Feed your headphones.The ART HeadAmp4 four-channel stereo headphone amplifier offers 1/8″ and 1/4″ I/O as well as lower noise, lower distortion and more output in a stackable metal case. It lets you easily add additional headphone outputs to any mixer, computer audio interface, workstation, iPod, media player or laptop without creating any additional load on the existing headphone source.Individual level controls for the four headphone outs and 1/4″ and 1/8″ connections give you great flexibility for connecting to virtually any source, including studio phones, in-ear monitors, custom earpieces (or all of the above).ART HeadAmp4 Specifications:Signal To Noise Ratio: > 90dBIMD (SMPTE): 0.01%Maximum Input Level: +14dBVMaximum Output Level: 20dB per channelOutput Impedance: 51 Ohms per channelTotal Harmonic Distortion: <0.01%Power: 12V DC (Adapter included)Dimensions: 4.5 x 2.875 x 1.5 inches (150mm x 75mm x 38mm)Weight: 1.3 lbs (590g)