The Minibox Amplifier add on card for the HiFiMan HM-901 & HM-802 Audiophile High Resolution Digital Portable Music Players. The HiFiMan MiniBox amplifier module was designed by the famous portable amplifier designer Three Stone. This is incorporated with the two OPA627 op-amp and four BUF634 buffer chips in DIP packing instead of SMT packing. The Minibox design provides wide frequency range and extremely low distortion solution. Minibox amplifier module is very powerful so that it can drive most of the headphones with a 3.5mm plug. It enables the HM-901 & HM-802 to sounds more clean, tight and listeners feel like they are being surrounded by the music. And buy this Head Direct HifiMan HM-901 / HM-802 Minibox Amplifier Card Now £159.00.