Benchmark’s AHB2 power amplifier: cool running, powerful and small in stature
1st June 2016
Offering an unusually light, small and cool running product, for its inherent power and facilities, Paul Rigby reviews the Benchmark AHB2 power amplifier
Despite the cooling vents fixed to the sides of the small chassis which might give a hint to its potential, this solid state power amplifier surprises in that it offers 100W of power into 8 Ohms and can be switched from its stereo mode to a monoblock in bridged mode to push out 480W via 6 Ohms. All this from a 6kg amp.
If you read this review and fancy grabbing a sample for your hi-fi chain, then make sure that the XLR inputs don’t catch you on the hop because that’s the only input game in town here. There are no other options available, unless you grab a converted cable.
Speaker connectors offer both standard RCAs or SpeakON Neutrik-type connectors. While we are around the back of this box, you’ll also see another Neutrik for the monoblock bridging mode, the latter is set via a simple toggle switch.
Also in this busy backplate rear area, you will see a 12v trigger for remote control of multiple units, for example or to offer control from another Benchmark product plus a three-position sensitivity selector switch here offering a progressively louder base sound as you cycle through each setting.
The front panel is sparse and, apart form the on/off switch, is occupied with response lights for clipping, muting and temperature concerns.
Inside, the AHB2 utilises class A/B power with Class H. The latter the implementation of the THX-AAA standard (Achromatic Audio Amplifier) that employs a feed-forward error correction amplifier running in parallel with the high-power main amplifier.
Also, the company declares that, “…the AHB2 uses a resonant switching power supply that has a very fast control loop. This control loop responds to audio-frequency load changes and keeps the supply voltage constant without the use of a large bank of capacitors. This active regulation is much more effective than capacitive energy-storage. Maximum power output of the AHB2 does not vary with line voltage or audio loading. The power supply rails maintain a constant voltage during audio peaks.”
Benchmark also talks about the low noise nature of the amplifier, “Most power amplifiers have far too much gain and consequently they suffer from poor noise performance. The AHB2 is 17 dB quieter than some of the very best power amplifiers on the market. A rear-panel gain switch can be used to set the AHB2 at higher gain settings if necessary. The low-gain setting is designed to interface directly with Benchmark DAC2 converters.”
Starting with Dakota Staton’s album ‘Round Midnight from the original Capitol release, issued in 1960, I connected the Benchmark to my Quad 57 electrostatics, which are not the easiest speakers to drive. Because of that, I had to up the gain on my pre-amp just a few clicks more than usual. This confirmed that, with hard to drive speakers, I would recommend grabbing two Benchmark amps and using them in mono block mode.
That said, my initial view of the sonic qualities of the the amp were good. More than that, I was impressed by the well behaved nature of the output. Staton’s vocal delivery was calm, even and smooth without any edginess to her delivery and certainly without any brightness or blooming during crescendos. Her even-handed vocal delivery was very pleasant indeed. If anything, if I was going to be overly picky, it might have been nice to have had a touch more insight and sparkle to add slightly more life into the vocal treatment but I’m being greedy here and probably butting up against the price point, as opposed to the design or its implementation.
As for the instruments backing Staton, I was impressed by the tonal accuracy of the introductory strings and the clarinet. Both, backed by the similarly impressive low noise nature of the soundstage, had room to express themselves that enhanced the richness of their performance.
One thing that I did listen out for was the previously subdued nature of both the piano and the percussion which were often pushed back into the mix but also partially masked by noise. The Benchmark initially removed that noise to reveal more about each instrument while the improved clarity gave each instrument more of a say in the mix and a more prominent position.
More than any of the above, though, was the ease which music was delivered to the ear. There was no apparent hurry to the AHB2. It does what it does and does it well and there’s plenty of time so kick back and release that tension because you’re in good hands. That’s the sort of feeling that you get from this box. You trust it, in other words. You know that it won’t insert some nasty frequency to scare the life of you. There will be no wincing or hiding behind the sofa with the AHB2.
From jazz vocal to dub – a more contemporary release, Rootmasters’, Elephant Puddle (2007), featuring The Orb’s Alex Patterson and a chance for the Benchmark to display its bass qualities.
To be frank, the soundstage for this sequence of music is a mess. There are threatening frequencies all over the place here with dynamics in the potentially chaotic region, the potential for blooming and smearing in the midrange with muddy bass and bright voices plus inaccurate percussion. I’ve heard this occur, in varying degrees, with many hifi components to various degrees but the AHB2 never suffered any of those issues. Not one. Everything was in order and everything was in its place. Part of the reason for this was the low noise so, right from the off, the music was much more focused than many other components. This increased the clarity and the spacious nature of the playback which meant that any available space – and there wasn’t a great deal to begin with here – was utilised to separate and control each bank of frequencies. In addition, the tonal accuracy had a much better chance of impressing while the bass was pretty spectacular: rousing, on an emotional level, but also informative and characterful. Bass was never one dimensional but had a layered personality of its own.
Taking a more orchestral point of view I then turned to the spaghetti western soundtrack, Django, from 1966 and Luis Bacalov and the minor piece of music, more mood music really, called Town of Silence.
I was taken by, of all things, the tonally accuracy of the bongo drums on the piece plus the tiny but significant reverb tail that each strike to the drum affected. Not only those, though, the very twangy guitar obviously had its effect from plucked strings and I was happy to hear actual effort that successfully portrayed the string being moved. This gave the guitar extra power and force in its presentation. Finally, the piano offered a sinister role on this trick. The added reverb and bass-focused nature of the keys delivered an imposing sense to the track.
Neat in construction, busy in terms of features and small in stature, the AHB2 is quite remarkable in how it goes about its business of delivering music. I’ve seldom heard such a balanced, easy on the ear power amplifier as this that also provides tonal accuracy plus an attractive space in the midrange. The AHB2 would be an ideal fulcrum to any hi-fi system, acting as the heart around which you can build up your hifi chain. It’s dependable and rock solid. The perfect heart to any hifi.
BENCHMARK AHB2 POWER AMPLIFIER
Tel: 03301 222500
GOOD: bass impact, low noise, transparency, clean output
REFERENCE SYSTEM USED
Origin Live Sovereign turntable
Origin Live Enterprise 12” arm
Transfiguration Proteus cartridge
Icon Audio PS3 phonostage
Aesthetix Calypso pre-amp
Icon Audio MB 845 Mk.II monoblocks
Quad ESL-57 speakers with One Thing mods
Vertex AQ & Atlas cabling