Combines the tone sweetening magic of the Echoplex Preamp with a three band EQ and mid range frequency adjustment so that you can dial in the perfect bass tone. Whether you need to punch up a solo, boost your signal in a live mix or sculpt more edge into the sound of a passive bass, the Thump Bass Preamp packs incredible versatility into an MXR mini housing. True hardwire bypass. Cannot be powered by a battery. Requires a 9 volt AC adaptor (not included).