HPA-9 was derived from NuPrime DAC-10H, which won The Absolute Sound Product Of The Year 2015 award. The headphone amp of DAC-10H was compared to high-end standalone headphone amp costing as much as $3000. Today’s best headphones can cost as much as a high-end DAC. Their owners demand a headphone amp that fully exploits their potential. High resolution DAC chips are starting to be incorporated into smart phones and that would further drive the need for high performance headphone amp that can be used with a wide range of in-ear and over-ear headphones. Phono input is included for vinyl enthusiast.
The following design features allow HPA-9 to outperform majority of the headphone amps on the market costing many times more.
JFET Input Stage: The single-ended JFET (Junction Field Effect Transistor) structure is powered by voltage with the characteristics of a solid-state semiconductor very much like a vacuum tube. The HPA-9 therefore produces a sound very close to a triode’s. The high 2nd harmonic also contributes to the sound’s warmth and neutrality, with an especially rich midrange.
The amplification circuit: The HITACHI 2SA872 and 2SC1775 transistors are no longer in production. However, we managed to acquire sufficient inventory for HPA-9. We have chosen these transistors because of three important features of a small-signal amplification transistor: high HFE for high current capability to power hard-to-drive headphones, wide bandwith (FT) and low output capacitance (low COB). The result is a natural, high-resolution, detailed and wide-bandwidth sound.
Non-feedback, pure Class A output stage design: Non-feedback design with very low nonlinear distortion is difficult to accomplish, but when achieved, provides a smooth sonic characteristic. The design’s best example is the Swiss darTZeel NHB-108 amp priced at about $20,000USD. The HPA-9 uses a 40W transistor specification for the output stage and an extremely precise KOA 0.1R.13W resistor with ideally quiet current consumption. Such an innovative design makes the HPA-9 a one-of-a-kind headphone amp.
World-class power supply: HPA-9 uses twelve 2200uF capacitors to form a capacitor bank array, and when the auxiliary capacitors are included, provides 30400uF of reserved power capacity. We are not aware of any other headphone amp using such a design, typical rather of high-end power amps. The massive capacitance array provides abundant power to drive any high-impedance headphone.