The Mackie HM-400 is a rack-mountable, 4-channel headphone amplifier designed to provide versatile headphone amplification for artists, musicians, and engineers monitoring through headphones in live stage applications and home, project, commercial, and mobile-recording studios. It features a stereo main output via XLR and 1/4″ jacks and twelve 1/4″ TRS stereo headphone outputs—three per channel—fed by a customizable blend of inputs.

One stereo main input via XLR and 1/4″ jacks can be mixed with a per-channel 1/4″ stereo aux input. Each channel offers 2-band EQ for quick tone shaping, stereo balance or main/aux input mix control, and output level adjustments. Also on each channel are switches for muting left and/or right signals and operating in stereo or mono. 7-segment LED meters display main input and per-channel output levels.

The HM-400 ships with an IEC power cable and occupies 1 RU in a standard 19″ rack.