"The HPA4 is Benchmark’s latest headphone amplifier. This amp is unusual in that it features a THX-888 Achromatic audio amplifier, which is claimed to reduce distortion by 20–40 dB through a patented feed-forward design, resulting in the world’s most linear amplifier. In addition to the THX amp circuitry, Benchmark has gone slightly nuts (in a good way) with the volume control, offering 256 levels in 0.5 dB steps via an array of relays. The idea is to limit noise and allow the user to dial-in volume precisely."
"The HPA4 is a high-voltage, high-current design to allow low-sensitivity headphones to work well. In addition, the damping factor is high (near zero ohms output impedance), with the aim of sounding the same with low-, medium-, and high-impedance headphones."
"I thought the HPA4 sounded as good as any headphone amp I’ve heard for dynamic headphones, and it might be the best of the lot depending on your circumstances."
"The HPA4 is exceptionally good at presenting a layered, dynamic, yet relaxed sound. You can hear these rich results on, for example, Eliza Gilkyson’s Hard Times in Babylon (Red House), where the instruments not only are clearly differentiated but also sound fully rendered, as live instruments do. You also can hear the overtones of each instrument as they decay, which makes them sound more real."
"... wish the review sample didn’t have to go back."
- Tom Martin, The Absolute Sound
"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