Pass Labs didn’t simply resurrect the HPA-1 and give it a new badge. The original HPA-1 was eCoustics Headphone Editor W. Jennings’ longtime reference, a class A workhorse that earned its place on the rack, and the new HPA-1c builds directly on that legacy. The core amplifier design stays the same because it didn’t need reinventing, but the move to replace aging components opened the door for meaningful improvements.
The updated power supply and better circuit board grounding give the HPA-1c a more stable electrical foundation, lowering noise and tightening regulation for a noticeably darker background. Pass Labs also added local regulation to the servo circuit and achieved about a 10 dB drop in the overall noise floor.
That translates to more low-level detail and improved clarity, especially with sensitive headphones that expose everything. And just like the original, the HPA-1c remains a full-function line-level preamp with enough drive and composure to sit confidently at the center of a reference loudspeaker setup.
The HPA-1c isn’t picky about what you plug into it. It works comfortably with headphones from 15 ohms all the way up to 600, and it was designed as a power amplifier first, not a conventional headphone amp, which is why it handles low impedance planar designs with real authority. The low feedback wide bandwidth circuit is fully discrete, and the class A direct coupled MOSFET output stage keeps the signal path honest.
A custom low noise toroidal transformer with a Faraday shield anchors the power supply, and the audio circuits benefit from discrete regulation that keeps the performance stable and the noise floor buried. This is very much a Pass Labs take on a modern reference headphone amplifier, and the engineering reads exactly like that.
Pass Labs HPA-1c Specifications and What They Actually Mean
The HPA-1c offers a gain of 8 dB, which gives most headphones the lift they need without adding noise or softening dynamics. Its frequency response extends from 10 Hz to 100 kHz with only a 1 dB roll-off, which means it stays linear and composed well beyond the limits of human hearing. Output power is serious: 3.5 watts into 20 ohms for current-hungry planar headphones and 200 milliwatts into 300 ohms for high-impedance dynamics. Harmonic distortion and noise remain under 0.005 percent at 1 volt, which keeps low-level detail intact and prevents the amp from smearing transients.
With a 50k ohm input impedance, the HPA-1c plays well with a wide range of DACs and line sources. Output impedance stays below 2 ohms, ensuring tight control across different headphone designs. Class A operation draws a steady 23 watts, and the chassis measures 11 by 13.5 by 4 inches at 14 pounds — a hint at the size of the transformer and the heat sinking inside.
Connectivity remains intentionally simple: two single-ended line inputs and one quarter-inch headphone output. There are no balanced headphone outputs or balanced input options, which fits the HPA-1c’s design philosophy of keeping the signal path short, direct, and discrete.
The HPA-1c uses a precision stepped relay volume control that delivers consistent and repeatable level adjustments. Each step maintains accurate left and right channel tracking, which helps preserve proper balance as you change volume. The operation is straightforward and predictable, making it easy to set listening levels without drift or imbalance.
The Bottom Line
The HPA-1c shows that Pass Labs didn’t just refresh the HPA-1 for nostalgia’s sake. The lower noise floor, the cleaner power supply, and the refinements to grounding and regulation all make a measurable and audible difference, especially with modern planars and high-sensitivity headphones that expose everything. It still doubles as a legitimate line-level preamp, and it still carries that unmistakable Pass Labs build ethic that feels engineered to last.
The bad news is the price. At $4,045, the HPA-1c sits in rare air, and it now walks into a much tougher neighborhood than the original did. Bryston, Violectric, Ampsandsound, and several others have serious entries in this tier, each with their own strengths and loyal followings. Pass Labs has made a meaningful upgrade, but the competition is tougher than ever, and buyers in this bracket will expect nothing short of excellence.
For more information: passlabs.com/products/hpa-1c/
Where to buy: $4,045 at Moon Audio
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