The Cadmus Dual Boost is based on the ZVEX Super Duper, which is two of their SHO boost circuits in series and independently switchable.
The SHO is an extremely simple MOSFET booster, small enough that even two of them together have fewer components than most single effects.
The Super Duper is similar in concept to the Box of Rock, which adds a 3rd SHO stage as well as a tone control. That effect is more of an overdrive while this is a two-stage clean boost, though with both stages engaged this one can get into clipping if desired.
The Cadmus is a direct clone of the Super Duper with no added features other than pull-down resistors on each input to help prevent popping.
Note that since the channels are identical to individual SHO circuits, the two gain controls exhibit the characteristic “crackle” of the SHO when they are adjusted, since they are directly biasing the MOSFETs. This is normal.