"This is a review and detailed measurements of the Benchmark HPA4 headphone amplifier and preamplifier. The company was kind enough to loan me one for testing. It is a collaboration between Benchmark and THX to implement the "888" standard."
"Are your socks blown off as mine are? Second harmonic distortion is at an incredible -140 dB. That is insanely good. THD meter is running out of zeros to describe it as a percent!"
"Once we get to 1 volt, the IMD measurement floors at the same level as my analyzer. We cannot measure how good it is!"
"Crosstalk performance is beyond imagination: Worst case crosstalk is -123 dB at 20 kHz!!!"
"Perfect frequency response to 200 kHz!!! - It doesn't get more perfect than this."
"Perfect phase match to 200 kHz!!!"
"Using the 1/4 inch headphone jack ... distortion is ever so slightly above pre-amp mode but it is still exceptionally low at -138 to -140 dB. This is by far class leading as the THX AAA 789 could "only" muster -130 dB."
"The full dynamic range, 133 dB, is absolutely superb and bests the THX AAA 789's measurements by whopping 10 dB."
"Lower THD+N than THX 789 at all power levels. 445 milliwatts of power (exceptional). Distortion at max power = -113 dB!! Most important thing is the power level. The HPA4 sails past the THX AAA 789, providing almost half a watt of output or three times more."
"Lower THD+N than Massdrop THX. Max power = 3.5 watts (superb). Distortion = -112 dB at full power."
"Across incredible range of 110 dB of attenuation, you have perfect channel matching. There is a balance control anyway if you did need to adjust anything."
"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 (@Amirm), Audio Science Review
"Before I dig into the sound of the LA4 it is important to know that it employs a wide bandwidth design. The LA4’s bandwidth is specified at 0.2 Hz to 500 kHz."
"Most of the wide bandwidth designs I have heard exhibit ... a purity in tone with superb timing and speed ... the LA4 proved to be no exception."
"The Benchmark LA4 yielded a change that was quickly apparent in several areas. Notably were; bass, upper midrange, treble, low-level listening, and the ability to distinguish the colorations of other components that were contributing to my overall sound."
"Acoustic guitar, piano, and harmonica among many other instruments are presented with speed, clarity, and coherency that made them sound more “present” in the room and less like a recording."
"The Benchmark LA4 is simply the most transparent, least colored, and most revealing component I have had in my system to date. I look forward to it joining my stable of reference components."
- Ken Redmond, The Audio Beatnik
"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