The Keeley Compressor pedal is built using tone-tested components and true bypass switching for a clean, unaffected sound when the pedal is off. Metal film resistors and capacitors ensure the cleanest compressor on the market. Hand-matched transistors to less than 1% tolerance ensures you get a perfectly compressed signal, no chance for unwanted distortions. The Keeley Compressor is the new standard for guitar compression. It won the Editor's Pick Award from Guitar Player Magazine and, most recently, the Reader's Choice Award for the stompbox category. It features an internal attack control to make it suitable for high-output active basses. It also features an input sensitivity control which allows it to be used in the studio for keyboards, drum machines, for mastering, and other line-level uses. Low current draw, just 5mA. Uses a standard 9V DC battery and has an AC adapter connection.