A project from Madbean which he no longer supplies PCBs for, which is based on the Carl Martin Plexitone. The switch allows you to put either the Crunch or Hi-Gain pot in circuit and so effectively makes this a dual channel effect allowing you to select between two preset gain levels. So only a SPDT stomp is required for the channel selection, but I have suggested a DPDT in the notes giving you a second pole for LED indication. A good opportunity to use those bi-colour LEDs.
One note, this is a high gain distortion and a few people have noted a problem with oscillation in their build, so keep cable lengths short and consider using shielded cables for input and output wires. I have added other suggestions to calm the oscillation people encountered with this pedal, so hopefully it won't be a problem, particularly when boxed.
Info about the original project:
The Boneyard is a highly modified Plexitone™, which is a high-gain distortion modeled after the classic 60's Marshall amps identified by their Plexiglass panels. The stock unit is powered by an onboard transformer running at +/- 12v and features volume, tone, two gain controls, a boost, and three footswitches for a wide variety of tonal options. To simplify the design, the Boneyard eliminates the transformer and instead uses a voltage inverter to power the effect at +/-9v. The Boneyard also eliminates the Boost function and converts the entire circuit to true-bypass.
And a version with the additional boost pot and switch