This HP4 Headphone Amplifier from PreSonus is available for purchase at the Music Store in Clermont Florida. This product is also available on our website. Tired of straining to hear the headphones? The HP4's four 130 mW headphone outputs are clear, clean, and screaming loud, all packed in a compact, 1/3U chassis. Features include balanced L/R line inputs and outputs, global mute, overall level control, and sum to mono. The line outputs can feed another HP4 or an HP60. Features include: · 4 screaming-loud (130 mW per channel) stereo headphone amps · Mono summing · Monitor level control and mute · Daisy-chain multiple units via monitor outputs · Compact 1/3U rack-mount chassis