"The Benchmark Media Systems HPA4 preamplifier is an exceptionally transparent and well-designed audio device."
"I found it to be an extremely neutral reference point that allowed me to hear more of what a connected speaker or headphone was actually doing and, in turn, how much my existing electronics were adding to the sound that I was hearing in my reviews."
- Carlo Lo Raso, Co-Editor, Secrets of Home Theater and High Fidelity
AHB2 - As a Headphone Amplifier - "My Daily Driver V2.0"
Hifiman Susvara Headphones - Driven by Benchmark AHB2
"Holy mother of Thor, this is dynamics, speed, transient response, resolution and transparency incarnate into a single metal box. There isn’t a clearer, a more resolving or a more transparent sounding amplifier out there, this is a wire with gain amplifier that doesn’t add anything into the mix."
"You can’t get a more impactful, a faster or cleaner sounding amplifier.
"Benchmark’s HPA4 is the first item of audio kit I have encountered that peels apart the ying and the yang of audio to expose the fault line between those of us for whom measurements are all that matters… and those of us that approach audio from a more emotional, less scientific direction. But in another sense it might also bridge the divide."
HPA4 Driving the Audeze LCD-5
"It had been the arrival of Audeze’s latest flagship planar headphone the LCD-5 that had prompted me to ask if I might borrow an HPA4."
"With the LCD-5 being a statement 14 Ohm/90db design, I felt I owed it to Audeze and myself to try driving the headphone with an amplifier whose specs suggested that it could easily cope with the requirement for current."
"The LCD-5 and HPA4 made an impressive partnership."
"On more energetic material, such as Marcus Miller’s M2 album from 2001, and the aptly named track Power, the LCD-5 showed that the HPA4 couples deep reserves of low-end grunt with a good level of dynamic expression. At loud but not silly volumes, the boom and snap of Miller’s slap bass technique had timing and tonal qualities that to my ears – alas, I do not have Miller’s talent but I do play bass – sounded uncommonly real through the LCD-5 headphone."
"I’d encourage anyone in the market for a high-end headphone amplifier to audition an HPA4."
"It is a device that achieves stellar measurements, yet sounds excellent too; evidence that the science-based approach can deliver high musicality."
"The HPA4 can drive pretty much anything, its resolution is truly remarkable, and you will likely hear your music with an acuity as never before."
AHB2 - Mono Mode - "The Playback in Mono Mode is Off the Charts"
"The HPA4 and AHB2 have been a fixture in our reference set for several years now."
"In stereo mode we get a nice 100 watts (8 ohms class A/B) but in mono that goes to an impressive 380 watts!"
"We set the small switch on the back of the AHB2s to mono and connect each speaker to an AHB2."
"The playback in mono is 'off the charts' ... there's no going back really. You have been warned!"
"Benchmark Media Systems Inc from Syracuse, New-York is an American company and has been one of the top pro-audio manufacturers for thirty years. In recent years they have also ventured into the consumer market with considerable success."
"In collaboration with THX came the AHB2 power amplifier and not much later they developed a suitable headphone amplifier and preamplifier, the HPA4 and LA4 respectively."
"With the hard-to-drive HiFiMan Susvara headphones, the HPA4 showed each instrument in dramatic bas-relief. It accomplished this by presenting cleaner, better-articulated bass and manufacturing a sharper midrange focus than I had experienced previously with either my solid state reference, the Pass Labs HPA-1, or the tubed Linear Tube Audio Z10e.”
- Herb Reichert
"The LA4 preamplifier was the widest-bandwidth, widest-dynamic-range, lowest-noise, lowest-distortion preamplifier I had encountered at that time ... to those virtues, the HPA4 adds equally superb balanced and single-ended headphone outputs."
"Class A" is the highest level awarded in the "Two Channel Preamplifier" category.
"Like other Benchmark equipment he has tested, the affordable LA4 challenged the resolution of JA's test instruments, with "superb" channel separation, "extremely low noise, and virtually no power-supply-related spuriae.""
"Benchmark's LA4 is the widest-bandwidth, widest-dynamic-range, lowest-noise, lowest-distortion preamplifier I have encountered."- John Atkinson
"The LA4 is probably the most transparent and revealing audio component I've ever used. It does not seem to leave any fingerprints on the sound." - Kalman Rubinson
"I can't think of many amps with dual hi-fi and pro functionality. Maybe Bryston and the odd ATC, but there aren't a lot. However, to this shortlist, we can add Benchmark."
"Two things strike you upon first seeing it – it's surprisingly compact, and it also has the sort of features that make it more at home in a studio than a listening room lounge space."
"You can bridge theAHB2to make it a monoblock, or bi-wire it to a single speaker; there are only balanced connections incoming, as well as a choice of gain to match the speaker. You get normal speaker binding posts plus a pair of Neutrik'sSpeakOn connectors on the output side."
"Thumbs firmly aloft then for this compact, versatile, thoughtfully designed, well-built stereo power amplifier."
HPA4 - "Satisfied my Engineering Mind and my Audiophile Lust"
"Spending a month with the HPA4 forced this old triode-tube lover to first acknowledge, then accept, and finally enjoy a new type of engagement, one that satisfied my engineering mind and my audiophile lust to look and listen into the hidden nooks and distant corners of every recording. Thank you, Benchmark."
- Herb Reichert, Stereophile
The HPA4 is not just a "Reference Stereo Headphone Amplifier"; it is also a "Reference Line Amplifier" with "Relay Gain and Input Control."
"The fully balanced relay-controlled gain stage applies up to 15 dB of gain or up to 127.5 dB of attenuation for a total range of 142.5 dB. There are 286 volume control steps in precise 0.5 dB increments."
"During my first day of HPA4 listening, I noticed that every digital and analog recording ... sounded cleaner, better sorted, and more macrodynamic."
"The HPA4's sharp-focus specificity is something I associate with recording studio sound but almost never encounter in home systems."
"The THX-888 headphone amplifier board "is a unity gain (current) amplifier with feedforward error correction." Feedforward error correction is also used in the AHB2 power amplifier."
No Difficulty Driving the Susvara Headphones
"With most headphone amplifiers, the tires go flat trying to drive HiFiMan's Susvara open-backed planar-magnetic circumaural headphones.
"The HPA4 exhibited no difficulty driving low-sensitivity, low-impedance planar magnetics."
As a line preamplifier, the HPA4 performed almost identically to Benchmark's superb-measuring LA4, which Kal Rubinson reviewed in January 2020, so I will refer you to that review. This report therefore focuses on the HPA4's behavior as a headphone amplifier."
"The headphone amplifier's frequency response was flat in the audio band and down by just 1 dB at 200 kHz. With the very low output impedance, the response into 300 ohms was identical to that into the high 100k ohms load, and there wasn't any audio band rolloff with impedances as low as 10 ohms."
"Both the response and the superb channel matching were identical at lower settings of the control and from the unbalanced headphone output."
"From balanced inputs to balanced headphone output, the Benchmark had extremely low noise, with the power supply–related spuriae in its output close to –130dB, even with the volume control set to +15dB. With the volume control set to unity gain, the noise floor was 12dB lower!"
"The THD+N percentage was extremely low throughout the audio band into both 100k ohms and 300 ohms."
"I concluded my report on Benchmark's LA4 preamplifier by saying it was the widest-bandwidth, widest-dynamic-range, lowest-noise, lowest-distortion preamplifier I had encountered at that time. To those virtues, the HPA4 adds equally superb headphone outputs."
"Suffice it to say that, as with every Benchmark product I’ve used or reviewed, everything works smoothly, precisely, flawlessly."
"I must single out for special mention the volume control. While the whole unit is completely relay controlled, with a total of forty “precision relays switching high-precision metal-film resistors,” each channel has its own gain control with 256 steps in 0.5dB increments."
"By far, without question this is the best volume control I have ever encountered."
"The LA4 has been widely tested with results that tell the same story as those from the AHB2 power amplifier, i.e., the measurements merely confirm the manufacturer’s claims except in those instances where the limits of the test gear are reached before this or that specification can be precisely verified, almost every tester reporting that the unit beats, often handily, any other ever tested in its product category, regardless of price."
HPA4 - "Cleanest, Quietest, Most Neutral, Dynamic and Precise"
"Allow me to rave about the HPA4’s built-in headphone amp. Designed using similar technology as the AHB2 and licensed from THX (Benchmark calls it the THX-888 Amplifier), this is the cleanest, quietest, most neutral headphone amp I’ve ever heard."
"The HPA4 has no trouble playing music dynamically and precisely through any headphones I own."
"When the folks at Benchmark suggested a review of their HPA4 for Tape Op, my first reaction was, “Isn’t this aimed more at the audiophile market?” Benchmark’s Rory Rall replied that I should consider its use as a reference-grade monitor controller, with a world-class headphone amp built-in. He recommended I pair it with my Benchmark DAC3 B digital-analog converter and use it to drive my Benchmark AHB2 power amp."
AHB2 - "A Silent Transmitter of Musical Energy"
"When I previously reviewed the Benchmark AHB2, I described it as being as close to a straight wire with gain as I’ve ever heard – “a silent transmitter of musical energy.”
I stand by that description after four years of living and listening to it."
DAC3 B - "The HPA4 Allows the DAC to Run Wide Open"
"The HPA4 is built on the idea of avoiding any sort of bit-stripping volume control in the digital realm. So a full-output DAC sends it line-level audio."
"The volume knob is a 256-step precision encoder, driving relays that engage resistors, in 0.5 dB steps."
"I can’t think of anything else that will get you closer to the sound coming out of your sources."
"Combined with Benchmark’s DAC and power amp with excellent speakers and headphones plugged in, this is quite the monitoring chain."
"When playing music you love, it will fire all the pleasure synapses."
DAC3, LA4, AHB2 - "Matched My Idea of Reference Sound"
"Benchmark is an audio brand that started in Texas in 1983. The company then moved to the founder's hometown of Syracuse, New York, and all products are still designed, assembled, and tested at the Syracuse factory. This benchmark has officially arrived in Japan."
"I had the opportunity to listen to all the products of the American audio brand Benchmark Media Systems, and I was very impressed by how well they matched my idea of reference sound."
"The biggest appeal that all the five models we tested have in common is their sound quality, which you can absolutely trust as a reference."
LA4/AHB2 System - "HiVi 2020 Grand Prize" - Amplifier Category
"A compact amplifier with outstanding high performance that is compatible with AV systems."
"In the areas of tonal neutrality and transparency, the B sounds like every other Benchmark I’ve heard, which is to say neutral and transparent. But the DAC3 also has new conversion processing, which is said to make for a 3.5dB increase in headroom above 0dBFS, in turn preventing the DSP intersampling overloads."
"This increase in headroom ... is said to result in subtly improved sound."
LA4 - "Line Amplifier"
"Benchmark prefers to call the LA4 a line amplifier (which may be the more correct term because that is what preamplifiers in fact do: amplify the signal) and offers it in two versions: linestage only, and the identical linestage with an onboard headphone amplifier, called the HPA4."
AHB2 - "A Genuinely Innovative Design"
"Before properly introducing the preamp, however, it is worth the while to recall that the AHB2amplifier is a genuinely innovative design, even, if you will, revelatory, and it set new standards in having by a wide margin the lowest noise and distortion and the widest bandwidth of any amplifier on the market then or now."
DAC3 B, LA4, AHB2 - "The Presentation is Uncanny in its Purity"
"There’s a complete absence of any sort of artifacts or noise; on very clean recordings, the presentation is uncanny in its purity."
"My first taste of this remarkable new amplifier came earlier this year in April at Chicago's AXPONA where I discovered it driving a newly redesigned Studio Electric Pasadena loudspeaker, also bearing the Benchmark trademark. Now called the SMS1, the Pasadena's crossover had been reworked by Benchmark, upgraded with very low tolerance components, and the new look, more in line with the look of the rest of the Benchmark product line up, had been adopted."
"The subsequent sound in this room was one of the most musically engaging I encountered at this year's event, a remarkable result considering its modest overall system price of just over $7000, sans source."
The DAC3 HGC received Stereophile's top "A+" rating.
Jim Austin wrote, "The DAC3 was all about depths, in several respects . . . I heard deeper into the music."
The concise conclusion to John Atkinson's Measurements sidebar: "All I can say is 'Wow!'"
In a Follow-Up, Jim Austin wrote of using the Benchmark processor with the same company's AHB2 power amp—a combination of high source output voltage and modest amplifier gain that he describes as "optimal for minimizing noise and distortion"—and reported hearing "richer and more interesting" reproduction of very subtle details.
- Stereophile Magazine
"Class A+" is Stereophile's highest award for Digital Processors