I'd really like a stereo input selector with relays, but those things are hard to find! (Apart from some of dubious quality on the *Bay)

Better make my own then. This one's got a custom footprint for an ESP32 devkit module, but it can also be controlled with a rotary switch.

I decided to use five Panasonic TQ-2 relays. The ESP32 module and relays are powered separately, power ground and signal ground are separated to avoid injecting any clicks, pops or noise into the audio channels.

The whole project is open source, free to use as you wish. Eagle project files, gerbers, the Eagle library for the ESP32 module and BoM are all available on the hackaday.io project page.

And, wouldn't you know, Hackaday presented this little side project on their blog!