[sdiy] 2164 Korgasmatron VCF

[David G. Dixon]

> I don't know if you posted any details before... but what is your
> "dial in a zener voltage" method. Is it just adding series resistance
> or something more complex ?

Yeah, basically.  In this case, the zeners are connected on one end to the
negative input of the opamp, and on the other end to the centre tap of a
100k pot.  One end tap of the pot is connected to the opamp output, and the
other to a 30k resistor which is grounded.  That gives me full zener range
from 3.3V to the rail.  The pot can be a trimmer as well.

I suppose one could also put the pot between the zeners, but I'd have to try
it and see.