While there are lots of quality kits for preamplifiers, I have never really found a decent way of adding more inputs to a preamp. The existing ones are either of dubious quality, spec'ed like a spaceship, or both.

So I decided to make my own input selector. With relays. And an ESP-32 module! A year, and four revisions later, you can buy it on Tindie for $69.

The entire project is fully open source, no strings attached.

So what is it?

It is a programmable input selector for preamplifiers, the size of a Post-IT note, with:

• Four stereo inputs
• One stereo output
• Mute
• Mains power on/off through a solid state relay control
• Break-outs for all ESP-32 pins

It's controlled by a rotational encoder and IR remote, and you get the great build instructions that you've come to expect from a Muffsy kit.

The PCB, all onboard components, ESP-32, rotational encoder and IR receiver are all included in the kit. You also get the fully functional software for it, as well as the Eagle project files for the PCB.

The benefit of using an ESP-32 is that you can program it yourself, and use other functions like touch sensors, Wifi and Bluetooth.