Alto Professional HPA6 | Six-Channel Stereo Headphone Amplifier with 18 Headphone Outputs Six independent high-power headphone amplifiers in a compact, 1RU size Supplies six fully independent mixes for up to 18 pairs of headphones Stereo Aux Input on each channel level adjustments for click/loop monitoring Additional Direct Input on front panel: mix in additional sources instantly Mono and Left/Right Mutes per channel for two mono mixes per channel Six independent high-power headphone amplifiers in a compact, 1RU size^ Supplies six fully independent mixes for up to 18 pairs of headphones^ Stereo Aux Input on each channel level adjustments for click/loop monitoring^ Additional Direct Input on front panel: mix in additional sources instantly^ Mono and Left/Right Mutes per channel for two mono mixes per channel