From the source:
This ll discrete, MOSFET based circuit provides nearly 30db of
unadulterated clean gain boost with a minimum amount of tone coloration.
Note that you can also use this as an attenuator by turning the Boost
knob counterclockwise away from the noon position. It can also be used
as a powerful buffer with an input impedance of around 5M Ohms and an
output of around 1K Ohm, best used after your effects chain. This device
does not create distortion or overdrive on its own. However, it can be
used to drive your favorite amp or pedal into singing distorted sustain.
Simple, yet effective. Top notch components and circuit design assure
that your signal arrives to its destination in a truly pure state.
When you look at the circuit you can see it’s basically a modified SHO.
