Designed for High Impedance and Low Sensitivity Headphones - Boost Volume and Reduce Battery Drain of Portable Players. Easy to Carry and Use In The Outdoors - Built-In Rechargeable Battery (Charged Via USB). Increases Your Headphone's Bass & Sound - Robust Metal Casing For Everyday Use. New Amplifier IC with Higher S/N and Lower Distortion - Ultra Low Signal to Noise and Distortion Specification. Portable Headphone Amp for iPod, MP3 Player, Laptop or Mobile Phone The PHE5AS with its 1/8" stereo input and output provides listeners portable amplification that both increases sound quality while extending the battery life of portable players. Both high and low frequencies stand out more adding life to otherwise dull, muddy headphones. The volume adjustment is a great addition allowing you to boost or attenuate levels further. With the bass boost engaged you can listen to music at low volumes while maintaining a flat even response or add fullness at normal listening levels. The on/off power button lets you cut audio without clipping and the LED indicator gives feedback to let you know what state the amplifier is in. With the included USB charging cable and two 1/8" to 1/8" stereo cables, the robust, rechargeable, PHE5AS gives you everything you need to elevate your listening experience today.