Optical compression provides a more transparent, studio like sound. None of the snappy rubber band attack that is associated with other types of compressors. This is for the guitarist who wants that "can't tell when it's on but miss it when it's gone" style compression. But it also has a huge amount of squish on tap if you want it. The BYOC Optical Compressor can put a serious strangle hold on your signal and you will definitely know that it's on when you turn the compression knob up. This is a very easy build. Low parts count and only 2 knobs. It can be run off a single 9v battery or 9v DC power supply. But it can also work with a 12, 15, or 18v DC power supply for even more headroom without having to do anything special to the pedal....Just plug in a negative tip 18v power supply.