[sdiy] SSM2164 state variable filter

[David G. Dixon]

> Hmm ... starting to sound a bit familiar.  :-)  I used carefully balanced
> (+) and (-) feedback in my low distortion multiphase VCOs.  For example:
> http://www.electro-music.com/forum/topic-19841.html
> I didn't set these up for filter operation because they are dedicated to
> multiwave mixing.

Yes, I recall you doing something similar.  I thought it was in your sine
oscillator...