HPA4 - Receives Stereophile's "Class A" Rating for Headphone Amplifiers
"The HPA4 adds a THX888 amplification stage to Benchmark's LA4 line preamplifier to allow it to drive even low-impedance headphones with aplomb."
"It keeps the LA4's balanced and single-ended preamplifier outputs and adds a headphone output on a 4-pin XLR jack and a single-ended headphone output on a 1/4" jack."
- Stereophile, 2023
"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."- John Atkinson
"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
"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."
"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."
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."
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."
"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."
"The benchmark combination offers a full range of equipment that can hardly be topped, leaves nothing to be desired in terms of sound, and meets professional requirements without any ifs or buts."
HPA4 - "Has the HiFiMan 100% Under Control"
"The HPA4 has the HIFIMan one hundred percent under control, eliciting neutral timbres, tons of spatial information and crisp dynamics."
AHB2 - "First Choice for Driving Difficult Boxes"
"I connected everything the household had to offer in terms of speakers - Spendor S3 / 5, Ayon Seagull / c, Quad ESL57. It goes without saying that the American coped with the dynamic boxes with ease. But even the quads, which have some meanness on the part of their impedance, did not pose a challenge for the amp."
"In short, it is the best tool and therefore the first choice for everyone who wants to drive difficult boxes to maximum performance without going into personal bankruptcy."
HPA4 - "Rediscovered so Many of My Favorite Works"
"Since the HPA4 arrived, I have rediscovered so many of my favorite works all over again with improved detail retrieval dynamics and transparency that it’s hard to pull myself away!"
"It drove my power hungry Abyss Phi TC headphones with complete authority, but it was still dead silent and nimble enough to amplify my easy to drive Focal Utopia headphones."
"Rarely have I come across such a wonderfully revealing amplifier that can drive many different types of headphones so darn well! The solid build construction and various controls make the price tag seem a bit low based on the other headphone amplifiers in this market space."
HPA4 - "Once I Heard it, I Could Not Live Without it"
"You’ll have a tough time finding a cleaner, quieter, more transparent line amplifier and headphone amplifier anywhere, at any price."
"I found it to be a new reference. Once I heard it, I could not live without it, so I purchased the review sample."
"The HPA4 deserves my highest recommendation."
"The HPA4 is the latest product from Benchmark Media Systems, an upstate New York audio manufacturer."
"We think very highly of the products that Benchmark and John Siau, the company's director of engineering, have been launching in the market - and I'm certain our readers share that opinion."
"Benchmark calls it a headphone amplifier, but it’s really two products in one, combining the LA4 Line Amplifier introduced in 2018, with a headphone amplifier. It is also based on the same THX Achromatic Audio Amplifier technology used in Benchmark’s acclaimed AHB2 power amplifier."
"With DAC, preamplifier and power amplifier, Benchmark knows how to build a bridge between the professional sector and home hi-fi. Very beautiful."
HPA4 - "A Whopping Six Watts into 16 Ohms"
"If you value transparent, precise sound, but at the same time want a certain level of comfort and at least a little elegance, you are in good hands with the Americans."
AHB2 - "A High Degree of Precision"
"The DAC3, HPA4 and AHB2 are all characterized by their wonderfully transparent sound and their high degree of precision. At the same time, sufficient amenities are offered to offer adequate comfort. A successful mix."