Keeley’s most popular pedal, the Keeley compressor has become an industry standard for stomp box compression. The sound will inspire, and your music will flow freely-just plug the compressor pedal in and let your head, heart, and fingers fly. The sound quality of the Keeley compressor is rarely heard in the stompbox arena and is only seen in very expensive rackmount or tube equipment. The Keeley 4 Knob Guitar Compressor is a true audiophile and studio-grade compressor, with exotic rackmount-quality in a stomp box. The Keeley compressor pedal ships with the 9V DC jack at the top end of the guitar pedal and use the same type of power supply used by nearly all guitar effect manufacturers.