3080 VCA question

[jhaible]

> But if you want to control modulation signales etc. as well, especially
> for pitch control, you should better stay away from simple otas. Too
> much shift. Anyway, a dc blocking cap at the audio input as allways a
> bad idea. You might use for dc.

Sometimes it helps to swap the function of the signal input and the Iabc
input of the OTA. The signal input is bidirectional and suffers from
offset drift, the Iabc input is unidirectional without offset drift. The
output can be made unidirectional with a low leakage diode. Sometimes
this is enough for a good 1-quadrant CV multiplication.


> btw. don't follow the linear/expo dual vca path like formant,

I always thought the Formant dual VCA a stupid solution as well.
Maybe it is, maybe it isn't. I never tried the Formant dual VCA,
but there is another dual VCA made from cascaded variable
gm stages that sounds marvelous: The Minimoog VCA.

JH.