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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, 4 ... 67, 68, 69  Next [all]
Author OBX voice card (with non-custom CEM3310 equivalent circuits)
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
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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
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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
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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!
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