Benchmark AHB2 Power Amp: The Quietest and Cleanest Amp on Planet Earth?

[Sonnie Parker]

I really don't know, but Benchmark makes the claim, and if it's not, it's most certainly "one of" the quietest and cleanest amps in the universe.

Benchmark Media Systems AHB2 Power Amplifier - https://benchmarkmedia.com/collections/amp/products/benchmark-ahb2-power-amplifier



You can see the full specs on their website, but here are some notables:

SNR & Dynamic Range
Rated output relative to output noise, inputs shorted

• 132 dB A-weighted, Stereo Mode
• 135 dB A-weighted, Mono Mode
• 130 dB Unweighted, 20 Hz to 20 kHz, Stereo Mode
• 133 dB Unweighted, 20 Hz to 20 kHz, Mono Mode

Noise Relative to 2.83 Vrms
Output noise relative to 2.83 Vrms, A-weighted, inputs shorted

• -112 dB, Stereo Mode
• -109 dB, Mono Mode

THD+N
1 kHz, 80 kHz LPF, at full rated output into any rated load

• < -118 dB (< 0.00013%), Stereo Mode
• < -118 dB (< 0.00013%), Mono Mode

THD
1 kHz, 20 kHz LPF, at full rated output into any rated load

• < -119 dB (< 0.00011%), Stereo Mode
• < -120 dB (< 0.00010%), Mono Mode

Those are crazy good numbers... and verified by Amir at AudioScienceReview who has the AHB2 at the top of his list for amps: https://www.audiosciencereview.com/...-and-measurements-of-benchmark-ahb2-amp.7628/

A black pair landed at my shop today and I happily brought them home with me, since I paid good money for them. These will power my ML 15A's in mono mode. I learned from talking with Rory Rall of Benchmark that they have paired up the AHB2 amps with several MartinLogan speakers over the past few years at various audio shows to show how well they pair with electrostatic speakers.

Lately I've been considering a little higher end gear to make sure I'm not missing anything in my music listening. Yet I've always been a proponent of not being able to identify any audible differences in quality solid state amps, which includes most all amps as far as I'm concerned, provided they are not over-driven. I am NOT stating there are no audible differences, and it does NOT mean I am NOT hearing a difference. I'm just not good at identifying the differences like some others that are apparently able to do so. However, what I don't want is anything to possibly hinder me from hearing the best I can hear, or at least that is what I am chasing right now. I believe the AHB2 amps will be a significant part of my music listening system.

While investigating these amps I enjoyed reading Benchmark's VP and chief designer John Siau's application notes... some very interesting articles; https://benchmarkmedia.com/blogs/application_notes

The first paragraph of his Listening vs. Measuring article caught my attention right away.

At Benchmark, listening is the final exam that determines if a design passes from engineering to production. When all of the measurements show that a product is working flawlessly, we spend time listening for issues that may not have shown up on the test station. If we hear something, we go back and figure out how to measure what we heard. We then add this test to our arsenal of measurements.

Even though measurements show no flaws, they still listen, and if they identify something different, they figure out a way to measure what they heard. This is truly amazing to me. Take a look at the products they make, and take a look a the specs, and look at the unbelievably crazy good specs verified by numerous people taking measurements with the best gear available to do so. Then imagine that these guys at Benchmark STILL listen for differences and THEN figure out a way to measure those differences. They firmly believe that if they hear a difference, they should be able to measure it.

I appreciate what Paul Seydor of the abo!ute sound wrote in his review of the AHB2... here are a few clips from his review...

I don’t have much to say about the sonic qualities of Benchmark’s new AHB2 power amplifier because there isn’t that much to say. Used within its limitations and for its intended purposes it is in any practical sense perfect. I know this is not the sort of thing we’re supposed to say about products, but it has been evident for a very long time now that solid-state electronics, particularly linestage preamplifiers and power amplifiers, have reached a point where they are effectively a solved problem such that it is exceeding difficult to tell one from another even in the most exacting A/B comparisons. Ferretting out differences typically involves zeroing in on a very specific and limited characteristic or set of characteristics with such concentration as to leave one tired, uncertain, or both: in other words, an activity that is the very antithesis of what is involved in listening seriously, even critically—to say nothing of pleasurably—to music. [I must point out that this view is not shared by the TAS editorial staff. —RH]

That said, even by contemporary standards of the most sophisticated, exotic, and expensive electronics, this new amplifier is something of a technological tour de force.

As a remarkable number of audiophiles still tend to listen with their eyes rather than their ears, there continues to be a prejudice in favor of size, weight, and bulk, especially as regards speaker systems and amplifiers. I have no wish to engage the double-blind test debate here, but I do think there’s a lot to be said for not knowing what you’re listening to when evaluating components, particularly when it comes to electronics. The truth is that if electronics, particularly solid-state electronics, are correctly designed, they just work: When they don’t sound neutral the reason is typically some limitation or flaw in the design, being pushed beyond their rated power, an interaction with untoward speaker loads and/or cabling, or a flavor the designer consciously built into it (e.g., the exceptionally pretty Gundry dip Bob Carver designed into his Sunfire amplifiers). (full review) (underlined emphasis by me)

This to me is when honesty and reality are harmonized beautifully by a reviewer.

Then we have our good friend Kal Rubinson's review of the AHB2 at Stereophile... which is where I was surprised to learn that the AHB2 was a collaboration between Benchmark and THX... another interesting bit of technology and information. Kal seems to be more like one of us, instead of being like so many of the other reviewers for which I withhold the words that might describe them, partially out of respect for what they do. I admit, there's just not many reviewers I trust or care for... sorry, but I can't apologize for them. Benchmark might thank Kal for tilting my decision to purchase these amps based on his comments as follows....

Benchmark and THX make much of the AHB2's lack of audible noise: something good systems aren't troubled by in any case. That said, it was probably the AHB2's low noise level that revealed to me much more apparent low-level detail in already-familiar recordings. I qualify that statement with apparent because, after hearing the AHB2 uncover previously unheard subtle details, I found I could now hear them when I returned to my other amps. I suspect that, being newly informed of their existence, my ear/brain could more easily extract those details from the output provided all along by my other amplifiers. This made a much greater impression on me than any subjective awareness of a lower noise floor, per se. (full reivew)

Thank Kal for turning me on to O-Zone Percussion Group: La Bamba... that's some good stuff... diggin' the Jazz Variants.

The AHB2 is simply another part of the chain in my chase for the near perfect two-channel system build. I'm not there yet, but I'm close, and I hope the AHB2's will play a big part in not holding anything back from my reaching audio nirvana.

 

[Kal Rubinson]

Nice write-up and thanks. I am sure that you are aware of this but you should pay attention to the gain setting in the AHB2 and select the lowest setting that permits you to achieve the maximum loudness you need or can tolerate. I started playing with that when I had my old Audio Research MP1 preamp which had a relatively high noise floor. Lowering the gain of the AHB2 meant increasing the gain (lowering the attenuation) in the MP1 and that, effectively, increased in S/N ration of the output signal.

Since the MP1 is gone, I still do that to optimize system noise levels and, at present, they are inaudible even with my ear directly at the speaker drivers. It means having successfully dealt with one sound parameter.

 

[Sonnie Parker]

I figured I would start at the lowest setting and see if it will be loud enough for me, and I suspect it will be. I have it set lower that what my currents amps require right now in the HTP-1, since it has adjustable gain.

When I get the SHD... not sure yet how that might match up.

 

[Sonnie Parker]

Tested this amp for 2 weeks at my home, but the Schiit Aegir came out as the more coherent sounding, better details and more revealing in my system.
I too was overwhelmed by the numbers and the unique technique used, but as very often in audio, numbers aren't everything.
So in the end after extensive listening on the Quad stats the Schiit in 2x mono setup came out as a clear winner.

View attachment 37825

Different strokes for different folks... it's all about what you like and what works best for you, that is for sure.

In my case, being that I can't very well identify the differences, especially the inaudible, I fully rely on the measurements to let me know there is nothing standing in the way of what I should be hearing, even if I can't say what it might be. I definitely don't want to rely on what others might think, as people hear things differently, so ultimately, measurements mean everything to me.

 

[Kal Rubinson]

Tested this amp for 2 weeks at my home, but the Schiit Aegir came out as the more coherent sounding, better details and more revealing in my system.

Unfortunately, I'd need at least ten.

 

[Sonnie Parker]

So I didn't pay that much attention to it initially, as I'm not planning on changing again anytime soon, but now I see. They would never work for me, that is for sure.

 

[AJ Soundfield]

I fully rely on the measurements to let me know there is nothing standing in the way of what I should be hearing

With electronics like these, me too. Hence me not particularly interested, despite having speakers with well north of 100db/w sensitivity, where distortion and noise performance/gain structure indeed matters.
Of course if the looks and audiophile street cred meet your needs...all good.
For speakers like your 87db MLs those uber numbers you listed should have no audible consequences vs another transparent amp, in an actual listening (vs "listening") test. What can very well become amp "audible", is power vs load...and any subsequent misbehavior.
The good news there is it's well capable of driving a 4 ohm load like yours, though the drop to 0.5ohm at 20k, despite little content there, could give some amps fits.
Only question is do they have enough dynamic power for your listening needs. Most likely do. We'll see

cheers

 

[Sonnie Parker]

So far they've done very well. I won't know for sure until I get the SHD and get it all tuned.

 

[3dbinCanada]

Tested this amp for 2 weeks at my home, but the Schiit Aegir came out as the more coherent sounding, better details and more revealing in my system.
I too was overwhelmed by the numbers and the unique technique used, but as very often in audio, numbers aren't everything.
So in the end after extensive listening on the Quad stats the Schiit in 2x mono setup came out as a clear winner.

View attachment 37825

Did you evaluate the sound and compare through controlled listening tests?

 

[3dbinCanada]

If you did not ensure matched volumes as the bare minimum during the tests let alone blind listening tests, then your selection was made on loudest test wins. The results of such a listening test are inaccurate and filled with subjective bias resulting in inaccurate results.

 

[Sonnie Parker]

If you noticed that drastic of a difference between any two amps (and even more so these two amps), my belief would be that the inferior amp had a serious issue outside of it's normal operation. Even the best of ears that I know of only ever hear more subtle differences. I would say if you are able to hear that drastic of a difference, you have Superman hearing and could get rich easily (if you aren't already).

 

[3dbinCanada]

But listening for a longer period of time is IMHO much more useful and valuable compared to fast A-B comparisons. For me there is nu use at all in A-B-X testing. None, Nada, Zero. Your brain can't adapt that fast.

There in lies another error in your testing methods. Accurracy of human hearing memory is accurate to at best 30 seconds. This fact is well known and why fast A-B comparisons were established.

Subtle differences can only be detected when listening for a longer period with very different music. With recording one you think A is better, with recording two you vote for amp B.
Only after many hours and many tracks I begin to form an opinion that involves all ingredients that matter to me.
As an example: For a short period an amp can sound like more/better highs, but in the longer run it becomes irritating, it introduces listening fatigue. Fill in your own evaluation points important for your listening in your environment on your speakers. Electrostatics are very very reveiling and can be a pain in the for an amp. Maybe wit other speakers my choice woould have been the other way around.

Without level matching and long term memory errors skewing your results, your outcome of the test is a biased subjective want.

is the only way to go to accurately assess amps.

 

[AJ Soundfield]

But listening for a longer period of time is IMHO much more useful and valuable compared to fast A-B comparisons. For me there is nu use at all in A-B-X testing. None, Nada, Zero. Your brain can't adapt that fast.

Unlike your echoic memory, there is no time limit on ABX or other forms of control tests. Your statements there reveal the limits of your knowledge of the subject.
The real "problem" with controlled tests is that they conflict with uncontrolled results, i.e, imaginary and/or intensity etc differences are no longer causing the results.
FYI I have an ABX component for just such matters. I have also tested, without their knowledge, literally hundreds of Golden Eared old guys aka Audiophiles, including some known "reviewers" who made the exact same type statements as you regarding amplifier, cables, etc "sounds". The results were very amusing, though predictable.
As long as you're happy with the Schitt, or XYZ, great. Your personal experience. That's as far as it goes when referencing real sound quality for any other observer of the real soundfield, outside some others mind.

cheers

 

[AJ Soundfield]

I was just musing here that my personal choice on my terns, on my equipment (read that again) was the Schiit. Nothing more nothing less.
I respect anyone's choice.

That's how I interpreted what you said. Your personal eperience, no more, no less.
Btw, I have a Schitt Freya and have also "heard" both Aegir and Benchmark. Didn't hear anything to separate them from any competent SS design driving a reasonable load. YMMV.

 

[Sonnie Parker]

For me there is nu use at all in A-B-X testing. None, Nada, Zero. Your brain can't adapt that fast.
Subtle differences can only be detected when listening for a longer period with very different music. With recording one you think A is better, with recording two you vote for amp B.

Simply clarifying what you wrote... you don't have an ABX box, so you've never done any ABX? However, your statements contradict this, as you state there is "no use" in ABX testing, which would infer that you have done ABX testing. You also state our "brain can't adapt that fast."... but you haven't tried it... so how do you know this? What would you say to the several enthusiasts that have actually proven that we "CAN" tell a difference in ABX testing from one product to another... and that our brains can adapt... are they lying? Does Floyd Toole have zero credibility with you (he has done extensive blind testing).

At any rate... this has gone way off topic. I certainly don't doubt people can hear differences, but the use of drastic phrases when comparing two amps are likely going to do exactly what they did... mislead people and potential buyers... whether intentional or not. IMO we should try to be more careful in our descriptions. The professional reviewers are able to do this, which is why I trust "some" of them more than individual users that may not properly represent the real differences they are hearing.

 

[3dbinCanada]

As mentioned before I don't have an AP or other very expensive equipment to do that kind of level matching. So I can't (even I would, which I don't) perform an evaluation like that.
In all my audio years I have NEVER been present at a testing done like that. Never, ever! But that can me my bad. Can you please share how many amp evaluations you have attended that were done like that.
Always willing to learn.

First off, like AJ Soundfield mentioned, its great that you enjoy the equipment you have. I enjoy mine as well and we can both agree that its important in itself.

I've read lots and only only once participated in an adhoc blind listening test at an audio retail shop. I had purchased lots of equipment from them in the past and the sales person knew me. The sales man was trying to up sell me to seperates over a top model AVR made by a certian manufacturer so I asked him to take a bet of $100 and set up a comparison between the unit I was interested in buying and the equipment the sales person was suggesting. We agreed to an 85db output standing 6 feet away (measured by a Radio Shack SPL meter using C weighting) using the same source CD player using its analog outputs and same speakers. The toggling was between the separates and AVR. The AVR was configured in Pure Direct with all DSP turned off as was the separates. I asked him to sit and listen after he showed me the switch. He guessed less than 50% correct as to which unit was actually amplifying. He felt kinda sheepish and tried to tell me about long term testing benefits. I ignored him not wanting to make him feel worse than he already was feeling.

I told him to push the volume of both into the 100 db area and we ran the tests again. This time the salesmen was able to identify more than 90 percent of the time which was being used.

I also didnt ask for the money. The fact that he had something to mull over was enough for me.

The moral of the bet was to demonstrate that differences in sound of solid state amp will only manifest itself if your pushing the power envelope of the test unit or if the listening area is so quiet and well below the SNR of the unit being tested while running near full power. Those are the only 2 conditions. Hanging a low impedance speaker onto an amp is in effect pushing the power envelope.

 

[Kal Rubinson]

Always willing to learn.

Apparently, not. You have been told of the weakness of your position by several and you do not make the effort to understand them.

My last response.

OK. Your loss.