The Fab Suisse is a small overdrive with amazing vintage tones. Since this pedal is built around the classic Blues Breaker circuit and a 3 band EQ, it is a low headroom pedal that you get to push to 10.
The circuit combines the front end of a Blues Breaker along with it's diodes for soft clipping in the feedback loop of the op amp. Also, it has the "Marshall style" 3 band tone controls. Between the two sections, there are LEDs in hard clipping mode which produce more of an open sound with more headroom and less compression, and also a soft clipping mode. The toggle switch, being and on/off/on, enables the clipping elements to be disconnected from the circuit altogether, giving a third option which is no clipping mode or boost. This mode has the most headroom out of the three with the distortion coming out of the op amp by itself.
Here are the three toggle options:
- Left: Hard clipping
- Middle: Boost mode (op amp clipping)
- Right: Soft clipping