Benchmark AHB2 amplifier - what to expect?

Just do it! 😉

Due to a recent house move, I have been experimenting with two sets of stereo systems I have assembled over the years and found things quite interesting, especially with speakers, preamp and amplifiers matching, in my case Harbeth Compact 7-ES / B&W 702 S2, amplifiers MC MHA 150 / Benchmark ABH2 / Rotel 1552 MkII / PS Audio Stellar S300. Preamp is PS Audio BHK. Sources are HIFI Rose 250 streaming transport / Technics 1500 turntable / Audio Lab CD transport. DACs are Schitt Audio Multibit / Gustard X16.

IMHO BM ABH2 paired well with Harbeth speakers and BHK preamp, it delivered stunning sound stage and resolution, at the same time well preserve the musicality of the whole chain without sounding too analytical or bright for most of the recording quality and materials. When switching to BW 702s, the chain sounds good, but could be a bit too bright or fatiguing for certain recordings. Harbeth also tolerated class D amplifiers such as PS Audio Steller very well, even through its sensitivity is only 87db. So much for trusting the specifications.

So at the end my BW 702s sounds best with BHK preamp and Rotel 1552 MK II. The BM amplifier coupled with BW’s high sensitivity and sheer resolution power are just too much for my ears.

Hopefully this experience is helpful for other folks.

 

 

 

 

Agree, it’s really one of many BM designs with practical and beneficial sonic paybacks than the voodoo claims from other brands. “Gain Staging” can boost your system S/N ratio tremendously along with the use of true balanced connections.

I wish more amps had gain adjustments like the Benchmark. Accuphase comes to mind for the gain feature. I always wanted to try an Accuphase amp, however, way pricey (for me anyway)

I got the message a day after I signed up for email notification when available. BM also provides a preorder link

I see the message on their site. Thanks!

I have already placed my order back in March (with a $1K deposit with the dealer here in SG) and hoping to receive it in May.

@mktmkt
Thanks for sharing the info on ahb2 future availability. How did you get that message? What is the source? Did you put in the pre-order?

"Thank you for your patience. We are now accepting orders for the AHB2 power amp. Shipping will begin the first week of May." :-)

I'm now on the email list when the amps get back in stock. I guess if you had one and decided to move on to something else, now would be the time to list it

Hi jetter,

Yes I agree of your assessment of price comparison between one A21 and 2 AHB2.

What I didn’t made clear in my earlier post was, since AHB2 can run distortion free till the last watt (100 watt), it can go very loud. I am upgrading because I want more of this goodness, but there is no real push for me to upgrade to monos.

AHB2 is all quality watts, right from .1W to 100W. For me, it is the end of search for a perfect system.

Since my speakers are 101 db efficient and my current 80 watt amp will run you out of the room, I'm probably good with a single unit. However, I always wanted monoblocks.

A21 = $2,500

2 AHB2 to equal power of A21 = $6,000

Several posters wanting two for enough power

Not everyone's choice in amps in $6K range

@aberyclark

I have owned AHB2 for a year (using it with Benchmark DAC3 HGC).
I am very impressed with the clarity, tonal balance, sound staging and separation. I am adding second one to add more power for my inefficient ATC speakers. Not that the one AHB2 cannot drive the speakers. But I sometimes do feel the need to crank it up more than probably I should.

I did try A21 in my system, but it didn't compare with AHB2 at any level (other than power), and I sold it right away.

Now waiting for the second AHB2, and stay with it for a foreseeable future.

This amp has re-defined 'music' for me.

Has anyone owned the ABH2 for a considerable amount of time and then decided to change? Just curious on long term impressions on the Benchmark.

I've been running back and forth in my mind between tubes (Quicksilver, Rogue stereo 100, mc275) or stay with SS. I figure if I get an abh2, I can always add "color" thru my Rogue Rp-5 premap by changing tubes. However, if I go tubes, I can adjust my subs for any lack of bass. 

Decisions.

Kijanki,. Good stuff. I agree 100% with those quotes. I am firmly in the "I want to hear it accurately" camp.  Also low noise is exactly what one wants with HE speakers, all else aside.

I would like to add to the discussion regarding the strong reactions to the AHB2 and other amps. I find that audiophiles  (but never reviewers! LOL) present strong, hyperbolic statements in regards to components or systems that represent emotional reactions, rather than absolute conclusions to the value/sound of the gear. Readers should realize that and not react overly to someone's strong description, as it may not reflect the experience of every user. 

There is such a huge variance in listener preferences that one is bound to encounter strong negative and positive reactions to any given product. John Siau is cordial and correct in his analysis; the Benchmark products would be categorized imo more as "studio sound" rather than smoke-filled club sound. They do not editorialize, but neither did I find them to assault the ears. Many audiophiles seek what is imo a dullish, bloated, euphonic, but distorted sound and they consider that "real". Well, that depends on how much accuracy you want and how much tonal coloration/warmth. Of course, that varies with listener and system. 

Anyway, in my testing in the review I agree that the Benchmark products are neutral in a good way, not sterile. Are there more warm sounding components? Of course. But, often you have an expense associated with obtaining that warmth. I do not wish to give up either extreme definition or tonal richness, and obtaining both can be like balancing on a razor's edge. 

Finally�, don't forget, the speaker system has an overwhelming impact on the final result. It's not terribly convincing to declare a component warm, thin, tube-like or not, based on a listen with one speaker system. One may say, "... in my rig it sounded..." and be accurate, but this in no way captures the span of results possible. Try a product with dynamic, ESL and high efficiency speakers, a few amps and cables, then conclude. Most cannot, so any declaration based on one setup should be taken with a caveat, spoken or not.  

I appears that link above doesn't work, not to mention very long discussion.  Let me show quotes from original post and two responses.

OP:

I don't pretend to be a professional reviewer (in fact this is the first time I've been moved to review any equipment), so can't explain exactly the differences, but it was akin to listening to a live acoustic performance versus listening to music through loudspeakers. The difference was not slight - it was dramatic. There is no "tingle factor" and no goose-bumps when listening with the Benchmark. If anyone says that the Benchmark is more accurate - frankly I don't care - I listen to music with my ears, not an oscilloscope! It was dull and lifeless by comparison. If you listen to live music there's inevitably background noise (you're sharing the auditorium with other people) and the acoustics are possibly not as good as a recording studio, but despite all the drawbacks, live music is so much more exciting to listen to. Similarly with the valve amps, an evening listening to music is thoroughly enjoyable. With the Benchmark it was little better than loud background music. Furthermore, the inclination was to turn down the volume of the Benchmark and turn up the SETs - inaccuracies, slight background noise and all! Music should be a thrilling experience and the Benchmark sadly doesn't offer thrills.

Response1 (John Siau):

Peter,

This is John Siau, VP of Benchmark.

Thanks for taking the time to document your experience with the Benchmark AHB2.

The AHB2 is well suited to use with high-efficiency speakers. The low noise allows noise-free operation with very high efficiency speakers.

Of equal importance, the AHB2 virtually eliminates the zero-crossing distortion that is normally produced conventional Class AB push-pull output stages. This is especially important for high efficiency speakers because the amplifier will spend so much time in low power region where crossover distortion can become most audible. The AHB2 behaves like a Class-A amplifier in that it is free from this very objectionable form of distortion.

But the AHB2 isn't for everyone. If you prefer an amplifier that enhances your listening experience then the AHB2 is not for you.

Your SET amplifier is specifically intended to add the euphonic qualities produced by the single-ended tube topology. This specific character is produced by the unique non-linearities that are characteristic of single-ended tube topology. The SET topology provides significant coloring of the music in a way that many people enjoy. If this is what you prefer, then you will be very unhappy with most other power amplifiers.

The AHB2 and SET amplifiers are on the very opposite end of the spectrum. You are completely correct when you say that the difference is dramatic.

The AHB2 is a much different listening experience. In contrast to an SET amplifier, the AHB2 is designed to be virtually distortion-free. The output of the AHB2 will sound exactly like the input. The AHB2 will not enhance or improve what goes in.

Please understand that this is a mater of taste. Many people enjoy the coloration produced by SET amplifiers.

Amplifiers can fall into three categories:

1) Amplifiers that add nothing to the audio
2) Amplifiers that add musically-disturbing distortion
3) Amplifiers that add musically pleasing coloration

The AHB2 falls into category 1, your SET amplifier falls into category 3.

Technically "coloration" is distortion but I think the word "distortion" gives a completely misleading description of something that may actually enhance the sound.

Again, it comes down to a matter of preference.

Response 2:

My experience with the Benchmark AHB2 driving sensitive speakers is somewhat different. In my current setup with Benchmark DAC2 HGC/AHB2, I am driving a pair of Klipschorns with a 105 dB sensitivity so in that sense they would be comparable to the Avantgarde speakers.

In my 25 years of of experience with mostly tube amplifiers of all sorts, I have never come across a more emotionally involving amplifier than the AHB2. It is exactly because it doesn't "interpret" the music by adding coloration or any artificial sense of ambience or reverberation that it is so fascinating to listen to. The AHB2's ability to reproduce the timbre and texture of acoustic instruments is beyond anything I have experienced before - just listen to brass or woodwind! - and the precision with which it reveals the actual acoustic properties of the recording venue, whether it be a small café or a concert hall, is second to none. At least to my ears. I think what captured my attention from the very first instant was how honest and genuine the sound is. If it is in the recording, it is there, otherwise not.

This amplifier keeps me on the edge of my seat in excitement and anticipation even with recordings that I have known for years and not thought very highly of, so in my view it is the very antithesis of boring. I don't remember having ever been so moved by reproduced music as with this Benchmark combo. FYI, I almost exclusively listen to classical music and much of it in hi-rez, but I have to say that well-recorded CDs are also much more enjoyable and listenable now than before.

Karsten

Randy, you mean my clumsy attempt to write review? Yes it was in comparison to Rowland 102, but it is likely not very useful, since Rowland 102 is based on old, first generation of Icepower modules. I can only say that AHB2 sounds wonderful to me and it is getting better in all respects every day, but again it means nothing taking into consideration my limited experience. Rowland was a good amp (I keep it for the second system), but AHB2 is outstanding.

I found interesting discussion on Audioasylum :
http://https//www.audioasylum.com/messages/amp/205426/review-benchmark-ahb2-with-avantgarde-speakers-what-a-disappointment

OP calls AHB2 a big disappointment in comparison to his SET amp, while in follow up discussion another person has completely different view. At one point John Siau, a lead engineer at Benchmark, explains why opinions can be so different.

I solved the problem with my remote. Receiving diode in DAC3 had one pin poorly soldered. This pin connects to ground plane that sinks a lot of heat. It looked like soldered by somebody who doesn’t have any experience (or is blind). I fixed it to avoid shipping it back and forth, but I would expect better from Benchmark. The problem is that almost everything else is SMT - a well controlled process, but hand soldering depends on the skill of a person. RCA was famous for cold solder joints in their TVs (I had one with two cold joints), because it was most likely assembled by cheap unskilled labor.

Neutrix connector IIRC - they are as close to gas-tight as you'll get (outside a lab)

BTW, were the comparisons above vs. the Rowland?

Did anyone purchase the Benchmark brand speaker cables with the special connector? I believe the cables are Canare star quads and are quite reasonable. I'm using star quads i purchased off ebay and they are fine speaker cables.

Douglas, Thank you for a fine review.  I had similar problems with position of connectors.  My speaker cable wires are thick and don't bend 90deg.  It forces them to go down on both sides of XLR input plug.  Since wire on the outside of the plug encroaches on both 12V  1/8" connectors I had to force the 1/8" plug in (almost impossible).

I find performance of the bass phenomenal.  There are low notes that were completely missing before (why?), not to mention better dynamics.  That is really strange since my speakers are benign load (6ohm, 3.6ohm min) while Rowland 102 has 5Hz -3dB limit and DF=4000 at low frequencies.  AHB2 has 0.1Hz -3dB limit and DF=350 at 20Hz.  I also find improved overall clarity from bass to high treble.  Unfortunately some recordings still sound veiled while some others now sound thin (veiled before).  It sounds wonderful on fine records but also ruthlessly reveals shortcomings of the poor recordings.  Imaging is improved, both width and depth. 

I played drum solo on Chesky Records test CD and was absolutely stunned.  It sounded like live set of drums playing in my living room.  Bass control is better than before and the transients are fantastic. Pink Floyd's "Hey You" shook my windows and made me jump at the moment when drums and bass came in.  Also sibilants are strong, but very clean, while upper trebles are delicate without brightness.  Violins "sing" and trumpets have wonderful "bite".  Shirley Horn "You won't forget me" title song with Miles Davis solo sounds great.  Same for "It had to be you" with Brandford Marsalis solo.

I put my ear, as close as I could, to the tweeter and it was completely silent.  Heat sinks get very warm when playing at high level for extended time, but stay lukewarm at comfortable listening levels.  So far AHB2 has only 25 hours of play time, but I expect further improvements to be subtle.  To your suggestion about incorporating pink LED I have to say NO (I was awake).

I encountered strange problem at the beginning.  My remote stopped working.  I tried it with different sets of batteries.  I unplugged AHB2 and DAC3 to no avail.  After about 20 min it started working again by itself.  I thought, that since power timer on AHB2 was set to 40min it could've turn off DAC3 since it works both ways, but now I cannot repeat it - it turns on fine in the morning.  I hope it was just a fluke.  I'm going to disable this timer anyway (don't need it).

I just finished my review of the Benchmark DAC3 DX and AHB2. They were extremely good with the hybrid horn PureAudioProject Trio15 Horn 1 Speaker (also reviewed). I wasn't sure how well the class AAA technology would work with the horn, but it was exemplary. 

Kijanki, Keep us updated how the Benchmark sounds going forward

Viber6, It is strange that Benchmark specified 18A max current with 18A current protection threshold and both channels driven, while now they specify 29A at 1ohm, both channels driven.  Perhaps they improved something or is it just specsmanship?

Viber6, I got AHB2 on Friday and so far I like what I hear.  It started with recessed midrange, then sharp midrange, then softer midrange with extended highs.  Bass got deeper.  It sounds like if I would add sub to my older class D.  What shall I expect in the future?  How did it change in 60 days?  My guess is that it will become a little bit more open and refined.  Even now, it is far better than previous class D amp.  Veil on the treble is gone, both extensions improved, better imaging, incredible bass control and slam, nice and natural attack and decay.
Bryston is great amp (I read reviews),  but it costs more and doesn't have as high WAF (wife acceptance factor), since AHB2 makes pair with DAC3 HGC.  I bought new since it is hard to find used one, while new registered original owner gets 5 year warranty (and 30 day trial).

dpac996--I have owned a Bryston 2.5 B SST2 for a few years.  It is the most neutral, accurate amp I have ever had.  I tried a new Benchmark AHB2, broke it in for nearly 60 days, and found it very close to the Bryston in tonal character and detail, but a little warmer than my Bryston, so ultimately not as revealing.  The interesting thing is that Benchmark has the best specs in the business, while Bryston specs are excellent but not quite as low.  Still, I found the Bryston to have more accuracy and resolution, so always use your ears as the final arbiter.  Also puzzling is that the Benchmark clipped on less power than my Bryston into the very low impedance of my electrostatic speakers, despite the fact that peak current on the Benchmark is pretty high.  

I like my amps to be as neutral and revealing as possible. If I want to add flavor ( warm, etc) I’ll do it on the pre amp side ( tube rolling)

Toetapaudio, thank you for the info. I will keep it in mind. SST Ampzilla Monoblocks are too expensive for me, but perhaps Son of Ampzilla II is worth listening to, if Benchmark doesn’t work for me. I suspect that it has a lot to do with amp-speaker synergy. Many reviewers praised imaging of AHB2 including depth of the soundstage while one guy stated that it was the worst imaging he ever heard - completely flat with no depth whatsoever. He even said that his 10 year old son called it awful sounding. How this could be? I can understand that AHB2, being very revealing, can mercilessly uncover shortcomings of the system or recording, but I don’t know how imaging can be so bad, while it is supposedly great with another amplifier.

On the other hand nothing surprises me after reading reviews of electric toothbrush on Amazon. One guy wrote that toothbrush is no good and gave it one star, the reason being that it stopped working after it was bitten by his dog. Perhaps there is not a lot of idiots, but they must be strategically placed, because I encounter one every single day.

@kijanki 
I made a review of  Benchmark ABH2 vs Nord SE vs Spread Spectrum Technologies. The SST is hands down better being more open and natural, with improved transparency, more controlled bass, denser and more musical.

For background where I am coming from, the BEl Canto C5i in my smaller two channel family room system is probably the most neutral, airy, and transparent amp I have owned. It uses more recent generation IcePower modules, 60/w ch. More of the same power is all I could ask for. I’ve used all flavor of speaker with it (OHM, Triangle, Dynaudio) and they all sound best ever at low to modest volume. Just lovely! Never warm, never hot, with imaging and soundstage to die for, though the unique tonal character of each speaker does still come out.  Teh sound with any of these dynamic speakers more resembles the fast airy sound of electrostats like ML or Quad than with any other amp I have used there.  

Of course it is an all digital integrated amp (with both line level and phono inputs to boot), so there is more new technology at play there than just newer Icepower.

Compared to BC ref1000m amps, which is one generation older, that I still use in my main bigger system, Dynaudios can sound a tad hot depending on setup, Triangles a bit cold and analytic, OHMs right on target (that system is designed around optimizing the sound with my large OHM 5 speakers). Pre-amp is Audio Research sp16 (tube).

Kijanki, 
Agree 100%. When you find the right system synergy, you know it. 
Let us know what your thoughts are after you spend some time with the AHB2!

When amp sounds bright or warm it means that it is adding own harmonics to the music.  Slightly warm amp might be nice to shield against bright sounding records, but many people made a quest of finding the warmest sounding gear, warmth being treated as a virtue - the more the better.  I prefer an amp that doesn't have character of its own.

John Siau said that warm sound is great for voice or guitar but bad for instruments that have more complex harmonic structures than simple overtones.

His exact quote:

Personally, I do not like what warm sounding equipment does to the sound of a piano. Warmth is wonderful on vocals, guitars and certain instruments, but it beats against the streched overtones of a piano. The overtones in a piano occur at slightly higher than harmonic ratios, and these create beat notes with the exact integer ratios produced by electronic equipment (and speakers). Too much harmonic distortion will make a piano sound out of tune.

Thank you Mapman.  One of my resolutions is to spend much more time with music (and perhaps little dance) and much less with TV.

BTW Kijanki congrats on your retirement.   Now is the chance to do more of things you enjoy to engage the mind and body, like listening to great sounding great music, than perhaps before.  Perhaps a little dance even here and there?   

I don't like too warm, because that, to me implies a shelved down presence region and recessed high end.

Not only that.  According to technical director of Benchmark Media John Siau, overly warm sound can make instruments with complex overtones, like piano, to sound like out of tune.

Class D is not for those seeking a "warm" sound for sure, though my Dynaudio monitors tend to skew that way somewhat. In the limited time I had to listen, the Benchmark amp struck me similarly, ie not for those seeking a warm sounding amp.

Aberyclark, I sure will, but it will only be my impression, coming from entry level class D.  There are more experienced people to write reviews.  Also, remember that I'm not looking for "warm" sound.

SHE SAID YES!!! and I placed the order a moment ago. With 30 day free trial (when ordered directly from Benchmark) I don't risk anything.

Be sure to give us your impressions. I'm looking to purchase one as well. As a temporary stop gap last August, I purchased the Nuforce (class a/b) sta200 for $499 (origially $1400). I was blown away (maybe my old B&K amp was too far gone and anything was a major improvement). I still plan on a new amp early this year. 

I have a 101 db efficient speakers and the quieter, the better. I narrowed down to go tubes (QS Horn Monos) or the benchmark. 

Back in April/May of last year I auditioned, with the intent to buy, the AHB2. I read pretty much every report, paper, review, etc on this piece because I was in the market for an amp --looking for a good fit with my Dynaudio Contour S3.4 LEs. My first AHB2 amp arrived and a problem developed shortly after; I connected everything up properly, turned it on, played some music, then listened for a bit then it went into protection mode. I called Benchmark and they were phenomenal with sending me out a new unit. The second unit was stable with no issues. I found the sheer resolution very remarkable; The bass was tight and tuneful. The midrange was transparent and open. It easily drove the Dyns with precise control. After some time however, the sound grew fatiguing to me, and I noticed that it did not sound all that great when played at low to medium-low volume. In the past I drove my dyns with a Pass X250.5, Plinius SA102, and I know how amazing they can sound at pretty much any level. There was just something missing about the AHB2 presentation; like the soul was sucked out and I could not connect to the music.
At this time a lightly used Bryston 4B SST2 popped and I bought it. The Bryston was heads and tails a better match. Back the AHB2 went. I kept the Bryston. The Bryston has very low distortion on paper, perhaps not as low as the AHB2, but to me its another "who cares" lesson because its all about the end synergy. It’s either there and the system has that warm, organic sparkle, or its flat and annoying. The Bryston and Dyn match was superb.
Cheers

Mapman, that is what I suspected - newer class D amps use either Hypex or Pascal modules.

Randy, I suggested, that it is the very last moment we can buy something like that, since we're retiring in May.  I also stressed out benefit of additional amplifier to make second system (Paradigm Studio/60 v2, Benchmark DAC1, Rowland 102).  SHE SAID YES!!! and I placed the order a moment ago.  With 30 day free trial (when ordered directly from Benchmark) I don't risk anything.

Willemj, It is combination of class AB and class H, where supply voltage is modulated according to amplitude of the input signal in order to reduce wasted power.  I wouldn't mind good class D, but Benchmark AHB2 got Stereophile 2017 recommended component class A and has great reviews everywhere else (I'm already tired from reading reviews).

Thank you all.  I will post small review.

Correct.  Did not mean to give that impression.

The AHB2 is not class D, even if energy consumption is low.

"Honey - I just saved us some money on our elec. bill !!  Here is some jewelry!"

When she asks about the new box reference the elec. savings again.

Kijanki my recollection is the treble was very good and I did not notice any issues with high frequency "air".

I suspect the Benchmark or alternately many good quality newer generation quality Class D amps in the last few years like those from Bel Canto can be a step up from Icepower of prior generations, in particular when it comes to high frequency "air". I have a Bel Canto C5i digital integrated in my second system that supports that theory.

Mapman, thanks.  I know it was a while ago, but how would you assess trebles?  Was it an "airy" presentation?  My Rowland is a little bit on the darkish side according to one editorial review.  AHB2 might be good step-up for me from entry level class D, not to mention that is also very efficient with idle power of only 20W total and 0.5W at standby.  I also like the fact that it utilizes quiet SMPS  since it is efficient, plus line/load regulated and not sensitive to DC on mains (no transformer buzzing etc).

It's a very good choice I'd say and one I would consider as well.   Have heard it in BEnchmark room at shows with DAC 3 and liked it very much.