Carl Martin Opto-Compressor One day while Carl was adding some compression to a guitar track in his studio, he thought, why hasn’t anyone built a small opto-compressor for guitarists?  An optical compressor performs gain reduction control via a light source into a photo sensitive cell. As the light source gets brighter, the photo sensitive cell sends a signal to reduce dynamic range, or what becomes a compressed signal.  Welcome to the Vintage Opto-Compressor….an old-school compressor from the days where coloring was an important factor to the sound. The 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.  A short time with this compressor will allow you to find some of those classic guitar sounds which may somehow have escaped you before.  Again, like all the Vintage pedals, the Opto-Compressor comes in a solid diecast housing with cool chicken-head knobs, CM color and graphics and a 9v battery compartment.  Due to the nature of compressors, we highly recommend a regulated power supply (like the CM Big John) or a large stock of batteries. Credit: Carl Martin.