The MXR Custom Shop took its La Machine Fuzz effect and added an old-school sub-octave circuit to it to create the Sub Machine.
You’ll find in the Sub Machine the same La Machine Fuzz circuit, with its volume, tone, fuzz controls and Octave Up mode, with the addition of a sub-octave circuit with its own level control so that you can easily mix the effects.
Icing in the cake, MXR added a Series/Parallel switch so that you can send the sub-octave signal to the fuzz or alongside to get different effects.
The Sub Machine also features a true bypass.
The details are online at www.jimdunlop.com.