PreSonus 4-Channel Headphone Amplifier Are you and your session players and bandmates tired of straining to hear underpowered headphones? We were too, so we created the PreSonus HP4 headphone-distribution systemThese headphone amps are louder than you're ever likely to need for session and stage use, so be careful with that level control! Yet the sound is clear and clean, with a wide dynamic range. At last, everybody will be able to hear! Simplicity is the HP4's hallmark. You get left and right line inputs, left and right line outputs with level control, and the four headphone outs. You can sum the stereo signals to mono, adjust the individual headphone levels, and mute the rear-panel Monitor outputs while leaving the headphone outputs active. So while the HP4 is simple to set up and use, it has all the features you need to create a versatile headphone system. The compact HP4 can sit on a tabletop or can be screw-mounted to a standard rack tray (not included), where it requires just 1/