[sdiy] discrete SSM2018?

[eq927 at freenet.carleton.ca]

I tried a VCA circuit using both OTA's in a LM13600AN  (also CA3280) 
that relied on "matched offsets" to differentially cancel CV-feedthrough 
- it did not work well at all - often the result was worse than using a 
single OTA. The offsets of the two "matched" OTA's can be different in 
direction as well as magnitude. This was tried with six LM13600AN and 
two CA3280.

On a similar topic, the VCA in the NE570 compander uses an op amp to 
linearize a diff pair. It would probably make a fairly nice VCA if the 
control input were brought out to a pin.
Mike