The AT-PHA100 Portable Headphone Amplifier is small (width and length comparable to a smartphone) but packs a powerful punch. Engineered using select audio components, and enclosed in all-aluminum casing to protect the circuitry, the AT-PHA100 gives headphones a rich, detailed boost throughout the sonic range with ultra-low distortion.<br><br>The AT-PHA100 is equipped with both analog and digital inputs (3.5 mm jack and USB micro-B, respectively) and 3.5 mm headphone jack. It also features a high/low gain switch, machined aluminum volume knob, and five-stage sampling indicator for digital input. The internal lithium polymer rechargeable battery lasts up to 14 hours when amplifying an analog signal, and up to 6 hours when amplifying a digital signal.<br><br>The amplifier comes with two rubber bands and a rubber mat for strapping the unit to a smartphone or other portable device, a 1m USB cable (USB 2.0 to USB micro-B) and a 10 cm audio cable terminating in a 3.5mm gold-plated stereo mini plug at each end.