[sdiy] VCF caps in modern synths

David G Dixon dixon at mail.ubc.ca
Fri Jan 8 21:50:12 CET 2021

I have the same experience.  Poly film caps oscillate much easier than C0G
caps of the same value.  I have replaced C0G with WIMA polyester to get
stable oscillation in filters.


From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Tom
Sent: Friday, January 08, 2021 7:26 AM
To: ColinMuirDorward
Cc: synth-diy at synth-diy.org
Subject: Re: [sdiy] VCF caps in modern synths

[CAUTION: Non-UBC Email]

On 8 Jan 2021, at 16:02, ColinMuirDorward <colindorward at gmail.com> wrote:

Yesterday I did some very non-scientific testing of 3320 4pole BPF built
using C0G vs polypropylenes. The test may have been more about the
tolerances of the caps rather than the dielectric, since my polys are 2.5%
vs the C0Gs at 5%. I noticed that at lower frequencies, the polypropylene
version would go into oscillation before the C0G version. Any thoughts on

Yes, I think you're right. That seems more likely to be an effect of the
tolerance to me.


       Electric Druid
Synth & Stompbox DIY

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