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Review and Measurements of Benchmark AHB2 Amp

SIY

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As for the time domain, at least few of the local audio designers are confident of its importance. Also, the one I talk to often is pretty confident of using subjective listening tests in evaluating the sound quality, even if it's not DBT. However he's a trained pro - such are usually trained to use their ears professionally while their eyes are being open, you know ;)

Time and frequency domain are absolutely equivalent. As soon as you hear woffle like that, you're dealing with marketing.

Likewise, the suggestion that "professionals" don't need to use DBTs to establish audibility is nonsense, unless those "professionals" are also non-human.
 

Soniclife

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I'd guess that the main reason for this somewhat complex power section of this amp is to make it as lightweight as possible - since manufacturer's strategy is direct sales, it's pretty important to keep the weight as low as possible - amps need to live through shipping process. In the end, it's the cost - packing cost and shipping cost
I see no difference between direct sales and via a dealer here, amps sent to dealers are sent the same way as to people's homes. The dealer has additional transport on top, if anything.
 

DonH56

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The complexity of the power supply is to support class-G operation. That is, it is fundamentally a class-AB amplifier with power supply rails that track the incoming signal level. That greatly improves efficiency so the amplifier can be much smaller and lighter while delivering much more power while wasting far less energy as heat (so it runs cooler) than an equivalent conventional AB amplifier (that wastes ~half of its energy as heat).

Feed forward compensation is very common (many if not most op-amps use it) but I am not sure it has been applied, at least as effectively, to an audio power amplifier. I have downloaded the patents, just need to read them...

The performance and stability exhibited in the power cube test is pretty amazing.

I want one. Actually, I want seven...
 

SIY

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Frankly, what I want is that Power Cube.

/checks lottery ticket
/looks disgusted
 

FrantzM

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The complexity of the power supply is to support class-G operation. That is, it is fundamentally a class-AB amplifier with power supply rails that track the incoming signal level. That greatly improves efficiency so the amplifier can be much smaller and lighter while delivering much more power while wasting far less energy as heat (so it runs cooler) than an equivalent conventional AB amplifier (that wastes ~half of its energy as heat).

Feed forward compensation is very common (many if not most op-amps use it) but I am not sure it has been applied, at least as effectively, to an audio power amplifier. I have downloaded the patents, just need to read them...

The performance and stability exhibited in the power cube test is pretty amazing.

I want one. Actually, I want seven...

I only want/need a pair
 

Matias

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Feed forward compensation is very common (many if not most op-amps use it) but I am not sure it has been applied, at least as effectively, to an audio power amplifier. I have downloaded the patents, just need to read them...

Hegel amplifiers also use their special feed forward tech named SoundEngine.
https://www.hegel.com/technology/soundengine
 

DonH56

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Hegel amplifiers also use their special feed forward tech named SoundEngine.
https://www.hegel.com/technology/soundengine

Thanks. I have read Hegel praised elsewhere but have never heard one of their amplifiers. I am almost certain I've seen a few others over the years. @restorer-john undoubtedly knows; I think he posted some references and schematics when this came up before. I should recall, just too little sleep to remember today...
 

orangejello

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@orangejello thanks for the feedback. IMO listening impressions shouldn't be dismissed in this forum as heresy or blasphemy. As long as you don't drop the subjective adjective bombs like "musical" and "airy", you're safe here. ;)

Were you looking at the AHB2 as an upgrade for the NAD? I ask because if you're at the M2 V2 level already, perhaps the AHB2 wont really give you a marked improvement. The AHB2 would only be "better" if you're coming from distinctly worse measuring gear like a tube amp or the Rotel integrated :facepalm: that I'm currently running.

Still, I think your Benchmark deserves more time on your rack.

Yes. I am going to give it more time. The NAD M22 v2 has very good performance numbers, and in that respect it is not embarrassed by the Benchmark. I got the AHB2 to see whether it was the case that, as some people assert here, things that measure well should sound the same and the if something measure better it "might" sound better. It would be nice if that were the case because it makes putting together a system so much easier.

As for Bruckner and being careful about listening at too loud a volume, thanks for the words of caution. I think I was cranking it up too much. It is seems that I do this when listening to new equipment. My ear is happier today.

I had a get together with a few friends to listen to AHB2 in their system. They didn't immediately take to it. They both preferred the NAD. They agreed that the AHB2 serves classical music pretty well because of its ability to unravel complex signals - which makes following individual instruments in a large orchestral setting much easier. I also agree with that. The NAD is not shabby in this respect. It just seems that the Benchmark is a little better.

We were listening through some Dynaudio speakers. In addition, I use Swans M6 speakers in my system. The Swans measure quite well, and I have listened to lots of components through them. Neither speakers are particularly hard to drive. But what I hear is that the NAD controls the speakers better. Everything has more punch with the NAD. Bass, using the NAD, is the best I have gotten out of the M6s. It is tightly controlled, and tonally accurate. This is not to say that the Benchmark is not decent in this respect. It is just that the NAD seems to excel at this with my speakers.

So the question of whether the AHB2 is an upgrade is certainly not clear. My friends did not say that AHB2 was bad, just that it was dull to listen to.

I wouldn't take all of this too seriously though. I find that these kind of listening session only produce a first level take on equipment. I think that what we are talking about with respect to these amps is very nuanced, and it requires careful attention to actually discriminate what is going on. I find that sitting around late at night with my full attention focused on what I am hearing gives better insight. But it was definitely interesting that neither of my friends were immediately taken by the AHB2.

One friend had an RME ADI DAC available. So we drove the AHB2 directly with it. Despite its measurables, no one like this setup at all. It just sounded thin and anemic. We switched to a Hegel DAC and everyone felt that was a nicer listening experience. If measurements were all that mattered, the RME / AHB2 combo should have been a slam dunk.

Then there is this nagging image that I cannot shake when I listen to the AHB2 - that it sounds "grey". I have often had that experience with SS gear in the past. The NAD doesn't have this "grey" quality. (To the snide out there - no I am not drinking too much when I am listening - I am only drinking appropriately:).

I will keep experimenting with the AHB2 for a bit longer and see if I can warm to it. I know that sometimes I have to get calibrated to new components. I came to like the NAD pretty quickly, but it did take a while to get the full measure of the improvements that it made. Maybe that will happen with the AHB2 as I give it more time.

There is also the issue of recordings. It might be the AHB2 (and the RME for that matter) is delivering more of the truth. Perhaps what I am hearing is the miserable artifacts of the heavily processed nature of modern recording. I will have to pay attention to whether there are consistent sonic signatures when I listen to the AHB2, or whether it is chameleon like and changes with every recording.

Anyway it is a privilege to get to play with this lovely stuff.
 

orangejello

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Tell us what recordings you are using for the evaluation.

Sometimes I listen to some recordings that are unbearable because of their poor quality because my second system is now very resolutive and does not forgive the wrong doing. Songs that I enjoyed many years ago I am unable now.

Bruckner, recording? Year? The current orchestral recordings I can not stand because they are excessively bright because they use a very high tuning.

Nice insight. Bruckner's Fifth from a Naxos recording, 1996. Scottish Symphony I think. I picked it up at a thrift store for a buck a couple of days ago. Yes the crescendos are pretty screechy and through the ABH2 they are definitely cringe-worthy.

I also have a mint Japanese vinyl pressing from around 1982 of Klemperer's 1960's version on Angel. Those Japanese pressing from that period are stellar. That sounded extraordinarily good though the AHB2, and sounds much better to me than many of the digital orchestral recordings that I have listened to, vinyl vicissitudes and all. The AHB2 almost made me jump up when Klemperer thwacked the music stand with his baton really hard. Seems he does it several times. I don't think I would have been able to identify the cause of that spurious noise on less resolving equipment. By that time though, I think my ears were shot from listening to the Naxos version at too loud a volume.

I also listened to a recent - 2006 - recording of some woman playing the Mozart Clarinet Concerto K. 622 on Decca, I believe - to lazy to get up and look up the particulars. That was quite beautiful in terms of the rendering of the clarinet timbre and the laid back, yet highly resolved quality of the recorded orchestra. The body of the deep registers of the clarinet was fully rendered in the recording apparently, because the AHB2 communicated it easily.

Listened to "Johnny Hodges And The Ellington Men* ‎– The Big Sound" on mint Japanese vinyl from the 80's. Wow. Extraordinary.

Listened to a bunch of RVG Bluenote and Prestige stuff on vinyl and CD. Those are uniformly good.

And streamed Dr. John's memorial service live from the Orpheum in New Orleans on WWOZ this morning. Nice send off for that wonderful soul :)

I listened to avant-garde Jazz and Classical too. But my partner puts the kibosh on that stuff pretty quickly. Admittedly an acquired taste

And so on...

.
 

orangejello

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Just a thought.. could it be that the "cleaner" system ends up being played at a louder level without knowing because there is less distorsion? That might give a headache.
Yup. Agreed. I just wasn't paying attention.
 

orangejello

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restorer-john

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The performance and stability exhibited in the power cube test is pretty amazing.

Except the power cube test is CEA-2006 or basically the 'maximum power' (old EIA/IHF A-202) burst test using 20 cycles at 0dB and 480 cycles at -20dB. Hardly stressful for an amplifier. It's a nice test, nothing gets too hot, it's easy to determine peak clipping on a scope because it is precise and clear, unlike the continuous sine where the waveform can flatten, sink, recover etc and stuff gets hot, fast. It gives you arguably the best numbers you can get. It's also kinder on older gear, which this Benchmark is not. But continuous it is not.

It's already been shown to fail to hit its rated specifications in Amir's testing (it shut-down at 133W@4R both channels driven in considerably less than 5 minutes on a purely resistive load). I also note, that Stereophile only tested the amplifier with one channel driven. Something I have never seen done before for a stereo power amplifier.
"and with just the left channel driven, the AHB2 clipped at 108W into 8 ohms (20.3dBW) and 210W into 4 ohms (20.2dBW), both powers slighter greater than those specified by Benchmark, which are with both channels driven."
I am wondering whether JA also discovered the amplifier shut-down at ~133W@4R on a continuous basis, so he tested one channel driven only. Considering he apparently had two examples of the amplifier to test, this seems very strange.

John_S has completely ignored my post on a possible overly sensitive protection and seemingly left the thread. He hasn't returned since this, and the questioning of the Xover distortion plots of 'competitor's amplifiers'.

I wrote:
So John, with all that SOA in silicon and heatsinking, a beautiful regulated SMPS, do we also have a protection circuit that won't let the amplifier deliver >~133W@4ohms in a continuous manner into a purely resistive load? Seriously? If the amplifier is shutting down prematurely as the sweep time on the AP is a bit long*, perhaps the protector is a bit pessimistic/overactive wouldn't you say?

He had said earlier that :
It just protects the amplifier from test bench abuse.

Apparently, testing the amplifier in accordance with standard procedures in order to verify its rated continuous specifications is classed as 'test bench abuse'. I think not. There is a big difference between 133W and 190W.

1561268670585.png

(AP's sweep time for the test is considerably less than 5 minutes)

So, what can the amplifier actually achieve, both channels driven in accordance with standard continuous testing procedures? We don't know. Stereophile didn't test it properly and Amir didn't precondition the amplifier or run the tests for 5 minutes in case he damaged the unit.

Maybe the FPGA running the protector needs a firmware update to allow the amp to hit its specification on the bench?

Doesn't anyone have the guts to run an amplifier at full power as per the FTC requirements into its rated loads these days or am I the only one?
 
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zalive

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Apparently, testing the amplifier in accordance with standard procedures in order to verify its rated continuous specifications is classed as 'test bench abuse'. I think not. There is a big difference between 133W and 190W.

Unfortunately there doesn't seem to be any way to go around this. If the amp shut down at, say, 175W no one would blink twice, it would be classified as being close enough to published specs, however 133W is like two thirds of declared power at 4 Ohm. This is way too much and it sheds a different light to a product - especially when taking into account it's 100W at 8 Ohm continuous.

@John_Siau should explain the procedure how to test the AHB2 for continuous power and get specification numbers they declared.
Or Benchmark should correct their specifications, in case what @amirm measured is true. Otherwise I cannot see this as an honest business policy.
 

maty

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@orangejello

Just now, 5th Bruckner Symphony from the vinyl box set:

Eugen Jochum, Berliner Philharmoniker - Bruckner - 9 Symphonien (1967), Vinyl Box, Deutsche Grammophon, Germany

Anton Bruckner / Berliner Philharmoniker, Symphonie-Orchester Des Bayerischen Rundfunks, Eugen Jochum - 9 Symphonien / Te Deum (Vinyl, LP) | Discogs



Symphonie No. 5 in B Flat Major

DR Peak RMS Filename
----------------------------------------------------------------------------------------------

DR12 -4.56 dB -22.71 dB A Bruckner Symphony No. 5, In B Flat Major (72-50) 1 Adagio, Allegro
DR13 -1.80 dB -21.80 dB B1 Bruckner Symphony No. 5, In B Flat Major (72-50) 2 Adagio
DR15 -1.22 dB -23.28 dB B2 Bruckner Symphony No. 5, In B Flat Major (72-50) 3 Scherzo-Molto Vivace
DR14 -2.03 dB -22.07 dB C Bruckner Symphony No. 5, In B Flat Major (72-50) 4 Finale
----------------------------------------------------------------------------------------------

Number of files: 4
Official DR value: DR13


CD, 2003

Anton Bruckner, Eugen Jochum, Berlin Philharmonic Orchestra, Bavarian Radio Symphony Orchestra - Bruckner: Symphonies Nos. 1 - 9 - Amazon.com Music
 
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zalive

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@orangejello :

1. How much working hours behind the AHB2 by now? Unlike guys who cling on science only, my experience is that burn-in period should be finished for the assesment as particularly during in-between time electronics can sound funny. Though as some audiophiles have stated, if it doesn't sound really good from the beginning, it will never likely sound great. Still this has to be done.

2. Since you listened at high volume it's possible you provoked some nasty distortion on peak power transients...the one which protection circuits which shut the amp down didn't allow to show at measurements (protection from bad measurement, huh? :oops:).

3. Now this is why audiophiles I know prefer plugging equipment in their own system at their own home, because this is what will get the final result which they will be listening to. All is being taken into account, synergy/interoperability between components and the room as is, resulting in a sound. It doesn't really matter to me whether the final result is from a specific distortion profile or from higher fidelity - as long as it sounds like more fidelity in my perception. However, objectivists gonna tell you that you shouldn't trust your ears at all but instead you should trust graphs even if you don't enjoy that much in your subjective listening impression. Kind of completely absurd to me.
 

KSTR

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I think manufacturers should *not* make any assumption about the genres of music the amp will have to play back in the real world. Especially assuming that music would never contain full scale sine shows they may have missed the evolution of music over the last 30 years or so. Full scale bass sines and/or music with very low crest factors over a long time *are* standard in modern music. Real-world stress is approaching test bench conditions and can actually exceed them at times (especially for the PSU when the amp is constantly overdriven into clipping).
I agree that this (ab)use case is not likely to be encountered very often for products like the AHB2 and therefore it is legitimate to scale down the resources for "sane use".
 

maty

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Off topic

@orangejello :

1. How much working hours behind the AHB2 by now? Unlike guys who cling on science only, my experience is that burn-in period should be finished for the assesment as particularly during in-between time electronics can sound funny. Though as some audiophiles have stated, if it doesn't sound really good from the beginning, it will never likely sound great. Still this has to be done...

I copy what I have reproduced in other forums a month ago when I was looking for info about Denon PMA-800NE after seeing the measurements on the famous Polish site. H2 at -73 dB and nothing else < 90 dB caught my attention.

[Reviewers] Amazon.com

https://www.amazon.com/Denon-Analog-Component-Amplifier-PMA-800NE/dp/B07HB8GRB7#customerReviews

-> https://www.amazon.com/gp/customer-...f=cm_cr_arp_d_rvw_ttl?ie=UTF8&ASIN=B07HB8GRB7

-> -> https://taralabs.com/cascade-noise-burn-in

https://taralabs.com/images/stories/cascade/CASCADE%20NOISE%20BURN-IN.mp3.zip

[ Although there have been other “burn-in” test discs used by audiophiles in the past, the discs have mostly been a mix of pink noise and sweep test tones. The new CASCADE noise burn-in disc is a proprietary combination of white noise with frequency tone bursts and pink noise mixed at different levels.

However, what makes it really effective is a series of descending and ascending (cascading) multi-octave square sweeps for better and more complete results than any other “burn-in” discs that have been made to date… and bla bla bla ]

- End off topic -
 

Soniclife

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I think I was cranking it up too much. It is seems that I do this when listening to new equipment.
You, and most of the rest of us, it's normal behaviour, but it does make meaningful comparisons impossible. Try to keep an SPL meter handy so you know what's going on. I would think to really get to the bottom of these 2 amps you would need to level match very closely, and done blind I predict a draw.
 
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