Keeley DS-9 is a unique distortion pedal combining the best of the famous green and orange stompboxes from the past, now adding a bass boost for zero loss of low frequencies. Level controls the amount of output signal, Dist controls the amount of distortion. There are two more knobs - Tone acting as a tone shaping function and Bass boost for boosting that low end, making your sound more powerful. Toggle switch gives you the ability to switch between SD and DS mode. Pedal has true bypass switching and can be powered by 9V battery or 9V center negative power supply (optional).