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

Jay Schwichtenberg jschwich53 at comcast.net
Fri Jan 29 03:57:33 CET 2021


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 <mailto: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
>     <mailto: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
>     >>
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>     >> Synth & Stompbox DIY
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