"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
"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 $2,995 price tag seem a bit low based on the other headphone amplifiers in this market space."- Peter Pialis, Headphone.guru
"Benchmark Media Systems’ LA4 preamplifier presented an utterly realistic reproduction of what was contained on each recording I played through it -- and weak recordings stood out more than usual. The LA4’s clean, analytical abilities are unmatched by any similarly priced preamplifier I know of. The LA4’s touchscreen brings it up to date with current user interfaces, and permits functions, such as balance control and muting at the device."
"If you want a preamp that editorializes, look elsewhere."
"If, like me, you value a high-resolution, totally neutral musical performance, add a Benchmark LA4 to your system, particularly if you already own a Benchmark DAC."
- Erich Wetzel, SoundStage! Hi-Fi
"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. 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."
- Gary Galo, Audioxpress.com