Designed by renowned portable amplifier designer, Three Stone, the Minibox Amplifier Module provides a super wide frequency range and extremely low distortion. Three Stone handpicked (2) OPA627 OP-AMPS and (4) BUF634 Buffer in a DIP design over the standard SMT design to provide listeners with a clean, tight soundstage and the feeling of being totally surrounded by their music. This powerful amplifier module will drive some of the most demanding headphones on the market.