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OBX voice card (with non-custom CEM3310 equivalent circuits)
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page Previous  1, 2, 3 ... 65, 66, 67, 68  Next [all]
Author OBX voice card (with non-custom CEM3310 equivalent circuits)
mOBiTh
medbot wrote:
It's just not right to have such a powerful sounding synth using those little plastic shaft knob-less pots. Congrats on the build though, this one has been on my SDIY bucket list for years and it's great to see the rare finished one in the wild!


I built mine with metal shaft pots and Davies clone knobs. looks and feels great but a little cramped at times.
atol
Hi,

I haven't yet made the effort to read through these 66 pages of this thread but i was wondering if there'll be a new batch of the OBX voice boards, as i'm in desperate need of them...

Thanks!
Christian
jvq
I received my full set of boards this week to build a 4-voice CrowBX, yay!

The amount of shopping and planning involved is daunting, but also part of the fun.

I just wanted to share this with whoever else is shopping now: it seems that trendsetter.com (mentioned previously in this thread) has LS318's in stock in PDIP 8L format. I just ordered myself a set of 8. Should be a little easier to install on the voice boards than the TO-78 package.
oberling
oldcrow wrote:
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!


ah - so that's why D3B indeed should not be connected to D2A (Pin 11 on A7). Probably D3 Anode (also connected to base of Q18) is right then...
slowly but surely the filter expansion board seems to make sense... nice MOD btw.
Still missing the understanding of how to control it via B3-6...
jvq
The host board BOM lists 3x 3362P 100k trimpots. That is the wrong type; 3362P don't fit at all. Those 100k trimpots should be 3296Z.
jvq
I have a question about the TO220 regulators on the host and voice boards. They look like they're all supposed to be screwed down onto the PCB. Should I take any special measures to isolate them (mica?) or provide thermal coupling (thermal paste)?
oberling
Ok, so by kind of reverse engineering I found the following:
The filter expansion PCB contains the circuit for FilterEnv->PitchOSC2 modulation as well. In combination with sync this should give the nice harmonic sweeps posted way back by oldcrow.
If i conclude correctly X1L (connector B5) is used for turning this mod on and off (using a potentiometer here one should be able to adjust the intensity). As it's a PNP transistor here I presume the potentiometer should be adjusting between 0-N volts (5V 15V?) since its base is connected to GND.

Next is the CD4052. Only output X is used. I compared the SEM-schematic with the crOwBX schematic and the filter expansion additions. I think there are 4 modes implemented by the filter expansion PCB: X0 low pass filter; X1 high pass filter; X2: bandpass filter and X3: continuous notch filter. The connectors used for switching the modes are X3B (connector B4) and X4B (connector B3). I think it doesn't make a difference if it's X3B=B3 and X4B=B4 or X3B=B4 and X4B=B3.
Low pass, high pass and band pass are straight forward. The continuous notch filter is realized as a vactrol controlled crossfader between high pass and low pass as described on electro-music.com (I am sure it is also described elsewhere but this was the first schematic I found that is very similar to the one on the filter expansion PCB). The connector used for the voltage control of the crossfader is X2L (connector B6). And I don't quite know the voltage range again seriously, i just don't get it
Also: if the Notch filter has the right voltages it should be possible to only use modes X2 and X3 - the notch filter should be adjustable to be only low pass or only high pass (like on the OB-6 or SEM).

Has anyone used the crossfader or can read the schematic posted over at electro-music.com and tell me about the CV range?

help
oberling
jvq wrote:
The host board BOM lists 3x 3362P 100k trimpots. That is the wrong type; 3362P don't fit at all. Those 100k trimpots should be 3296Z.

The 3362P R83 is certainly a tight fit but works for me (bend up the resistor R159 slightly). If you are using a carrier board you can/should omit R52 (but that one should certainly be a 3296Z). R143 also fits for me.

jvq wrote:
I have a question about the TO220 regulators on the host and voice boards. They look like they're all supposed to be screwed down onto the PCB. Should I take any special measures to isolate them (mica?) or provide thermal coupling (thermal paste)?

I only screwed them down to the PCB before soldering - no thermal paste or anything. screwed from the bottom of the PCB with the nut on top of the component lying flat on the PCB. That's necessary because if you screw them down with the nut below the PCB the rest of the screw will eventually get in the way of the next voice card below.
oberling
Digging deeper on the vactrol based crossfader I now think I found a good documentation for the schematic on birthofasynth.com. There it says that the circuit sweeps from one to the other channel from 0V to 6.5V. Then if I understand correctly you can adjust the offset by the center trim (notch trim on the expansion PCB).
jvq
oberling wrote:

The 3362P R83 is certainly a tight fit but works for me (bend up the resistor R159 slightly). If you are using a carrier board you can/should omit R52 (but that one should certainly be a 3296Z). R143 also fits for me.


Thanks oberling! Looking closer now I see how 3362P's would fit in some of those spots. It just confused me because the silkscreen shows 3296-style trimmer outlines. I am going with 3296Y because side access is blocked in some spots. Yes, and skipping R52. smile

oberling wrote:

I only screwed them down to the PCB before soldering - no thermal paste or anything. screwed from the bottom of the PCB with the nut on top of the component lying flat on the PCB.


Thanks, that's what I am doing so far. I'm still working on the host board and my PSU is not ready yet. I noticed the screw direction thing in some photos but had not realized why that was. smile
oberling
mOBiTh wrote:
medbot wrote:
It's just not right to have such a powerful sounding synth using those little plastic shaft knob-less pots. Congrats on the build though, this one has been on my SDIY bucket list for years and it's great to see the rare finished one in the wild!


I built mine with metal shaft pots and Davies clone knobs. looks and feels great but a little cramped at times.

... so how about those? Guinness ftw!

The closest to the original ones I found for a reasonable price and a decent amount. The pointer is a little more narrow and the handle a little thicker but I think it comes close enough. Of course now I need to design a new front panel...
jean_schön
oberling wrote:

... so how about those? Guinness ftw!



could you share the part number and where you got them, please?
jimfowler
Anybody know of a reason this:

https://intellijel.com/eurorack-modules/shifty/

would not work for controlling the crOwBX?
oberling
jean_schön wrote:
oberling wrote:

... so how about those? Guinness ftw!



could you share the part number and where you got them, please?


I found mine on ebay at a surplus seller (CandHsurplus) from california - seems it has been a one-of offer (75 of them for 80$ - a steal (+ shipping and import duty... still very ok for those solid knobs)). No further description was given than "Skirted pointer knob lot of 75 pcs 1/4" with set screw" - so I don't know the manufacturer and/or part number.

But farnell has some like them: EHC (ELECTRONIC HARDWARE) MS91528-3F2B ROUND SKIRTED KNOB W/ ARROW IND, 6.35MM.
... and they have ridiculous prices for them... Dead Banana
Mine have a flat surface on top though - not that kind of roof-like thing.

Raytheon might have produced similar knobs too: There is an auction running currently with the title RAYTHEON (3)1 1/2", (3) 1 1/8" Skirted-Bevel Knobs & (1) 1/14" Pointer Knob containing a bunch of those farnell-like knobs in different shapes and sizes (not enough for a whole crOwBX though).
oberling
jimfowler wrote:
Anybody know of a reason this:

https://intellijel.com/eurorack-modules/shifty/

would not work for controlling the crOwBX?


It says there it's basically an analog shift register. That means you will clock it and on each clock you give it an analog voltage that the unit outputs (samples and holds) on the currently clock selected output. Then it switches to the next output to be sampled according to the selected algorithm.

While I don't see why it would technically not work with the crOwBX I cannot really imagine how this would be useful (despite for the fun of just doing it) for an actual polyphonic synth... I would imagine that this module is a lot more fun triggering various different sounds/module chains.
... yeah well but that's just like... my opinion man lol
jimfowler
It is purported to be a "voice allocation" device primarily, which should put it on par with the Hexinverter midi2cv device in that specific functionality.

"One of the primary uses for Shifty is to take a monophonic sequence source and route each new note of the sequence to up to four different synthesizer voices in a specific pattern."

- Jim
oberling
I don't know which algorithm the hexinverter midi2cv unit has - but it certainly already has a voice allocation algorithm by itself. The manual states for "Polyphonic 1 Channel" mode that the notes are assigned "to outputs one after the other". It does not state however how it deals with "too many notes at once" - which ones are played/stored for later.
livewire
atol wrote:
Hi,

I haven't yet made the effort to read through these 66 pages of this thread but i was wondering if there'll be a new batch of the OBX voice boards, as i'm in desperate need of them...

Thanks!
Christian


Crow's Shopify site says more OB-X voice boards are to arrive in March 2017, if that helps. Yeah, I could use five more boards myself.
atol
livewire wrote:
atol wrote:
Hi,

I haven't yet made the effort to read through these 66 pages of this thread but i was wondering if there'll be a new batch of the OBX voice boards, as i'm in desperate need of them...

Thanks!
Christian


Crow's Shopify site says more OB-X voice boards are to arrive in March 2017, if that helps. Yeah, I could use five more boards myself.


Thanks - where do you see that? I only see 'sold out' https://cs80-com.myshopify.com/products/crowbx-voice-board-rev-2
livewire
atol wrote:
livewire wrote:
atol wrote:
Hi,

I haven't yet made the effort to read through these 66 pages of this thread but i was wondering if there'll be a new batch of the OBX voice boards, as i'm in desperate need of them...

Thanks!
Christian


Crow's Shopify site says more OB-X voice boards are to arrive in March 2017, if that helps. Yeah, I could use five more boards myself.


Thanks - where do you see that? I only see 'sold out' https://cs80-com.myshopify.com/products/crowbx-voice-board-rev-2


On this page:
https://cs80-com.myshopify.com/products/crowbx-four-voice-board-set
jvq
I am having trouble with my noise generator. The trouble starts when programming it using the hex file from cs80.com.

I am using a PIC12C508 and the TL866 'Minipro' universal programmer. According to this programmer, the binary should be 1024 bytes. But when I convert the noise generator hex file from cs80.com I get a 8192-byte binary.

I tried truncating the binary and writing that into the PIC. But now I get no noise on pin 3 or anywhere else.

I'm not sure if I have a fried PIC or if I am using the programmer wrong.
jvq
jvq wrote:

I'm not sure if I have a fried PIC or if I am using the programmer wrong.


I did brick one PIC chip but the main problem was that I was using the programmer wrong.

The HEX files generated by the official Microchip PIC software combine several pieces of data. I had to pick apart the configuration 'word', and patch the unofficial Linux minipro software to even get it to write config fuses to a 12C508.

I think the problem all along was that I was not setting the configuration fuses, which probably meant pin 3 was not configured for output. But now it's working. smile
atol
No matter where i look, there is nothing which can be ordered, everything is marked as 'sold out'. Big bummer seriously, i just don't get it

livewire wrote:
atol wrote:
livewire wrote:
atol wrote:
Hi,

I haven't yet made the effort to read through these 66 pages of this thread but i was wondering if there'll be a new batch of the OBX voice boards, as i'm in desperate need of them...

Thanks!
Christian


Crow's Shopify site says more OB-X voice boards are to arrive in March 2017, if that helps. Yeah, I could use five more boards myself.


Thanks - where do you see that? I only see 'sold out' https://cs80-com.myshopify.com/products/crowbx-voice-board-rev-2


On this page:
https://cs80-com.myshopify.com/products/crowbx-four-voice-board-set
jimfowler
Keep your eye on scott's site. I waited months and finally the board sets showed back up as available. Just gotta be vigilant.
Bob1991
Finally finished upgrading my 4-voice OB-X to a 6-voice (and in the future 8-voice) thanks to oldcrow's upper tray board! And I can say that Oldcrow nailed the sound. They sound just the same to the original cards. Took some months and a bit of debugging - VCO's didn't work because I had my FET's oriented the wrong direction due to the confusing silkscreen. Also found some wrong parts in the BOM (thanks to everybody in this topic), but now it is working properly, with one exception and that is op-amp latch-up if I push the oldcrow voicecards to the limits by setting the resonance almost to maximum, and having some loud/high pitched VCO's. Will try substituting A11 for LM1458, and if this doesn't sound good, try the clamping diodes on the TL072. Like somebody else stated, I also used taller standoffs for the upper tray board metalwork so that the underlaying board doesn't detune because of heat generation. Now it is is a real tight fit to the top panel, but it fits just right :-)




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