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

ColinMuirDorward colindorward at gmail.com
Fri Jan 29 00:18:14 CET 2021


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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