Sennheiser HDVD 800 Headphone Amplifier with DAC Symmetrical signal processing from input to output for both digital and analog inputs. Short signal paths featuring premium components insure resolution, detail and dynamic integrity. Simultaneous operation with up to four dynamic, high-impedance headphones, two via four pin XLR input and two via high-quality 6.35 mm (1/4) jacks. Precision engineered Burr-Brown DAC with 24/192 resolution. Frequency response: 0.3 Hz to 100 kHz. THD, total harmonic distortion: &lt; -110 dB (1 kHz / maximum gain) XLR (AES/EBU), optical, coaxial (S/PDIF) and USB digital inputs (2.0 / 3.0), XLR and RCA analog inputs, XLR output. Unit ships without AC power cord.