ART HeadTAP 2-Ch Headphone Tap Passive operationConnects to PA or monitor amplifierVolume control regulates headphone output Internal resistors protect the phonesProtects the amplifier low impedance loadsConnects to headphone amps to provide extra monitoring capability in studios Sometimes floor monitors are a problem There isn't enough room for them onstage or someone sits in and can't hear the monitors, or the drummer can't hear them well enough Or perhaps it's a pickup gig or a rehearsal and you didn't have enough time to set them up In any case, sometimes it's preferable to just to put on headphones and somehow connect them to the PA