My previous tone control/pre-amplifier board was based around a cheap PCB from AliExpress. It worked well, but as everything in my amplifier started to be controllable through a smartphone application, I wanted this to change too.
The biggest reason too make every digitally controllable was the volume control. The volume on the cheap AliExpress board was done through a simple potentiometer. But having to walk up to your amplifier every time the volume is too loud, is often annoying. Especially when watching TV.
So first I started looking at digital potentiometers. There are many variants out there, even ones which save their last state to an EEPROM. At first I thought this was the ideal solution, until I came across tone control ICs.
These ICs are sparse as I think many of them are ASICs not really available to the general public anymore. They are mostly used in cars as far as I can see.
One such IC that is fairly easy to get, is the TDA7439DS from ST.