This is a Voltage Controled Volume control based on the LM13700 IC, dual transconductance amplifiers with builtin output buffers.
Why not just a potentiometer?
Because i dont want the precious audio signal rerouted trough god knows where 1 or 2 meters catching up all kind of noise.
Controlling the op amp transductance with a (filtered) external dc voltage/current sounds like the best approach, and makes the board modular friendly!
Project is created with:
- Eagle
Just open it with eagle
:D