Sallen-Key question at end...Re: [sdiy] lowpass gate etc (apologies to Kurt Cobain)

[anthony]

> at the risk of having people say that I have balls the size of Texas...
> (or perhaps saying they are the size of BBs... :^)

> I'll start by saying that probably most people will not be able to tell 
> the
> difference between most filter capacitors.  Woah.


I've often thought as much. I suspect that people can tell the difference 
between whether a whole package is well or poorly made though. I'll bet we 
could tell the difference between a 2SC710 and a 2SC2240 too - but those are 
active parts.


> You mentioned Polystyrene... which is probably the best overall cap for
> filter applications.  Sliver Mica would be a close second... equal in 
> almost
> all parameters except is has larger dielectric absorption.  I have not 
> done

I geek out over my polystyrenes. I have some nice ones.

I forgot to ask about polycarbonate. I have a lot of those, but most of them 
are larger values - like a big stack of Philips 470nF. And some from 2.2uF 
to 4.7uF. I'm guessing these might be great for LFOs. How would it compare 
to a nonpolarized electrolytic in an LFO?

> Can you hear the distortion ???   I'm not sure I can.  Audiophiles will 
> swear
> they
> can (otoh they are Audiophiles, what would you expect from them :^)

Even if it could not be measured they could hear it.

> I think the biggest thing that you can hear is capacitor tolerance. 
> Capacitors
> with
> a tight tolerance (or matched caps) will usually result in higher "Q" 
> values...
> they
> will probably resonate better and over a wider range of frequencies. 
> Cutoff
> slopes
> can be better as well, and I think that you WILL hear those effects.


> If I was looking for different sounding filters, I'd probably just choose
> different
> filter topologies (didn't Kurt Cobain sing "what else could I be... all
> topologies..." ?)

Heh!
Funniest Kurt Cobain joke I have ever heard!

> A State Variable will sound different than a Sallen-Key for sure. I think 
> the
> component
> variations might be too subtle to make a lot of difference

Sallen-Key just made me remember my question about the ones that use diodes:
Does it help to match the diodes?

> H^) harry