The Simple Compressor was born to emulate the old fashioned way of achieving compression. Originally, to get compression you would connect an LDR across your amp’s volume control, and then illuminating it with an incandescent lamp driven from the output of the output transformer. That way, the louder the sound was, the brighter the lamp, and more signal was shunted to ground by the LDR. This kind of compression produced nice second order harmonics and a huge amount of sustain.
The Simple Compressor is the effect pedal version of this kind of compression, and is really clean: you won’t hear any kind of distortion or hiss added to it. In the Simple Compressor there’s no diodes or clipping elements in the signal path, so there’s no clipping at all (as it would happen in the Dynacomp, for example). The Simple Compressor is a very subtle effect, but you’ll miss it once you turn it off!
Download here the manual for the Simple Compressor Kit: