This is a balanced input, 100 watt (8 ohm) per channel stereo power amplifier. It has a signal to noise (SNR) ratio of 132db in stereo mode, A-weighted, with a Total Harmonic Distortion+Noise (THD+N) of < 0.0003% at full power.
The AHB2’s output has three settings and it can be used as a mono-block. The amps full specs can be found HERE.
When the Benchmark AHB2 came out I remember reading a couple of the reviews thinking what a neat little thing it was; Stockholm syndrome, I had been conditioned by Naim shoe boxes. Later a friend who was using Pass amps was very keen to listen to the Benchmark based on the superb specs, but life intruded and so it never happened, but my peaked curiosity remained.
The only Benchmark gear I have owned was a DAC1, which I used for two years. An excellent bit of kit and not greatly bettered by the Naim DAC that replaced it, but the extra nDAC inputs were very handy at the time and the added PSU improved the Naim further.
The double boxed Benchmark AHB2 took a few weeks to arrive due to the supply issues that are bedevilling the world at the moment, it had to return from another reviewer. So, what was supplied had been run in.
This power amp is a reassuringly heavy be-finned black box, I love the industrial business-like styling. My intention was to listen to the amp through my Nearfield system before putting it up against my main system’s Naim 300DR.
If like me, you have an interest in Audio Visual (AV) then the Tomlinson Holman eXperience (THX) will be very familiar, something developed for George Lucas and first used for ‘The Last Jedi’, back when Star Wars films were worth watching. THX was sold by Lucas to Razor Inc in 2016. When the AHB2 was released it was the first time I had seen THX associated with a HiFi amp.
The Benchmark AHB2 uses both feedback and feedforward error correction. The feedforward is a technology called THX Achromatic Audio Amplifier (THX AAA), achromatic indicating it is colourless. The development of THX AAA is discussed HERE. The video interviews Laurie Fincham, a man with an impressive CV. It briefly covers a number of areas including different amplifier topologies, before going through feedback and feedforward and moving on to the Benchmark AHB2 use of these techniques.
The Benchmark explanation of the feedforward technology can be found HERE.
Many amplifier designs use negative feedback. This trades off some of the gains for other performance benefits.
Feed-forward allows the identification and removal of any introduced noise and errors.
HiFi specifications are an interesting subset of lies, damned lies and statistics. Above I quoted the power output of the Benchmark AHB2 into 8ohms, Benchmark provides a series of measurements at different loads in their specifications, it is refreshing to see the complexities of such specifications acknowledged.
The ultimate question is whether these stellar measurements are reflected in what is heard?
The tracks were selected to allow:
· Comparison of local and Qobuz sourced versions of the same tracks;
· Comparison of standard and remastered versions of the same track;
· The presentation of uncompressed LP rips served digitally;
· The presentation of vinyl played via my turntable;
· Comparison of older and modern tracks, with their different mastering priorities;
· How problem tracks and LPs were presented.
Qobuz Playlist: https://open.qobuz.com/playlist/7688378
I warmed up my ears by listening through the review playlist a number of times before slotting in the Benchmark AHB2. This moved from using the Hugo TT RCA outputs to the balanced XLRs.
Turning on the AHB2 resulted in SILENCE as the FPGA controlled routines checked that all is correct, with two red lights illuminated on the front. After a few seconds, the lights went out and ….silence still reigned. The amp took about twenty minutes to come fully on song before which it could be shrill and the bass less than controlled. Once warmed up this is NOT the case.
My immediate impression was of the sheer detail being presented. I can understand why this amplifier is valued by professionals, it is superbly informative. The Benchmark controlled my Sound Artist LS3/5a in a vice-like way. The control of the bass was such that I almost felt the speakers were working downwards by an extra octave. The AHB2 was even-handed across the frequency spectrum with a balanced mid-range presence.
Is great detail a good thing? It is certainly impressive and will have the listener in raptures as they hear the previously unheard. A number of years ago I listened to a Schitt Yggdrasil in my system, this was incredibly detailed but to me, over time, I felt as though I was present at a musical autopsy. I could see all the parts but the musical joy and engagement was diminished. I never had this impression with the Benchmark AHB2, but that is not to say that it is a completely positive experience.
Let us start with unblemished pleasure, having installed the Benchmark I started with Mussorgsky’s Picture at an Exhibition transcribed for the organ and played by Jonathan Scott. This is on YouTube. I have converted it to WAV at 16/44.1. I would love to buy a slew of his transcriptions but I can’t find them. The downloaded file is not stellar. Principally the lower octaves are missing. As much as I love the transcription generally its failings prevent me from listening to it for too long, my attention just drifts. I expected this to be starkly highlighted by the Benchmark AHB2, but no. Of course, the Acoustic Artist LS3/5a do not produce the deeper bass, but what was produced was clear and insightful. I simply got on with enjoying the organs three registers as they weaved and wefted the music with Scott’s skills clearly on display.
On to Mozart’s Requiem conducted by Karajan (1976) singing the Communio Lux Aeterna, as I am rehearsing this at the moment it was a joy to hear this sung by truly competent singers! The 140 gave me a bit more in the mid-range, but here the acoustic was beautifully presented with the choir splendidly laid out. The diction was clearly reproduced.
Next up was a live rendering by Mary Black of Columbus, my favourite version of this song. When you watch this on the DVD you can see the drummer in the opening using timpani mallets initially on a cymbal before moving to a drum, crescendoing and diminishing just before Mary enters. This is heard, but barely, through most amps I have tried. Through the Benchmark AHB2 it was more clearly present and correct; as, unfortunately, was the blithering idiot who left their phone turned on, grrrrrrrr. The support from the double bass was well rendered, you could hear the player as they leant into the notes then back off – and there are those mallets again, I had not noticed them there before.
Son of Man, Tarzan, Phil Collins is a track that usually suffers from excessive ssssses. These were not completely absent here, but I was distracted by how well the rest of the track was produced, a low drone that underpins the music when listening through the NAP140 was being clearly presented as proper bass and the bass drum had some real kick. I had to restart the track to concentrate on the sibilance. Yes, it is there, but there is so much more and the Benchmark was making the best of what was available.
This amplifier could in theory be one that while being superb at revealing detail is a devil with poorer quality music, it is not. However, there are occasions where that clarity is less than welcome. Alan Parsons Project has released a live album, The Neverending Show: Live in the Netherlands. I have been thoroughly enjoying it, especially as the lead vocalist sings better than most that Parsons uses. However, with the Benchmark AHB2 the backing vocalists are revealed in all their mediocrity.
In a nearfield system, the proximity of the speakers to your ears allows the equipment to maximise its delivery of information. Moving to the main system can mean some of the finer detail is not so readily apparent, but there is a gain in sound staging. Time to move the Benchmark AHB2 downstairs into my main system.
My main speakers are Naim SBLs with Avondale crossovers. I have a very healthy respect for these speakers which are wonderfully informative.
The Icon 4 has single-ended outputs so my first move was to use simple XLR adapters into the Benchmark AHB2, this is not ideal. I started by firing up the digital front end, my immediate impression was wow! I had never heard the speakers disappear so effectively via the dCS. What was present was informative detail, a well-balanced sound stage and well-controlled underpinning bass.
I worked my way through a sequence of Qobuz sourced files each as impressive as the last. I decided to compare the local with the remastered Qobuz versions of Bohemian Rhapsody. The mastering choices of the remastered version were once again laid bare. The local CD rip was full of extra detail, but the lead vocals were perhaps short of a touch of body that they had through the Naim 300DR.
I was blown away.
I have been listening to a large amount of vinyl recently while writing the review of the Chord Huei. Most recently I had been listening to Alan Parsons Project, Ammonia Avenue. This had been simply excellent when I listened to it. I bought my LP12 online with a sense of rising anticipation. Once again extra detail was revealed, but my enjoyment and engagement was reduced. I was enjoying the music, but I knew it should be better. I decided to take a break and return to the system the following morning.
Overnight I kept asking myself why my digital front end would sound so good and the turntable does not engage to the same degree? A thought came to mind.
The following morning I teed up The Beatles, Blue Album. I had been playing this a few days before. Again, still very good with extra information, but not as engrossing.
The thought that had entered my mind the previous night was, ‘Dynamic Swings’. I played Muse, Origin of Symmetry, New Born. In the track, the opening minute or so is quiet, restrained before it goes bat-shit crazy. Through the 300DR the emotional engagement and excitement makes this a real moment, but not through the Benchmark AHB2. More informative, but less drama. Once I had noticed this I went back through my music, and yes, this was consistent. It does not mean the music through the Benchmark lacks power or grunt, it has this in spades. But, when the music calls for a dynamic swing it is just that bit more restrained. But that bit takes a song and makes it into an occasion.
The Benchmark AHB2 is an excellent amplifier that gets stunningly close to Mr Walker’s, ‘Wire with gain’. It presents an immense amount of information that is reproduced in an engaging and musical way. When compared to a more traditional class AB amplifier costing twice the price, but one with a large power supply & transformer, it fails to have the same macro-dynamic abilities. I would love to hear the THX AAA technology within such an amplifier, although I suspect there would be a range of issues that would need attention.
I came very close to buying the Benchmark AHB2, it does many things that I love. Ultimately the macro-dynamic swings that I love were not as present with the Benchmark AHB2, but I could imagine many people prioritising its strengths. If you prefer music that leans more on micro-dynamics, where the detail of the individual musician is key, then this may well be your choice; the Mary Black track above is good evidence of its music enhancing strengths.
The Benchmark AHB2 amplifier is a superb achievement and excellent value for money.