Cebek PM-13 module is a mono pre-amplifier with “Fuzzybox” function for an electrical guitar. It basically offers two effects; signal limitation and harmonics generator. Both combined offer a better sound for an electrical guitar. The module includes two potentiometers, “Signal limitation” which increases the parameter if you turn to the right. The potentiometer indicated as “harmonics generators”, operates in the same way, injecting harmonics in to the output signal when you turn it to the right.