Benchmark AHB2 Power Amplifier Review
Rafael Todes samples this pro audio power amplifier both in the studio and at home…
Benchmark Media Systems
AHB2 Power Amplifier
There's an interesting parallel universe to be discovered in the neighbouring domain of pro audio – after all, engineers should want the same as audiophiles, namely great sound. True, they also demand greater reliability and ruggedness due to the rigours of continuous usage and often transportation. Yet for some strange reason, very few products truly bridge this divide – never the twain shall meet, it often transpires.
Companies like dCS and Chord Electronics spring to mind as exceptions to this rule, but perhaps it's an easier job for digital converters as they're not being asked to directly power banks of studio monitors or PA loudspeakers. As far as the latter is concerned, B&W has famously made in-roads to the great temple of recording that is Abbey Road, and Quad electrostatics are sometimes found in the vans of recording engineers. Still, amplifiers are less likely to cross the great divide.
In my experience as a professional musician who's regularly performing live and/or recording, I can't think of many amps with dual hi-fi and pro functionality. Maybe Bryston and the odd ATC, but there aren't a lot. However, to this shortlist, we can add Benchmark. I first heard about this brand over a decade ago, when it made an excellent – by the standards of the time – and reasonably priced DAC. Based in Syracuse, New York, the company was founded thirty years ago by Allen H. Burdick, who died recently. His initials adorn the AHB2 power amplifier that you see here.
Two things strike you upon first seeing it – it's surprisingly compact, and it also has the sort of features that make it more at home in a studio than a listening room lounge space. You can bridge the AHB2 to make it a monoblock, or bi-wire it to a single speaker; there are only balanced connections incoming, as well as a choice of gain to match the speaker. You get normal speaker binding posts plus a pair of Neutrik's Speakon connectors on the output side. The front panel has a power switch and a light display, which can be decoded with reference to the manual. The amp performs a series of self-tests on start-up, and the various lights come on to show current warning, clipping, temperature problems, or power supply loss.
It runs very cool all the time yet provides a quoted 100W RMS into 8 ohms, both channels driven, and nearly twice that into 4. It's an interesting design, developed jointly with THX. The company says the AHB2 shows no traces of the crossover distortion and delivers less than 0.00011% total harmonic distortion in stereo mode – which is extremely low, if you were in any doubt. It uses a switching power supply – explaining its light 6kg weight and small size – and runs in Class H, with a novel Class AB output stage and multiple power supply rails to improve efficiency.
I normally like to leave an amplifier on to burn in for a few days, before getting my head around what it's doing. However, in the case of the Benchmark, it switches itself off after forty-five minutes of inactivity. Just as well then, that the manufacturer says that it needs little warm-up to fully come on song. The AHB2 duly found itself installed in my reference system, comprising a Townshend Allegri Reference preamplifier complete with fully balanced inputs and outputs, plus a dCS Bartok streaming DAC. I initially gave the amp my pair of B&W 802D3s to play with, appropriately enough a cousin of the speakers than can be found at Abbey Road Studios, just down the road from me.
I often use a PS Audio PS10 power mains regenerator because it makes a massive difference to my reference system's sound in some instances. When I first fired up the AHB2 without it, the soundstage was surprisingly two dimensional. I live in central London, where there's a lot of noisy mains, and I found the Benchmark to show this in no uncertain terms. Hooking it up to the PS10 brought the soundstage back to something approaching what I'm used to from my reference VAC PHi 200 valve monoblocks.
Properly set up, I was impressed by its creamy character; there's no audible distortion to speak of, and you end up with a rounded and mellow sound. Perhaps surprisingly for a pro audio product, it was pleasant and quite detailed, but in no way the type of analytical character I'd expected. I rather liked the even-handedness and general 'considerateness' of the sound; it was grown-up and polite without any artificial edge.
For example, with a recent recording of Strauss's Heldenleben with Vasily Petrenko and the Oslo Philharmonic, things were pleasant and almost tonally rich. There was plenty of power and space and a generally broad-shouldered and gutsy sound. Yet compared to my reference tube design, I did find the palette of colours to be more limited; the AHB2 made everything seem just a little warm, and the texture of the instruments wasn't quite as well resolved. The wonderful range of tonal hues that go to make up a full-sized symphony orchestra just wasn't there, but I could see how the Benchmark would work in a studio. Where you want to hear detail and fault find, this tonal balance would be just the job.
I then moved it upstairs to my other system, where I've been running a medley of classic monitors of late – Yamaha NS-1000Ms, Quad ESL63s and a recently acquired pair of Rogers LS3/5as. These were being driven by a classic Marantz 8b tube power amp – and as coincidence would have it, manufactured in New York back in 1961, fifty-two years before the ABH2 was made in almost the same place! Interestingly, I found the Benchmark power amp worked better in this set-up; its obvious strengths were able to shine through more easily.
Driving the NS-1000Ms, there was a distinct improvement over the B&Ws. This amp had enough power and grip to get the Yams going, and their more revealing midband helped to extend the range of tonal colours that I could hear it painting. I could still tell that it had a certain 'studio' style to the way it makes music, but many will regard that as a strength. Listening to Simon Rattle conducting a hi-res recording of Haydn's 88th Symphony, I enjoyed the phrasing of the slow opening; the music was well ordered, tidy and laid out neatly in front of me with a sense of poise and control. This isn't a gushing, emotive performer; instead, it brought a more matter-of-fact style to the proceedings – just what you'd expect from a piece of pro gear.
Driving the Quad electrostatics, things were more impressive still. These speakers can be a tricky load to drive, but the AHB2 just shrugged them off, apparently not in the least bit bothered by what it was being asked to do. I found the sound was strong and grounded; bass was taut and controlled with nice grip and the midband was crisp and clean, with plenty of detailed information that a sound engineer would find helpful. Playing Kraftwerk's Tour de France, I was pleasantly surprised by the soundstage, which of course is a Quad electrostatic forte. Things sounded more immersive and three dimensional than you might expect from electronic music such as this, beautiful though it is. It's not the most spacious amplifier I've heard in terms of stage depth but is excellent at the price, nonetheless.
Reviewing the AHB2 was interesting for me, as it reminded me of just how quirky and eccentric my own hi-fi systems have become. The Benchmark is, as its name suggests, more of a jack-of-all-trades that attempts and succeeds to do a lot very well. It's a great leveller because whether I was playing classic rock from REM in the shape of Welcome to the Occupation, or a Debussy prelude, it had a consistent, even, ordered and mature sound backed up by lots of loudspeaker load driving ability. As all good studio gear should do, it focuses more on the mechanics of the music than the inner subtleties of the piece in question. That kind of goes with the territory…
Thumbs firmly aloft then for this compact, versatile, thoughtfully designed, well-built stereo power amplifier. Benchmark's AHB2 is a class act that delivers an awful lot at its price. It also doubles up as an excellent do-it-all stereo power amplifier in someone's home when not being hammered by a dishevelled studio engineer. I make recordings of orchestral and chamber music, so am keenly aware of its abilities both one way and the other.
Gifted violinist Rafael is one quarter of the Allegri String Quartet, playing second fiddle. Once a member of the CBSO under Sir Simon Rattle, he now teaches at London’s Junior Royal Academy. A long-time audiophile, he’s still on a quest for the perfect sound.
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