A prototyping board for synth circuits. It is laid out similarly to a solderless breadboard but with ±12 V and ground rails on both edges, unconnected rails down the middle, and footprints for a Euro/Kosmo style power header with reversal protection diodes and bypass capacitors. Hugely useful for quick one-off circuits, or even not so quick ones — the Megamodule auxiliary PCB is actually one of these. An alternate version also has footprints for a couple of 1/4″ jacks.

Schematics, KiCad design files, Gerbers, documentation