"The LA4’s relay-managed volume control has 256 steps of adjustment of 0.5dB each, and is fully balanced -- each channel has its own dedicated attenuator. Each increment of volume adjustment produces a satisfying click from the 40 relays inside. Other circuit features include precision-timed relay closures, gold contact points in the relays, and metal-film resistors."
"The LA4 has an expansive specified frequency response of 0.1Hz-500kHz, -3dB. Other impressive specs include a signal/noise ratio of >137dB (A-weighted) and total harmonic distortion (THD) of <-125dB (<0.00006%). Benchmark has also tested the LA4 for “immunity to radiated and conducted radio frequency interference.”"
"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."
"Operation of the user interface is intuitive -- I found the LA4’s many features easy to find and adjust."
"The LA4 was designed from the ground up as an ultra-low-noise, ultra-low-distortion mate for the AHB2 power amplifier, which my brother Hans reviewed on SoundStage! Access in June 2015. Our measurements of the AHB2 confirmed that it had the lowest noise and distortion of any power amp we’ve ever measured. Benchmark claims that the LA4 (and HPA4) “may be the only preamplifiers or line amplifiers that [exceed] the signal-to-noise ratio of the ultra-quiet AHB2.” If so, the LA4 may be closer to the elusive ideal of a “straight wire with gain” than almost any other preamplifier on the market at any price."
"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
"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
"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
"Going into this test, based on measuring previous Benchmark products, I expected excellent performance. The benchmark HPA4 shattered even that high bar."
"It brings such a high performance to the table that leaves no doubt whatsoever about its transparency. No stone has been left unturned to optimize audio performance of this device. Even obscure measurements like ultrasonic interchannel phase shift is nailed."
"And then we have tons of power without messing with balanced cables and such. Plug in any headphone and you are in heaven."
"The preamp performance is even higher still, breaking and shattering any expectation one would have in a lab instrument let alone a consumer hi-fi."
"It goes without saying that the Benchmark HPA4 garners my strongest recommendation for a headphone amplifier and preamplifier. It doesn't get better than this folks."
- Amir Majidimehr, Audio Science Review