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

The Mackie HM-400 is a 19-inch rackmount 4-channel headphone amplifier built for studios, houses of worship, and practice spaces that need to give several people independent control over their own headphone mix from a single rack space. A main input with level control feeds the whole unit, and each of the four channels adds an aux input with balance control, letting a user blend the main program with their own monitor mix instead of being stuck with one fixed feed. Stereo outs on the main section let you pass the signal along to other gear in the chain.

Each channel drives three headphone outputs, for 12 total across the unit, so a full vocal booth, drum room, or rehearsal space can plug in without running out of jacks. Seven-segment LED metering per channel plus a main meter gives a visual check on levels without needing headphones on to confirm signal is present, and mute plus stereo/2-channel mode switches per channel add quick control when someone needs to step out or check a mono mix. Built-Like-A-Tank construction means it is built to live in a rack and get used daily without the amplifier itself becoming the thing that needs troubleshooting.