HPA4, LA4 - Lab Report - Amirm, Audio Science Review

"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."

Preamp Output

"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!!!"

Headphone Output

"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."

300-Ohm Headphone Load

"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."

33-Ohm Headphone Load

"Lower THD+N than Massdrop THX. Max power = 3.5 watts (superb). Distortion = -112 dB at full power."

Stepped Volume Control

"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."

Conclusions

"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

Read the entire review at AudioScienceReview.com →