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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 ... 66, 67, 68, 69  Next [all]
Author OBX voice card (with non-custom CEM3310 equivalent circuits)
oberling
whooooaaaaa - that sounds incredibly massive! very well done! I really must update my 4 voice crOwBX to an eight voice now! ... But then again deckard's dream is just around the corner... screaming goo yo
GryphonP3
Just to confirm, are these compatible with original OBXs? One of my voices just went out, I am wondering if it would be a better option to replace the card with one of these than to try to go into the original and do a repair.. I have poked around a bit but this thing flopped miserably, and it might be a better option to replace it for longevity..
oberling
GryphonP3 wrote:
Just to confirm, are these compatible with original OBXs? One of my voices just went out, I am wondering if it would be a better option to replace the card with one of these than to try to go into the original and do a repair.. I have poked around a bit but this thing flopped miserably, and it might be a better option to replace it for longevity..


That's what they were initially planned for. That's why the crOwBX front panel and carrierboard/hostboard etc. were designed for debugging purposes only at first by oldcrow.
I think the audio demo of Bob1991 shows impressively how indistinguishable the crOwBX voice cards are soundwise from the original ones in his unit. It would be nice to know however which parts of the BOM were wrong according to Bob1991.

And finally the PCBs are currently out of stock sadly...
Bob1991
GryphonP3 wrote:
Just to confirm, are these compatible with original OBXs? One of my voices just went out, I am wondering if it would be a better option to replace the card with one of these than to try to go into the original and do a repair.. I have poked around a bit but this thing flopped miserably, and it might be a better option to replace it for longevity..


Ofcourse you can replace them with a CrOwBX card, but I don't think it will be very difficult to fix your broken voicecard. All original parts with the exception of the CEM3310 are fairly easy to obtain. If i had the chance to buy them for a normal price, I'd still go for an original voicecard, just because of sentimental feelings :')
If you can borrow an oscilloscope, probe the big chip with the tempco's on it (A3/CA3086). Probe pin 6 with respect to ground, and probe pin 8 with respect to ground. Confirm that there is a ramp waveform present. If so, probe pin 4 and 16 of A7 (the 4063 chip )the same way and confirm the ramp waveform is still present here. If so, we're gonna try to debug your filter, EG's and VCA. 90% chance there is just a broken transistor or op-amp.

Quote:
t would be nice to know however which parts of the BOM were wrong according to Bob1991.

Nothing new, everything is said in this topic, a little summary:

-R1/R2 should be 0.1% 100k to improve tuning stability. Maybe R3/R4 as well, although this less critical
-Used 2N3905's (like in the original) instead of 2N3906's
-Take note of the JFET orientation; silkscreen 'silhouette doesn't match the printed GateDrainSource legs
- T1 and T4 should be 100k instead of 10k (correct in BOM, wrong at silkscreen)
- Only for retrofit in original OB-X: Cross-wire pins 12 and 13 on the 4053 (IC A7) to obtain the correct filter tracking response
- I found the part changes in the BOM confusing:
"Part value changes (rev1 to rev2 only): Change R122, R127 to 47K". I did not change that, thus still on 39k, but for as long it works and I don't notice different behaviour, it's okay I think.. It's part of the envelope generators, but they sound ok..

I will create another audio demo in the next days. More closed filter and resonance tryouts and more solo played voices so you can hear trigger them all separate from each other.
jean_schön
Are there any MTA-type headers with a pitch matching that of the switches, which i think is about 4,7 mm/ 0.185? i guess MTA-100 will work for the pots, but anyone who went with a flying wire setup, what did you do for the switches?
jimfowler
Everything working upon initial power-up except I'm about 2 octaves off per VCO. I play C0 but tuner says C2. I've had to lower R9 and R10 to get closer...any harm in lowering those values until I get C0 when I play C0? Otherwise, it's well in tune across ~6 octaves and sounds really really great. Can't wait to get the other 3 cards installed!!!

- Jim
JanneI
Hi all! I'm finally getting started with the crowbx build. Since this is a huge thread, I was wondering if anyone has a list of things that needs to be modified, compared to the original build info? All I found was this: http://radiantsuicide.com/crowbx/

Cheers,
Janne
jimfowler
My advice, as one who has just recently finished (as in a few days ago) a 4-voice, is as follows:

1. Read the ENTIRE thread. Twice.
2. Search the ENTIRE thread for any posts by users "oberling" and "nordcore" as they have detailed most of the things you should look out for during the build.

My tactic was to print the BOM and make notes to the right of the parts as I read the thread. It's tedious and dull but beats the hell out of having to take things apart over and over again.

There are lots of little things that those who have gone before us have worked out via trial and error. As a result, my build was seamless and worked perfectly upon first try. Were it not for those folks, I'd still be de-soldering things to make everything fit and scratching my head as to why I can't get my oscillators to tune.

It sounds absolutely killer so very much worth the time/effort invested.
JanneI
Thanks for the encouragement! Good to hear that it's possible to get it fully working in one go. If you happen to have those side notes available, I'd be more than happy to have them for reference!

Cheers,
Janne
jimfowler
it's working!!! proof that there are at least two living crOwBX 4-voices out there. infinite thanks to those of you who directly (or indirectly) helped me out.



oberling
congratulations jimfowler! Glad to see another of those in working condition hihi Looking good with those knobs btw.!
nidas
My 4-voice crowBX is also alive and kicking - working great.
livewire
When will more of these boards be offered for sale?
JanneI
Hi! Can someone tell me does the 2n3905 (instead of 2n3906) Q21/Q22/Q25 really matter for 4-voice crowbx system? Thanks!
oberling
JanneI wrote:
Hi! Can someone tell me does the 2n3905 (instead of 2n3906) Q21/Q22/Q25 really matter for 4-voice crowbx system? Thanks!

Hi! I can only tell you that I didn't use any 2n3905. To my ear my crOwBX sounds wonderful. Maybe it would sound even better with 2n3905 - who knows...

If I understand correctly the old conversations in this thread (search for "2n3905" in this thread) the only noticable effect was when using the voices in combination with the vintage OB-X cards. The crOwBX cards sounded louder and it was the hope that they would sound equally loud when deploying them with 2n3905.
JanneI
oberling wrote:
JanneI wrote:
Hi! Can someone tell me does the 2n3905 (instead of 2n3906) Q21/Q22/Q25 really matter for 4-voice crowbx system? Thanks!

Hi! I can only tell you that I didn't use any 2n3905. To my ear my crOwBX sounds wonderful. Maybe it would sound even better with 2n3905 - who knows...

If I understand correctly the old conversations in this thread (search for "2n3905" in this thread) the only noticable effect was when using the voices in combination with the vintage OB-X cards. The crOwBX cards sounded louder and it was the hope that they would sound equally loud when deploying them with 2n3905.


Thanks! I have the change to put 2n3905's, so that's what I'll do, even if it's uncertain it'll do any difference smile

BTW, all the 100uF caps in ALL the boards (except carrier) are a real pain in the... They should be put last when EVERYTHING is done. In all boards. I've looked the pics on this thread and still I found myself desoldering all of them. :(
JanneI



-Voice card: only cards 2 and 4 needs this, but it don't harm to do all.
-Slot adapters: can be done to all of them. Solder ALL the connectors first, then press caps as close to the connectors as you can. It should fit between those boards
-Carrier: normal mount ok
-Host: opposite side (and 5mm 10uF caps!!) if you like to get the panel mounted as close as possible to get those plastic shaft alpha pots out as much as possible. Highest components will be switches and multiturn trimmers.
JanneI
Here's my take on the voice card trimmers. Both ENVs with 10k single turn, all others multi-turn and accessible without the need to take the card(s) out.

[/img]
JanneI






JanneI
Standoff and spacer dimension that I used:

FOR VOICE CARDS (x3):

screw M3
-------------- (voice card1)
spacer M3 18mm
-------------- (voice card2)
standoff M3 25mm
-------------- (voice card3)
spacer M3 18mm
-------------- (voice card4)
screw M3


FOR CARRIER, HOST AND PANEL (x6):

screw M3
---------------(carrier card)
spacer M3 6mm
---------------(host card)
standoff M3 11mm
---------------(panel)
screw M3


JanneI
Wiring is done. Next is the calibration. All the voice cards seems to work straight away but I did find one problem with the host board:

Filter Env Decay works like a on-off -switch, same thing with all the voice cards, so I'm guessing it has to be host card issue?

This thing sounds incredible!

aladan
Looks great JanneI!
oberling
JanneI wrote:


while I do think this is a really great idea I also hope you use an insulated screwdriver for all the settings hihi
JanneI
oberling wrote:
JanneI wrote:


while I do think this is a really great idea I also hope you use an insulated screwdriver for all the settings hihi


That's exactly what I have ;-)
JanneI
Has anybody mounted those voice card extra fine tune pots on the carrier board? I was just wondering how this would sound as a 4 part unison mode with all the voice cards detuned just a tiny bit?
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