[sdiy] 2164 Korgasmatron VCF

[David G. Dixon]

> Zener diodes in an inverting feedback loop will clamp, not give
> unity gain. They can essentially carry an unlimited amount of current
> and so they completely oppose any change in current at the input. Of
> course
> they will have ~some~ variation as the zener knee voltage changes.

In my circuit, which is significantly different from the original concept,
there is a separate pot for adjusting the zener voltage of the back-to-back
zeners.  Replacing these with anti-parallel triple diodes gives the same
effect, although the diodes don't clip as hard at the highest setting.
Also, with the diodes, the resonance amplitude is a stronger function of the
resonance setting, which to me is a negative, because it gives less control
over the sound.  It's probably a toss-up which to use, but the zeners take
up less board space.

Again, I don't know how good any of this will be in the actual circuit.  I'm
keeping my fingers crossed...