B-Stock, Apogee Groove, usb dac and headphone amp, usb 2.0 connection to mac and pc, up to 24 bit / 192khz audio, ess sabre dac, enhances your itunes, tidal, spotify, pandora or other music listening experiences, constant current drive provides smooth frequency response with any headphones, quad sum dac, 4 dacs per channel for highest dynamic range and lowest distortion, asynchronous clocking, multi-color leds for status and level indication, powered by usb, top panel buttons adjust and mute volume, premium aluminum build quality, built in the usa, d/a conversion: thd+n: -107 db with 600 Ohms load @ 16 dbu, thd+n: -100db with 30 Ohms load @ 10.5 dbu, dynamic range: 117db a-weighted, frequency response: 10hz - 20k +/- 0.2db, max output level: 225mw into 30 Ohms, 40mw into 600 Ohms, system requirements: mac osx 10.8 or higher (no driver required), windows 7 or higher, 32 and 64 bit (driver download required), Includes USB connector cables A and C and carrying pouch, dimensions lwh: 95 x 30 x 16 mm, B-Stock with full warranty, may have traces of use.