The MXR Double-Double Overdrive serves up two classic overdrives in a single housing. Changing between the two is as simple as a flick of the Lo/Hi switch: the low gain circuit belts out rich, fiery midrange tones while the high gain circuit kicks up the gain and emphasizes highs and lows. Use the treble and bass controls to season your overdriven sound and then crank the level and drive controls to turn the heat up to your liking. True hardwire bypass. Powered by 9 volt battery or AC adaptor (ECB003)