The Freq City Sound AAA Powered Belt Pack Amp delivers clear audio right to your in-ear monitors with the signal boost of an active amplifier, and it can run up to 12 hours on two AAA batteries (not included) We put in new batteries before each show to be on the safe side and then use the same batteries for sound check at the next show or let them run out a rehearsal. This powerful belt- or strap-worn in-ear amp is specially designed for musicians and performers whose instruments require stationary play. Every part of the Freq City Sound AAA Powered Belt Pack Amp is engineered to withstand the rigors of the road, from the smooth rotary volume control to the overbuilt metal enclosure and belt clip. Locking XLR/TRS combo input, which helps keep foot traffic and stage mishaps from disconnecting your monitor source. The Freq City Sound AAA Powered Belt Pack Amp uses a standard 3.5mm output jack to drive in-ears, headphones, or earbuds, and it even features an internal switch for selecting mono or stereo use.