AHB2 - "This stable and load-independent behavior ... is something not often encountered"
"This stable and load-independent behavior of the output stage is something not often encountered and adds, of course, another positive point for the device."
"AHB2's output power, near its clipping limit, was measured at 108Wrms per channel into 8 Ohm loads and at 190Wrms per channel at 4 Ohm loads, easily confirming the specs given by the company itself."
"Based on this performance, the amplifier seems more than capable of driving difficult loads."
"Damping factor was estimated above 200, therefore, no system frequency response discrepancies, due to loudspeaker's impedance variability, should be expected."
"In distortion measurements, AHB2's behavior was impressive with a total harmonic distortion and noise (THD+N) figure at 0.0009% for 8 Ohm loads and 0.0012% for 4 Ohm loads (measured at 1/3 of its maximum power) and harmonic distortion at 0.0005% and 0.0009% for 8 and 4 Ohm loads respectively."
"Intermodulation distortion (SMPTE) was also low, at 0.0005% and 0.0007% (8/4 Ohm loads). This performance clearly shows that the Benchmark/THX design approach works in practice as intended (at least from the distortion point of view) and the result is a power stage with very low distortion, indeed."
"The frequency response of the amplifier (with an 8 Ohm load) was practically flat with a slight attenuation towards the high-frequency part of the spectrum which is very progressive and does not exceed 0.3dBr at 60kHz."
"The noise performance of the amplifier was, also, top-class. With a reference level corresponding to 1Wmrs/8 Ohm, the signal to noise ratio was measured at -109dBr (A) (with a 1kHz input signal) and the dynamic range at 129dB."
"In both spectrum graphs, there is an apparent absence of noise components from the power supply and their intermodulation products in the low-frequency range (the 50Hz component is hardly distinguishable), all of them being below -130dBr. This is a remarkable behavior, especially with the output stage under load conditions, which justifies the choice of a switch-mode power supply."
"Finally, the square wave response shows a very good transient behavior, without any particular problem. Slew rate was estimated at 16V/uS and rise time at 3.5mS, a value that corresponds to a conventionally calculated bandwidth of 100kHz."
- Dimitris Stamatakos, AVMENTOR.net
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
"The benchmark combination offers a full range of equipment that can hardly be topped, leaves nothing to be desired in terms of sound, and meets professional requirements without any ifs or buts."
"The HPA4 has the HIFIMan one hundred percent under control, eliciting neutral timbres, tons of spatial information and crisp dynamics."
"I connected everything the household had to offer in terms of speakers - Spendor S3 / 5, Ayon Seagull / c, Quad ESL57. It goes without saying that the American coped with the dynamic boxes with ease. But even the quads, which have some meanness on the part of their impedance, did not pose a challenge for the amp."
"There are many things that come into play when putting together a hi-fi system, one of which is synergy."
"After the arrival of the Benchmark Media Systems AHB2, I immediately thought of the matching HPA4 that colleagues Jaap and Yung were very pleased with."
"The key question, of course, was whether the HPA4 would really provide an audible improvement."
"Well you bet! The synergy between preamp and power amplifier is nothing short of magical, not to mention the DAC3 B that I got from importer Helios for the occasion."
"Not only a few curtains disappear, the whole window is gone."
- Geoffrey Vanhouwaert, Alpha-Audio