HPA4 - Review - John Gatski, Everything Audio Network

July 31, 2018

HPA4 - Review - John Gatski, Everything Audio Network

HPA4 - "One of the most transparent audio products I have ever heard at any price"

"Marvelously open and clean" 

"This new custom designed, 256-step relay volume control HP amp/line stage is incredible in its transparency and ability to get out of the way when listening to accurate sources with accurate headphones. Just as impressive, the line stage delivers volume control that many an esoteric analog or digital preamp could only dream of."

"The HPA4 is a co-design by Benchmark and THX, Ltd. using the THX Achromatic Audio Amplifier (AAA™) technology that was implemented in the Benchmark AHB2 amplifier a couple of years ago. According to Benchmark, the THX AAA™ reduces harmonic, intermodulation and crossover distortion by 20 to 40 dB to guarantee a realistic and fatigue-free listening experience."

"I cannot stress enough how the HPA4 just gets out of the way so you can listen to your music and the components in your chain. The HPA4 is sonically neutral, distortion free and deeply dynamic. At any level, it will let the music shine through with no added color."

"The rotary relay gain control features 256 steps in 0.5 dB increments. The HPA4 includes four independent 256-step attenuators: two for the left and right headphone outputs, and two for the left and right line outputs."

"The HPA4 includes IR remote control and can be operated using the optional Benchmark remote. You can use it with Benchmark’s highly rated DAC3 converters, as well as any other source with an analog output. When paired with a Benchmark DAC, a single remote control will operate both units."

"Besides the impressive performance, the HPA4 is Benchmark’s first product with a LCD touch screen that enables most functions of the unit. The screen provides access to advanced features such as balance control, input level offsets, input names, screen dimming, remote control, and function locking. Help screens explain the special functions. The HPA4 includes independent on-screen mute buttons for the headphone and line outputs. Both can also be muted with the volume knob or with the optional remote control."

"The key to a superior volume control is how it sounds when you turn it down ..."

"... you should be able to hear the gentle room reverb of drum cymbal or ringing piano note decay as you turn the volume down."

"The Benchmark HPA4 with its precision relay and ultra quiet amp section, sounds the same at reduced levels as it does when it is turned up."

" When I turned down level, I could still hear the exquisite, precise imaging of the brushed drum cymbals, the snare rim shots and the tasteful Steinway piano notes. I am talking about real musical accuracy, not some euphonic coloration definition of being musical. I am talking about the way music sounds live in a great room, dimensional and full. That is what I hear from the HPA4."

"For headphone listening, I had a long list of demo cans, including my AKG K702 Anniversary, Sennheiser HD-650, AKG K812, Oppo PM1 planar magnetic headphones and the Audeze LCD-XC... the HPA4 handled all of them with ease."

"The Benchmark HPA4 is one of the most transparent headphone amps I have ever heard — at any price. Just as impressive is the line stage, which delivers volume control that many an esoteric analog or digital preamp could only dream of."

"The line output  was routed to a Benchmark AHB2 amp and a pair of Martin Logan Impressions electrostatics. 

"As a line-stage the HPA4 was quite adept ... I found myself relying on the HPA4, as well, for other product reviews because it is so transparent. From an accuracy standpoint, it sounds better than $20,000 preamps I have heard. And oh-so clean."

"To say I am impressed with Benchmark HPA4 would be an understatement. One of the best HP amps and line stages I ever have heard in terms of transparency and accuracy. The ultra-low distortion, its ability to drive any headphone, plenty of connections and the cool factor of the LCD screen menu selection: it is darn near perfect."

"Based on my impressions, the Benchmark HPA4 receives two Everything Audio Network Stellar Sound Awards. One for its headphone amp and one for its line stage. Folks, it is that good."

- John Gatski, Everything Audio Network

Read the full review →

EAN Stellar Sound Award



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HPA4 - Lab Report - Paul Miller, Hi-Fi News
HPA4 - Lab Report - Paul Miller, Hi-Fi News

October 09, 2018

"Here's a brand that's aptly named - its products providing a 'benchmark' technical performance. The HPA4 is no exception with its relay-switched stepwise volume attenuator calibrated in 0.5 dB steps over a 'useable' 105 dB range."

"Distortion and noise are vanishingly low."

"The frequency response is ruler flat (+/- 0.01 dB) from 1 Hz - 100 kHz."

"The [line output] source impedance is a sensible 30 Ohms and the maximum output a huge 22 V."

"Via the headphone amp, the maximum voltage is 11.2 V and ... the maximum power output is a substantial 4.4W/25ohm and 7.7W/8ohm."

"So, not only will the HPA4 drive the toughest headphone loads but its ... insignificant -102 dBV (8uV) residual noise also ensures exceptionally quiet backgrounds when listening with the most sensitive headphones/earbuds."

"Distortion is broadly unaffected by loading."

"The source impedance is a low <0.6 Ohms up to 10 kHz, increasing to 0.78 Ohms at 20 kHz."

- Paul Miller, Hi-Fi News
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HPA4 Review - Andrew Everard, Hi-Fi News
HPA4 Review - Andrew Everard, Hi-Fi News

October 09, 2018

Hi-Fi News "Outstanding Product" Award

"Benchmark describes its product as a 'reference Stereo Headphone Amplifier and Reference Line Amplifier with Relay Gain and Input Control', which should give you some idea of what's going on here, but only hints at the fact that this is actually two completely separate products packed into one relatively compact unit."

"The headphone section is powered by a power amp from THX, employing the same AAA (Achromatic Audio Amplifier) technology first used by the company in its AHB2."

"Benchmark's line amplifier uses relays for input selection, gain control and muting while four independent 256-step attenuators ... feed the the headphone ... and preamp outputs."

"As PM notes in his Lab Report, this design gives the HPA4 not only outstanding performance, but also rather impressive - to say the least - signal delivery."

"All of a track or two should do the trick, as whether with revealing headphones ... or used as a preamp, the HPA4 simply drops jaws with the sheer impact, openness and vivacity of the way it plays music."

"It was one of those real 'performer in the room' experiences and I was instantly transported back to the time I spent monitoring the recording as it was being made ..."

 - Andrew Everard, Hi-Fi News, November 2018

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"Noise, Resolution & Benchmark"

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"Through the Benchmark amps those quiet sounds were richer and more interesting. There seemed to be more going on in those quiet moments. It's harder to describe than it was to hear."

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