In bass clarity and authority and in midrange transparency, the Pass Labs HPA-1 is without peer.

John Atkinson, Stereophile

The HPA-1 headphone amplifier was designed ground-up to become what we believe is one of the very best sounding headphone amplifiers available today. With low feedback, wide bandwidth and a direct coupled MOSFET output stage, this musical instrument drives even the most difficult headphone loads with ease, power and grace. The HPA-1 also functions as a line-level preamplifier that sonically rivals much higher-priced competition. The measured performance is superb and the sound even better.

  • Gain (dB)  8 db

  • Frequency Response 10hz – 100k  -1 dB

  • Output Power into 20 ohms  3500 mW

  • THD + Noise  < 0.005 at 1V out

  • Out Power into 300 ohms  200 mW

  • Input Impedance  50K Ohm

  • Output Impedance  < 2 ohms

  • Power Consumption (Watts) 23

  • Unit Dimension (W x D x H) (In.)  11 x 13.5 x 4

  • Unit Weight (LBS)  14

As balanced headphone operation is the audio fashion du jour, it might be felt that Pass Labs's sticking with single-ended operation could work against the HPA-1. But regardless of circuit topology and the active devices, it's the sound quality that matters, and on that count the HPA-1 scores big-time. Yes, it's an expensive headphone amplifier; but I venture to suggest that, in bass clarity and authority and in midrange transparency, the Pass Labs HPA-1 is without peer.