I also made this small passive stereo mixer for a performance that should have happened a month ago.
It’s two stereo inputs or four mono (normalled so I can plug TRS cables), 1st and 3rd channels are hard-panned left, 2nd and 4th hard-right.
I wanted to control the volumes of each channel of two stereo Ciat Lonbarde instruments (Dogslit and Fourses Tarp) before they go into my norns and Otis.
It works well but being passive I’m losing too much signal, plan is to make another active one but keeping it as small as possible (main trouble is the size of a DC socket).
I’m thinking of making a PCB for this as i’m in the process of learning Kicad, will probably add a way to switch the output to mono too. 