In the ZVEX lab, we have modified the well-loved ZVEX Super Duper 2-in-1 pedal to mimic the legendary Sunn Concert Bass amplifier, a solid state monster with distinct distortion and low end popular with enthusiasts of downtuned, primal, and punishing guitarists and bassists. The input and output capacitors of the pedal have been voiced so the low-end is retained, and transistors were selected to give the instruments sharp teeth while still sounding organic.
source: www.zvex.com/