I managed to fry my pic by placing it in the wrong (tl072) socket! Have some spare 12f675's lying around.
kynsi
I can now confirm that the 12F675 works! thumbs up
LED-man
All parts from reichelt and mouser received.
Ls318 from miross uk ordered.
I build a 4voice with a further voicecard for sale or replacement.
So the building can start by me.

Any idea for a good polyphon midi cv ?
Have only found marienberg and motm650.
sonicwarrior
The MIDIbox CV 1 has a poly mode:
http://www.ucapps.de/midibox_cv.html

And I think the MIDI interface from nordcore also has a poly mode. As you also registered @ sequencer.de and speak German you could ask him here:
http://www.sequencer.de/synthesizer/viewtopic.php?f=13&t=63127
LED-man
sonicwarrior wrote:
The MIDIbox CV 1 has a poly mode:
http://www.ucapps.de/midibox_cv.html

And I think the MIDI interface from nordcore also has a poly mode. As you also registered @ sequencer.de and speak German you could ask him here:
http://www.sequencer.de/synthesizer/viewtopic.php?f=13&t=63127


Thanks, both projects are known.
I have one midi/cv from nordcore - for my modular its cheap and great, but not usable for the obx due to the software setup by using ctrlr.
The ucapps device is to big and expensive for a diy project.
The hexinverter device dont have enough functions.

so i'm looking for a other device -only for the obx.
kynsi
I've built and use the midibox cv1 and it's pretty small and cheap.. Only two pcb's: the pic-based core and the aout_ng. Gives you 8 12 bit cv's and 8 gates.
LED-man
My friend order the marienberg midi cv. Interface.
Good for me.. have enough to solder here..
sonicwarrior
kynsi wrote:
I've built and use the midibox cv1 and it's pretty small and cheap.. Only two pcb's: the pic-based core and the aout_ng. Gives you 8 12 bit cv's and 8 gates.


Only one PCB with the Jan Speck PCB:
http://www.sdiy.de/en/projects/midiboxcv.html
Downside is the expensive MAX525. Maybe someone wants to design a single PCB with more current options like the aout_ng.
magman
I've built one of the HexInverter MIDI2CV modules to use with my CrOwBX and should hopefully get it working tomorrow (miss-ordered by one chip, which should be delivered tomorrow). This looks to be a nice simple 4 channel poly MIDI to CV adaptor that I have designed a basic 1U panel for, to compliment my CrOwBX.

I'll post photo's and panel designs once I've got everything working.

Regards

Magman
oldcrow
I am back from my west coast conference and it looks like my voice board shipment has arrived. I will do an inventory tomorrow and stock board sets at that time. Right now, shower and sleep! Dead Banana

--Crow
/**/
randel
I've found a very small typo on the Voice Card BOM:

Quote:
Optional: for compliance with Oberheim ECO for PW trimming on VCOs, change R3/R74 to 46.4K 1% and
R15/R16 to 34.8K 1%


I believe that R3 should read R73.

Crow, you've done a wonderful job of documenting your work - feel some satisfaction in knowing that we're actually reading it!

-Randel
Nordcore
LED-man wrote:
I have one midi/cv from nordcore - for my modular its cheap and great, but not usable for the obx due to the software setup by using ctrlr.


Whats the problem with that? You set it up once and than you're done.
The settings are memorized permanently, after you've pressed the "store" button in the ctrlr panel.
( You can even build a software which has the required obx-settings as "factory default". Software is open source, can be compiled with a complete "no cost" development chain, and updated via midi... )
LED-man
Nordcore wrote:
LED-man wrote:
I have one midi/cv from nordcore - for my modular its cheap and great, but not usable for the obx due to the software setup by using ctrlr.


Whats the problem with that? You set it up once and than you're done.
The settings are memorized permanently, after you've pressed the "store" button in the ctrlr panel.
( You can even build a software which has the required obx-settings as "factory default". Software is open source, can be compiled with a complete "no cost" development chain, and updated via midi... )


Yes, all is correct what you wrote.
But my friend have other requirements.
My midi cv from you works fine in my modular synth.
oldcrow
Thanks, I find small errors every day, it seems. d'oh! --Crow

randel wrote:
I've found a very small typo on the Voice Card BOM:

I believe that R3 should read R73.

Crow, you've done a wonderful job of documenting your work - feel some satisfaction in knowing that we're actually reading it!

-Randel
oldcrow
Hey folks, the final board sets have been stocked for 2013, see the sales link off http://www.cs80.com/crowbx

Once they're gone, that is it until Feb. 2014. screaming goo yo screaming goo yo screaming goo yo

I'll have some new things for 2014, so stay tuned...

--Crow
/**/
randel
Happiness is a warm LS318 PDIP. Or a tube of them.

Thanks for the micross lead, EMwhite!

randel
Making progress...even my wife comes out to stuff on occasion!

We pour wine, put on our reading glasses, and search for the elusive R139 on the board...

EMwhite
I'm glad others were able to take advantage of them applause

With 12 voice boards in build, have you worked out your mounting plans as of yet? Are you dropping in an 8 voice and building a crOwBX 4-voice or do you have an alternative mounting system and will be driving all 12 from the crOwBX Host board?

Curious... thanks!
The Real MC
That's some serious $$$ in components, Randel...!
mOBiTh
12 voices! drooooooool...

my effort is on hold till payday cos i've overspent drastically recently.

just need my panel and then i'm ready for testing razz
randel
EMwhite wrote:
I'm glad others were able to take advantage of them applause

With 12 voice boards in build, have you worked out your mounting plans as of yet? Are you dropping in an 8 voice and building a crOwBX 4-voice or do you have an alternative mounting system and will be driving all 12 from the crOwBX Host board?

Curious... thanks!


My ridiculously ambitious plans are to build the rest of the OB-X, minus the keyboard, and put it all in a big box with a front panel.

I've been experimenting with quad and octal DACs under microprocessor control, and trying to map out the functionality of the OB-X CPU. This will take some time, for sure.

Recently, I was fortunate to purchase a 4 voice OB-X, so my immediate plans may change. I may try to expand that instrument to 8 voices, and extend the CV bus beyond the case to an external box that will hold another 8 voices.

With this setup, depressing a note would trigger two voice cards, so the fine tuning on the external voice cards will have to be done manually, and I intend to mount the cards vertically.

The Unison mode should sound pretty good... Rawk!
ttown23
oldcrow wrote:
Hey folks, the final board sets have been stocked for 2013, see the sales link off http://www.cs80.com/crowbx

Once they're gone, that is it until Feb. 2014. screaming goo yo screaming goo yo screaming goo yo

I'll have some new things for 2014, so stay tuned...

--Crow
/**/


Heya Crow, was trying to order the vintage board sets, but still says 'sold out'. Any idea when those will be back in stock? Also, do you have the upper panel carrier boards to hold an additional 4 voice cards in the vintage OBX? Thanks!
oldcrow
I do not (yet) have tray boards for vintage OB-X expansion. I'd need to take dimensions from one to make new ones.

I'll have some bare voice boards stocked this week after I see what is left once 4-voice sets run out. Carrier boards and voice+slot pairs I will also add to the catalog this week. --Crow

ttown23 wrote:
Heya Crow, was trying to order the vintage board sets, but still says 'sold out'. Any idea when those will be back in stock? Also, do you have the upper panel carrier boards to hold an additional 4 voice cards in the vintage OBX? Thanks!
ttown23
oldcrow wrote:
I do not (yet) have tray boards for vintage OB-X expansion. I'd need to take dimensions from one to make new ones.

I'll have some bare voice boards stocked this week after I see what is left once 4-voice sets run out. Carrier boards and voice+slot pairs I will also add to the catalog this week. --Crow

ttown23 wrote:
Heya Crow, was trying to order the vintage board sets, but still says 'sold out'. Any idea when those will be back in stock? Also, do you have the upper panel carrier boards to hold an additional 4 voice cards in the vintage OBX? Thanks!


Gotcha, thanks. I check back later this week.

I could take dimensions of the lower vintage OBX tray, if that helps?
randel
oldcrow wrote:
I do not (yet) have tray boards for vintage OB-X expansion. I'd need to take dimensions from one to make new ones.


Crow-

I currently have an 8 voice OB-X in my studio, and would be very happy to take dimensions and high-res photos of the upper tray to help facilitate this process. Please let me know what I can do!

I'll also try to assemble a list of the mechanical hardware and Molex connectors needed.

As the new owner of a 4 voice, and several crOwBX cards, I'm very interested in vintage OB-X expansion.

Thanks!
kynsi
I'm in the middle (or more correctly, near the end) of a 6-voice obx repair. The top voice-carrier board, for voices 5-8 is exactly the same as the one for voice 1-4. Just not all the output components are mounted.
oldcrow
The only critical info I need is the hole mounting dimensions for the board as it mounts to the chassis/frame. I can infer the per-voice board mounting numbers from existing boards. --Crow

randel wrote:
I currently have an 8 voice OB-X in my studio, and would be very happy to take dimensions and high-res photos of the upper tray to help facilitate this process. Please let me know what I can do!

I'll also try to assemble a list of the mechanical hardware and Molex connectors needed.

As the new owner of a 4 voice, and several crOwBX cards, I'm very interested in vintage OB-X expansion.

Thanks!
mandzaro
First of all, thank you Oldcrow for amazing project.

And a question – would it be possible to replace all Molex crimp connectors on the boards with some MTA’s not crimp?

Martin
oldcrow
Molex crimp connectors? everything is MTA. SlayerBadger! SlayerBadger!

Edit: or do you mean on an OB-X tray board? I'd need to see one.

mandzaro wrote:
First of all, thank you Oldcrow for amazing project.

And a question – would it be possible to replace all Molex crimp connectors on the boards with some MTA’s not crimp?

Martin
mandzaro
Thanks, everything with connectors is clear now.
oldcrow
Out for the week on holiday travel, shipments resume next week!

--Crow
/**/
oberling
Hi there - i'm just soldering my evenings away with this great project and am wondering now whether R165 is 27K Ohm as depicted on the silk screen or 33KOhm as in the BOM and Schematic...

edit: actually it's 27K just on the silk screen
shauschildt
Crow
I have to say this is a really great project..I don't know how I hadn't heard about this until now.
As an owner of a mint 4-voice OB-X, I would definitely purchase a new tray board (& 4 voice-set) as a package, once available..How much would that cost altogether?
Again, I'm really excited about this and keep it up!

Best,
S/H
ultravox
Man-oh-man!! I'm soooo glad I kept up with my soldering skills. Now I'll have a 4-voice OB-X (crOwBX) and an ARP 2600 (TTSH).

I'm sure that in time there'll even be a buildable Jupiter 8 and CS-80 out there. love

Til then I'm ordering a crOwBX!
doepferiano
Crow

Is there any hope to see a reissue
of the Board Rev.2 for Oberheim OBX ?
:(((

thanks!
mOBiTh
doepferiano wrote:
Crow

Is there any hope to see a reissue
of the Board Rev.2 for Oberheim OBX ?
:(((

thanks!


Do you mean in January when he re-stocks everything? hihi
doepferiano
I have to put an alarm on! smile
Chok
Hello Scott

I have several questions:

- For the LT1013, which it is necessary to take; the LT1013 CN8 or DN8
Reichelt

- Can you one take 555 cmos (which consume clearly less) ?

- There is incoherence between the values of the BOM and the setting-up concerning the trimmers of the voicecard, Which are the good values for trimmers ?

Thanks
sonicwarrior
Chok wrote:
- For the LT1013, which it is necessary to take; the LT1013 CN8 or DN8
Reichelt


Mouser is both cheaper and handles ICs better than Reichelt. If the exact number isn't specified it usually doesn't matter so just take the cheapest one.
oldcrow
Either flavor of LT1013 is fine. I use CN here.

Which trimmer values need clarification?

Yes, CMOS 555 are fine. I use them here.

Crow
/**/

Chok wrote:
Hello Scott

I have several questions:

- For the LT1013, which it is necessary to take; the LT1013 CN8 or DN8
Reichelt

- Can you one take 555 cmos (which consume clearly less) ?

- There is incoherence between the values of the BOM and the setting-up concerning the trimmers of the voicecard, Which are the good values for trimmers ?

Thanks
Chok
Hi Scott

For the T1 and T4: on part placement board, value is 100k, in BOM, 10k hmmm.....
oldcrow
Ah, OK. I use 100K here. I will tweak the bom. --Crow

Chok wrote:
Hi Scott

For the T1 and T4: on part placement board, value is 100k, in BOM, 10k :hmm:
randel
I've made a dimensioned drawing of the OB-X voicecard carrier board, and a PDF can be found here: http://www.redshift-consulting.com/obx_motherboard.pdf.



I'm working on a drawing of the metalwork.

-Randel
killbot
Crow, any thought for an OBX card I can use as a drop in replacement in my OBXA?

if it is possible to configure the discrete OBX card to work in the OBXA you could greatly increase the number of OBX type synths available for use

I'd buy a set of 8 of those in a heartbeat as I'm sure most OBXA owners would
Nordcore
The OBXA uses CEM3340 VCO Chips and CEM3320 VCF Chips. W/O these you would at least need a lot of discrete parts to emulate them, a really complete non-integrated version of the 3340 is next to impossible.
EMwhite
I think he just wants to put OBX cards in his Xa; if the signals (voltages) and master frequency signal and tuning signals are compatible, it should be just a matter of working out a different connector/board layout to match and if not, some on-board signal conversion which may be more trouble that it's worth and possibly not even fit in the small amount of room remaining.

It would be interesting, fitting a series of OBX voices into OB-Xa. Surely there would be gives and takes on both sides in terms of functionality lost and audio girth added.

I might be wrong on all accounts:
Dead Banana
oldcrow
The OBXa board is a bit different in that it uses a lot of Curtis chips. While I could create discrete equivalent circuits for them, I have other projects happening at the moment so OBXa/OB8 is not really on my list right now. One day, perhaps... --Crow


killbot wrote:
Crow, any thought for an OBX card I can use as a drop in replacement in my OBXA?

if it is possible to configure the discrete OBX card to work in the OBXA you could greatly increase the number of OBX type synths available for use

I'd buy a set of 8 of those in a heartbeat as I'm sure most OBXA owners would
mOBiTh
If it's vaguely possible, I could maybe try it with my OBXa.

I'm going to go compare sizes...

EDIT: So the OBX voice cards are about 15mm wider than the OBXa cards.

The card tray in the OBXa is designed with only a couple of mm between cards so there would need to be some card overlapping jiggery pokery to allow cards 2 and 4 to fit - molex extenders might well work?

The card electrical connection positions appear to be identical - some mounting post rework would need to be done - probably not a massive drama.

From the point of view of the orientation of control and supply voltages etc, I'm gonna take a wild guess and say they're probably very similar (!). Haven't got time to check the manuals just now.

Whether you could get two tiers of four OBX cards (to make an eight voice) in the OBXa I'm not absolutely sure. It probably is possible but won't be trivial...

I'm fairly sure this was discussed somewhere else but can't think where, hmmn hmmm.....
oldcrow
Thomas Henry made the 3340 in a common form:

http://electro-music.com/forum/topic-54623.html

The Interdesign "analog PSoC" kit Curtis used to make his 3310, 20 30 and 40 had rather simple cells, so the circuit itself is not particularly esoteric.

So it can certainly be done. --Crow

Nordcore wrote:
The OBXA uses CEM3340 VCO Chips and CEM3320 VCF Chips. W/O these you would at least need a lot of discrete parts to emulate them, a really complete non-integrated version of the 3340 is next to impossible.
Nordcore
That's what I was thinking about: you need a lot of parts to come close, and still did not have the excellent temperature stability. (The integrated multiplier scheme of the 3340 does not need a tempco which fits the transistor-pair. )
Using these VCOs on a voice board with its given size would require SMD parts. (I think submodules would make some sense ... )
The Real MC
Not only are the molex connectors in different locations, but the OBX card is not electrically interchangeable with the OBXa. And mixing OBX/OBXa cards wouldn't work because you would never get filter cutoff or filter resonance to track between the cards.
The Real MC
oldcrow wrote:
Thomas Henry made the 3340 in a common form:

http://electro-music.com/forum/topic-54623.html

The Interdesign "analog PSoC" kit Curtis used to make his 3310, 20 30 and 40 had rather simple cells, so the circuit itself is not particularly esoteric.

So it can certainly be done. --Crow


Do a patent search using "douglas r curtis". Lotsa of interesting info on the CEM3340 and the current mirrors that were common across the CEM lineage.

CEM3320 - #4,514,704
linear/log converter used in CEM3310/3320/3340 - #4,004,141
killbot
thanks for the brainstorm session everyone,

dang if all that is true it's time to put that idea in the permanent back burner folder

Crow please disregard the question and revert all spare brain power towards more important projects like CS 80 voice boards,

also if you need a blank CS80 voice board I have one thats had quite a few but not all it's parts harvested.

I just saw how similar the crOwBX boards were to some OBXA boards I'm refurbishing and said hey could I somehow get a pile of these and jam them in there? turns out I should have measured them first before asking questions

the crOwBX card is some pretty exciting stuff,

I saw that and started dreaming of a 88 key master controller with polyphonic aftertouch, ribbon controller, hopped up mod section, ability to control a rack of 8 crOxBX cards and assign them to a split or layer between other clone voice card rack units,

add another 16 crOwS80 cards in another rack that would likely be 20U or something,

or another rack full of JP8 or JP6 or P5rev2, control the whole thing with the same keyboard, assign those sound sources to different places in the stereo field with level control between them, recall a ton of stuff from memory where possible including your performance settings,

yeah I know all that is a super PITA, would still be really cool to try and pull it off and since there is a big group of people into this type of stuff might as well start tossing some ideas about polydreams out there.


there are good synth times ahead

Thanks Crow! you'll be getting my full kit order or maybe 2 in the start of next quarter, I hope you keep these available for some time to come.
lilakmonoke
just some short kudos from a fellow wiggler. you guys are totally insane in all the good ways! im a lover of all things oberheim and my vintage 2voice and xpander will follow me to the grave. copying an OBX is such a brilliant and bold endeavour that tom himself would probably support it. i would love to go on that trip too but dont have enough know how so for now am just being amazed ... keep going!
flts
accidental masterplan:

2013: lose 90% of existing diy backlog by selling, giving away and finishing things. order PCB sets for TTSH and crOwBX.

2014: lose money by ordering a few thousand parts. lose friends by spending endless evenings soldering. wonder why the hell i decided to pick such huge projects once again. gain clones of two of the synths i always wish i could own.

-> profit!
oMan
Hi, I am in the last quarter to finish the 4 VOC + Host + Carrier PCB.
@Crow: when do you think you do have some additional doc for calibrate and/or measurement points and jack wiring ready?

Please forgive me if I missed important informations.
Did I miss the link for it?
oldcrow
I'll have the host board calibration document ready shortly. It has been a busy holiday month. --Crow

oMan wrote:
Hi, I am in the last quarter to finish the 4 VOC + Host + Carrier PCB.
@Crow: when do you think you do have some additional doc for calibrate and/or measurement points and jack wiring ready?

Please forgive me if I missed important informations.
Did I miss the link for it?
oMan
[quote="oldcrow"]I'll have the host board calibration document ready shortly. It has been a busy holiday month. --Crow

[/quote]
I second that :zombie:
This week is havy family traffic so no time for electronics anyway :deadbanana:
flts
I made a quick "shopping list" type combined spreadsheet for a 4 voice system for myself. I thought it might be useful to others so feel free to have a look if you want to:

[url]http://tinyurl.com/npo669n[/url] (shortened it because the forum software didn't like my original Google Spreadsheets link)

It is probably not 100% complete and accurate but I tried to combine everything in the individual BOM sheets to one. One thing to note in particular is that I've lumped all the different tolerance resistors together - I only have 1% metal film around anyway so I combined the 5% and 1% rows of same resistance values. So if you want to use 5% as well, the resistor values aren't probably too useful for you.
ttown23
Heya Crow, first of all, Merry Christmas!

Secondly, do you known when you'll have the upper tray done for the OB-X?

Thanks!
bugfight
just getting started on this. hopefully this is a good place for questions. 1st up: is there any doco that allows searching for particular part numbers? (ie find R7 by text search) this would help while stuffing, but i think would be very helpful when troubleshooting, since most designators are underneath the part. even the schematics seem to be unsearchable.
oldcrow
The vector fonts required for silkscreen printing on the boards makes that text not searchable in a pdf. I will try to make a variant of the silkscreen that uses proportional fonts for pdf use. I cannot use that on a board or the alignment of everything gets skewed. --Crow

bugfight wrote:
just getting started on this. hopefully this is a good place for questions. 1st up: is there any doco that allows searching for particular part numbers? (ie find R7 by text search) this would help while stuffing, but i think would be very helpful when troubleshooting, since most designators are underneath the part. even the schematics seem to be unsearchable.
lilakmonoke
are there any audio files around? id love to hear what this sounds like. i could go through all 70 pages now but ... wonderful project you guys are the true heroes of this forum.
spneca
lilakmonoke wrote:
are there any audio files around? id love to hear what this sounds like. i could go through all 70 pages now but ... wonderful project you guys are the true heroes of this forum.


There are audio files if you scroll down to the bottom of http://www.cs80.com/crowbx/.

Also:

Crow, can you list the hardware needed for this (i.e. standoff heights, etc...)?
lilakmonoke
i listened to those before, thanks! in the portamento sweep, thats definitely that obx sound i just played one a while ago. it was surprisingly tame and belonged to chris clark. i think ill jump ship as soon as i have found somebody in berlin that would help me building this. thats the one oberhim synth that im missing all the time ... although having recently rediscovered the matrix-1000 with a patch editor. instant boards of canada!
flts
@Crow,

Happy new year! Do you have an estimate of when the next batch of European board orders will be shipped? Wondering roughly when to expect the two sets of boards I ordered to arrive here.
oldcrow
Happy New Year everyone. I've shipped all but 3 orders before a combination of the holidays, snowstorms and waiting for the post office to deliver my new box of shipping envelopes happened.

These final 3 (including yours flts) ship this week. I will notify each recipient by email when they ship.

Crow
/**/

flts wrote:
@Crow,

Happy new year! Do you have an estimate of when the next batch of European board orders will be shipped? Wondering roughly when to expect the two sets of boards I ordered to arrive here.
flts
yay, thanks!
bugfight
oberling wrote:
Hi there - i'm just soldering my evenings away with this great project and am wondering now whether R165 is 27K Ohm as depicted on the silk screen or 33KOhm as in the BOM and Schematic...

edit: actually it's 27K just on the silk screen


can't find an answer to this, wondering the same thing
spneca
@Crow,

I have purchased an HAA15-0.8-A and modified it with the 10K resistors as shown on your site. However, even with the trimmers at their extremes I am only getting +/- 16.65V, not +/- 19. Am I missing something?

Also, what height should the standoffs be between the voice boards for a 4 voice set?
bugfight
this might be of some interest if others have the condor HAA15-0.8-A
the design is a bit different, not only the part numbers but the values.
i couldn't find a schematic so i just went by the LM723 datasheet.
long story slightly less long, i found that i needed 510r resistors in parallel with R58 and R83 to get to 19v.
i don't really follow how this psu design is working, and these result in lower resistor values than indicated in the datasheet.
i'm guessing there is gain and feedback from the output transistors...
magman
One thing to watch with some Power one PSU's is that there are links that are installed by default to configure them for a 12V range, these need to be cut to make these PSU's work at 15V. I seem the recall that they are labelled WV1 and WV2.

Worth checking spneca, as this could account for the low voltage you are getting at the moment.

Regards

Magman
magman
Double post -sorry.
Regards

Magman
magman
Even a triple post -the system went a little slow on me earlier.

Regards

Magman
oldcrow
This was one of the leftovers going from rev1 to rev2. R165 (and R124) should be 33K, although 27K will work. --Crow

bugfight wrote:
oberling wrote:
Hi there - i'm just soldering my evenings away with this great project and am wondering now whether R165 is 27K Ohm as depicted on the silk screen or 33KOhm as in the BOM and Schematic...

edit: actually it's 27K just on the silk screen


can't find an answer to this, wondering the same thing
spneca
magman wrote:
One thing to watch with some Power one PSU's is that there are links that are installed by default to configure them for a 12V range, these need to be cut to make these PSU's work at 15V. I seem the recall that they are labelled WV1 and WV2.

Worth checking spneca, as this could account for the low voltage you are getting at the moment.

Regards

Magman


That was it! Thanks.
oldcrow
As magman noted the VW1 and VW2 jumpers, if installed, need to be cut. I will note this on the web page entry about power supply modification.

spneca wrote:
@Crow,

I have purchased an HAA15-0.8-A and modified it with the 10K resistors as shown on your site. However, even with the trimmers at their extremes I am only getting +/- 16.65V, not +/- 19. Am I missing something?

Also, what height should the standoffs be between the voice boards for a 4 voice set?
spneca
oldcrow wrote:
As magman noted the VW1 and VW2 jumpers, if installed, need to be cut. I will note this on the web page entry about power supply modification.

spneca wrote:
@Crow,

I have purchased an HAA15-0.8-A and modified it with the 10K resistors as shown on your site. However, even with the trimmers at their extremes I am only getting +/- 16.65V, not +/- 19. Am I missing something?

Also, what height should the standoffs be between the voice boards for a 4 voice set?


Thanks. Looking at the picture now, I can see that it had been done.
oldcrow
I will measure the spacing for the one I assembled. I used a motley selection of spacers and washers to make sure everything was as square as possible. I will also list the panel to host and host to carrier hardware.

spneca wrote:
@Crow,

Also, what height should the standoffs be between the voice boards for a 4 voice set?
mOBiTh
mOBiTh wrote:


Incidentally the board spacing I measured yesterday to be 23.5mm between the two centre voice cards, and 17.5mm between the outer pairs. mr Crow might be able to confirm this? spacers will be nice to have once the build is complete but in the mean time those molex connectors feel pretty solid. £100 solid in fact... Dead Banana



Here are my measurements from before if they help?

I need to get back to this project ASAP...
flts
FWIW for anyone not in possession of LS318, it seems Micross UK still has the PDIP version in stock. I just ordered a bunch for myself, another bunch for friend who's building another unit, and some extras. Ended up costing something like 5.4 euros a piece when shipping and taxes were factored in.
mOBiTh
I got 16 from Micross UK - they come labelled as LS38 it seems (which is detailed in the spec document)
sonicwarrior
mOBiTh wrote:
they come labelled as LS38 it seems (which is detailed in the spec document)


Yep, this also mentioned in my group buy thread and confused me at first.
oMan
Found the 1rst document for Calib the host Card.
Thank You so far This is fun!
ttown23
Heya Crow, any update on the cloning of the vintage OB-X upper 4 card holder?
oberling
oldcrow wrote:
Ah, OK. I use 100K here. I will tweak the bom. --Crow

Chok wrote:
Hi Scott

For the T1 and T4: on part placement board, value is 100k, in BOM, 10k hmmm.....


I just checked the BOM - T1 and T4 are still listed as 10k.
One other issue i have is with R177 being too close to R168 - R177 doesn't fit for me (using the Digikey 3362R-1-103LF as written in the BOM).
It also looks like it's not supposed to fit in the voxcard brd png. How did you solve that? My idea would be to desolder R168 and replace it with a "bent over R169" one... But that wouldn't look that neat, wouldn't it?

edit: spelling
home_listening
Just a couple of questions;

I've seen them before on the website, but currently can't seem to see the schematics on the crowbx website anymore... could anyone provide me with a link?


Also, is it essential to use the 6.8uf tantalum capacitors over an electrolytic equivalent?

Thanks and kind regards
ultravox
Hi Crow,

Your website lists the four voice board set as "sold out". Does this mean the end of production of will you restock? I did see on your that if it's listed as "out of stock" then more boards were on order.

Thanks!
oberling
Hi ultravox,

it's some pages back - but it's definitely findable (from end of October '13):

oldcrow wrote:

Mid-November is the last chance this year to order crOwBX bare board sets. I will not have my next sets of boards in stock until Feb. 2014 at the earliest as the holiday season will be in full swing, never mind Chinese new year which pretty much shuts down China industry for 2 weeks.

--Crow
/**/



... although he might have changed is mind as well in the meantime... hihi
ultravox
oberling wrote:
Hi ultravox,

it's some pages back - but it's definitely findable (from end of October '13):

oldcrow wrote:

Mid-November is the last chance this year to order crOwBX bare board sets. I will not have my next sets of boards in stock until Feb. 2014 at the earliest as the holiday season will be in full swing, never mind Chinese new year which pretty much shuts down China industry for 2 weeks.

--Crow
/**/



... although he might have changed is mind as well in the meantime... hihi


Hehehe, thanks for finding that! I thought I read every post but I guess I missed a few! razz
LED-man
Who has completed a 4voice System ?

Which parts can leaved by building a 4voice ?
Known issues ?
After an invest of more than 1500$ it would be nice to hear some nice sounds..
oMan
Finally, I calibrated the Host Board,
when will be the next step (Carrier Board Calibration) be ready?
Btw please could somebody post a picture for wiring between the Front panel and Host board?
As I am not an audio specialist but an electronic hobbyist, I would really lief a look how others made this. eyes...
LED-man
oMan wrote:
Finally, I calibrated the Host Board,
when will be the next step (Carrier Board Calibration) be ready?
Btw please could somebody post a picture for wiring between the Front panel and Host board?
As I am not an audio specialist but an electronic hobbyist, I would really lief a look how others made this. eyes...


i need this document too as soon as possible,
i´m wondering about other guys here - has nobody finished the obx ?

few pictures from other buildings would be nice.

my OBX build is here:
http://www.dsl-man.de/display/MAIN/Obx+-+Building+Tips
mOBiTh
I'm planning to move my text to avoid the knobs overlapping.

Still need to find time to learn fpd though seriously, i just don't get it
LED-man
mOBiTh wrote:
I'm planning to move my text to avoid the knobs overlapping.

Still need to find time to learn fpd though seriously, i just don't get it


look here for a bigger panel wink
bigger custom panel POC
EMwhite
mOBiTh wrote:
I'm planning to move my text to avoid the knobs overlapping.


You are not going to be able to use skirted or even 1/2" knobs, unless you plan on going with a flying wire type of panel to host board mount. It's actually not a bad idea but LOTS of wiring. Scott took great pains to squeeze all of the controls into a 6 width MOTM format and had to leave rom for the complement of 1/4" jacks below.

I worked on this panel for hours in order to change the look/feel slightly and I stress the word 'slightly'. My goal was to have it look more like the OBX, to provide more separation between text, and ultimately, to provide room for Davies knobs and an actual OBX volume knob.

The aesthetic obsessive in me also did other things like re-order the LEDs which will require a bit of 'rigging' in order to get two of the three LEDs wire formed into their correct spot. I do this all the time (make and already LARGE project even LARGER by tweaking aspects of it).

Well I just received the knobs that were back ordered from the UK but haven't even started building the host board yet; however, my panel lines up with the host board perfectly so it's just a matter of sourcing the correct pots (the ones that Scott prescribed are the type that have a knurled grip on the plastic pot shaft and are not intended to have knobs attached). I'm going with this:



You've got 7 days to learn FPE and then 1 day to submit your panel if you want to take advantage of the 20% off special which is running through the end of the month. And believe me, it's worth your while because at $150 or so, the savings of $30 is nothing to sneeze at consider how many parts you'll need to complete this project hihi
mOBiTh
EMwhite wrote:
mOBiTh wrote:
I'm planning to move my text to avoid the knobs overlapping.



I worked on this panel for hours in order to change the look/feel slightly and I stress the word 'slightly'. My goal was to have it look more like the OBX, to provide more separation between text, and ultimately, to provide room for Davies knobs and an actual OBX volume knob.


You've got 7 days to learn FPE and then 1 day to submit your panel if you want to take advantage of the 20% off special which is running through the end of the month. And believe me, it's worth your while because at $150 or so, the savings of $30 is nothing to sneeze at consider how many parts you'll need to complete this project hihi


Oh you've made a cracking job of that mate! That's exactly what I was aiming for. Have you got a matching coloured Oberheim knob? I reckon it would be easy to spray one to match if not. I saw some for sale somewhere.

Right I need to get my skates on - cheers for the heads-up on the discount!
oldcrow
Hey folks, will have more crowbx calibration docs soon, I got my MOTM-480 MkII production model done and shipped off to Robert just in time for NAMM.
Now that the deadline for that is done, back to crowbx.
Isaiah
oldcrow
Ooh, does mean your CS(R)-80 project is closer to completion?
oMan
oldcrow wrote:

Now that the deadline for that is done, back to crowbx.

Rockin' Banana! nanners
Good news!
mOBiTh
LED-man wrote:
mOBiTh wrote:
I'm planning to move my text to avoid the knobs overlapping.

Still need to find time to learn fpd though seriously, i just don't get it


look here for a bigger panel wink
bigger custom panel POC


I don't want a bigger panel because that would mean shit loads of wiring I don't have time for, and other mounting issues. seriously, i just don't get it
LED-man
carrier calibration document is online:
find here

thanks oldcrow
michaelvertex
Anyone want to build one of these for me? If you have the time AND skill, PM me
mOBiTh
panel ordered screaming goo yo

just need to solder the transistors and mod the psu and I'm about ready for calibration
ttown23
oldcrow wrote:
Hey folks, will have more crowbx calibration docs soon, I got my MOTM-480 MkII production model done and shipped off to Robert just in time for NAMM.
Now that the deadline for that is done, back to crowbx.


Heya crow, any time frame for when the vintage OB-X upper tray will be ready?

Thanks!
Sir Ruff
michaelvertex wrote:
Anyone want to build one of these for me? If you have the time AND skill, PM me


Another interested party here...
LED-man
oldcrow wrote:
Hey folks, will have more crowbx calibration docs soon, I got my MOTM-480 MkII production model done and shipped off to Robert just in time for NAMM.
Now that the deadline for that is done, back to crowbx.


Hi oldcrow,
our obx pcbs are ready for final calibration.
we need the calibration document for the voicecards, please.
and few HQ-pictures of jackwiring.



http://www.dsl-man.de/display/MAIN/Obx+-+Building+Tips
mOBiTh
Sir Ruff wrote:
michaelvertex wrote:
Anyone want to build one of these for me? If you have the time AND skill, PM me


Another interested party here...


I'm not sure how viable it would be in terms of time and cost but I would happily build people them...
mOBiTh


Panels arrived!!!!!!!!!! w00t

Still in protective plastic but looking great.

Hope the holes are in the right place!
LED-man
mOBiTh wrote:
Sir Ruff wrote:
michaelvertex wrote:
Anyone want to build one of these for me? If you have the time AND skill, PM me


Another interested party here...


I'm not sure how viable it would be in terms of time and cost but I would happily build people them...


4voice system:
as a builder you can only lost... too much time - more than 100h.
the Projectmanagement/planning needs minimum 20h
ordering and sort parts 30h, have ordered from 5dealer few times.
soldering/building: minimum 50h
troubleshooting: 10-20h
EMwhite
Not true... (well yes, it's true) If you are really good, you can do it in 2 1/2 weeks at least that's what it sounds like Crow did.

But if, in theory, some rich guy says "I want one and will pay you $2000 just for the labor" ... for a $3,500 four voice synth then ... I have yet to hear one assembled and put though it's proper paces but to some people that might not be too much to pay. Time will tell if this is the best Ober-esque endeavor ever accomplished, or an expensive science project hihi Obviously we are all hoping for the former. If nothing else, the voice cards ought to be good for use in an actual OBX should you stumble across a basket case.

But congrats on that panel, mOBiTh, it looks great. Love getting mail from FPE can't wait to hear the finished product.
LED-man
EMwhite wrote:
Not true... (well yes, it's true)

But if, in theory, some rich guy says "I want one and will pay you $2000 just for the labor" ... for a $3,500 four voice synth then ... I have yet to hear one assembled and put though it's proper paces but to some people that might not be too much to pay. Time will tell if this is the best Ober-esque endeavor ever accomplished, or an expensive science project hihi Obviously we are all hoping for the former. If nothing else, the voice cards ought to be good for use in an actual OBX should you stumble across a basket case.

But congrats on that panel, mOBiTh, it looks great. Love getting mail from FPE can't wait to hear the finished product.


how is your building status ?
do you have a project website with pictures from your build,
it would be nice to share some infos to other "few" builders.
Sir Ruff
EMwhite wrote:
Not true... (well yes, it's true) If you are really good, you can do it in 2 1/2 weeks at least that's what it sounds like Crow did.

But if, in theory, some rich guy says "I want one and will pay you $2000 just for the labor" ... for a $3,500 four voice synth then ... I have yet to hear one assembled and put though it's proper paces but to some people that might not be too much to pay. Time will tell if this is the best Ober-esque endeavor ever accomplished, or an expensive science project hihi Obviously we are all hoping for the former. If nothing else, the voice cards ought to be good for use in an actual OBX should you stumble across a basket case.

But congrats on that panel, mOBiTh, it looks great. Love getting mail from FPE can't wait to hear the finished product.


Maybe it's too early to know what the expected costs are since not many people have built them yet, but I can't see why this wouldn't be a viable option in terms of price.
LED-man
Sir Ruff wrote:
EMwhite wrote:
Not true... (well yes, it's true) If you are really good, you can do it in 2 1/2 weeks at least that's what it sounds like Crow did.

But if, in theory, some rich guy says "I want one and will pay you $2000 just for the labor" ... for a $3,500 four voice synth then ... I have yet to hear one assembled and put though it's proper paces but to some people that might not be too much to pay. Time will tell if this is the best Ober-esque endeavor ever accomplished, or an expensive science project hihi Obviously we are all hoping for the former. If nothing else, the voice cards ought to be good for use in an actual OBX should you stumble across a basket case.

But congrats on that panel, mOBiTh, it looks great. Love getting mail from FPE can't wait to hear the finished product.


Maybe it's too early to know what the expected costs are since not many people have built them yet, but I can't see why this wouldn't be a viable option in terms of price.


hmm... my build is 95% complete, i can told you exactly all prices..
but i´dont know that you would know it wink
material : arround 1700€
time: 100h + calibration of the voiceboards, testing and maybe further troubleshooting.
EMwhite
LED-man wrote:
how is your building status ?
do you have a project website with pictures from your build,
it would be nice to share some infos to other "few" builders.


Mine is terrible where terrible = I have all of the boards (for a 6-voice btw), the LS318 PDIPs, a handful of other components, and a panel complete but NOWHERE. I'm about 6 months behind which is to say that I planned on having the Host board done by Thanksgiving, two-voice done by Christmas and should be done with 4-voice before my birthday (next week) d'oh!

Always happy to see others progress and I've been to your website, thanks for doing that. I don't lack motivation, just time and focus if that makes any sense.
The Real MC
LED-man wrote:
our obx pcbs are ready for final calibration.
we need the calibration document for the voicecards, please.


You can use the OBX service manual for calibrating. The trimpots are the same designators.

The only exceptions are the trimpots for the EGs (R150, R151, R198, R176, R177, R199), OldCrow will have to supply calibration info for those.
mOBiTh
EMwhite wrote:

But congrats on that panel, mOBiTh, it looks great. Love getting mail from FPE can't wait to hear the finished product.


Thanks Mike!

I've seen it in person now and it looks fantastic - super chuffed.

Thanks again for your help and advice 8_)

More building this weekend w00t
mOBiTh
The Real MC wrote:

The only exceptions are the trimpots for the EGs (R150, R151, R198, R176, R177, R199), OldCrow will have to supply calibration info for those.


In the mean time, just guess right?! hihi
oldcrow
Hey folks, I finally have the voice card calibration doc up on the site.

Next week I will be ordering PC boards for another run of crowbx as well as my initial run of the CS80 filter MkII module boards.
LED-man
oldcrow wrote:
Hey folks, I finally have the voice card calibration doc up on the site.

Next week I will be ordering PC boards for another run of crowbx as well as my initial run of the CS80 filter MkII module boards.


It's peanut butter jelly time!

Thanks
YashN
And this is why Old Crow is so busy and leaves us Polysix owners with battery leaks in the dark! razz

Good job on the OB clone board!
mOBiTh
8_)
mOBiTh
Can't see any discussion of J112 orientation and it's not in the voicecard doc so:

Qu1: I have a RevA voice board (ARGH) - looks like the orientation is the same as the other boards - is this right yeh?

Qu2: The little orientation graphics imply that two of the J112s sit with middle leg back (q7 and q8) and two sit with middle leg forward (q11 and q12). Correct?

Work is ruining my life - another two weeks I think...

Dead Banana
oldcrow
Hello, yes the J112s are mount the same as on the RevB. Same orientation, same middle lead seating. --Crow

mOBiTh wrote:
Can't see any discussion of J112 orientation and it's not in the voicecard doc so:

Qu1: I have a RevA voice board (ARGH) - looks like the orientation is the same as the other boards - is this right yeh?

Qu2: The little orientation graphics imply that two of the J112s sit with middle leg back (q7 and q8) and two sit with middle leg forward (q11 and q12). Correct?

mOBiTh
Thanks boss 8_)
mOBiTh
oberling wrote:
oldcrow wrote:
Ah, OK. I use 100K here. I will tweak the bom. --Crow

Chok wrote:
Hi Scott

For the T1 and T4: on part placement board, value is 100k, in BOM, 10k hmmm.....


I just checked the BOM - T1 and T4 are still listed as 10k.
One other issue i have is with R177 being too close to R168 - R177 doesn't fit for me (using the Digikey 3362R-1-103LF as written in the BOM).
It also looks like it's not supposed to fit in the voxcard brd png. How did you solve that? My idea would be to desolder R168 and replace it with a "bent over R169" one... But that wouldn't look that neat, wouldn't it?

edit: spelling


BOM is still incorrect here by the way it seems - T1 and T4 should be 100k multiturns according to the crow.

Damn you Digikey for sending me 1K's instead evil
The Real MC
mOBiTh wrote:
T1 and T4 should be 100k multiturns according to the crow.


I knew they made 10 multiturn and 20 multiturn pots, but 100K multiturn pots?!? Guinness ftw!

razz lol!
aladan
The Real MC wrote:
mOBiTh wrote:
T1 and T4 should be 100k multiturns according to the crow.


I knew they made 10 multiturn and 20 multiturn pots, but 100K multiturn pots?!? Guinness ftw!

razz lol!


The first ever synth where you needed a drill with screwdriver bit for calibration smile
mOBiTh
hihi
Isaiah
Is anyone building their 4-voice as a keyboard or deviating from the layout of the front panel PCB?
I'm considering both, though it seems like a big task...

OldCrow
Will there be more 4-voice sets in stock after Chinese New Year?

How difficult would it be to tap patch points on each voice card for?:
Osc 1 / 2 CV Inputs
Osc 1 / 2 Outputs
Osc 1 / 2 PWM Inputs
VCF CV Input
EG 1 / 2 outputs
oldcrow
Well, CNY is over, so...yes SlayerBadger! I will order boards to stock 12 more 4-voice sets set for avilability mid-March 2014.

As for tapping the various parts of a voice card, all of these are done without much trouble. Mostly some resistors and jacks, etc. --Crow

Isaiah wrote:
OldCrow
Will there be more 4-voice sets in stock after Chinese New Year?

How difficult would it be to tap patch points on each voice card for?:
Osc 1 / 2 CV Inputs
Osc 1 / 2 Outputs
Osc 1 / 2 PWM Inputs
VCF CV Input
EG 1 / 2 outputs
oMan
Hi, for one out of four VOIC the quoted cal procedure has worked. My (VOIC IV)
Code:

Using a digital voltmeter, observe the voltage
value on pin 14 of TL074 op-amp IC1 to common. Apply a gate voltage (+5v) to the gate input to
operate the EGs. This puts both EGs in maximum sustain mode. Adjust trimmer R198 until a reading
of 5.00v is observed. Now checking the voltage reading from pin 14 of TL074 op-amp IC5 to common
and adjust R199 for a reading of 5.00v. This completes the calibration for both EGs.
 


Now, I tried VOICard II (because I need cut of some of white Headers, they disturb the mechanical Position at the Carrier board, but this is an other story.)

VOIC II doe not behave correctly, so I took the VOIC II away again and tried the IV again.
But now it doesn't work anymore. I measure only about 200 Millivolts or so.
Furthermore the current in the +5V supply rises high! luckily there is an current limiter in the 5V supply to about 60mA. The Voltage is falling down below 1Volts.

But I wonder where the high current come from.
Does any of the other builders had this error, too?

A question, should the calibration for this point work without putting the Card at the carrier, too?
mOBiTh
mr crow!

those 300p mica caps on the voice boards - how critical are they in terms of value and type? ie. can I just use ceramic caps, or am i missing something?

can't find the ones I ordered d'oh!
mOBiTh
So I've found:

7 x 330pF mica (Argh need 8!)

4 x 270pF mica

14 x 33pF mica

20 x 330pF polystyrene

a load of ceramics (390pF and 270pF)


What do you reckon the best choice is? Can't tell from the schematic what these are doing exactly?
Isaiah
oldcrow wrote:
Well, CNY is over, so...yes SlayerBadger! I will order boards to stock 12 more 4-voice sets set for avilability mid-March 2014.

As for tapping the various parts of a voice card, all of these are done without much trouble. Mostly some resistors and jacks, etc. --Crow

Isaiah wrote:
OldCrow
Will there be more 4-voice sets in stock after Chinese New Year?

How difficult would it be to tap patch points on each voice card for?:
Osc 1 / 2 CV Inputs
Osc 1 / 2 Outputs
Osc 1 / 2 PWM Inputs
VCF CV Input
EG 1 / 2 outputs


Great news on both points, thanks.

The reason I ask about the patch points is the possibility to add per-voice (not global) modulation like the OB-XA, OB-8 and Prophet 5 Poly-Mod.
Like Osc FM and/or Osc PWM by the Filter EG, and VCF FM by one of the Oscs.
They're both modulation routings I like on my SEM.
I'd just add VCAs (some AC-, some DC-coupled depending on the source and destination) in multiples of 4 as needed.

But maybe to do that is to miss the point of the OB-X, I don't know.
It's kind of a dinosaur (that's a good thing!) - powerful, muscular, primitive, heavy.

What do you think, guys?
oldcrow
Those 330pF mica caps are the tuning capacitors for the filter. If you have film type (polystyrene, polypropylene) they will probably sound the same. I have not actually tested the timbre differences, if any are audible. --Crow

mOBiTh wrote:
mr crow!

those 300p mica caps on the voice boards - how critical are they in terms of value and type? ie. can I just use ceramic caps, or am i missing something?

can't find the ones I ordered :doh:
mOBiTh
oldcrow wrote:
Those 330pF mica caps are the tuning capacitors for the filter. If you have film type (polystyrene, polypropylene) they will probably sound the same. I have not actually tested the timbre differences, if any are audible. --Crow

mOBiTh wrote:
mr crow!

those 300p mica caps on the voice boards - how critical are they in terms of value and type? ie. can I just use ceramic caps, or am i missing something?

can't find the ones I ordered d'oh!


cool - thanks for the quick response. How come they're mica and not ceramic, was it just for tolerance reasons? Some of the mica's I've found at work are 5% and some are 2%.

I've ordered a couple more 330pF 2% for one of the voice cards anyway, so at least a matching pair for that card. Not so cheap these mica caps...

Will test the polys if I get chance too (although not too excited by lots of reassembling etc!)
oldcrow
It sounds like you have a short or improperly-installed IC somewhere. Remove the carrier from the host board, check host board IC directions and apply power to the host board. Measure the supply voltages and if something is not what it should be it is time to examine solder joints for bridges or overflow. If the host checks out, install the carrier with no voice cards and again measure everything. Next is a single voice card, etc.

oMan wrote:
VOIC II doe not behave correctly, so I took the VOIC II away again and tried the IV again.
But now it doesn't work anymore. I measure only about 200 Millivolts or so.
Furthermore the current in the +5V supply rises high! luckily there is an current limiter in the 5V supply to about 60mA. The Voltage is falling down below 1Volts.

But I wonder where the high current come from.
Does any of the other builders had this error, too?

A question, should the calibration for this point work without putting the Card at the carrier, too?
oldcrow
Capacitor technology has changed a lot in 35 years. Back then mica parts were the standard for tuning circuits because they were the cheapest option in the picofarad range that didn't have a +80%/-20% tolerance. Newer ceramic types are probably fine these days, but I've not done a listening test for those. I tend to spec the parts used for tuning that the original design had in order to lessen the likelihood I'd be losing control of one of the "intangibles" that made the OBX sound recognizable as an OBX.
In reality I suspect any differences would only show up on a scope.

I am building another crOwBX and will try film caps for the filters.

Crow
/**/


mOBiTh wrote:
cool - thanks for the quick response. How come they're mica and not ceramic, was it just for tolerance reasons? Some of the mica's I've found at work are 5% and some are 2%.

I've ordered a couple more 330pF 2% for one of the voice cards anyway, so at least a matching pair for that card. Not so cheap these mica caps...

Will test the polys if I get chance too (although not too excited by lots of reassembling etc!)
The Real MC
mOBiTh wrote:
How come they're mica and not ceramic, was it just for tolerance reasons? Some of the mica's I've found at work are 5% and some are 2%.

I've ordered a couple more 330pF 2% for one of the voice cards anyway, so at least a matching pair for that card. Not so cheap these mica caps...

Will test the polys if I get chance too (although not too excited by lots of reassembling etc!)


Crow provided Jameco as a source for those caps. They are silvered mica caps which have really low ESR, excellent stability, and tight tolerance. Essential parameters for critical RC circuits, especially with a pair of filter OTA cells per voice that you REALLY want resonance quality as close as possible between voices in a polyphonic.

If you're just building a single voice monophonic, you can get away with plain mica or film (but not polyester) caps.

Stay away from ceramics for RC filter circuits, they have significant temperature coefficients and wacky tolerance that make them unsuitable.
mOBiTh
The Real MC wrote:
mOBiTh wrote:
How come they're mica and not ceramic, was it just for tolerance reasons? Some of the mica's I've found at work are 5% and some are 2%.

I've ordered a couple more 330pF 2% for one of the voice cards anyway, so at least a matching pair for that card. Not so cheap these mica caps...

Will test the polys if I get chance too (although not too excited by lots of reassembling etc!)


Crow provided Jameco as a source for those caps. They are silvered mica caps which have really low ESR, excellent stability, and tight tolerance. Essential parameters for critical RC circuits, especially with a pair of filter OTA cells per voice that you REALLY want resonance quality as close as possible between voices in a polyphonic.

If you're just building a single voice monophonic, you can get away with plain mica or film (but not polyester) caps.

Stay away from ceramics for RC filter circuits, they have significant temperature coefficients and wacky tolerance that make them unsuitable.


yeh makes sense.

the polys i've got are 1% toll - but i wonder about ESR? I've yet to gain any real understanding of how much variance there is between cap types at audio frequencies...

the other factor in my head is that I'm not looking for perfect symmetry between voices (well tuning maybe!) - that's one of the things i love about my Xa and I'm pretty sure it sounds 'bigger' in unison because of it.

i might designate my easiest to remove voice board as an experimentation board...
mOBiTh
crow another RevA board variation:

There are two extra 10n ceramic caps on the RevB - should I bodge these onto the RevA board?

What did they do?

Also there is a 100n/10n pair near the centre bottom of the board that is reversed on the RevA board - is this bad labelling on the board? Can't see the traces well enough to see if the actual traces are reversed also... hmmm.....

How come there actually are variations between RevA and B? Are these to do with the 3310 part of the circuit?
oMan
oldcrow wrote:
It sounds like you have a short or improperly-installed IC somewhere. Remove the carrier from the host board, check host board IC directions and apply power to the host board. Measure the supply voltages and if something is not what it should be it is time to examine solder joints for bridges or overflow. If the host checks out, install the carrier with no voice cards and again measure everything. Next is a single voice card, etc.


This was what I feared, I did not want to unassemble the mechanical composiztion.
But You are right it must be somewhere at the both boards.
I found it, I misplaced a resistor at the hostboard.
The R150 should have been 33K but I placed 10R.
Directly above are 2 10R restors, I think thats why I had this placement error d'oh!

So, have a big we're not worthy to you.
mOBiTh
The Real MC wrote:
mOBiTh wrote:
How come they're mica and not ceramic, was it just for tolerance reasons? Some of the mica's I've found at work are 5% and some are 2%.

I've ordered a couple more 330pF 2% for one of the voice cards anyway, so at least a matching pair for that card. Not so cheap these mica caps...

Will test the polys if I get chance too (although not too excited by lots of reassembling etc!)


Crow provided Jameco as a source for those caps. They are silvered mica caps which have really low ESR, excellent stability, and tight tolerance. Essential parameters for critical RC circuits, especially with a pair of filter OTA cells per voice that you REALLY want resonance quality as close as possible between voices in a polyphonic.

If you're just building a single voice monophonic, you can get away with plain mica or film (but not polyester) caps.

Stay away from ceramics for RC filter circuits, they have significant temperature coefficients and wacky tolerance that make them unsuitable.


Hey mate - thanks for the insight!

Will just wait for my two matching 2% micas to arrive then.
mOBiTh
so after loads of fucking around I finally have a powered up hostboard




time to start tweaking

need a bigger bench for sure...
mOBiTh
crow my LFO only hits around 12Hz maximum - any thoughts on this?

oh and the sine is actually a triangle!

cheers

m
fracinfrucer
So, the title of this thread was a little deceptive... lol What an awesome project!! thumbs up
mOBiTh
mOBiTh wrote:
crow my LFO only hits around 12Hz maximum - any thoughts on this?

oh and the sine is actually a triangle!

cheers

m


so i'm not sure if there is something up with my R83 100K trimpot but I found R66 (68Kohm) to be too small, so I've swapped it for a 100K which gives me 20Hz max for the LFO.

am I doing something daft?! would love to get this mounted on the panel asap now so I can start getting all those jacks wired in hihi eek!
ttown23
Hey Crow, it seems that my last post was somehow lost in the shuffle.

Any idea on when the top PCB carrier board for the vintage OBX will be ready? I'm badly in need Guinness ftw!
oldcrow
Thats one of the little convenient omissions of the OBX nomenclature: the "sine" *is* in fact a triangle.

For the LFO, it sounds like a resistor in the initial range setting is incorrect. Do you have R66 = 68K?

mOBiTh wrote:
crow my LFO only hits around 12Hz maximum - any thoughts on this?

oh and the sine is actually a triangle!

cheers

m
oldcrow
Er, well, I wasn't really working on one until I had an actual OBX in the workshop to work with. Anyone care to loan me an OBX for a few months? screaming goo yo

ttown23 wrote:
Hey Crow, it seems that my last post was somehow lost in the shuffle.

Any idea on when the top PCB carrier board for the vintage OBX will be ready? I'm badly in need Guinness ftw!
oldcrow
Well it started as an OBX voice card. But then I needed something to test the card, and then I thought "hey, I could mount 4 voices here and it would still fit," and, well, this is the result. SlayerBadger! SlayerBadger!

fracinfrucer wrote:
So, the title of this thread was a little deceptive... lol What an awesome project!! thumbs up
oldcrow
Hey folks, I have ordered bare boards to stock 15 more 4-voice crOwBX board sets to arrive on March 14th, 2014. I will make the inventory available on the sales site once they are checked in. --Crow SlayerBadger! SlayerBadger! SlayerBadger!
ttown23
oldcrow wrote:
Er, well, I wasn't really working on one until I had an actual OBX in the workshop to work with. Anyone care to loan me an OBX for a few months? screaming goo yo

ttown23 wrote:
Hey Crow, it seems that my last post was somehow lost in the shuffle.

Any idea on when the top PCB carrier board for the vintage OBX will be ready? I'm badly in need Guinness ftw!


Well, I totally would if I were out in your neck of the woods!

Unfortunately mine is with my tech here in L.A., waiting on an upper voice card tray... I bought an OB-Xa upper tray thinking that it would work with minor mods, but alas, this is not the case. I could send you the OB-Xa upper tray if that helps though?
JohnnySlick
oldcrow wrote:
Well it started as an OBX voice card. But then I needed something to test the card, and then I thought "hey, I could mount 4 voices here and it would still fit," and, well, this is the result. SlayerBadger! SlayerBadger!


With the mention of new voice boards in stock soon and you working on a second crOwBX, do you consider the project "mission accomplished?"

I know you had mentioned that this was leading into a CS80 clone, but I also remember you mentioning a few "like to haves" over the course of this thread.
oldcrow
I considered the project completed once I got my 4-voice unit fully assembled and tested. w00t

JohnnySlick wrote:
With the mention of new voice boards in stock soon and you working on a second crOwBX, do you consider the project "mission accomplished?"
numan7
will it be possible to order the carrier and slot adaptor board set (for a 4 voice) when the new parts come in?

cheers
The Real MC
oldcrow wrote:
Er, well, I wasn't really working on one until I had an actual OBX in the workshop to work with. Anyone care to loan me an OBX for a few months? screaming goo yo


Can't bear to be without it. Can you measure them at AHMW? It's a bit of disassembly to get to the bare tray and motherboard, you decide whether to take your measurements at start or end of AHMW. Or the night before, I'm staying at Hampton Inn.
mOBiTh
oldcrow wrote:
Thats one of the little convenient omissions of the OBX nomenclature: the "sine" *is* in fact a triangle.

For the LFO, it sounds like a resistor in the initial range setting is incorrect. Do you have R66 = 68K?

mOBiTh wrote:
crow my LFO only hits around 12Hz maximum - any thoughts on this?

oh and the sine is actually a triangle!

cheers

m


I changed my R66 from 68K to 100K - still wondering whether I have a duff trimpot.

Are there likely to be any other implications of swapping the resistor value (eg to external inputs?) to my untrained eye it looks ok hmmm.....
randel
The Real MC wrote:
oldcrow wrote:
Er, well, I wasn't really working on one until I had an actual OBX in the workshop to work with. Anyone care to loan me an OBX for a few months? screaming goo yo


Can't bear to be without it. Can you measure them at AHMW? It's a bit of disassembly to get to the bare tray and motherboard, you decide whether to take your measurements at start or end of AHMW. Or the night before, I'm staying at Hampton Inn.


I posted a dimensioned drawing of the upper carrier board a few months back. The file may be found at:

http://www.redshift-consulting.com/obx_motherboard.pdf

I, too am very interested in this, and would be willing to throw a few dollars at the project if it would help.

I have a 4-voice OB-X that I've recently brought back from the dead.
ttown23
randel wrote:
The Real MC wrote:
oldcrow wrote:
Er, well, I wasn't really working on one until I had an actual OBX in the workshop to work with. Anyone care to loan me an OBX for a few months? screaming goo yo


Can't bear to be without it. Can you measure them at AHMW? It's a bit of disassembly to get to the bare tray and motherboard, you decide whether to take your measurements at start or end of AHMW. Or the night before, I'm staying at Hampton Inn.


I posted a dimensioned drawing of the upper carrier board a few months back. The file may be found at:

http://www.redshift-consulting.com/obx_motherboard.pdf

I, too am very interested in this, and would be willing to throw a few dollars at the project if it would help.

I have a 4-voice OB-X that I've recently brought back from the dead.


Yes we really need this. It does us vintage OBx owners no good to have these wonderful voice card replacements if we don't have the upper carrier tray...!
oldcrow
Yes, I have this, which helps but doesn't tell me quite everything I need to know. Is the board thickness more than 1.56mm for example? What connectors are used on the edge, pillar heights, etc. I can figure some of that out but having access to the actual board will still greatly assist me.

--Crow

randel wrote:
I posted a dimensioned drawing of the upper carrier board a few months back. The file may be found at:

http://www.redshift-consulting.com/obx_motherboard.pdf

I, too am very interested in this, and would be willing to throw a few dollars at the project if it would help.

I have a 4-voice OB-X that I've recently brought back from the dead.
oldcrow
The other inputs to the LFO CV multiplier should not be affected. Is the -15V rail voltage as used by the LFO trimpot actually -15V? --Crow

mOBiTh wrote:
I changed my R66 from 68K to 100K - still wondering whether I have a duff trimpot.

Are there likely to be any other implications of swapping the resistor value (eg to external inputs?) to my untrained eye it looks ok :hmm:
mOBiTh
oldcrow wrote:
The other inputs to the LFO CV multiplier should not be affected. Is the -15V rail voltage as used by the LFO trimpot actually -15V? --Crow

mOBiTh wrote:
I changed my R66 from 68K to 100K - still wondering whether I have a duff trimpot.

Are there likely to be any other implications of swapping the resistor value (eg to external inputs?) to my untrained eye it looks ok hmmm.....


Yep the rails are perfect - it's an odd one. In circuit with no power, the resistance across the 100k trimmer was 44K I think, is this about right?
mOBiTh
Next source of immense frustration:

Appears the PICKit 3 won't program a 12Cxxx - how extremely annoying....... very frustrating

I cannot understand making a product that doesn't work with half your other products - maybe I'm missing something but this just seems fucking retarded.

I tried using my GQ-4X but that failed on verify.

Edit: Not seeing anything on pin3 so I'm guessing the pic is now a right off. What amplitude noise should we expect anyway?
numan7
numan7 wrote:
will it be possible to order the carrier and slot adaptor board set (for a 4 voice) when the new parts come in?

cheers


?

cheers
oldcrow
I might have a few extra once the board sets are bundled, will know more when boards arrive and I count up the overage. --Crow

numan7 wrote:
will it be possible to order the carrier and slot adaptor board set (for a 4 voice) when the new parts come in?

cheers
Isaiah
Isaiah wrote:
oldcrow wrote:
Well, CNY is over, so...yes SlayerBadger! I will order boards to stock 12 more 4-voice sets set for avilability mid-March 2014.

As for tapping the various parts of a voice card, all of these are done without much trouble. Mostly some resistors and jacks, etc. --Crow

Isaiah wrote:
OldCrow
Will there be more 4-voice sets in stock after Chinese New Year?

How difficult would it be to tap patch points on each voice card for?:
Osc 1 / 2 CV Inputs
Osc 1 / 2 Outputs
Osc 1 / 2 PWM Inputs
VCF CV Input
EG 1 / 2 outputs


Great news on both points, thanks.

The reason I ask about the patch points is the possibility to add per-voice (not global) modulation like the OB-XA, OB-8 and Prophet 5 Poly-Mod.
Like Osc FM and/or Osc PWM by the Filter EG, and VCF FM by one of the Oscs.
They're both modulation routings I like on my SEM.
I'd just add VCAs (some AC-, some DC-coupled depending on the source and destination) in multiples of 4 as needed.

But maybe to do that is to miss the point of the OB-X, I don't know.
It's kind of a dinosaur (that's a good thing!) - powerful, muscular, primitive, heavy.

What do you think, guys?


Sorry to quote myself, my question got buried and I'm very curious to hear thoughts hihi
oldcrow
Should certainly be possible; I've done that with filter EG to VCO on a test board, so anything is pretty much doable. --Crow

Isaiah wrote:


(per-voice mod stuff)

Sorry to quote myself, my question got buried and I'm very curious to hear thoughts :hihi:
Isaiah
Thanks, Scott. Good to have my suspicions confirmed hihi

As I said before, I just wonder if adding Prophet 5 Poly Mod-style modulation bus would be missing the point of the OB-X.

My initial thoughts (I won't be tackling this before the Summer) are to replace the shared Pulse Width control with one per Oscillator (1 & 2).
It's not difficult to match them up and I like different width pulses.

If I were to then add the extra modulation, I think it would be like this:
Oscillator 2 output depth control (VCA per voice) with switches to route to Osc 1 Frequency, Osc 1 PW, VCF Frequency.
Filter EG output depth control (VCA per voice) with switches to route to Osc 1 PW, Osc 2 PW, Osc 2 Frequency.

That omits the P5's (possibly) redundant EG to VCF routing.
But maybe the Osc 2 to Osc 1 Frequency makes the X-Mod switch redundant. Maybe not.
Although it's fixed depth FM, I imagine Oberheim would have selected a musical depth.
Also, FM on the Prophet 5 is surely sweeter due to Osc 2's triangle wave, no?

When I patch VCO 2 to FM VCO 1 on my SEM, the pitch goes sharp (about 8 semitones).
How does the OB-X get around this? Are the waveforms de-coupled / centred around 0V?
What I normally patch on my SEM is VCO 2 synced to 1 (nothing unusual there) but then FM or PWM VCO 2 with VCO 1 (the opposite of most fixed-architecture synths).

Just to confirm, on the OB-X Osc 2 is the sync slave and it modulates Osc 1 in X-Mod mode, right?

Sorry, I'm rambling...
mOBiTh
sir crow

I've got some jumper/header/jack wiring questions (apologies if they're obvious!)

1) Host board FT1-4 - what are they for?

2) I'm only having a stereo output pair of jacks so for JP3 and JP5 do I just wire T and G to the tip and sleeve of the jacks? I assume TS is the 'feed through' into the mono summing part of the circuit, that a L+R jack insertion would therefore break? (Although if it's the latter, I can't see much harm in there being a permanent mono feed that is never broken??)

3) My panel allows either a single CV/Gate input to drive all four voices in Unison, or four individual CV/Gates. Should I just normal the individual jacks to the unison jack? Will the octave switch still work in this case? Or should I somehow normalise through the host board, eg. for CV:

CV(unison_jack_in) -> JP11(host_pcb_cv_in) -> JP1 -> 4xCV(in_jacks_switch_con)

Bit lost on this last bit at the moment hmmm.....
mOBiTh
IT LIVESSSS!!!!!!!!!!!!!

OH FUCKING HELL THIS THING SOUNDS AWESOME!!!!!!!!

w00t w00t w00t w00t w00t screaming goo yo screaming goo yo screaming goo yo screaming goo yo hihi hihi hihi hihi hihi
Isaiah
mOBiTh
Congratulations! Rockin' Banana!

Could you describe the X-Mod function, please?
How deep is the FM? How does it sound with the oscillators synced?
I haven't seen or heard any demonstrations that obviously demonstrate the X-Mod.
mOBiTh
Isaiah wrote:
mOBiTh
Congratulations! Rockin' Banana!

Could you describe the X-Mod function, please?
How deep is the FM? How does it sound with the oscillators synced?
I haven't seen or heard any demonstrations that obviously demonstrate the X-Mod.


cheers! ok to clarify, I've only tested it single voice so far and haven't done any calibration much (although it was pretty tuneful to my ears).

first year anniversary today so I have more pressing demands on my time hihi

more to follow over the weekend!! MY ASS IS BLEEDING
Isaiah
mOBiTh
Look forward to hearing your thoughts once it's up and running.
Especially regarding potential mods (see my post above about adding Prophet 5-style polyphonic modulation) and whether modern, high-spec components kill off too much of the variation between voices.

Congratulations on the anniversary! w00t
randel
oldcrow wrote:
Yes, I have this, which helps but doesn't tell me quite everything I need to know. Is the board thickness more than 1.56mm for example? What connectors are used on the edge, pillar heights, etc. I can figure some of that out but having access to the actual board will still greatly assist me.

--Crow


Crow-

My measured board thickness is 1.42mm.

The connectors are all Molex KK 396 series, with circular pins and 16.18mm mating length. The 10-pin part is 26-20-2102, for example.

Molex Part

The only really critical alignment is between the voice cards and the large tray card, and you have all of the voice card measurements. The rest of the connectors (10, 5 and 4 pin) terminate to wire in a crimped housing, and do not have to be precisely located.

The voice cards are mounted to the tray card via an aluminum 3/8in hex standoff with 6-32 threads like this.

I'm a little reluctant to send you my lower tray (if it were lost in shipping, I'd be a broken man), but am happy to take any additional measurements or provide any photography that you need.



Thanks!
randel


Isaiah
Isaiah wrote:
When I patch VCO 2 to FM VCO 1 on my SEM, the pitch goes sharp (about 8 semitones).
How does the OB-X get around this? Are the waveforms de-coupled / centred around 0V?


I just looked at the schematics and Saw from Oscillator 2 goes through a DC-blocking cap (not sure how I missed it before.)
I should try that with my SEM...
mOBiTh
crow!

problem 1: having similar issues with PORTAMENTO trimming on the host board as I had with the LFO, except I can't find an easy fix.

basically my maximum portamento time is about 20% of what it should be, maybe worse.

i'm kinda guessing the per-voice portamento is done on the slot adapters? is this right? can you give me an incoming CV range I should be expecting to the slot adapter (if this is the case) - the schematic is pretty confusing here... hmmm..... is R12 supposed to be cut yeh?

problem 2: with the four slot adapter jumpers installed (I did this by mistake originally) this makes the voice bypass the pan circuit right? with this bypass in place the synth output level was good - nice and loud and full. however, now that i'm using the pan circuits (ie R7/14 cut) the level is extremely low, well in amongst the noise floor. this is the same for all four of my voices - so what am I missing? Actually my RevA voice is somewhat louder, but not useably.

help
oldcrow
Start with slot adapters first: no locations marked "jumper" should be used. Those are only to make the adapter a fully passive device that does not use the portamento or pan mixing circuits--this was to turn the adapter into a riser for servicing voice cards on an OBX. So, R6, R7, R12, R14 are open with nothing installed.

For the portamento CV path on the hostboard, since you are using a 4-voice carrier board most of the single-voice portamento circuit can be omitted as described in the doc.

Checking things in order, verify pin 8 of opamp quad IC20 follows the setting of the portamento control from 0V to ~5V. R144 and R148 should be open and a jumper installed for R165. Make sure resistors R138 to R143 are the values given in the part list.

One note: If you had the unit under power with slot adapter jumper R12 installed you may have damaged host board transistor Q8. R12 grounds molex pin BB-1, which is used to convey the portamento CV multiplier's output to the card slots on the carrier board.

Check things and let me know. I'll examine what issues you could be having with the output. --Criow

mOBiTh wrote:
crow!

problem 1: having similar issues with PORTAMENTO trimming on the host board as I had with the LFO, except I can't find an easy fix.

basically my maximum portamento time is about 20% of what it should be, maybe worse.

i'm kinda guessing the per-voice portamento is done on the slot adapters? is this right? can you give me an incoming CV range I should be expecting to the slot adapter (if this is the case) - the schematic is pretty confusing here... :hmm: is R12 supposed to be cut yeh?

problem 2: with the four slot adapter jumpers installed (I did this by mistake originally) this makes the voice bypass the pan circuit right? with this bypass in place the synth output level was good - nice and loud and full. however, now that i'm using the pan circuits (ie R7/14 cut) the level is extremely low, well in amongst the noise floor. this is the same for all four of my voices - so what am I missing? Actually my RevA voice is somewhat louder, but not useably.

:help:
mOBiTh
Cheers for the quick reply!

So I've done all those checks prior to porta-CV leaving the host board, but got confused as to what CV range should be hitting the slot adapter. Is it 0-5V there too?
mOBiTh
So the CV range I get leaving the host board on KEYCV are:

-2.4V (Porta_min) -> -13.9V (Porta_max)
oldcrow
This sounds about right. I am not near either crowbx at the moment but I will check when I am able. --Crow

mOBiTh wrote:
So the CV range I get leaving the host board on KEYCV are:

-2.4V (Porta_min) -> -13.9V (Porta_max)
mOBiTh
oldcrow wrote:
This sounds about right. I am not near either crowbx at the moment but I will check when I am able. --Crow

mOBiTh wrote:
So the CV range I get leaving the host board on KEYCV are:

-2.4V (Porta_min) -> -13.9V (Porta_max)


cheers, the missus is calling anyway hihi

so I wanna understand the porta circuit better - which components affect the time constant exactly? C7 (on the slot adapter)?

I need to read the 13700 datasheet at some point but wine first. Guinness ftw!
oldcrow
In an effort to make voice cards more manufacturable, I've been converting my test layout to SMT. This is a work in progress so not everything is changed as of yet, and some stuff like trimpots will remain through-hole.

Near the 'VCO1' and 'VCO2' labels are the improved expo transistor pair packaging layouts. SMT, DIP, T-series (can), discrete transistors, and 3 places for the tempco. I *think* that will cover it. SlayerBadger!

This sort of board is the kind I plan to make a batch of for OBX owners who do not necessary want to assemble their own. --Crow

boops
oldcrow wrote:
In an effort to make voice cards more manufacturable, I've been converting my test layout to SMT. This is a work in progress so not everything is changed as of yet, and some stuff like trimpots will remain through-hole.

Near the 'VCO1' and 'VCO2' labels are the improved expo transistor pair packaging layouts. SMT, DIP, T-series (can), discrete transistors, and 3 places for the tempco. I *think* that will cover it. SlayerBadger!

This sort of board is the kind I plan to make a batch of for OBX owners who do not necessary want to assemble their own. --Crow


Hi, i am a obx owner,And need 2 ...thanks
mOBiTh
So I've got working noise and one nicely tuned voice so far (I think!)

Im getting increasingly nervous about repeated insertion and removal of the voice cards (way too much pcb flexing going on without the front panel attached), so I'm loathed to continue until I've got an answer to the two main issues, which are:

1) major loss of level using the adapter boards' pan circuits, levels are fine when bypassing these.

2) too short max portamento time. currently around 2secs over five octaves instead of one octave.

I imagine I'll also run into some stuff with the remaining voice cards as I tune them up, especially the Rev A...

Will Have a deeper look at those pan circuits with a scope tmrw
oldcrow
The panning circuit on the slot adapters uses a 50K pot as well as 2x 150K and 2x 47K resistors, make sure those are all correct and that R7 & R14 are open. I presume you are plugging the slot adapters into the carrier because they will not connect to the front panel's "single voice" volume VCA; the panning circuits expect the carrier board's stereo volume VCAs to be there. Oh, and..make sure the mute switch is to the left for carrier board VCA muting. Mute switch to the right is for single voice/host board VCA muting.

Is the max. portamento time roughly the same for all voice cards?

mOBiTh wrote:
So I've got working noise and one nicely tuned voice so far (I think!)

1) major loss of level using the adapter boards' pan circuits, levels are fine when bypassing these.

2) too short max portamento time. currently around 2secs over five octaves instead of one octave.
mOBiTh
oldcrow wrote:

Is the max. portamento time roughly the same for all voice cards?


Nope they're different - I have two normal ones and one way too short and one way too long one. I could really use an explanation as to how the lag circuit works so that I can fault find? From my tests all the voltages and component values are ~identical so I can't understand the huge difference in behaviour at the moment.

Which components set the lag time constant?

As for output level, maybe my problem is the XMUTE switch? I'm not using a mute switch but do I still need to make any connections here (on the host board) or do I just leave the switch connections open? Looks like it should just be left unsoldered from the schematic? About to chase levels with a scope, will report back.

Have just spent a couple of hours moving capacitors around and trimming molex pins to get the boards to actually fit in together, and one at a time (this required putting some caps on the reverse side of the board to the silkscreen). Must get myself a desoldering station!! Photos to follow to save other people some time...
mOBiTh
For RevB voicecards the mono output level is 1V P-P (approx) for all three.

For RevA voicecard the mono out is 8V P-P!!! I'm guessing there are some component changes I've missed somehow hmmm.....


After the initial pan circuit I get 10% level of the results above.

Also there appears to be no actual panning going on on the final stereo output - it's mono'd somehow. Hmmn.

Back to one voice card now so I can trace the audio signals across the carrier board...
mOBiTh
Aha so the xmute connection is important after all hihi

I've shorted GND(xmute) to OUT(vol) on the carrier board and this has raised the output level to 1V P-P. Useable but not exactly generous.

Crow is this the spec? I would have expected 2.2V P-P??

Can I just change R51 and R28 (Carrier Board) from 22K to 47K resistors?

Pan now works too.

Back to chasing portamento and the extra gain of RevA...
mOBiTh
Ok so the XMUTE jumper on the carrier board has the side-effect of causing a gradually increasing DC offset on the output - no good!

Need some clarification here please mr crow...

Went back through BOM and RevA errata and have found no anomalies.

Crow if you could confirm what P-P output voltages you're getting on your revA and revB boards that would be very helpful please.

Cheers

M
oldcrow
Which output are you measuring from? 1Vp-p is line level which is what to expect from the carrier board output headers.

You do not short XMUTE (that means external mute, btw) to OUT/vol. It mutes by taking XMUTE to ground. Leave it floating for no mute function.

The portamento circcuit on the slot adapters is a self-zeroing programmable lag circuit that uses the OTA to control charge time on the integrator cap (C7). The output of the integrator is the pitch CV, which also is fed back to the input of the circuit to set the new zero point. The part most responsible for the different lag rates between units is the OTA. R2 and R3 tolerances also affect it to a smaller degree.

Yes, you can change the recovery opamp feedback resistors from 22K to 47K.

mOBiTh wrote:
Aha so the xmute connection is important after all :hihi:

I've shorted GND(xmute) to OUT(vol) on the carrier board and this has raised the output level to 1V P-P. Useable but not exactly generous.

Crow is this the spec? I would have expected 2.2V P-P??

Can I just change R51 and R28 (Carrier Board) from 22K to 47K resistors?

Pan now works too.

Back to chasing portamento and the extra gain of RevA...
mOBiTh
Great stuff, plenty to look into on the lag side of things. Luckily those OTAs are socketed so I can try swapping them.

Which leads me to my tracing the signal on my RevA board - I discovered the final 13700 was probably at fault - it now seems to have died 'inexplicably' when I prodded it's input pin with a scope probe.

I get the same signal on RevA and RevB boards at C13 (which leads into the final VCA) so I'm hoping swapping the 13700 will solve the problem (just need to find a spare, shame it wasn't socketed). The VCA CV voltages are the same going into Q25 also.

I'm surprised I killed the OTA so easily - did I do something really stupid??

So anyway, my MASTER L and R outs are still extremely low level now I removed my XMUTE silliness. More chasing tmrw... hmmm.....
oldcrow
It is very easy to destroy an OTA such as the 13600/700 with nothing more than a momentary grounding of the Iabc signal. screaming goo yo

mOBiTh wrote:
I'm surprised I killed the OTA so easily - did I do something really stupid??
The Real MC
mOBiTh wrote:
Which leads me to my tracing the signal on my RevA board - I discovered the final 13700 was probably at fault - it now seems to have died 'inexplicably' when I prodded it's input pin with a scope probe.

I get the same signal on RevA and RevB boards at C13 (which leads into the final VCA) so I'm hoping swapping the 13700 will solve the problem (just need to find a spare, shame it wasn't socketed). The VCA CV voltages are the same going into Q25 also.

I'm surprised I killed the OTA so easily - did I do something really stupid??


You should NEVER probe iabc pin with a scope probe. Scope probes measure voltage. iabc pins are current not voltage. Depending on the scope probe and oscilloscope, you can damage the OTA. The correct measurement tool is a current probe, you need one in the microamp range of the OTA.
mOBiTh
The Real MC wrote:
mOBiTh wrote:
Which leads me to my tracing the signal on my RevA board - I discovered the final 13700 was probably at fault - it now seems to have died 'inexplicably' when I prodded it's input pin with a scope probe.

I get the same signal on RevA and RevB boards at C13 (which leads into the final VCA) so I'm hoping swapping the 13700 will solve the problem (just need to find a spare, shame it wasn't socketed). The VCA CV voltages are the same going into Q25 also.

I'm surprised I killed the OTA so easily - did I do something really stupid??


You should NEVER probe iabc pin with a scope probe. Scope probes measure voltage. iabc pins are current not voltage. Depending on the scope probe and oscilloscope, you can damage the OTA. The correct measurement tool is a current probe, you need one in the microamp range of the OTA.


Thanks for the info guys!!! Showing my ignorance here hihi

My scope/probe combo is 1MOhm so I hoped it wouldn't hurt.

Found a spare so will chuck that in tonight. Should I swap Q25 as well do you think?
sneak-thief
Just out of curiosity: can you kill a CEM VCO by probing it?
The Real MC
sneak-thief wrote:
Just out of curiosity: can you kill a CEM VCO by probing it?


A very open-ended question and the answer is yes you can.

With the exception of power pins, you shouldn't be probing ANY active component unless you know EXACTLY what that pin is.
mOBiTh
Ok sorted my RevA board - R114 was an order of mag lower than it should have been - oopsies! screaming goo yo

So I'm left with a pair of issues (pre-tuning up the rest of the voice cards!)

1) The main gain is still wrong (way too low) on the carrier board.

Everything seems to be in order so my theory is it's something to do with the with the CV signal opening up the VCA. I can measure this as +10V at max vol and 0V at min vol on the OUT(vol) terminal from the host board. This seems logical, is that right?

At max vol, if I measure the voltage at the junction of Q1 (2N3906) and R56 (10K) I get -12.6V. If I artificially raise this voltage towards 0V the VCA opens up. Hmn.

At min vol, the Q1-R56 junction shows -13.9V and the VCA is fully closed. Also, the volume control works in a perfectly linear fashion, so it's behaving correctly it just seems the voltage range is not sufficient to open up the VCA.

Does this make sense? hmmm.....

I replaced Q1 as a precaution and have resoldered and checked the entire board.

Any ideas Crow? Sorry to be a pain! Do these CVs match yours?

(PS: Also I tried swapping LM13700s in the lag circuits and it made no difference. I need sleep...)
mOBiTh
Incidentally - my bodge to raise the CV was lowering the resistance of R57:

By straddling R57 with a 10K (=8K2) the VCA the CV at R56 was about -8V and the synth output five times the amplitude.

Seems like a 4K7 instead of 47K for R57 would give about the correct output level...

hmmm.....
The Real MC
Sounds like the right direction. R57 limits the control current to the common base Q1 so lowering R57 will allow more current into the iabc pin.

You're measuring wrong. You are trying to troubleshoot a current controlled circuit with a voltmeter. The answer is simple ohms law.

Measure the value of R56 (with power off and one leg pulled). Reassemble R56.

With the hostboard powered on, measure the voltage across R56, then divide by the value of R56 and you have the current drawn out of the iabc pin. If you measure negative voltage, just swap the probes. Measure at min volume, repeat for max volume (read next paragraph before starting). iabc at min volume should be around 0.0000001 amps (0.1uA), max volume should be around 0.001 A (1mA). You might want to make a table of values.

Do not exceed 2ma on the iabc pin. You can prevent this by calculating the product of R56 and 2mA (ohms law again), and this will give you the maximum voltage not to exceed.

As you swap resistors for R57, make sure the volume is at min before powering on. As you monitor the voltage across R56 while increasing the volume, make sure you do not exceed that maximum.
mOBiTh
Got it, thanks so much for the rigorous explanation mate, that's extremely helpful smile

What a wonderful place this is!

The Real MC wrote:
Sounds like the right direction. R57 limits the control current to the common base Q1 so lowering R57 will allow more current into the iabc pin.

You're measuring wrong. You are trying to troubleshoot a current controlled circuit with a voltmeter. The answer is simple ohms law.

Measure the value of R56 (with power off and one leg pulled). Reassemble R56.

With the hostboard powered on, measure the voltage across R56, then divide by the value of R56 and you have the current drawn out of the iabc pin. If you measure negative voltage, just swap the probes. Measure at min volume, repeat for max volume (read next paragraph before starting). iabc at min volume should be around 0.0000001 amps (0.1uA), max volume should be around 0.001 A (1mA). You might want to make a table of values.

Do not exceed 2ma on the iabc pin. You can prevent this by calculating the product of R56 and 2mA (ohms law again), and this will give you the maximum voltage not to exceed.

As you swap resistors for R57, make sure the volume is at min before powering on. As you monitor the voltage across R56 while increasing the volume, make sure you do not exceed that maximum.
mOBiTh
So my hunch was right and MC's advice was perfect! 8_)

With a 47K R57 I had 0.0001mA through R56 - 10% of desired.

So changing R57 to 4.7K did the trick (and gave me 0.00097mA) I now have a nice healthy output.

Thanks so much guys - lag circuit time hihi
oldcrow
I am trying to figure out why you needed a much smaller current limiting resistor. Did you install R58/R134 (not used)? Those would try to use the internal OTA linearizing diodes instead of the external biasing. --Crow

mOBiTh wrote:
So my hunch was right and MC's advice was perfect! 8_)

With a 47K R57 I had 0.0001mA through R56 - 10% of desired.

So changing R57 to 4.7K did the trick (and gave me 0.00097mA) I now have a nice healthy output.

Thanks so much guys - lag circuit time :hihi:
mOBiTh
Re. Portamento time - changing C7 to 440nF on my worst board has brought the time to around 2secs per octave so I know I can get them all within range - thanks for that Crow!

they're fairly different on my OBXa so I'll aim for similar variance.

voice tuning next - but first another, no-doubt career destroying, department team building day to survive. grim... Dead Banana
mOBiTh
oldcrow wrote:
I am trying to figure out why you needed a much smaller current limiting resistor. Did you install R58/R134 (not used)? Those would try to use the internal OTA linearizing diodes instead of the external biasing. --Crow

mOBiTh wrote:
So my hunch was right and MC's advice was perfect! 8_)

With a 47K R57 I had 0.0001mA through R56 - 10% of desired.

So changing R57 to 4.7K did the trick (and gave me 0.00097mA) I now have a nice healthy output.

Thanks so much guys - lag circuit time hihi


Do you mean R34/R158 - 15K? Does it say somewhere that they're not used then?!
mOBiTh
mOBiTh wrote:
oldcrow wrote:
I am trying to figure out why you needed a much smaller current limiting resistor. Did you install R58/R134 (not used)? Those would try to use the internal OTA linearizing diodes instead of the external biasing. --Crow

mOBiTh wrote:
So my hunch was right and MC's advice was perfect! 8_)

With a 47K R57 I had 0.0001mA through R56 - 10% of desired.

So changing R57 to 4.7K did the trick (and gave me 0.00097mA) I now have a nice healthy output.

Thanks so much guys - lag circuit time hihi


Do you mean R34/R158 - 15K? Does it say somewhere that they're not used then?!



I saw on the schematic a couple of "try instead of" labels - didn't realise they implied those resistors were optional, oops.

So what exactly are the linearising diodes linearising? Is it essential I roll back to 47K and remove the 15K resistors?
oldcrow
In the schematic it says "try instead of D1~D6/D7~D12". If you have them in there it is no problem, you just need to readjust the current, which you did. SlayerBadger!

For other builders however: omit R34 and R158 from the carrier board if you are using the external diode networks. screaming goo yo

mOBiTh wrote:

Do you mean R34/R158 - 15K? Does it say somewhere that they're not used then?!
oldcrow
The internal (uses 15K bias resistors) and external (D1~D6, D7~D12) linearising diodes are a method of extending the headroom of the amplifier a few dB into the "soft clipping" region, which is part of the OBX sound. A modern VCA like the V2164 or THATcorp parts do not need this sort of trick, but if anything those devices are *too* clean. Guinness ftw! I had to add in a soft clipper for the V2164-based M480 MkII filter, for example. The linearizing diodes add a "predistortion curve" that gets flattened back out as the signal approaches saturation levels. I call this effect "squashing," in the same manner a vacuum tube's saturation point would squash/soft clip a signal instead of a far uglier square-edged transistor hard clip. Another place this was used a lot was headroom extension of the record heads of analog tape.

mOBiTh wrote:
I saw on the schematic a couple of "try instead of" labels - didn't realise they implied those resistors were optional, oops.

So what exactly are the linearising diodes linearising? Is it essential I roll back to 47K and remove the 15K resistors?
mOBiTh
oldcrow wrote:
The internal (uses 15K bias resistors) and external (D1~D6, D7~D12) linearising diodes are a method of extending the headroom of the amplifier a few dB into the "soft clipping" region, which is part of the OBX sound. A modern VCA like the V2164 or THATcorp parts do not need this sort of trick, but if anything those devices are *too* clean. Guinness ftw! I had to add in a soft clipper for the V2164-based M480 MkII filter, for example. The linearizing diodes add a "predistortion curve" that gets flattened back out as the signal approaches saturation levels. I call this effect "squashing," in the same manner a vacuum tube's saturation point would squash/soft clip a signal instead of a far uglier square-edged transistor hard clip. Another place this was used a lot was headroom extension of the record heads of analog tape.



Make's sense, cheers for the explanation!
mOBiTh
oldcrow wrote:

For other builders however: omit R34 and R158 from the carrier board if you are using the external diode networks. screaming goo yo



screaming goo yo


Hang on, where are all the other builders??? seriously, i just don't get it
flts
^- got most of the parts (except for panel and hardware) sorted out here, just waiting for life to get out of the way so i can start soldering...
Techman
Nearly there. Have completed all boards for a four voice, just waiting for some trimmers and edge connectors which should arrive by the weekend. Then testing starts in earnest w00t

Good that the R34/R158 issue was caught because I also stuffed those along with the diodes. I think perhaps a note in the BOM may be required as the schematic is a little ambiguous on this point. thumbs up

Oh, and R59 4n7 is missing from the hostboard BOM
mangros
I'm taking it slowly, keeping an eye on this thread for any tweaks as I go. So far:

Built host/carrier/one voicecard.
Mounted to a drilled out 4U panel.
Decided which colour knobs to use.
Built Oakley PSU (adjusted to 19V)
Made 19V>15V regulator board.
Built but not tested Hex MIDI>CV.

No power has been connected to anything yet though...

Assuming it all goes well I'll be putting an Oakley Little LFO and Equinoxe behind the same panel. Don't know yet whether to bring everything out to front jacks or just route a few obvious connections via switches/attenuators.
oMan
Please can someone tell me the Value for R166 at the Hostboard?
R165 should be 33K, and R166 ?
oldcrow
R165 and R166 are both jumpers that are installed if a carrier board is to be used. --Crow

oMan wrote:
Please can someone tell me the Value for R166 at the Hostboard?
R165 should be 33K, and R166 ?
oMan
oldcrow wrote:
R165 and R166 are both jumpers that are installed if a carrier board is to be used. --Crow

Clear but their values? Zero Ohms?
flts
^- Yes, "jumper" means just a piece of wire / lead that connects two spots together, no resistor.

Finally soldered the first few SMD caps yesterday... It's on.
mOBiTh
So I've come back to it today and something very strange has happened in my absence!

The audio now cuts out, seemingly whenever the level gets to hot due to extreme filter modulation or resonance settings. Hmmn hmmm.....

It wasn't doing this two days ago so I'm at a loss as to what happened in the mean time (aside from lots of beer Guinness ftw!).

I've tried two different voices and they're both similar - a thump and the voice is mute. It'll eventually come back once the resonance (and modulation) is reduced, or the power is reset.

So, scoping the voice output (which is what cuts out, not something on the carrier board) the output level is now now up to 8V P-P which I'm certain is significantly higher than what I had before (will check shortly).

Tried it again now and the output is permanently mute. All voltages are measuring ok on voice boards and main boards.

Also, I notice the filter modulation control appeared to be working back to front! hmmm.....

EDIT: After cooling for a bit the audio is back. With just VCO1 switched on it is 1V P-P ish but once the resonance and second VCO are switched in the amplitude quickly reaches 5V+. More tmrw after some sleep...
oldcrow
It sounds like you have an opamp or OTA going into oscillation. Check the resistors around each OTA to make sure they're the correct value as the signal levels work in the microvolt range. Also, *carefully* check to see if a part is unseemly hot--that will be the one latching up. --Crow

mOBiTh wrote:
So I've come back to it today and something very strange has happened in my absence!

The audio now cuts out, seemingly whenever the level gets to hot due to extreme filter modulation or resonance settings. Hmmn :hmm:

It wasn't doing this two days ago so I'm at a loss as to what happened in the mean time (aside from lots of beer :guinness:).

I've tried two different voices and they're both similar - a thump and the voice is mute. It'll eventually come back once the resonance (and modulation) is reduced, or the power is reset.

So, scoping the voice output (which is what cuts out, not something on the carrier board) the output level is now now up to 8V P-P which I'm certain is significantly higher than what I had before (will check shortly).

Tried it again now and the output is permanently mute. All voltages are measuring ok on voice boards and main boards.

Also, I notice the filter modulation control appeared to be working back to front! :hmm:

EDIT: After cooling for a bit the audio is back. With just VCO1 switched on it is 1V P-P ish but once the resonance and second VCO are switched in the amplitude quickly reaches 5V+. More tmrw after some sleep...
Techman


Next for the smoke test MY ASS IS BLEEDING
oberling
hi crow and all,

reading the schematics (at least i try to - it's the first time, i try to do stuff like this :-D ) i find that the front panel pots are connected to 5V and GND and operate as simple voltage dividers - their middle pin goes more or less directly into an op amp. Therefor i assume that it's not necessary for the potentiometers to stand 0,5W - 0,25W would be ok as well... is that correct? I would like to buy some with longer shafts (in 9mm housing for the footprint to fit) but didn't find any that where able to take 0,5W as those alpha pots are specified to.
magman
oberling wrote:
hi crow and all,

reading the schematics (at least i try to - it's the first time, i try to do stuff like this :-D ) i find that the front panel pots are connected to 5V and GND and operate as simple voltage dividers - their middle pin goes more or less directly into an op amp. Therefor i assume that it's not necessary for the potentiometers to stand 0,5W - 0,25W would be ok as well... is that correct? I would like to buy some with longer shafts (in 9mm housing for the footprint to fit) but didn't find any that where able to take 0,5W as those alpha pots are specified to.

Given that these pots have a resistance of 100k, the current and hence power dissipated is minuscule (if my calculations are correct, about 25mW, or 0.00025W), so this shouldn't be a concern for most commercially available pots.

Hope this helps

Magman
oberling
Thanks a lot It's peanut butter jelly time! also for the explaination - much appreciated... simply Ohm's law.

magman wrote:
oberling wrote:
hi crow and all,

reading the schematics (at least i try to - it's the first time, i try to do stuff like this :-D ) i find that the front panel pots are connected to 5V and GND and operate as simple voltage dividers - their middle pin goes more or less directly into an op amp. Therefor i assume that it's not necessary for the potentiometers to stand 0,5W - 0,25W would be ok as well... is that correct? I would like to buy some with longer shafts (in 9mm housing for the footprint to fit) but didn't find any that where able to take 0,5W as those alpha pots are specified to.

Given that these pots have a resistance of 100k, the current and hence power dissipated is minuscule (if my calculations are correct, about 25mW, or 0.00025W), so this shouldn't be a concern for most commercially available pots.

Hope this helps

Magman
ttown23
randel wrote:
oldcrow wrote:
Yes, I have this, which helps but doesn't tell me quite everything I need to know. Is the board thickness more than 1.56mm for example? What connectors are used on the edge, pillar heights, etc. I can figure some of that out but having access to the actual board will still greatly assist me.

--Crow


Crow-

My measured board thickness is 1.42mm.

The connectors are all Molex KK 396 series, with circular pins and 16.18mm mating length. The 10-pin part is 26-20-2102, for example.

Molex Part

The only really critical alignment is between the voice cards and the large tray card, and you have all of the voice card measurements. The rest of the connectors (10, 5 and 4 pin) terminate to wire in a crimped housing, and do not have to be precisely located.

The voice cards are mounted to the tray card via an aluminum 3/8in hex standoff with 6-32 threads like this.

I'm a little reluctant to send you my lower tray (if it were lost in shipping, I'd be a broken man), but am happy to take any additional measurements or provide any photography that you need.



Thanks!


Awesome!

I would totally send you mine.... but I don't have one!
oldcrow
I've started work on a tray board. Bare ones are likely going to be USD$50.00 given the size. The aluminum support frame is up to someone else. screaming goo yo
3vcos
Just curious, did anyone ever estimate how much it would cost to build a 4 voice? I'm really interested in how much a mouser Or digikey BOM would be for each board.
flts
^- We're beginning to build 4 voice units with a friend. I think we're up to around 750-800 euros now for everything required excluding nuts and bolts (cheap), front panel (I suppose around 150 euros a piece @ Schaeffer) and some kind of nice case to mount everything in.

So I guess we're talking around 1000 euros per finished 4-voice unit here with the sources that we used. For US wigglers I suppose that would be $1000 since you don't have to factor in all the extra VAT and customs fees when ordering from Mouser, Digikey etc. There's been some benefit for the fact that I've been stockpiling a bit and ordering some other things as well, so we've been able to hit some price breaks that wouldn't be sensible if you just bought the minimal required parts yourself.

Of course, this doesn't include the price of MIDI/CV interface that most of us would probably want to run the system as well. We haven't yet decided what to use.
Isaiah
oldcrow wrote:
I've started work on a tray board. Bare ones are likely going to be USD$50.00 given the size. The aluminum support frame is up to someone else. screaming goo yo


Could this be used to interface the control board and the voice cards instead of the carrier board?
Does it have the portamento circuitry on board?
sneak-thief
The original OB-X carrier board just has panning pots for each voice and a 3080-based VCA for the main volume control. This isn't what you're looking for.
Isaiah
Ah, thanks.
Old Crow's L-shaped PCBs for the CrOwBX have the portamento circuitry on board it seems...
Techman
Was scratching the old noggin yesterday while following the Carrier Board calibration procedure. I couldn't get the portamento to work at all when adjusting R143 on the Host Board. Took me a while to realise that the Portamento calibration measurement at C1_KEYCV requires that the Slot adapter is installed first then measure on the Slot adapter CC-1 point d'oh!

That's not mentioned in the Cal procedure BTW seriously, i just don't get it

Now onto Voice card Calibration.
oldcrow
It is board delivery Monday! In this edition I received my prototype VCO153 transpose retrofit that I've already started soldering (left), a +/-15V power supply I made to repair a CS15 (middle) and my new production board for the CS80 filter MkII. SlayerBadger! SlayerBadger! SlayerBadger!

Of interest here is the power supply board as I made it capable of using adjustable regulators for +/-19V at 1A -- enough for a crOwBX 4-voice.

mOBiTh
is that a crowbx midi interface on the left?
oldcrow
No, that is a transposer board for my 1U VCO153 (CS-80 VCO). It is something I've wanted to incorporate for years into that module as it "completes" the VCO by having the same footstop select modes the CS-80 does. It has a hardware MIDI that isn't really part of the plan but I had the space so decided to at least provide the possibility.

If I ever do MIDI for the crowbx it will be part of a backplane. SlayerBadger!

--Crow

mOBiTh wrote:
is that a crowbx midi interface on the left?
randel
oldcrow wrote:
I've started work on a tray board. Bare ones are likely going to be USD$50.00 given the size. The aluminum support frame is up to someone else. screaming goo yo


Crow, you absolutely rock!

Sign me up for one, and I'm happy to test, provide feedback, etc.

Please let me know if there is anything else that you need.

-Randel
ttown23
randel wrote:
oldcrow wrote:
I've started work on a tray board. Bare ones are likely going to be USD$50.00 given the size. The aluminum support frame is up to someone else. screaming goo yo


Crow, you absolutely rock!

Sign me up for one, and I'm happy to test, provide feedback, etc.

Please let me know if there is anything else that you need.

-Randel


Awseome, thanks Crow!!!

I can handle the aluminum support frame, for anyone interested Guinness ftw!
mOBiTh
oldcrow wrote:


If I ever do MIDI for the crowbx it will be part of a backplane. SlayerBadger!

--Crow



screaming goo yo
EMwhite
Will the tray be largely passive and host the adapters per voice card?

Also, what is ETA of power supply board?

Finally (selfish plug) I'm selling my panel, original OBX volume knob (for aesthetics) and the set of off-white brass insert Davies clone knobs pictured several screens above. (I've decommissioned my MOTM modular gear and no longer have the rails/mount in a convenient location so instead I've needed to change course and will be building a wider panel minus all of the jacks in a wood case to sit on top of my Kurzweil 250. Any takers? Contact me via PM.

Thanks Crow and all...
flts
^- I'm not sure if you'll get a better deal locally but sent a PM since I was about to order a panel pretty soon anyway.
oldcrow
The tray is intended for actual Oberheim OBX instruments. A tray board (there are two in an 8-voice OBX) holds four voice cards laid out flat and side by side. The board is about 90% connectors and mounting hardware, and 10% active electronics. Tray boards hold the final volume VCAs and voice panning circuits, although only the lower tray board needs the VCA circuits installed as the upper tray panning circuit is wired to the VCAs of the lower one. A crowbx carrier board is a sort of compact version of a tray board, though not exactly the same.

As for power supply, I will order boards for general sale once I test everything on the production prototypes. --Crow


EMwhite wrote:
Will the tray be largely passive and host the adapters per voice card?

Also, what is ETA of power supply board?
EMwhite
Ah, do trays are not useful or should I say compatible as part or CrOwBX host board/system?

T'you
oldcrow
Tray boards are for the vintage Oberheim OBX. You could use one with crowbx voice boards but you would need a set of cables to connect the tray to a host board. A tray board is 20"/50.8cm wide, too, so you would need a fair bit of room. You would also need either a host board that supported the portamento circuits per voice. I might do a bigger carrier board someday that holds eight voice cards (vertical) and has onboard portamento/pan/volume hardware but that would be down the road a ways.

EMwhite wrote:
Ah, do trays are not useful or should I say compatible as part or CrOwBX host board/system?

T'you
evilxyzzy
Sorry if this was answered, I just went through all 91 (!!) screens of this thread and couldn't find anyone who had tried this, of course I may have missed a screen or two...

Has someone side by side compared these cards to originals? Say by installing 4 new and 4 old in an OB-X?

I've been on again/off again working on an identical project to this but if the boards are close enough that you can't tell them from original then I won't bother with mine as I'd much rather make noise then spend time making it make noise…

Thanks!

-Tom
mOBiTh
Hey crow

Is there a definitive table/list of CVs and value ranges that the host board and slot adapters generate please, as presented to the voice cards themselves?

eg. vol cv = -14V (min volume) -> -2.5V (max volume)

This would make life a lot easier. Don't want to disassemble mine again unless I *really* have to.
The Real MC
mOBiTh wrote:
Hey crow

Is there a definitive table/list of CVs and value ranges that the host board and slot adapters generate please, as presented to the voice cards themselves?

eg. vol cv = -14V (min volume) -> -2.5V (max volume)

This would make life a lot easier. Don't want to disassemble mine again unless I *really* have to.


Resonance CV 0v=max (+)5v=min NOTE REVERSED ACTION OF CV

Attack/Decay/Release CVs 0v=min (-)230mV=max NOTE MINUS SIGN AND MILLIVOLT

edit: PW CV is interesting. 0v=50%, the pulse width narrows as the CV rises then at (+)5v produces zero pulse width. This is how the OBX can turn off audio from an oscillator as there is no waveform present at zero pulse width. If the pulse width trimpot on the voicecard isn't set up correctly, the OBX can't turn it off and this can cause autotune to malfunction.

edit: refer to Crow's correction below on VCO1F and VCO2F CVs.

All others are 0 to (+)5v where 5v is max
mOBiTh
The Real MC wrote:
mOBiTh wrote:
Hey crow

Is there a definitive table/list of CVs and value ranges that the host board and slot adapters generate please, as presented to the voice cards themselves?

eg. vol cv = -14V (min volume) -> -2.5V (max volume)

This would make life a lot easier. Don't want to disassemble mine again unless I *really* have to.


Resonance CV 0v=max (+)5v=min NOTE REVERSED ACTION OF CV

Attack/Decay/Release CVs 0v=min (-)230mV=max NOTE MINUS SIGN AND MILLIVOLT

PW CV 0v=50% (+)5v=minimum pulse width

All others are 0 to (+)5v where 5v is max


Good man! Determined to get to the bottom of this, this weekend.

So in particular, the Filter Modulation Amount (to the right of Filter C/O and Res), is 0V(min) -> 5V(max)?

Cheers!
The Real MC
mOBiTh wrote:
So in particular, the Filter Modulation Amount (to the right of Filter C/O and Res), is 0V(min) -> 5V(max)?


headbang
oldcrow
MC has it covered, save for one detail. VCO1F and VCO2F are CVs that go to the respective VCOs from modulation and reference sources that are not the pitch CV. As such, those CVs can go as low as -2V and as high as +8V, though in practice the 8V would not usually be seen. Setting the octave switch to -1 places a -1.000v reference on the VCOxF busses, for example.

--Crow
/**/

mOBiTh wrote:
Hey crow

Is there a definitive table/list of CVs and value ranges that the host board and slot adapters generate please, as presented to the voice cards themselves?
The Real MC
Another slight correction, please see my edited post on pulse width CV.
The Real MC
oldcrow wrote:
As such, those CVs can go as low as -2V and as high as +8V, though in practice the 8V would not usually be seen. Setting the octave switch to -1 places a -1.000v reference on the VCOxF busses, for example.


Is that what your host board does?

In the OBX, the octave switch in down position doesn't place a (-)1v reference on the VCOxF busses. With oscillator frequency pots all the way CCW, no modulation, no detuning, octave switch=down the VCOxF busses should be zero volts barring some mV offset from the opamps. Assuming correct calibration of trimpots, octave switch=normal bumps the VCOxF up one volt, octave switch=up bumps it up two volts. That's how I calibrated the OBX (and OBSX) according to the service manual.

The CVs can go in the negative range because the LFO triangle wave swings positive AND negative. You could approach the full range with the front panel modulation set to max and the mod lever all the way open, but as Crow said this isn't a common occurence.
mOBiTh
Checked my CVs and am observing the results you guys have already stated plus:


1) VCFF is 0-5V normally but with modulation will hit -3.3V (that's the lowest I got it to anyway) and +8.3V, is this range safe?


2) PW1&2 are -0.4 -> 1.977V approx (min value gives 50% duty cycle) - when oscillators are switched on, or 5V otherwise


3) One of my envelope voltages FDCY is -1.22V max so I've goofed there somewhere by the look of it.

EDIT: 4) My PORTACV is -2V (min) and -14V (max) - I don't get enough range though without drastically changing cap value.

However the STRANGEST thing about today's session so far is that the synth is no longer cutting out with high filter mod/res. Weird...


hmmm.....
mOBiTh
Fixed my FDCY CV - 3am blindness... screaming goo yo
The Real MC
mOBiTh wrote:
Fixed my FDCY CV - 3am blindness... screaming goo yo


Been there zombie
oldcrow
Hm, a minor delay in the delivery of the latest crowbx board batch.

"Your order is confirmed Mar 15, 2014 11:13 and schedule to ship on Mar 18, 2014. We will send you delivery details as shipped. Sorry, the scheduled shipping date is delayed to Mar 18th, 2014 due to reworking of the blemish batch. We will dispatch your PCBs as priority."

So, they'll arrive next week. screaming goo yo screaming goo yo
oldcrow
So I've been doing a couple of experiments on my single-voice crowbx. I wanted to try a couple things, the first of which is a "filter EG variable level modulates VCO#2" action:

http://www.cs80.com/crowbx/FilterEG_VCO2Modulate.mp3

This file is three short samples. First is the two VCOs tuned together but free-running (not synced). Second is VCO#2 responding to a small amount of filter EG while VCO#1 stays fixed and the last sample is what we're after: filter EG modulates VCO#2 which is synced to VCO#1 to obtain that 'harmonic glide' effect. --Crow

I'll have this as well as the four-voice crowbx at AHMW in a few weeks. SlayerBadger!
mOBiTh
w00t
mOBiTh
Right I'm getting close!

But have one final problem with my fourth voice (RevB) - it seems to pollute the VCO2L CV, lowering it slightly so that all four voice boards' VCO2 stays on at low level.

If I remove the fourth voice card (but not slot adapter) the other three voices work correctly. I can measure a 30mV ish difference on this CV bus.

The voice circuit is pretty difficult to figure out in this areas and I'm not sure where to start looking - any ideas please??? Obv if I detach R69 the problem goes away - so I've done this temporarily.

The other issue I had was accurately setting the filter init/scale. My freq counter won't pick up the resonance freq - I tried 1-2ing with an oscillator but I'm crap at suchthings...
oldcrow
Ah, you've found a minor oversight on my part. The fix: change host board R22 from a 33K to a 4.7K resistor. I had this problem on the filter tracking too: since there is no actual logic gate driving D2_TRACK or in this case D6_VCO2L, when enough voices are paralleled up on the carrier board the impedance of the pull-down resistors (and B-E junction in the case of the VCO2L control) diminished to the point the host board pull-up resistor value is too large to pull the signal to the acceptable positive threshold. Changing to the 4.7K will fix this. --Crow

mOBiTh wrote:
Right I'm getting close!

But have one final problem with my fourth voice (RevB) - it seems to pollute the VCO2L CV, lowering it slightly so that all four voice boards' VCO2 stays on at low level.

EMwhite
Is there a log of the various tweaks, corrections, recommended changes that is being kept as an 'official' list?
oldcrow
I write errata sections for each bill of materials. I will update the host board for this latest one. --Crow

EMwhite wrote:
Is there a log of the various tweaks, corrections, recommended changes that is being kept as an 'official' list?
mOBiTh
Coolio. Good job I love taking this thing apart so much screaming goo yo

So which host board resistors need changing exactly?

Anything else you can think of on the host board?

Cheers!
oldcrow
Peake wrote:
If this can be modded to add SEM-style HP/Notch/BP functions, it's mega-win and I'd be all over it.


Doo dee doo... SlayerBadger! Guinness ftw! SlayerBadger! screaming goo yo screaming goo yo screaming goo yo

Isaiah
oldcrow wrote:



thumbs up

Do the tapped FEG and VCF outputs require buffering or amplifying?

To implement the FEG-VCO2 on a 4-voice would require 4 VCAs so that one control can adjust that parameter on all the voices, right?

How would you implement the filter mode on a 4-voice?
4P4T rotary switch?

What about the sweep between LP and HP?
4 VC crossfaders?
phutureboy
oldcrow wrote:

What many have been dreaming of for ages...
mOBiTh
oldcrow wrote:
Ah, you've found a minor oversight on my part. The fix: change host board R22 from a 33K to a 4.7K resistor. I had this problem on the filter tracking too: since there is no actual logic gate driving D2_TRACK or in this case D6_VCO2L, when enough voices are paralleled up on the carrier board the impedance of the pull-down resistors (and B-E junction in the case of the VCO2L control) diminished to the point the host board pull-up resistor value is too large to pull the signal to the acceptable positive threshold. Changing to the 4.7K will fix this. --Crow

mOBiTh wrote:
Right I'm getting close!

But have one final problem with my fourth voice (RevB) - it seems to pollute the VCO2L CV, lowering it slightly so that all four voice boards' VCO2 stays on at low level.



Yo Crow

What I meant was, which resistor do I change to cure the filter tracking issue please?

EDIT: I see this one was already spec'd in the BOM screaming goo yo
mOBiTh
SlayerBadger! SlayerBadger! screaming goo yo screaming goo yo Rockin' Banana! Rockin' Banana! It's motherfucking bacon yo It's motherfucking bacon yo w00t w00t w00t w00t w00t w00t w00t w00t w00t w00t nanners nanners nanners nanners MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING

FUCK YEH!!!!
mOBiTh
Filter tuning still needs a tweak - will tackle this tmrw evening. Couldn't do it easily without a 4ch midi-cv.

Still have a dozen jacks to wire in too.

Time to go do some drinking in the sun Guinness ftw! It's peanut butter jelly time!

Thanks for doing this Crow - I've learnt a load, cursed a load, and spent a shit load, and now I have a fucking monster hihi
Techman
^- nice one. I have one voice calibrated. Still need to do the other three but the sunshine intervened 8_)
Sounding great so far...
oldcrow
The modifications I did to the voice board use a spare (onboard) OTA and opamp for the filter EG->VCO2 function, so that the level control for it can still come from a card edge CV.

The filter mode select uses a tacked-on analog switch to route the filter taps to the VCA. I used a 4PDT switch rigged to operate the analog switch address pins again from the card edge. The notch position is the only passive control as a CV-operated fader is enough parts I'd need to make a board for it. This is more a proof of concept at this time than anything. --Crow

Isaiah wrote:


Do the tapped FEG and VCF outputs require buffering or amplifying?

To implement the FEG-VCO2 on a 4-voice would require 4 VCAs so that one control can adjust that parameter on all the voices, right?

How would you implement the filter mode on a 4-voice?
4P4T rotary switch?

What about the sweep between LP and HP?
4 VC crossfaders?
Isaiah
oldcrow wrote:
The modifications I did to the voice board use a spare (onboard) OTA and opamp for the filter EG->VCO2 function, so that the level control for it can still come from a card edge CV.

The filter mode select uses a tacked-on analog switch to route the filter taps to the VCA. I used a 4PDT switch rigged to operate the analog switch address pins again from the card edge. The notch position is the only passive control as a CV-operated fader is enough parts I'd need to make a board for it. This is more a proof of concept at this time than anything. --Crow

Isaiah wrote:


Do the tapped FEG and VCF outputs require buffering or amplifying?

To implement the FEG-VCO2 on a 4-voice would require 4 VCAs so that one control can adjust that parameter on all the voices, right?

How would you implement the filter mode on a 4-voice?
4P4T rotary switch?

What about the sweep between LP and HP?
4 VC crossfaders?


Wowee zowee!
I didn't know the necessary spare parts for the FEG->VCO 2 FM were already on board.
Is there an unused card edge CV that can be assigned to this?
I'm thinking about a P5 Poly-Mod-style arrangement with a control for Filter EG Depth and switches to route it to VCO 1 PW, VCO 2 PW or VCO 2 Frequency.

Sorry, when you say analog switch is "tacked on", do you mean added to the original voice cards and included on the CrOwBX voice cards, or on a seperate PCB?
oldcrow
There are four unused connector pins called X1 through X4 that were part of the vintage voice board. Two pins were unused VCO modulation input options and two were unused PWM input options. (I think Oberheim had his eye on a kind of poly-mod but didn't finish it for the OBX release) I used three of these signals for the EG>VCO2 level control and filter mode select instead.

You can route the signals you describe in a similar manner to the filter mode select using an analog switch. When I say "tacked on" I mean I added the part to an existing board as a kludge. --Crow

Isaiah wrote:


Wowee zowee!
I didn't know the necessary spare parts for the FEG->VCO 2 FM were already on board. Is there an unused card edge CV that can be assigned to this? I'm thinking about a P5 Poly-Mod-style arrangement with a control for Filter EG Depth and switches to route it to VCO 1 PW, VCO 2 PW or VCO 2 Frequency.

Sorry, when you say analog switch is "tacked on", do you mean added to the original voice cards and included on the CrOwBX voice cards, or on a seperate PCB?
mOBiTh
so could these be used to give different VCO offsets for each voice card, ie. to trigger chords with a single CV/gate input? that would be super useful!

Think I'm going to make a small breakout panel to sit next to my main panel to house the midi interface and all the extra mods we come up with hihi
mOBiTh




Test rig!!!
spneca
mOBiTh wrote:




Test rig!!!


Nice Mutable Instruments Eurorack Module tester!
mOBiTh
Here's how I mounted my four voice card LEDs in the front panel - superglue and 6mm spacers with a blob of gluegun to hold them in place (not shown)





mOBiTh
spneca wrote:


Nice Mutable Instruments Eurorack Module tester!


Yep that's just powering the hexinverter midi-cv module.

That module tester would be really good if it did a few more obvious things.

For example. You can't just switch and leave the gate ON - it always pulses. Annoying!

Any you can't just set and leave the CV output - it will either LFO or octave jump - but no constant value!!!

Needs a software upgrade (maybe there is one?) but that's off-topic for sure...
Techman

Here's a bit of my test rig. Midi to CV duties performed by the PolyDAC in my Oakley modular.
The Real MC
Where'd you get the bat handle switches? I've been looking for those.
mOBiTh
The Real MC wrote:
Where'd you get the bat handle switches? I've been looking for those.


Do you mean my flatted ones?

EDIT!
These are Apem 5636A9 type (for on-on, can't remember the code for the on-off-on, 5639A9 I think)

These are my favourite flatted ones as the bats don't rotate like some do, so they stay tidy and aligned. I'm OCD about these things though hihi

I use them on everything - bought a load ages ago, I think from digikey.

Can check if you like?
oldcrow
Got a Fedex ship notification on the latest crowbx bare boards, Should be here 3/20 or 3/21. SlayerBadger!
fracinfrucer
oldcrow wrote:
Got a Fedex ship notification on the latest crowbx bare boards, Should be here 3/20 or 3/21. SlayerBadger!


Are you planning on doing more runs in the future? I know my skills are not ready for this project, but I will get there and don't want to miss out on this one. SlayerBadger!
mOBiTh
lol this thing hates me.

So my RevA voice has died in its sleep:

Powered it up today and instantly noticed -V LED was low level.

79M15 VReg is getting super hot on the RevA voiceboard and it's pulling the negative rail to -6V - argh. If I remove this voice, everything else is fine.

What's the best way to track this one down do you think?

There are no obvious shorts and it was working 'fine' as far as I know.

My ICs aren't socketed so it won't be easy to remove them for testing unfortunately (not sure this would be a good idea anyway?)

hmmm.....
The Real MC
mOBiTh wrote:
lol this thing hates me.

So my RevA voice has died in its sleep:

Powered it up today and instantly noticed -V LED was low level.

79M15 VReg is getting super hot on the RevA voiceboard and it's pulling the negative rail to -6V - argh. If I remove this voice, everything else is fine.

What's the best way to track this one down do you think?

There are no obvious shorts and it was working 'fine' as far as I know.

My ICs aren't socketed so it won't be easy to remove them for testing unfortunately (not sure this would be a good idea anyway?)

hmmm.....


Do you have a bench power supply with adjustable current limit? Ideally with a display for each rail that tells you how much current it is drawing? I would pull the 7915 and 7815 and directly power the voicecard from the power supply, with the voicecard removed from the hostboard. With the 7x15 regulators out you won't destroy them while troubleshooting. Do a quick test for hot components using the fingers. From there it is a process of isolation, pulling any component tied to the rail while refering to the schematic. Unfortunately you learned the hard way why these things are socketed Dead Banana

Thanks for the info on the switches.
mOBiTh
The Real MC wrote:


Do you have a bench power supply with adjustable current limit? Ideally with a display for each rail that tells you how much current it is drawing? I would pull the 7915 and 7815 and directly power the voicecard from the power supply, with the voicecard removed from the hostboard. With the 7x15 regulators out you won't destroy them while troubleshooting. Do a quick test for hot components using the fingers. From there it is a process of isolation, pulling any component tied to the rail while refering to the schematic. Unfortunately you learned the hard way why these things are socketed Dead Banana

Thanks for the info on the switches.


No probs, re switches!

Havent got a bench psu yet - it's next on the list. Just bought a desoldering station which we just trialled recently at work so removing the ICs won't be too tricky.

None of the ICs get hot currently (pun intended hihi ) - wondering if anything else could be at fault.

Also is there an obvious way of doing this, or should I just pull all the ICs and then insert them one by one, starting from the VCO end (for example?) and wait for the problem to reappear?

I'm wondering whether an IC has failed due to some other problem.

The main problem I have is that this is a RevA voicecard and not RevB and I have no schematic to work from, nor anything to directly compare with or take measurements from!

Calling Mr Crow for a bit of clarity here please!

hmmm.....
oldcrow
I will generally order board batches as demand permits. Right now, this equates to about 50 board sets a year, done in parts every 4 months or so.
This latest batch will be for 15 four-voice sets, with the next batch order looking to be June/July or so. --Crow

fracinfrucer wrote:
Are you planning on doing more runs in the future? I know my skills are not ready for this project, but I will get there and don't want to miss out on this one. :sb:
oldcrow
I will send you a revA schematic. Rev A is pretty much the same as Rev B, most of the changes are the addition of some sustain level trimmers and some nudging of parts positions for better mechanical fit. There is nothing between revs that would be the cause of what you are encountering.

"Big" issues like this are generally easier to fix. It is the subtle, intermittent problems that drive one crazy in trying to solve. screaming goo yo

That being said, try a couple basic unpowered tests. Measure the resistance from the -15v output pin on the 79x15 regulator to ground. With the positive probe to ground, and negative probe to the -15V output pin, I get a reading of about 1.25K on my revA board here. (Reversing the probes will show the diode drop resistance which is about 700 ohms). If this ~1.25K reading is not close, the first thing to check is the polarity of the supply capacitors beause a reversed electrolytic does all sorts of bad stuff, which usually ends in exploding--but not always. A reversed, polarized cap will get hot, so watch if if powering the board for further tests. Dead Banana

Of less likelihood but still worth examining is Q35, which is part of a -1V shunt regulator. Make sure Q35 and C49 just above it are installed properly. These parts cannot cause a direct short, however.

When that voice card is slotted into the carrier, make sure nothing is touching the board in front of or behind it. The supply caps in particular I had to mount at strange angles to avoid things from colliding.

One note on powering a voice card that is not in the carrier or host: you need to ground the ADSR CV inputs (I use some 1K pulldown resistors jammed into the connectors) or the opamps in the ADSR circuits might latch up. They are expecting a CV, not a floating input.

More later, Crow

mOBiTh wrote:
The main problem I have is that this is a RevA voicecard and not RevB and I have no schematic to work from, nor anything to directly compare with or take measurements from!

Calling Mr Crow for a bit of clarity here please!

hmmm.....
oldcrow
Another thing to check unpowered are the Iabc pins (pins 1 and 16) of the LM13700 OTAs. These pins are one diode-drop away from the negative rail, so a short here is definitely not good. Make sure you see significant resistance between the Iabc pins and ground, something around a few megaohms. A low value means either 1) a V/I transistor is not installed correctly or 2) that OTA section is already fried.
The Real MC
oldcrow wrote:
One note on powering a voice card that is not in the carrier or host: you need to ground the ADSR CV inputs (I use some 1K pulldown resistors jammed into the connectors) or the opamps in the ADSR circuits might latch up. They are expecting a CV, not a floating input.


Important detail as I start to assemble my voicecard without a hostboard... eek!
vicpop
oldcrow wrote:
Peake wrote:
If this can be modded to add SEM-style HP/Notch/BP functions, it's mega-win and I'd be all over it.


Doo dee doo... :sb: :guinness: :sb: :goo: :goo: :goo:



Are these modifications something that you're planning on adding to the PCBs officially in the future? Also, what are the final dimensions of a constructed 4 voice PCB set (not including front panel)?

I have a big chunk of free time coming up and I've been looking for a nice analog polysynth for a while...
oldcrow
I do not have plans to mass-produce boards with these options for a while. The main challenge is these still have to work in an actual OBX, so additional circuits would need to default to settings that made the voice cards appear to just be straight-up OBX voices. I have other projects I want to work on currently so a major crowbx revision is more a later half of the year thing for me--if it even happens this year.

I will publish how to do the mods I did for rev2 voice cards, however.

--Crow
/**/

vicpop wrote:
Are these modifications something that you're planning on adding to the PCBs officially in the future? Also, what are the final dimensions of a constructed 4 voice PCB set (not including front panel)?

I have a big chunk of free time coming up and I've been looking for a nice analog polysynth for a while...
Isaiah
oldcrow wrote:
I do not have plans to mass-produce boards with these options for a while. The main challenge is these still have to work in an actual OBX, so additional circuits would need to default to settings that made the voice cards appear to just be straight-up OBX voices. I have other projects I want to work on currently so a major crowbx revision is more a later half of the year thing for me--if it even happens this year.

I will publish how to do the mods I did for rev2 voice cards, however.

--Crow
/**/

vicpop wrote:
Are these modifications something that you're planning on adding to the PCBs officially in the future? Also, what are the final dimensions of a constructed 4 voice PCB set (not including front panel)?

I have a big chunk of free time coming up and I've been looking for a nice analog polysynth for a while...





If the revision (with the additional modulation and VCF modes) is definitely going to happen, I will probably wait.
These were modifications I planned to implement and I know the PCBs would be sat on my shelf for the rest of the year waah



Perhaps the four X card edge connections could be used like this:
X1
CV input for VCA on Filter EG's output for modulation purposes.
Default is VCA closed.
Panel - POLY-MOD section "Filter EG Depth" control.

X2
Binary input for analogue switch routing Filter EG (post-modulation VCA, as above) to VCO2.
Default is no modulation.
Panel - POLY-MOD section "VCO 2 Frequency - On/Off" switch.

X3
Binary input for analogue switch routing Filter EG (post-modulation VCA, as above) to VCO2.
Default is no modulation.
Panel - POLY-MOD section "Pulse Width - On/Off" switch.

X4
CV input feeding a comparator string to generate binary for the analogue switches.
00-LP
01-BP
10-HP
11-Notch
Default is 0V-00-LP
Panel could use a rotary switch or pot.


Alternatively:
X3
CV input feeding a comparator string to generate binary for the analogue switches.
00-No PWM by Filter EG
01-VCO1 PW
10-VCO2 PW
11-VCO1 and VCO2 PW
Default is 0V-00-No PWM by Filter EG
Panel could use a rotary switch or maybe an arrangement of two switches


What do you think, Scott?
oldcrow
Well, sort of putting the cart before the horse, here. screaming goo yo I have a plan, but it is way down the road. I am turning my attention to CS80 stuff for a while. Guinness ftw! Guinness ftw! And a vintage OBX tray board. SlayerBadger!

crowbx bare boards for the next batch arrive tomorrow! SlayerBadger! SlayerBadger! SlayerBadger!

Isaiah wrote:
If the revision (with the additional modulation and VCF modes) is definitely going to happen, I will probably wait.
These were modifications I planned to implement and I know the PCBs would be sat on my shelf for the rest of the year waah

Perhaps the four X card edge connections could be used like this:
Isaiah
oldcrow wrote:
Well, sort of putting the cart before the horse, here. screaming goo yo


My apologies hihi
My post was meant to sound less like "Scott, you should do X, Y & Z" and more like an attempt to be creative given the limited means (4 voltages) of controlling modulation and filter type while ensuring backwards compatibility...
No hurry at all. I enjoy watching your projects unfold Rockin' Banana!
oldcrow
Nah, I understood your intent. SlayerBadger! No worries.

I will be working on a crowbx voice board rev this spring for pre-assembled units. This one will have a lot of surface-mount parts as they're meant more for end-user sales as vintage OBX voice card expansion/replacement and I want to use my SMT assembly line to build them. Guinness ftw!

Isaiah wrote:
My post was meant to sound less like "Scott, you should do X, Y & Z" and more like an attempt to be creative given the limited means (4 voltages) of controlling modulation and filter type while ensuring backwards compatibility...
No hurry at all. I enjoy watching your projects unfold Rockin' Banana!
mOBiTh
oldcrow wrote:
I will send you a revA schematic. Rev A is pretty much the same as Rev B, most of the changes are the addition of some sustain level trimmers and some nudging of parts positions for better mechanical fit. There is nothing between revs that would be the cause of what you are encountering.

"Big" issues like this are generally easier to fix. It is the subtle, intermittent problems that drive one crazy in trying to solve. screaming goo yo

That being said, try a couple basic unpowered tests. Measure the resistance from the -15v output pin on the 79x15 regulator to ground. With the positive probe to ground, and negative probe to the -15V output pin, I get a reading of about 1.25K on my revA board here. (Reversing the probes will show the diode drop resistance which is about 700 ohms). If this ~1.25K reading is not close, the first thing to check is the polarity of the supply capacitors beause a reversed electrolytic does all sorts of bad stuff, which usually ends in exploding--but not always. A reversed, polarized cap will get hot, so watch if if powering the board for further tests. Dead Banana

Of less likelihood but still worth examining is Q35, which is part of a -1V shunt regulator. Make sure Q35 and C49 just above it are installed properly. These parts cannot cause a direct short, however.

When that voice card is slotted into the carrier, make sure nothing is touching the board in front of or behind it. The supply caps in particular I had to mount at strange angles to avoid things from colliding.

One note on powering a voice card that is not in the carrier or host: you need to ground the ADSR CV inputs (I use some 1K pulldown resistors jammed into the connectors) or the opamps in the ADSR circuits might latch up. They are expecting a CV, not a floating input.

More later, Crow

mOBiTh wrote:
The main problem I have is that this is a RevA voicecard and not RevB and I have no schematic to work from, nor anything to directly compare with or take measurements from!

Calling Mr Crow for a bit of clarity here please!

hmmm.....



So as nothing on the board was getting even slightly warm I pondered whether the LM7915 itself was faulty, yesterday.

When I got home, I installed the faulty RevA board to double check voltages - still same. However! Removing the RevA board now did not cure the problem and I found one of my RevB boards had an identical fault!! Weird.

Both boards had not hot components aside from the 7915.

Only had one spare 7915 to hand so I replaced it in on the RevA board - installed and tested and appears to be working (although haven't checked for audio yet - just PSU voltages).

My 7915 impedance measurements (probe red to ground and black to output), are 2.8k for the RevB boards and 1.5k for the RevA board. In reverse the impedance is always 550 Ohms.

hmmm..... Speculation to follow...
oldcrow
Heads up, I am putting some crOwBX bare board sets in inventory on the sales site. For those interested, go to http://www.cs80.com/crowbx and find the "Order Here!" link. SlayerBadger! SlayerBadger! screaming goo yo screaming goo yo SlayerBadger! SlayerBadger! Guinness ftw! Guinness ftw!

--Crow
mOBiTh
So I'm wondering whether repeated unplugging of the PSU has caused some damage to the negative regulators?

Other alternative seems to be that I have a bad batch of regulators!

Anyone got any thoughts on this?

I'll swap out all the 7915s as a precaution anyway.

Crow, do you think the incorrect neg rail voltage is likely to have damaged the OTAs or anything else? Didn't get chance to check it before work.

hmmm.....
oldcrow
Low negative rail voltage should not be a problem as far as damaging components goes. Oddly enough, I have encountered bad batches of 78/79-series regulators in the past, so it is at least possible.

mOBiTh wrote:
So I'm wondering whether repeated unplugging of the PSU has caused some damage to the negative regulators?

Other alternative seems to be that I have a bad batch of regulators!

Anyone got any thoughts on this?

I'll swap out all the 7915s as a precaution anyway.

Crow, do you think the incorrect neg rail voltage is likely to have damaged the OTAs or anything else? Didn't get chance to check it before work.

:hmm:
mOBiTh
oldcrow wrote:
Low negative rail voltage should not be a problem as far as damaging components goes. Oddly enough, I have encountered bad batches of 78/79-series regulators in the past


Cool, fingers crossed then! Wonder what other surprises this thing has in store? hmmm.....
The Real MC
mOBiTh wrote:
oldcrow wrote:
Low negative rail voltage should not be a problem as far as damaging components goes. Oddly enough, I have encountered bad batches of 78/79-series regulators in the past


Cool, fingers crossed then! Wonder what other surprises this thing has in store? hmmm.....


I bought a batch of new 2N2222 transistors from my local elex store a while back. If I put a differential of 15v from C to E, it would malfunction (current would flow regardless of base current). Not just one, they all did this. When I changed the circuit to 5V across C/E, then they worked right. This was for another project not the crOwBX. Subpar components do occasionally make it through, few suppliers perform 100% inspection on them.

It wouldn't hurt to try some 7915s from a different OEM IE Natl Semi or TI. Changing suppliers does help on occasion.
mOBiTh
The Real MC wrote:


It wouldn't hurt to try some 7915s from a different OEM IE Natl Semi or TI. Changing suppliers does help on occasion.


Yeh, I'll have three different types installed by the end of today hihi
Techman
mOBiTh wrote:
SlayerBadger! SlayerBadger! screaming goo yo screaming goo yo Rockin' Banana! Rockin' Banana! It's motherfucking bacon yo It's motherfucking bacon yo w00t w00t w00t w00t w00t w00t w00t w00t w00t w00t nanners nanners nanners nanners MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING

FUCK YEH!!!!


I'm there too love

A few issues along the way including voice3 osc1 having an inverse pitch to cv relationship!! Turned out that the tempco under the tranny pair ic was not soldered properly & so open circuit d'oh!

Only issue now is that I can't quite tune osc2 of voice1. I run out of travel on the init trimmer. Further investigation required.

This thing sounds huge It's peanut butter jelly time! It's peanut butter jelly time! It's peanut butter jelly time!
mOBiTh
Techman wrote:
mOBiTh wrote:
SlayerBadger! SlayerBadger! screaming goo yo screaming goo yo Rockin' Banana! Rockin' Banana! It's motherfucking bacon yo It's motherfucking bacon yo w00t w00t w00t w00t w00t w00t w00t w00t w00t w00t nanners nanners nanners nanners MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING

FUCK YEH!!!!


I'm there too love

A few issues along the way including voice3 osc1 having an inverse pitch to cv relationship!! Turned out that the tempco under the tranny pair ic was not soldered properly & so open circuit d'oh!

Only issue now is that I can't quite tune osc2 of voice1. I run out of travel on the init trimmer. Further investigation required.

This thing sounds huge It's peanut butter jelly time! It's peanut butter jelly time! It's peanut butter jelly time!


Good work. Yeh it's massive! w00t

So I had an oscillator I couldnt tune up first time around. It was nearly there though, and I reset all the trimmers to centre and had another go - was ok after that.
Techman
mOBiTh wrote:


So I had an oscillator I couldnt tune up first time around. It was nearly there though, and I reset all the trimmers to centre and had another go - was ok after that.


Yep, that's the plan tomorrow....after a couple of Guinness ftw!

Cheers mObiTh
oldcrow
One thing to remember when setting the range and scale is the trimmers are "inverted," that is to say, the range (init freq) is set in the higher octaves and the scale is "tuned down" to the lower octaves. Some VCOs are tuned the other way around (range low, scale high). --Crow

Techman wrote:
Only issue now is that I can't quite tune osc2 of voice1. I run out of travel on the init trimmer. Further investigation required.

This thing sounds huge It's peanut butter jelly time! It's peanut butter jelly time! It's peanut butter jelly time!
Techman





Ok, so it's all tuned up. Try as I might, I couldn't get osc2 of voice1 to tune, so I resorted to changing R9 from 4M7 to 3M3. That got the bugger in.
Photos show how much of a squeeze those 100uF caps are with the pan trimmers. Also shown is my jack wiring where I have normalled the gates and cvs from the single voice jacks to voices 1-4.
Thanks to Magmans tip on not using IC sockets for the carrier board. The voice cards would never fit if sockets were used.

Thanks too to Crow for an awesome design. thumbs up thumbs up
mOBiTh
one thing i've noticed crow is that the x-mod switch sends the synth sharp (haven't measured by how much) - is this to be expected?

x-mod sounds great, particularly with oscillator sync switched on.

also, i've noticed that if I tuned each voice card's max portamento time, one card at a time, when i load them all into the synth at once, suddenly the porta time is greatly increased for all cards.

is this a case of not enough current reaching the iabc pins of the four slot mounted pitch/lag 13700s?
oldcrow
Yeah the caps around the pan pot need strange angles. I wanted more space but was constrained by the carrier board needing to be no larger than a voice board. I will have to see whats up regarding your VCO trim issue. --Crow

Techman wrote:
Ok, so it's all tuned up. Try as I might, I couldn't get osc2 of voice1 to tune, so I resorted to changing R9 from 4M7 to 3M3. That got the bugger in. Photos show how much of a squeeze those 100uF caps are with the pan trimmers. Also shown is my jack wiring where I have normalled the gates and cvs from the single voice jacks to voices 1-4. Thanks to Magmans tip on not using IC sockets for the carrier board. The voice cards would never fit if sockets were used.

Thanks too to Crow for an awesome design. thumbs up thumbs up
mOBiTh
@techman - if you make those capacitor leads longer you'll have room for the trim pots without bending them. you may need to order some more though!
mOBiTh
oldcrow wrote:
I will have to see whats up regarding your VCO trim issue. --Crow



I retuned all of mine again today and found that it's quite a headfuck (again).

I found for some oscillators I was using the exact reverse method of some of the others! Again I ran out of room on one of them but resetting the pots and starting again got me there.

Failed to get the HFT in for a few of them, but I think because I forgot to set those pots low/centre before starting to tune. Bummer, but I'll probably revisit them again soon. I can probably centre the HFT pots using an L-shaped tweaker hihi


[s]http://soundcloud.com/mobithsynth/crowbx-arp1[/s]
Techman
Actually I used this method to tune the vcos ,and it worked with the Crowbx (after I beat odd 2 voice1 into submission)
http://www.techman.synth.net/page30a.html
Techman
mOBiTh wrote:
@techman - if you make those capacitor leads longer you'll have room for the trim pots without bending them. you may need to order some more though!


Nah, I've got plenty of caps. Just need to find the will to lever the voice cards off again. That always makes me nervous eek!
mOBiTh
Techman wrote:
mOBiTh wrote:
@techman - if you make those capacitor leads longer you'll have room for the trim pots without bending them. you may need to order some more though!


Nah, I've got plenty of caps. Just need to find the will to lever the voice cards off again. That always makes me nervous eek!


Yeh - it's not at all fun Dead Banana

Still, I've come up with an 'almost' non-destructive method using watchmaker screwdriver (for the ends, using a molex header for lever point) and plastic tire lever!

Plastic tire lever is great for separating voice card from slot adapter - insert and twist along length, starting with the long end - easy!

For future revisions it would be great if the carrier board was thicker and stiffer - I think this would help.
Techman
Just a quick one for Crow, which would help enormously with fault finding: PDFs of the boards in black and white with just the component placement, names and values. No tracks. The current board placement images are VERY difficult to read zombie
oldcrow
X-mod will cause VCO1 to go sharp since the FM of VCO1 by VCO2's ramp has the area of a single (VCO2) cycle across C22-Q1-R18 not quite averaging out to zero.

As for the portamento CV, it is split across the lag circuits in the same manner as the OBX control board did. If you wanted to give each circuit its own buffered CV, a 2N3906 would be needed for each lag circuit. Something for me to examine at some point. --Crow

mOBiTh wrote:
one thing i've noticed crow is that the x-mod switch sends the synth sharp (haven't measured by how much) - is this to be expected?

x-mod sounds great, particularly with oscillator sync switched on.

also, i've noticed that if I tuned each voice card's max portamento time, one card at a time, when i load them all into the synth at once, suddenly the porta time is greatly increased for all cards.

is this a case of not enough current reaching the iabc pins of the four slot mounted pitch/lag 13700s?
mOBiTh