These surprising and delicious details were evident from the bass up through the midrange and extreme treble, which nonetheless remained silky and diaphanous. One example was Hans Theessink's voice at the end of the phrase "as I lay sleeping," in "Late Last Night," from his album Call Me (CD, Blue Groove BG-4020): I could now distinctly hear how his gravelly tone faded off well before the fade of its ambient resonance. Yes, this was now audible through my other amps as well, when I returned to them—but until the AHB2, I hadn't heard it—or, at least, hadn't noticed it.
Similarly, the AHB2 uncovered so many of the little niceties peppering "Ride Across the River," from Dire Straits' Brothers in Arms: 20th Anniversary Edition (SACD/CD, Vertigo 9871498), that it was like savoring the spicy bits in a Xi'an broth for the first time. Classical music, of course, benefited from this newfound richness of information, as was clearly demonstrated by the last minute or so of Adám Fischer and the Budapest Festival Orchestra's recording of the Adagio of Bruckner's Symphony 7 (SACD/CD, Channel Classics CCS SA 33714). As the horns enter, the fading strings diminish but remain audible as they continue to provide the tonal foundation. The resulting impression was one of transparency, neutrality, and liveliness. I could hear into the ensemble and aurally navigate the soundstage. Or, better, I could just surrender to the warmly touching denouement.
In addition to quantity of soundstage detail, the AHB2 was also "large" in power output. It was clear that this 100Wpc (into 8 ohms) stereo amp had all the power needed to drive with aplomb my Bowers & Wilkins 800 Diamond speakers to any reasonable level. At an SPL of 90dB, the B&Ws are of neither particularly high nor low efficiency, but JA has told us what makes them difficult to drive:
"There are minima of 3.15 ohms at 91Hz, 3.1 ohms at 620Hz, and 3.67 ohms at 21kHz. Given that there are current-hungry combinations of 4 ohms and –52° electrical phase angle at 62Hz and 5.3 ohms and –39° phase angle at 8.6kHz, I believe this speaker should be rated as a 4 ohm load rather than the specified 8 ohms."
That seemed to present no problem for the AHB2, which, Benchmark claims, can pump out nearly 200Wpc into 4 ohms or 240Wpc into 3 ohms. In practice, I had to push the AHB2 to unreasonable and personally uncomfortable volume levels to get the least blink from one of its Clip LEDs. For this I used "Jazz Variants," from the O-Zone Percussion Group's La Bamba (CD, Klavier KD 77017), and the glorious conclusion of Saint-Saâns's Symphony 3, with organist Olivier Latry, Christoph Eschenbach, and the Philadelphia Orchestra (SACD/CD, Ondine ODE-1094-5). Both recordings are remarkably clean and spacious, with powerful bass; the AHB2 rose to the occasion, driving the two 800 Diamonds (sans subwoofer) to volumes louder than I ever hope to hear from them again (though it's nice to know I can). I also, very briefly, ran the AHB2 as a bridged monoblock into a single loudspeaker; it sounded the same, but I thought it would be pointless to try to get it to clip if I wanted to avoid annoying my neighbors. Just to let the power-hungry know. . .
Tonal balance is a curious audio parameter. Careful listeners often hear what sounds like an uneven or tilted frequency balance, even when measurements taken under lab conditions show it to be flat. Lots of real-world factors might account for this, including interaction of an amplifier's output stage with the complex input impedance of a loudspeaker. At first, I thought the AHB2 sounded less bright, and less full in the bass, than the other amps I had on hand, but after only a few days of listening I began to accept that it sounded more "right" than any of them. Now the treble wasn't so much un-bright as smoother and unaccented. The bass had all requisite extension and detail (see above), but seemed to be more naturally balanced with the rest of the audio band.
As time passed and I listened more, I grew to love the AHB2's sound, and undertook the rewarding effort of listening through it to as many different recordings as I could. It was a great pleasure, as old friends, some already mentioned, smiled anew. Yes, I could hear the differences between the different amplifiers, and that's the point. This compact, lightweight, cool-running, class-AB power amp is a real breakthrough in every way. I definitely did not look forward to giving it back to JA for testing.
Listening In the Country
I took the AHB2 along with me for a weekend at our country place, in Connecticut, to see if it would be as successful with my more modest system there. That's where I discovered that my new hero amp wasn't quite perfect. Oh, its power and resolution were still not to be faulted, but through a pair of Monitor Audio Silver 8 speakers, the sound was somewhat hard and thin. Could it have had something to do with the Silver 8s themselves? While that speaker's minimum impedance is 3.5 ohms at 165Hz, but with a benign phase angle, JA points out that "there is a combination of –34° and 4.5 ohms at 100Hz, a frequency where music can have high energy." Still, he says, "A 4 ohm–rated amplifier or receiver will have no problems driving this speaker to high levels." If so, I would expect the Benchmark AHB2 to be more than up to the task. But here's how it played out. A 16/44.1 PCM file ripped from the above-mentioned Theessink CD seemed robbed of some of its warmth and resonance. Familiar recordings of women's voices, such as Marianne Beate Kielland singing Finzi's "Come Away, Death" (with pianist Sergei Osadchuk; 24-bit/192kHz PCM download from SACD/CD, 2L 2L-064-SACD), and Sara K.'s cover of "Can't Stand the Rain" from her Hell or High Water (CD, Stockfisch SFR 357.4039.2), sounded strange. Both voices were higher, not in pitch but in tonal range, as if they'd been transformed from mezzo-sopranos (which Kielland is) to sopranos. Again, I would describe it as a loss of warmth and resonance in the fundamentals of their voices. Unfortunately for the AHB2, this loss pervaded the sound of whatever recording I played. I wrote it off as an example of an amp-speaker mismatch.
But the seed had been planted in my mind. Back in Manhattan, all seemed better again with the AHB2—except for one troubling event. I've been ripping my CD collection to my 16TB NAS for a couple weeks (already it seems like months), and have become randomly reacquainted with some old favorites—such as the marvelous Emma Kirkby singing Mozart's "Exsultate, Jubilate" (with Christopher Hogwood and the Academy of Ancient Music; CD, L'Oiseau-Lyre 168055), which I hadn't played in ages. Sadly, the divine Dame Emma sounded to have aged badly on this 1984 CD. Akin to what I'd experienced in Connecticut, her voice was robbed of its bell-like richness by the AHB2, only to have it restored when switching to my other amps. Despite this, I'm still addicted to the Benchmark's sound—and I'm still unhappy about shipping it off to JA.
Conclusions
Just because I found Benchmark Media Systems' AHB2 not to be absolutely perfect under all conditions—after all, what is?—doesn't mean that I want to represent it as anything less than a marvelous-sounding amplifier. The AHB2 was capable of drawing more music from my B&W 800 Diamonds than I'd anticipated, and, mostly, sounded better than the other amplifiers I've used to drive those speakers. Combine the AHB2's superb sound quality with its low weight, low noise, low heat, and low cost, and it's clearly an amplifier that must be heard—even by those who can afford amps costing as much as 10 times more. That makes the AHB2 more than a Benchmark. That makes it a bargain.
"There are minima of 3.15 ohms at 91Hz, 3.1 ohms at 620Hz, and 3.67 ohms at 21kHz. Given that there are current-hungry combinations of 4 ohms and –52° electrical phase angle at 62Hz and 5.3 ohms and –39° phase angle at 8.6kHz, I believe this speaker should be rated as a 4 ohm load rather than the specified 8 ohms."
That seemed to present no problem for the AHB2, which, Benchmark claims, can pump out nearly 200Wpc into 4 ohms or 240Wpc into 3 ohms. In practice, I had to push the AHB2 to unreasonable and personally uncomfortable volume levels to get the least blink from one of its Clip LEDs. For this I used "Jazz Variants," from the O-Zone Percussion Group's La Bamba (CD, Klavier KD 77017), and the glorious conclusion of Saint-Saâns's Symphony 3, with organist Olivier Latry, Christoph Eschenbach, and the Philadelphia Orchestra (SACD/CD, Ondine ODE-1094-5). Both recordings are remarkably clean and spacious, with powerful bass; the AHB2 rose to the occasion, driving the two 800 Diamonds (sans subwoofer) to volumes louder than I ever hope to hear from them again (though it's nice to know I can). I also, very briefly, ran the AHB2 as a bridged monoblock into a single loudspeaker; it sounded the same, but I thought it would be pointless to try to get it to clip if I wanted to avoid annoying my neighbors. Just to let the power-hungry know. . .
Tonal balance is a curious audio parameter. Careful listeners often hear what sounds like an uneven or tilted frequency balance, even when measurements taken under lab conditions show it to be flat. Lots of real-world factors might account for this, including interaction of an amplifier's output stage with the complex input impedance of a loudspeaker. At first, I thought the AHB2 sounded less bright, and less full in the bass, than the other amps I had on hand, but after only a few days of listening I began to accept that it sounded more "right" than any of them. Now the treble wasn't so much un-bright as smoother and unaccented. The bass had all requisite extension and detail (see above), but seemed to be more naturally balanced with the rest of the audio band.
As time passed and I listened more, I grew to love the AHB2's sound, and undertook the rewarding effort of listening through it to as many different recordings as I could. It was a great pleasure, as old friends, some already mentioned, smiled anew. Yes, I could hear the differences between the different amplifiers, and that's the point. This compact, lightweight, cool-running, class-AB power amp is a real breakthrough in every way. I definitely did not look forward to giving it back to JA for testing.
Listening In the CountryI took the AHB2 along with me for a weekend at our country place, in Connecticut, to see if it would be as successful with my more modest system there. That's where I discovered that my new hero amp wasn't quite perfect. Oh, its power and resolution were still not to be faulted, but through a pair of Monitor Audio Silver 8 speakers, the sound was somewhat hard and thin. Could it have had something to do with the Silver 8s themselves? While that speaker's minimum impedance is 3.5 ohms at 165Hz, but with a benign phase angle, JA points out that "there is a combination of –34° and 4.5 ohms at 100Hz, a frequency where music can have high energy." Still, he says, "A 4 ohm–rated amplifier or receiver will have no problems driving this speaker to high levels." If so, I would expect the Benchmark AHB2 to be more than up to the task. But here's how it played out. A 16/44.1 PCM file ripped from the above-mentioned Theessink CD seemed robbed of some of its warmth and resonance. Familiar recordings of women's voices, such as Marianne Beate Kielland singing Finzi's "Come Away, Death" (with pianist Sergei Osadchuk; 24-bit/192kHz PCM download from SACD/CD, 2L 2L-064-SACD), and Sara K.'s cover of "Can't Stand the Rain" from her Hell or High Water (CD, Stockfisch SFR 357.4039.2), sounded strange. Both voices were higher, not in pitch but in tonal range, as if they'd been transformed from mezzo-sopranos (which Kielland is) to sopranos. Again, I would describe it as a loss of warmth and resonance in the fundamentals of their voices. Unfortunately for the AHB2, this loss pervaded the sound of whatever recording I played. I wrote it off as an example of an amp-speaker mismatch.
Just because I found Benchmark Media Systems' AHB2 not to be absolutely perfect under all conditions—after all, what is?—doesn't mean that I want to represent it as anything less than a marvelous-sounding amplifier. The AHB2 was capable of drawing more music from my B&W 800 Diamonds than I'd anticipated, and, mostly, sounded better than the other amplifiers I've used to drive those speakers. Combine the AHB2's superb sound quality with its low weight, low noise, low heat, and low cost, and it's clearly an amplifier that must be heard—even by those who can afford amps costing as much as 10 times more. That makes the AHB2 more than a Benchmark. That makes it a bargain.
