The original Hot Tubes from the late-1970's gained cult status due to use by Sonic Youth among others. The pedal emulates Valves/Tubes pushed to break up and far beyond therefore anything after 12 O'clock on the Drive & Gain knobs sends the pedal into fuzz territory.
Single Coils manage to maintain a level of overdrive longer than a humbucker equipped guitar, likewise the choice of amp makes a huge difference.
EHX say "The Hot Tubes' unique paracyclic filter makes it a most versatile distortion device. From warm overdrive to vacuum tube Big Muff sustain to the heaviest metal tube driven screams, you won't find a creamier distortion than the Hot Tubes. Powered by AC adapter and toroidal transformer that drives two Electro-Harmonix tubes to maximum voltage!"