The Balanced Amplifier add on card for the HiFiMan HM-901 Audiophile High Resolution Digital Portable Music Player. The Balanced Amplifier Module was designed with some of the most expensive and high quality parts on the market today. It uses 4 OPA627 OP-AMPS and 4 OPA634 buffers. By using these high quality chips, the listening experience produced by the HM-901 is second to none. So buy this Head Direct HifiMan HM-901 Balanced Amplifier Card Was £189.00 Now £166.34.