Summary

This is a very simple passive audio device switcher. Button 1 switches the input device, and button 2 switches the output device. At any time, only one input and one output device can be used simultaneously. You can also use it with 1 input and 2 output devices, 2 input and 1 output device, or 2 input and 2 output devices.
It can be assembled with basic soldering and 3D printing skills.

What do you need for this craft?

1. 4 x 3.5mm minijack female (5pin) like this
2. 2 x Switch button with 9 or 12 pins. I built it with the 12-pin variant
3. 3 x M3 5mm screw + 3 x Brass Insert Nut
4. Thin wire
   Additionally, you may need Silicone Double Sided Tape or Hot Glue for fixing 2 buttons

Schematic