Shelby is a hi-gain distortion pedal, all done with FETs! There are two pairs of JFETs in mu amp configuration- basically like a pair tubes- which sound like a cranked amp. The distortion is real feeling and full of harmonics and beef. In total there are 3 stages of gain with 18V of headroom thanks to an internal voltage doubling circuit.
The Dist knob takes the pedal from hard crunch to full on dimed amp. The Tone knob is a harmonics control and will calm the bite of the distortion. Shelby is full of harmonics and overtones, with tons of presence and bite.
Shelby takes boosts very well. Hit it with a clean boost, Klon, Tube Screamer, treble booster...for beefy amp-like distortion. It’s really loud too, so will hit the front end of an amp with ease.