"The HPA4 combined with the Benchmark AHB2 power amplifier ranks as the quietest rig I've heard (or not heard). Even with the gain up to full with no signal, there is no hiss, hum, or buzz, even when I placed my ears within a in inch of the drivers on 89 dB sensitive loudspeakers."
"As a headphone amplifier, the HPA4 was first rate. Whether it was my most power-hungry headphones, which currently are the new Abyss Diana Phi, or my most sensitive IERs, such as the Empire Ears Phantoms, there was no added noise or lack of adequate gain."
"The Benchmark HPA4 exhibits virtually no noise, whether employed as a stereo preamp or headphone amplifier, and his highly transparent, with no audible colorations."
"The HPA4's front panel is a simple affair, with an on/off button on the extreme left side followed on the right by quarter-inch stereo and XLR balanced headphone connections and a large volume control that has four independent 256-step attenuators in half-decibel increments. This permits the volume level adjustments for the line level and headphone outputs to be completely independent from each other. The HPA4 also has a full color touchscreen for setup and control."
"The front panel controls offer several welcome features, including the ability to control both the headphone and line level outputs separately or ganged together. Unlike many preamp/headphone amplifiers, which automatically mute the line level when a headphone is plugged in, the HPA4 gives users the option of using both at the same time."
"In addition to its pair of stereo outputs, the HPA4 has one more output: a line-level summed mono, which could be useful in connecting a subwoofer if yours doesn't have stereo inputs."
"The HPA4 occupies a unique place, not only due to its features and performance, but also its price. Sure, there are plenty of decent line-level preamplifiers, DACs with built-in volume controls, and scads of headphone amps, but to get the same level of ergonomics and performance as the HPA4 for the same money from separate components could be a challenging proposition, depending on your needs."
"Benchmark calls the HPA4 a "Reference stereo headphone amplifier and reference line amplifier," and I found no reason to dispute this. It performed at reference level with whatever I threw at it. It is ergonomically elegant with a well-laid-out remote and front panel controls. Also, its headphone amplifier was able to support a wide variety of headphones and is the first component to utilize THX Achromatic Audio Amplifier (AAA) technology."
"If you are looking for a preamplifier/headphone amplifier that you can live with happily for a long time, you should consider the Benchmark HPA4 at the top of your must-audition list."
- Steven Stone, HomeTheaterReview.com
"This little unit will change the way you look and listen to amplifiers."
"My first taste of this remarkable new amplifier came earlier this year in April at Chicago's AXPONA where I discovered it driving a newly redesigned Studio Electric Pasadena loudspeaker, also bearing the Benchmark trademark. Now called the SMS1, the Pasadena's crossover had been reworked by Benchmark, upgraded with very low tolerance components, and the new look, more in line with the look of the rest of the Benchmark product line up, had been adopted."
"The subsequent sound in this room was one of the most musically engaging I encountered at this year's event, a remarkable result considering its modest overall system price of just over $7000, sans source."
- Greg Weaver, EnjoythMusic.com
Jim Austin wrote, "The DAC3 was all about depths, in several respects . . . I heard deeper into the music."
The concise conclusion to John Atkinson's Measurements sidebar: "All I can say is 'Wow!'"
In a Follow-Up, Jim Austin wrote of using the Benchmark processor with the same company's AHB2 power amp—a combination of high source output voltage and modest amplifier gain that he describes as "optimal for minimizing noise and distortion"—and reported hearing "richer and more interesting" reproduction of very subtle details.
- Stereophile Magazine
"Class A+" is Stereophile's highest award for Digital Processors
"Benchmark's LA4 is the widest-bandwidth, widest-dynamic-range, lowest-noise, lowest-distortion preamplifier I have encountered."
- John Atkinson, Stereophile
"The LA4 is probably the most transparent and revealing audio component I've ever used. It does not seem to leave any fingerprints on the sound."
- Kalman Rubinson, Stereophile
"Class A" is Stereophile's highest award for preamplifiers.