If you're tracking more than one musician at a time, or if everyone in the group wants to listen to the playback, you’re need a monitor distribution system. A distribution system allows everyone to listen in, and control the volume of his or her own headphones. The compact and flexible HA400 can power up to 4 pairs of headphones and up to 4 independent volumes, with outstanding audio quality – even at maximum volume! • Ultra-compact headphone amplifier system for studio and stage applications • 4 independent stereo high-power amplifier sections • Highest audio quality with virtually all types of headphones even at maximum volume • Phones Level control per channel • DC 12 V adapter included • Designed and engineered in Germany