Distortion 1.3 (?)

So after all the distortion testing, I've landed on a very simplified circuit:

This one only does soft clipping, but with a very reduced parts count compared to the soft/hard one.

It has no VCA and no switching, and CV control is simplified (which means that the upper 0.7V of the CV is not effective due to the voltage drop across the transistor, but it saves an op amp.

I had hoped that I could connect the output of IC1A directly to the VCA through a < 4.7k resistor, to make the VCA into a gain stage, but that introduced too much non-linearity into the equation. We need to use the non-inverting amplifier in the lower right corner, but it can be placed externally to save space on the distortion board. If we choose to have it on the board we should also reintroduce the CV circuit from the previous distortion to make cv 0-5V again.

Bottom: Output of VCA shows that the almost linear triangle input has been distorted. This is when connecting the output of IC1A directly to the VCA through a 3k3 resistor.

When using an op amp gain stage in between, most of the non-linearity is gone. What is left is introduced by the distortion circuit, see the output above.