The Engineer's Thumb is a compressor/sustainer developed by Merlin Blencowe (The Valve Wizard Website). It has controls for attack, ratio, release, threshold and level and works with the LM13700 IC, which works in the same way as the CA3080, which is also used in the Dynacomp and Ross Compressor.
The new version 2 uses pcb mount pots and an adaptor board for the footswitch. This makes wiring and assembly much faster and safer!
Installationguide: Install guide
Schematic and pcb: Engineer´s Thumb schematic and pcb
Wiring using a battery clip: Alternative Wiring
Partslist (BOM): Engineer´s Thumb parts
Drilling template: Drilling