BBE Opto Stomp Guitar Pedal with Optical Compressor Item #: BBE OS 

The BBE Opto Stomp is an optical compressor (from the B-Max bass preamp), with a soft-knee design. Players love this optical compressor so much that BBE decided to offer the same compressor circuit in a stand-alone foot pedal.
Opto Stomp soft-knee design offers transparent control of dynamics and very musical compression reminiscent of the classic designs of the best vintage optical-element compressors of the 50’s and 60’s.

Other features include switchable -15dB pad, LED compression indicator, non-slip rubber bottom, easy-access 9v battery compartment and included external power supply.