Glensound GS-HA013 Headphone AmplifierThe GS HA013 like other units in this range is small, robust and economical. It provides 1 off headphone amplifier in a compact format. It builds on the successful GS HA001 and adds switches to allow each input to be routed to the left ear, right ear, or both. A toggle switch turns the unit on off and a bright blue LED indicates that the unit is on and flashes when the battery is getting low. Audio input is on 2 XLRs normally feeding left & right