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

[harrybissell]

anthony wrote: <and I snipped>

> 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?

Polycarbonate is a good cap as well... It is better than polystyrene in
temperature
RANGE (polystyrene is good only to about 85C which means VERY careful
soldering...
probably not possible in IR Reflow and maybe even iffy in wave solder. Many
folks
solder these by hand. They would melt on a hot day in an automotive application.

Not usually a problem for s-diy).  Polycarbonate would be a real good choice for

an LFO, much better than a non polar lytic !!!

> > 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?

In filters like the Steiner-Parker Synthracon, it is just as inportant as good
cap
tolerance, in fact even more so. Matching of the tuning elements usually results

in greater CV rejection (less thump with fast changes of CV).   Try the old
PAiA 2720 bandpass and lowpass filters for a great example of just how BAD
CV thump can be  :^P

> > H^) harry