Benchmark Media Systems AHB2 Stereo Power Amplifier Reviewed

For years, the audio world acknowledged one main contender (at least at sub-five-figure pricing) for the quietest, cleanest, most neutral power amplifier around. That was the Benchmark AHB2 ($3,499 – buy at Amazon), whose specifications are still, for all practical purposes, unsurpassed, even by today’s excellent Class-D amps. The AHB2’s introduction in late 2014 was met with a wave of enthusiastic reviews and happy listeners, and the amp deservedly became a polestar for reviewers, audiophiles, and audio professionals.

The Benchmark AHB2 stereo power amplifier can output 100 watts per channel into eight ohms (190 watts into four ohms, 240 watts into two ohms) and, when switched into mono mode, it outputs 380 watts into eight ohms (480 watts into six ohms). In response to my query, Benchmark adds that, even in mono mode, the AHB2 can drive speakers with impedance that dips to one ohm in a few areas. At the same time, its noise and distortion figures are so superlative (less than 0.00013 percent) that audiophiles and reviewers were gobsmacked when the AHB2 was released. To achieve this performance, the AHB2 operates in Class H, using a feedforward error correction method licensed from THX (Benchmark’s website has white papers on this). The amp is compact, runs cool, and is supported by an established US manufacturer. Is it still the amp to beat? A lot has changed since they were launched, but this is our task and it is going to be fun …

What Makes the Benchmark AHB2 Stereo Power Amplifier So Special? 

• The Benchmark AHB2 has some of the lowest distortion and noise specs of any amp. Years ago, I was among those who believed that further lowering the distortion and noise specs of top audio amplifiers was pointless. But when I heard amps with ultra-low noise and distortion, I instantly loved the sound. Less irritation coupled with more detail have become big factors in my audiophile enjoyment.
• The Benchmark AHB2 has a neutral and extended frequency response. It’s rated at +0/–3 dB from 0.1 Hz to 200 kHz. Into a four-ohm load at the conventional frequency limits of human hearing, it’s –0.23 dB at 20 Hz, –0.32 dB at 20 kHz. The frequency response changes very little with speaker impedance.
• The AHB2 is compact and efficient physically. The small case (approximately 11 inches by four inches by 11 inches, including feet and connectors), light weight (13.5 pounds) and cool running allow the AHB2 to fit well into most systems, even desktop systems. It’s magnetically shielded to prevent interference with nearby equipment.
• The Benchmark AHB2 is designed, assembled, and tested in the United States. Benchmark has designed this amp from input to output, without relying on modules from another maker. This allows complete control over all aspects, including quality of components and the distortion characteristics of the finished product. 
• The AHB2 includes comprehensive protection circuitry, a full user’s manual, and a five-year warranty (in the United States).
• The Benchmark AHB2 is easily switchable from stereo to mono by flipping a switch on the back panel. An audiophile can start with one AHB2, then add a second when their power needs change or funds allow.
• Selectable sensitivity means the AHB2 can deliver lowest noise with almost any system. Again, just flip a switch on the back panel.
• The AHB2 has auto-ranging power input. Without user action, it accepts AC at 50-60 Hz and voltages of 100-120 or 220-240. If you travel internationally with an audio setup (remember, this is a pro audio product at heart), this is a great convenience and safety feature.
• The Benchmark AHB2 is an attractive audiophile amplifier that is sturdy without frou-frou. Your audiophile budget doesn’t go for a thick front panel or fancy casework. Instead, you get a professional, clean look.

Why Should You Care About the Benchmark AHB2 Stereo Amplifier?

Two remarkable things about the AHB2 are its relatively high power output, especially in mono mode, and its vanishingly low noise and distortion. Once you have heard a high-powered, ultra-clean amplifier, it’s hard to go back. When playing a top-quality recording, a high-powered amp like the AHB2 can give effortless reproduction of musical peaks with consistent timbres, no audible limiting, and no fear that the sound will fall apart when music gets loud and complex. Clean and uncompressed peaks can take the roof off a performance and move it into a freer, more open space.

The Benchmark AHB2’s remarkably low noise and distortion also make a real difference. Audiophiles talk a lot about lowering the noise floor — well, here is a component that does so audibly and measurably. When you use an amp with low noise and distortion, imaging and soundstaging are clearer, instrumental timbres truer, voices more natural, and previously fuzzy lyrics snap into focus. This is absolutely addictive.

A final characteristic of the AHB2 that many audiophiles will enjoy is its warmth. This is not an amplifier that is shrill, tizzy, or electronic-sounding. How much the apparent warmth is due to the AHB2’s lack of high-frequency distortion, how much to its slight high-frequency roll-off (less than –0.4 dB at 20 kHz), and how much to other factors, I can’t say. But I can say that the AHB2’s treble was generally natural and well-controlled, even on recordings with fiddles in high octaves or singers recorded with peaky mics. That was a musical pleasure.

Some Things You Might Not Like About the Benchmark AHB2 Power Amplifier

• This amp only accepts balanced (XLR) inputs. If your source DAC or preamp has only single-ended (RCA) connections, you can get adapter cables from Benchmark at quite reasonable prices.
• The rear panel is somewhat crowded in terms of layout. Benchmark recommends their own audio cables, which fit without interference and provide a neutral sound. Exotic speaker cables, interconnects, and power cords might not always fit.

Listening to the Benchmark AHB2 Power Amplifiers … 

I used two Benchmark AHB2 amplifiers as monoblocks in my reference audiophile system, with its multiple subwoofers disconnected, so the AHB2s played the entire frequency range. As always, I listened to a wide variety of music, including pop, rock, jazz, blues, classical, and bluegrass. I also briefly tried the AHB2s in combination with Benchmark’s own DAC3B and LA4 preamplifier (review forthcoming). In comparison to my reference Apollon amplifiers with PuriFi 1ET400A Class D modules, the AHB2s were a bit more relaxed in the treble. On most tracks, I enjoyed that; on a few, I missed the visceral excitement of the Apollon amps. On every track, I enjoyed the unforced detail and clarity of the Benchmark AHB2s.

Western swing band Asleep at the Wheel has won 10 Grammys since their founding in 1970, and their music brings a lot of fun to the scene. I had a fine time with “Walking the Floor Over You” (written by the late Ernest Tubb) from their album Western Standard Time. You don’t need to be country folk to end up tapping your toes or dancing to this song. Lead singer Ray Benson’s baritone was clear, smooth and lifelike; the simple drum line rang through; the steel guitar and fiddle were absolutely superb musically and sonically; and, as with everything I heard through the AHB2, vocals and instrumentals were easily followed as separate lines, as well as parts of the whole. All in all, the AHB2 presented the joy and energy of this performance, as well as its details. 

In 2024, singer-songwriter-pianist Laufey’s album Bewitched won Best Traditional Pop Album at the 66th Annual Grammy Awards. I enjoyed the Icelandic-Chinese artist’s take on “Misty” (a classic by pianist Erroll Garner and lyricist Johnny Burke), which melds an old tune, classic singing virtues, and up-to-date sound into a great track. Through the AHB2, I heard that Laufey’s voice was recorded with slight sibilance, but despite the close-up vocal recording, that sibilance was well-controlled, never irritating. Laufey has called Ella Fitzgerald an inspiration, and it shows, though Laufey has yet to attain Fitzgerald’s vocal freedom. The warm piano sound and brushed drums were recorded in a distinctly more recessed acoustic than the vocals, yet everything added up to a fine performance, more dreamy and less bouncy than Garner’s classic piano version. I especially appreciated the AHB2’s smooth, well-integrated treble, free of splashiness or grain, and its natural reproduction of the human voice. 

In 2019, Rolling Stone published the article “Why Guitarist Billy Strings Is the Bluegrass Star You Don’t Want to Miss.” If you haven’t read it yet, here are my reasons: Strings is a virtuoso, playing stringed instruments like the Devil; he knows every old song and writes new ones; he sings in tune; he collaborates with old and young alike; and he’s got outstanding bluegrass chops, combined with the raw energy of a rock star, without the rock star attitude. From Strings’s album Me/And/Dad, recorded with his father, Terry Barber, I put on “Little Cabin Home on the Hill,” which Strings and Barber play with enough intensity to wake the dead. Listening through the AHB2, I was loving it and singing along. Voices were natural, and I could hear that harmony vocals were not Strings double-tracked, but someone else (presumably Barber). The soundstage was wide, images distinct. For anyone remotely interested in traditional American music and how it’s evolving in the 21st century, this is a demo track musically and sonically. The AHB2, with its natural, detailed presentation, helped it sound its best.

Will the Benchmark AHB2 Power Amplifier Hold Its Value?

I believe the AHB2 will do well on the used market. It’s still head and shoulders above most amps in objective performance; its US maker is well-established and offers great service; it has gathered many awards and glowing reviews; and it’s still a current model. All those factors are positives.

Another positive is that the AHB2 will be easy to ship because of its light weight, small size, and rugged construction. For those reasons, I expect the Benchmark AHB2 to hold its value better than most audio components.

What is the Competition for the Benchmark AHB2 Power Amplifier?

Here are a few low-noise, low-distortion amplifiers that I’d consider auditioning along with the AHB2. They are all Class-D models.

The NAD Masters Series M23 uses Purifi 1ET400A Class-D amplification modules, the same low-noise and low-distortion modules as my reference amps. In stereo mode, the M23 is rated at 200 watts per channel into eight ohms, or 380 watts into four ohms. In mono mode, it provides 700 watts. It’s housed in a standard-sized case, and offers both balanced (XLR) and single-ended (RCA) inputs. Priced at $3,749, the M23 carries a three-year warranty.

I recently reviewed the Atma-Sphere Class-D monoblocks ($6,120 per pair; read my review) which, like the AHB2, are designed and built in the United States. Though their measurements are not quite as astounding as those of the AHB2, they have a smooth sound that many audiophiles will enjoy. They offer both RCA and XLR inputs, and output 100 watts into eight ohms (200 watts into four ohms). The case is similar in size and weight to the AHB2. Warranty is three years.

The Buckeye Amps PuriFi 1ET7040SA Monoblock, v2 uses PuriFi’s newer modules, designed to drive even low-impedance speakers at full-rated power. Priced at $1,790 per pair, the Buckeyes offer balanced input, switchable sensitivity, and are rated at 250 watts into eight ohms (500 watts into four ohms, 950 watts into two). Made in small, simple black cases, these amps come with a two-year full warranty and reduced coverage thereafter.

The Orchard Audio Starkrimson Mono Premium amps so impressed publisher Jerry Del Colliano that he privately called them contenders for our Product of the Year award. These small, no-nonsense amps ($2,500-ish per pair) use GaN technology to deliver 150 watts into eight or four ohms. (An Ultra version offers more power at a modestly higher price). Orchard’s warranty is one year.

Final Thoughts on the Benchmark AHB2 Power Amplifier …

10 years after its release, the Benchmark Media Systems AHB2 stereo power amp is still a standard-bearer in clean, neutral sound in the audiophile world. Although there are less expensive power amps with ultra-low noise and distortion, the AHB2 will be a compelling buy for many picky audiophiles. Besides its superlative sound with an apparent touch of warmth, the amp offers design by a storied, well-established firm, a five-year warranty, excellent customer service (if you ever need it), and the other advantages I’ve described above. You also get instant audiophile street cred. I greatly enjoyed having a pair of AHB2s in my system – their purity, neutrality, and seemingly unlimited power provided a clear window on the music and a lot of joy.

I suggest that any audiophile interested in a power amp of objective and subjective excellence should audition the Benchmark AHB2. If you haven’t heard a modern ultra-low-noise and distortion amp, you may be astounded at what you have been missing. For many audiophiles, the AHB2 will be an endgame choice, one that lets them stop thinking about upgrades and simply enjoy the music, which is much of the battle as we upgrade and improve our systems.