[sdiy] Using AS3320 as a CEM3320 replacement in vintage polysynths

Markus markusthegeek at yahoo.com
Fri Jan 29 04:29:02 CET 2021


 Hi all,
I built a module based on the AS3320 from scratch and the schematics looks exactly the same in the CEM3320 specification. so I would say you can replace these including the weird max. 2V resonance CV.
side note:as was said below between the AS3340 and CEM3340 the only difference seems to be the resistor on the PWM output pin 4 (AS 51k vs CEM 10k). you might also want to add some op amps and zener diode to get all waveform outputs up and down to the same level e.g. 0 - 10V...

gruss,Markus
    On Thursday, January 28, 2021, 07:07:46 PM PST, Jay Schwichtenberg <jschwich53 at comcast.net> wrote:  
 
   
Yep, me bad, sorry.
 
Jay
 
 On 1/28/2021 3:18 PM, ColinMuirDorward wrote:
  
 Jay is correct, but got his chips mixed up. The PWM issue is definitely on the VCO (3340) chip! Tom is asking about the vcf chip (3320) :) 
  On Thu, Jan 28, 2021, 4:12 PM Michael E Caloroso, <mec.forumreader at gmail.com> wrote:
  
Are you sure the PWM issue is the AS3320 and not the AS3340?
 
 MC
 
 On 1/28/21, Jay Schwichtenberg <jschwich53 at comcast.net> wrote:
 > I would go and read what's on Muffs about it.
 >
 > With the original AS3320 there are issues with the PWM affecting the
 > frequency. To resolve the problem it seems people had to add negative
 > voltage regulator (think it's -5V if I remember correctly).
 >
 > Then CEM and new AS chips seem to be better.
 >
 > Jay S.
 >
 > On 1/28/2021 10:46 AM, Tom Wiltshire wrote:
 >>
 >> Does anyone have any experience to offer having tried this? Are the
 >> old and new chips close enough to be direct replacements? Or maybe
 >> with a bit of trimming?
 >>
 >> There seems to have been a lot of focus on the AS3340 as a replacement
 >> chip (and there are a few little differences) but I haven’t seen or
 >> read much about the AS3320 as a drop-in replacement.
 >>
 >> Of course, changing all the filters to maintain consistency is a
 >> possibility, and then you have a few genuine CEMs for the next repair!
 >>
 >> Thanks,
 >> Tom
 >>
 >> ==================
 >>       Electric Druid
 >> Synth & Stompbox DIY
 >> ==================
 >>
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