Sennheiser HD800 Professional Studio Over-Ear Headphones and HDVD800 Digital Headphone Amplifier open, over-the-ear earcups high-definition 56mm ring radiator drivers with 40mm coil and 42mm magnets 9-foot shielded cable with four-wire, silver-plated oxygen-free copper (OFC) center conductor all digital inputs support up to 24-bit resolution at 192kHz sampling rate for playback of high-res music files rear-panel 5-stage gain switch for optimized use of low impedance headphones