Mackie HM-400 Pro Rackmount 4-Channel Headphone Amplifier w/12 Headphone outputs

The Mackie HM-400 fits four independent headphone channels and twelve headphone outputs into a single 19" rack space. It is built for rooms where a lot of people need to hear something at once: studios tracking a band, houses of worship running wired in-ears, practice rooms, and broadcast spaces.

L/R main stereo inputs feed the unit, with a level control and L/R stereo outputs for passing the signal along. Each of the four channels has three headphone outputs, an aux input with a balance control to blend the main and aux signals, EQ, and mute plus stereo/2-channel mode switches. That combination means a performer can bring in their own click or cue source and set how much of it they hear against the main mix, rather than accepting whatever the console sends.

Seven-segment LED metering appears on each channel and on the main, so a signal problem gets spotted at the rack instead of guessed at from the other side of the room.

Built-Like-A-Tank construction keeps it working in installs and rental racks that see constant use. For twelve sets of headphones with real per-channel control in one rack unit, the HM-400 is a straightforward answer.