VCF resonance cont

[Martin Czech]

...The 3080 works fine as a VC resonance control

yes, and it may introduce some error , too. 
Some circuits use a junction fet attenuator as q-control.
Take a look at Rick's ladder filter.

It also works nicely in my state var, no noise, no offset.
attenuation goes from 1.0 to , say , 1/100, that's enough
for res control.
The control voltage resolution was a bit poor at high q amounts,
but I fixed that with a z-diode/resistor feedback network in the
control voltage op-amp, so that the voltage won't move much at the 
high q end.

m.c.