NuPrime HPA-9

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.

Features:

• Single End JFET input stage circuitry design provides the very good second harmonics. And provide high input impedance and ultra low input bias currents. As well as high S/R.
• Non feedback output stage design provides low Temporal Distortion and natural sound.
• Pure Class A headphone amp design.
• Phono (RIAA) input module: Internal setting to MM or MC.
• Supporting up to 3 headphones simultaneously.
• Maximum headphone impedance support range from 8 ohm and up to 1K ohm. Although many headphones state that the nominal impedance is at 300 Ohms, however, during some frequency (100Hz for instance) the peak impedance is actually at around 700 ~ 800 ohm. The HPA-9 does not have such limitation.
• DC offset protection.

Specifications:

Inputs:

• • 1 x Phono Stage
  • 2x Analog Stereo RCA

Outputs:

• • 1 x 3.5mm earphone out
  • 2 x 6.3mm headphones out
  • 2 x pair of stereo RCA out

• THD+N: < -110 dB (1 kHz / maximum gain)
• Frequency Response: 0 Hz to 200KHz (-3dB)
• Dimensions: (W x H x D): 235 mm x 55 mm x 281 mm
• Weight: 5.5 pounds ( 2.5kg )
• Worldwide AC voltage: (90VAC~130VAC // 210VAC~ 250VAC) With Voltage Select Switch
• AC Fuse: Slow-blow, T1A, 250VAC

Innovative Designs

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.

Summary

To drive high impedance headphones properly by simply increasing headphone-amp power is insufficient. A brute- force, high-power design can cause the headphones to be played too loud, often resulting in long-term hearing loss. By providing large, instantaneous amounts of power through 30400uF capacitor array, a pure, Class A design of a high current and low impedance output stage, the HPA-9 is able to drive high-impedance headphones with ease while providing just the required amount of power for high efficiency earphones.