[sdiy] VCF caps in modern synths

[Gordonjcp]

On Sun, Mar 28, 2021 at 03:52:37PM +0200, cheater cheater wrote:
> > On Mon, Jan 18, 2021 at 11:49 AM ColinMuirDorward <colindorward at gmail.com> wrote:
> > In my 4pole 3320 BPF, the polypropylenes sound slightly better. The obvious difference is that at lower frequency settings, they go into self-oscillation more readily than the ceramics. To my biased ear, the ceramics make some small distortion perhaps, or for some reason add a slight edge to the sound. I did do a blind test using a 2pole 2164 SVF and the difference there is more noticeable than in any other filter I've tested. Here, the polys are a clear win. I want to use words like "liquid, juicy, lush" for the polys vs "bite, edge, grit" for the ceramics. However those are too strong words to describe a very subtle difference. I am waiting to find the right modern mono synth that I can do a capacitor "upgrade" on and test if it's possible to perceive a change in the sound in a factory-made unit. I have an uno synth on the way (was on sale for $135cad?!), perhaps I'll be lucky enough to find space inside that tiny case for four WIMAs.
> 
> The sound quality you're talking is "roughness" and is measured in Aspers.
> 
> Tiny capacitors have a very large voltage gradient across a very short
> casing. They're probably self-modulating, i.e higher voltage means
> less capacitance. Essentially self-filter-FM.
> 
> Look at this article:
> https://passive-components.eu/dc-and-ac-bias-dependence-of-mlcc-capacitors-including-temperature-dependence/
> 

Lots of pretty graphs, for sure.

Has anyone attempted to reproduce these experiments?

-- 
Gordonjcp