[sdiy] VCF caps in modern synths

[Eric Schlappi]

my two cents on filter caps:

I have experienced piezoelectric effects with x7r caps recently, I now only
use them for decoupling.

One of the bigger upgrades for my filters recently was upgrading from 5%
C0G/NP0 to 1% C0G/NP0. I had previously considered 1% too expensive but
they really aren't anymore and it can really make a difference as far as
getting your filter to oscillate reliably in edge cases.

On Fri, Jan 8, 2021 at 12:51 PM David G Dixon <dixon at mail.ubc.ca> wrote:

> 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
> Wiltshire
> *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
> this?
>
>
> Yes, I think you’re right. That seems more likely to be an effect of the
> tolerance to me.
>
> Tom
>
> ==================
>        Electric Druid
> Synth & Stompbox DIY
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