Based off a variety of simple opamp circuits, with the following design goals:
- 4 inputs per mixer
- Individual buffers for each input, to limit cross-talk between connected oscillators
- As close to unity output when one input connected and fully opened (hence, output A can be connected to input B1 for a 7-channel mixer)
- Peak LED for each output
Simulate this circuit on circuitjs
The level pots go in the wrong direction. Fix: Mount I/O board the wrong way, and connect the unconnected top left pin of the dual header row to its right sibling(ground). This will reverse the A/B output LEDs, but that's fine.