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WIGGLING 'LITE' IN GUEST MODE

OBX voice card (with non-custom CEM3310 equivalent circuits)
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page Previous  1, 2, 3, ... 67, 68, 69  Next [all]
Author OBX voice card (with non-custom CEM3310 equivalent circuits)
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
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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
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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
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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...
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