Carl Martin OptoComp

An optical compressor performs gain reduction control via a light source into a photosensitive cell. As the light source gets brighter, the photo-sensitive cell sends a signal to reduce dynamic range, or what becomes a compressed signal. The Classic Opto Compressor pedal's four controls (from left to right) are the Gain, which controls the 'pre-glow' of the optical circuit (the more you turn this up, the fatter the sound); Level, which controls the overall volume of the compressor; Compression, which controls how hard or soft the compression is; and the Attack control, which takes the signal from transparent to outright total squeeze.