Benchmark HPA4

Broad agreement that it is extremely quiet. Reviewers and owners report a black background and no hiss even with very sensitive IEMs, and two benches confirm a very low noise floor. The caveat comes from the most exacting bench: its residual noise is a little above the very best amps, so with ultra-sensitive IEMs and the volume turned well up with nothing playing, faint hiss is possible. One 2025 owner reported a buzz in one channel while ramping the volume from the remote.

“HPA4 without a doubt has the blackest background, the cleanest and the one that just gets out of the way of your music.”

Sandu Vitalie · soundnews

“If you have ultra sensitive IEMs and blast the volume when nothing is playing, you may hear some hiss.”

Amir Majidimehr · Audio Science Review

“The background was pitch black, no hiss.”

lithiumnk · Head-Fi

Mostly agreement that it has ample power. The benches measured about 4.4 W into 25 ohms, 3.5 W into 33 ohms and over 11 V of swing, and reviewers drove the Susvara, Abyss and LCD-5 with it. A minority dissent at the very hardest loads: one owner returned it for lack of drive with an Abyss, one video reviewer found himself near the top of its range with a DCA Expanse and RAAL CA-1a, and one Susvara owner preferred a large speaker amplifier. Feeding it a hot (balanced, studio-level) source and using its input boost helps, since the gain tops out at +15 dB.

“The HPA4 sails past the THX AAA 789, providing almost half a watt of output or three times more.”

Amir Majidimehr · Audio Science Review

“The HPA4 exhibited no difficulty driving low-sensitivity, low-impedance planar magnetics.”

Herb Reichert · Stereophile

“It’s a great unit but just doesn’t have enough power to drive my abyss.”

Savage4 · Head-Fi

Sources split three ways, in the classic argument. All three benches find distortion at or below the limits of their analyzers and a ruler-flat response, and most reviewers and owners hear a neutral, uncoloured amp that is detailed without being harsh. A sizeable minority — including Stereophile's listening reviewer, The Ear and a video reviewer, all of whom still recommend it — hear it as drier and more clinical than warmer amps, with less harmonic richness and depth; several owners who sold or returned it put it more bluntly. A small group heard no difference from far cheaper competent amps.

Broadly praised as a preamp-plus-headphone-amp: two balanced and two RCA inputs, XLR, RCA and mono line outputs, independent volume controls for headphones and line out, 12 V triggers and integration with Benchmark's DACs and remote. The caveats: it has no DAC, the 4-pin XLR headphone jack is not a true balanced output (it adds separate ground returns), there is no 4.4 mm jack or crossfeed, and the remote has no discrete input codes for home-automation users.

“I never seen such an advanced feature-set on a 100% analog headphone amp.”

Sandu Vitalie · soundnews

“it was pointed out by a reader that the HPA4's 4-pin XLR headphone output is not balanced but duplicates the single-ended output”

John Atkinson · Stereophile

“unfortunately they cannot seem to easily update with discrete input codes (my biggest and only real gripe)”

richsto · Audio Science Review

Mostly positive. The colour touchscreen won over reviewers who expected a gimmick, the 0.5 dB relay steps are precise and quiet, and the half-rack box fits on a desk or on top of a Benchmark DAC. The complaints are small: the chassis runs warm, the rear panel is crowded, input selection by remote is sequential, and one owner's universal remote needed every command pressed twice.

“The futuristic volume knob is amazing.”

Stereolab42 · Head-Fi

“In operation, the HPA4 runs quite warm for a headphone amplifier/pre-amp.”

Amir Majidimehr · Audio Science Review

“Especially unplugging cables connected to line input 4, balanced output right and balanced output mono when all inputs are populated does need slender fingers.”

Hans Beekhuyzen (YouTube)

Sources split, though unevenly. Every hands-on reviewer praises the thick machined aluminium case and connectors, and owners in the US get a five-year warranty (two years elsewhere). A minority of reports concern faults: Benchmark confirmed that a small 2018 batch shipped with the wrong RCA ground resistors (causing hum with some sources) and fixed them, one owner's unit failed in its input stage within two months in 2021 and was repaired, and one 2025 owner reported a buzz while adjusting volume.

Sources split. Reviewers and some owners call it fair or even cheap for what it does — a reference preamp and headphone amp in one box, with a long warranty and service. Dissenters, mostly owners and auditioners, say cheaper THX-based amps sound much the same, or that it doesn't sound special enough for the money. Its price has also risen from $2,999 at launch to $3,499.