Benchmark made its mark on the audio fraternity in the late 2000s with the unusually compact, yet full featured, converter and preamplifier... the DAC1, the latest DAC2 incarnation of which I reviewed in these pages a couple of issues back. But, the brand’s origins start in founder Allen H. Burdick’s garage back in 1983, when he started making electronics for the broadcast industry. The company was incorporated two years later and moved to its current home in Syracuse, New York. It still has a pro-heavy product range, but until last year that range didn’t include a power amplifier, even if there has been a reference amp that Benchmark engineers have used for product development for some time. This former in-house only model was designed by Burdick himself (hence his initials gracing the facia of the AHB2), but it went through some major changes when Benchmark started working with THX and its achromatic audio amplifier technology, or AAA for short.
You get some indication of this technological back-story when unboxing this power amplifier, but what hits you first is its unusually compact size for the power output rating. The AHB2 is less than half the size of most power amps; you can tell by the back panel if you look at the relative size of the speaker outputs just how small. This challenges the usual assumption that size equals power quite seriously and this must make marketing a bit of a challenge in some regions. But Benchmark must be encouraged by the success of the even more compact DAC1 and 2, and perhaps it sees the end of the era of room-filling electronics more clearly than most.
As ever with Benchmark, it seems size does not limit feature count; not only does the AHB2 have conventional four-way binding posts, but there’s a pair of Neutrik’s Speakon connectors as well. This is an indication of its studio inclinations in one respect, but also a reflection of the fact that Benchmark makes a monitor (the SMS1) with matching inputs and a bi-amp or bi-wire option when using them. The AHB2 only has balanced inputs however, it being a fully balanced design. This is fine for pro applications and Benchmark DAC/pre owners, but less convenient for many domestic users who remain firmly single-ended.
Getting back to the THX connection, apparently the core design of this amplifier and its Class H power supply were designed by that organisation. At its heart the AHB2 has a switching power supply, which explains its diminutive size: it’s a Class H design rather than Class D because it features a Class AB output stage, and it uses multiple supply rails to improve efficiency. The Class AB output stage is a bit different from most: the AAA element consists of a feed-forward error correction amp that seeks to minimise distortion by “measuring, inverting, and buffering errors in the main amplifier”. It is claimed to be superior to conventional feedback designs when it comes to measured distortion.