I needed a bench mixer for my Eurorack workbench setup--to replace the Frac-formatted audio bench gear here:

http://audiodiwhy.blogspot.com/2019/11/benched.html

The module here provides "audio in" from any 4 audio gear sources on the bench; the mixer output is sent to an audio power amp and 2 small speakers.

The bench mixer is 4HP and conforms to Eurorack standards. It's about 40mm deep and uses 10mA of power for each rail.

For the 4 inputs; each pair goes to a single output on a 5mm terminal block.

Each "Left" input is normaled to its corresponding right input for mono applications.

The project requires 3 PCBs--a front panel, main board, and board to accommodate the jacks. The jacks and main board use a 4 conductor 100 mil (2.54mm) pitch cable. Depending on your application you may also need to connect the "ground" from jacks board to main board (100mils, or just solder a wire between the boads).

If you are fabricating this, I recommend for the front panel using black solder mask with white silk. Check the box "don't include product number on the PCB" which costs a bit extra.

You can learn more about this project from the blog post:

https://audiodiwhy.blogspot.com/2023/04/bench-mixer-looks-and-size-matters.html

Happy building!