Superlux HA3D is a portable, stereo headphone amplifier designed for demanding and critical audio monitoring. This audiophile-quality headphone amp is ideal for adding headphone feeds for portable, studio, and audio enthusiast applications. The HA3D provides 3 independent headphone feeds from balanced or unbalanced line sources. Each headphone output is controlled by the associated level control, equipped with independent peak LED, and 1/4-inch output connector. With its extended bandwidth and high current/voltage drive capability the HA3D can drive headphones of various impedances to high levels with very low distortion, important for monitoring in high SPL environments. It can be powered from two-AA batteries or external DC. The HA3D will provide years of superb audio performance under the most demanding field conditions. General Features • 3 independent headphone outputs with individual volume controls • Frequency response from 10 Hz to 50 kHz • ≥120 dB dynamic range • High power driving capability, drives headphones to high levels with very low distortion • Individual peak indicators show overload of each headphone feed • Master Stereo / Mono switch • Powered by 2 AA alkaline batteries or adapter with 5～17V DC output • Versatile input and output connectors • Sturdy Aluminum alloy structure Dual Power • Internal battery power（2 × AA）for convenient, low cost power • Long battery life-more than 10 hours（Alkaline batteries, @ nominal drive level） • External 5～17V DC powering Flexible Inputs / outputs • 2 balanced XLR line level inputs or unbalanced 1/4-inch and 1/8-inch stereo inputs • Loop output to connect additional HA3D’s in series for extra headphone outputs Frequency Response：10 Hz～50 kHz, ±1.0 dB, any input to any output, gain control set to 50% Voltage Gain： （Gain, Loop, Out Headphone output）Bal. Line, -3 dB, 34 dB HP Input, -1 dB, 35 dB Output Clipping Level： +18 dBu m inimum with 600 Ω load +16 dBu m inimum with 300 Ω load