[sdiy] high quality expo VCA

[Seb Francis]

Fernando de Izuzquiza wrote:

> But still looking for a good VCA with expo/lin switchable response...

> Has anyone designed an expo circuit with the SSM2164? We have Mike Irwin LIN design, and the chip is
> originally expo so... it would be nice to switch between the two responses.

You could switch in and out a logarithmic amplifier between the CV and the VCA, I think that should allow expo/lin response with a SSM2018/2164/etc.

I've got a circuit in a book which uses a matched NPN-pair, 2 opamps, 4 resistors, a cap and a diode to do this.  I can describe the circuit in more detail if you want.  I believe you can also get single chips which do this.

Seb