Mackie HM-400, 19"" 4-Channel Headphone Amplifier, L / R main inputs and L / R stereo outputs, LED level display with 7 segments / channel and stereo input, 3 x Headphone outputs / channel, Aux input on each channel with balance control for mixing the main and the aux signal, Mute and stereo / 2-channel mode switch per channel, 12 x Headphone outputs