[sdiy] VCF caps in modern synths

Tristan tu at alphalink.com.au
Mon Jan 18 03:32:38 CET 2021


Was there an audible difference between the two capacitor types with the same frequency/resonance 
setting on the filter?

/Tristan

On Mon, Jan 18th, 2021 at 11:19 AM, Mike Bryant <mbryant at futurehorizons.com> wrote:

> Agreed lead inductance would be tiny.  I was thinking more of inductive
> coupling between the lead inductances if the capacitors are mounted close
> together, or close to a high level signal.  This can easily happen in the MHz
> range and adversely affect the audio performance.
> 
> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of
> Gordonjcp
> Sent: 18 January 2021 00:07
> To: synth-diy at synth-diy.org
> Subject: Re: [sdiy] VCF caps in modern synths
> 
> On Fri, Jan 08, 2021 at 03:29:44PM +0000, Mike Bryant 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?
> > 
> > Was this SMD or through hole ?   It’s possibly down to lead inductance or
> series resistance being higher in the C0G.
> > 
> 
> Lead inductance would be tiny, negligible at audio.  If your VCF is
> oscillating in the low GHz range you might have issues.
> 
> -- 
> Gordonjcp
> 
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