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emdot_ambient
Joined: Nov 22, 2009
Posts: 667
Location: Frederick, MD
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 Posted: Mon Oct 25, 2010 2:13 pm Post subject:
Thank Goodness for Small Miracles
Subject description: One small step for emdot |
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Finally, after almost 20 years, I actually got sounds out of my first DIY VCO. It's the first of 4 CEM3340 based VCOs I'm building for two 19" 5U synth voice panels.
I actually put the PCB together back in the early 90s from a PAiA kit (the EKx experimenter series). But I had never actually powered it up because I didn't have the $ for a real PSU and didn't trust myself building one...and had no clue how to DIY a front panel.
This weekend, after a lot of work figuring out what features I'm implementing, and what mods to do, I got it powered up and tested 2 of the 4 chips I have in stock. Haven't run it through an oscilloscope yet, but it sounds like all the wave forms are working and my triangle-to-sine shaper if working as well.
Also tested some mods to the PCB for boosting all the wave outputs to 10vpp from 5vpp. Don't know if the increase is the correct amount yet, but it definitely sounds louder.
Tested controlling the pitch from an external CV (ARP Axxe CV out). Check! And tested the PWM function. Check.
Wired up a mod to change the hard sync function to either leading edge or trailing edge, and to wire up a DP3T switch to select between those 2 sync modes and soft sync.
No sound examples yet, will get to that after I calibrate it and build the sine waveshaper on a real board (it's breadboarded now)...
...but, hey, it's the first small step, innit? |
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blue hell
Site Admin
Joined: Apr 03, 2004
Posts: 24514
Location: The Netherlands, Enschede
Audio files: 298
G2 patch files: 320
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Posted: Mon Oct 25, 2010 3:34 pm Post subject:
Re: Thank Goodness for Small Miracles
Subject description: One small step for emdot |
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| emdot_ambient wrote: | | ...but, hey, it's the first small step, innit? |
It sure is! Great you got it working after all that time 
_________________
Jan
also .. could someone please turn down the thermostat a bit.
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richardc64
Joined: Jun 01, 2006
Posts: 679
Location: NYC
Audio files: 26
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| Posted: Mon Oct 25, 2010 5:34 pm Post subject:
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Congratulations!
I've had a dual 3340 on perfboard untested for just about the same length of time. Even has the same triple sync methods incorporated.
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Revenge is a dish best served with a fork... to the eye |
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emdot_ambient
Joined: Nov 22, 2009
Posts: 667
Location: Frederick, MD
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| Posted: Mon Oct 25, 2010 6:49 pm Post subject:
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I must say that I was surprised with the sound of the pure wave forms. I had heard some people say they found CEM3340s rather thin, flat or just kind of meh.
That's not what I heard. Especially the pulse wave when you twiddled the PWM. It almost needed no filtration or anything. Big and fat and lovely by itself. I'm kind of stoked.
Still waiting on a few odds and end parts. And I'll have to pick up 3 more of those DP3T switches before the total project can be completed...and of course I had to fall in love with the NKK flatted toggle switches. The stoopid DP3T variety is over $14 for one of them  and I'm fool enough to buy them.  |
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RF
Joined: Mar 23, 2007
Posts: 1502
Location: Northern Minnesota, USA
Audio files: 28
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| Posted: Tue Oct 26, 2010 4:06 am Post subject:
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Huge congrats!
bruce
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"I want to make these sounds that go wooo-wooo-ah-woo-woo.”
(Herb Deutsch to Bob Moog ~1963) |
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TekniK
Joined: Aug 10, 2008
Posts: 1059
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| Posted: Tue Oct 26, 2010 7:04 am Post subject:
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| emdot_ambient wrote: | I must say that I was surprised with the sound of the pure wave forms. I had heard some people say they found CEM3340s rather thin, flat or just kind of meh.
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There's a lot of desinformation on the net,in this case to drop the sh prices of CEM 3340's..,or all those vintage synths that use them.. |
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EdisonRex
Site Admin
Joined: Mar 07, 2007
Posts: 4579
Location: London, UK
Audio files: 172
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| Posted: Tue Oct 26, 2010 7:31 am Post subject:
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I love my 3340 VCOs, they only sound thin if I use a high pass filter on them 
Congrats on restarting your building after so many years. I need to find some time to restart mine... too many boards in half finished states, too little time to finish them.
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EGM: What does retro mean to you?
Parker: Like, old and outdated.
Home,My Studio,and another view |
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emdot_ambient
Joined: Nov 22, 2009
Posts: 667
Location: Frederick, MD
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| Posted: Tue Oct 26, 2010 8:17 am Post subject:
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| TekniK wrote: | | ...to drop the sh prices of CEM 3340's... |
In that case...hey, these things SUCK!
...now can I please buy more for way less than $75 a chip?
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emdot_ambient
Joined: Nov 22, 2009
Posts: 667
Location: Frederick, MD
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| Posted: Tue Oct 26, 2010 8:21 am Post subject:
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| EdisonRex wrote: | | Congrats on restarting your building after so many years. |
Thanks, but it wouldn't have happened without places like the EM forums.
If things had been like this back in 1990, my house would be sinking under the weight of all my modular systems. Now it'll probably take till 2030 before I have to worry about that problem.
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v-un-v
Janitor
Joined: May 16, 2005
Posts: 8932
Location: Birmingham, England, UK
Audio files: 11
G2 patch files: 1
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Posted: Tue Oct 26, 2010 9:03 am Post subject:
Re: Thank Goodness for Small Miracles
Subject description: One small step for emdot |
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| emdot_ambient wrote: | | Finally, after almost 20 years, I actually got sounds out of my first DIY VCO. |
So there's hope for me also? 
I've got a fully populated SN voice, (and a whole box of other half-populated shit) that just needs some pots and switches adding, and a front panel- but my wife just sees my synth DIY as an indulgent luxury (getting it built, and finished that is )!! 
So congrats to you too! 
_________________
ACHTUNG!
ALLES TURISTEN UND NONTEKNISCHEN LOOKENPEEPERS!
DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKSEN.
IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
ZO RELAXEN UND WATSCHEN DER BLINKENLICHTEN. |
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valis
Joined: Sep 16, 2008
Posts: 121
Location: Oregon, USA
Audio files: 6
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| Posted: Tue Oct 26, 2010 9:12 am Post subject:
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| Congrats! That's terrific that you used a EKx kit. You sure don't see many of those around these days! I'm sure the VCO is worth some expensive toggle switches. |
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emdot_ambient
Joined: Nov 22, 2009
Posts: 667
Location: Frederick, MD
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| Posted: Tue Oct 26, 2010 9:42 am Post subject:
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What really shocked me was that it worked right from the start.
Took me a while to realize why the pulse wave was so low in volume (with 0V on the PWM you get no sound! once I applied a voltage there, BOOM! volume was equal to the other waves)...took longer to realize why the CV out from my AXXE wasn't modulating the pitch (I was just applying the voltage from the tip of the output's cord, once I connected the sleeve to ground, it worked).
So that's 3 in a row: PSU, Oscillator and sine waveshaper, all functional on the first try.
[Gotta be beginnner's luck]
Well...full disclosure, I did build a PAiA vocoder back in the early 90s and it worked right off the bat, too. But the power supply I cobbled together (scared the living bejeezus out of me) didn't last long at all. And before it fried the bypass on the vocoder stopped working... |
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drapdap
Joined: Oct 11, 2004
Posts: 204
Location: London
Audio files: 1
G2 patch files: 1
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Posted: Tue Oct 26, 2010 10:02 am Post subject:
Re: Thank Goodness for Small Miracles
Subject description: One small step for emdot |
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| v-un-v wrote: |
So there's hope for me also?
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No, no!
You go and buy a G2! |
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emdot_ambient
Joined: Nov 22, 2009
Posts: 667
Location: Frederick, MD
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| Posted: Tue Oct 26, 2010 2:10 pm Post subject:
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| valis wrote: | | Congrats! That's terrific that you used a EKx kit. You sure don't see many of those around these days! |
I know. I bought one kit of each type (VCO, VCF, VCEG and dual VCA) and built them back then. But I also bought enough PCB and chips to end up with 4 of everything (2 dual VCA, but 4 of each of the other boards).
So after I get the already built kit versions modified and tested, I still have to build 10 additional PCBs.
I'm using a lot of ideas from the Digisound 80 CEM modules to help me modifiy the VCO. The sync function, the 10vpp mod, the PWM responding to 0-10V instead of 0-5V...all that's from the Digisound circuits (though the sync function is actually documented in the CEM3340 datasheet). |
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