ATI Battle Class AB vs Class D Amplifier Shootout

Out-Of-Phase

Out-Of-Phase

Audioholic General
Better have your amp checked out first by a competent tech before going to all that trouble with shipping it to a subjective listener.
 
P

PENG

Audioholic Slumlord
I think I let Bruno weigh in here:



I don't think is discussing unicorn distortion, but I suppose it is possible.
Want to borrow my AT522NC ? (I am serious).

- Rich
I do, but shipping and import duty makes it an unrealistic proposition. Thank you for asking though. So despite each has it's own signature, do you like one much more than the other, and how do they compare to the A51?
 
A

Andrein

Senior Audioholic
Nobody said review was objective. So what is the point arguing and suspecting...? Such intensive level of reaction to a subjective review is also subjective )))
 
Trell

Trell

Audioholic Spartan
Nobody said review was objective. So what is the point arguing and suspecting...? Such intensive level of reaction to a subjective review is also subjective )))
While I think that most here appreciate the subjective part of the review, they are also missing the measurements.
 
panteragstk

panteragstk

Audioholic Warlord
While I think that most here appreciate the subjective part of the review, they are also missing the measurements.
Right. We just want to see if there is a measurable difference. Valuable information for those in the market for these amps.
 
lovinthehd

lovinthehd

Audioholic Jedi
Nobody said review was objective. So what is the point arguing and suspecting...? Such intensive level of reaction to a subjective review is also subjective )))
Well if it were a product pre-view I wouldn't expect much beyond the press release type info. For review I hope to see measurements, but the word "review" alone doesn't convey that so one must read and look for the measurements....as to what you prefer, that's up to you.
 
AcuDefTechGuy

AcuDefTechGuy

Audioholic Jedi
Gene says AH doesn’t have the time/resources for doing all the measurements.

It seems @shadyJ does most of the speaker measurements now. Which is awesome, BTW, Shady! :D

Next thing you know @Matthew J Poes will be doing most of the AVR/AVP/Amp measurements. Send them Matthew’s way please. :D

Of course, Gene would still do measurements, but just can’t do all of them.
 
RichB

RichB

Audioholic Field Marshall
For those interested in why amplifier distortion and phase can influence amplifier sound, there is this post by Benchmark's John Siau:

The differences can be measured and the measurements often imply that the differences can be heard.

Whenever an audio product produces a distortion component that is reproduced at a level above the threshold of hearing, there is a chance that it will be heard. The reality is that most amplifiers produce distortion at levels that are significantly above 0 dB SPL in a typical system. In contrast, the distortion produced by the AHB2 is at or below 0 dB SPL (do the math if you doubt this statement).

The sound of an amplifier's distortion is not masked by room noise. We can hear tones that are as much as 30 dB lower than the ambient noise.

An amplifier's distortion may also not be masked by the music, especially when the distortion is separated from the fundamental by several octaves. In musical signals, low frequencies normally have much higher voltage swings than high frequencies. The high-order harmonics produced by bass content can reach levels that are comparable to high-frequency musical content. How loud is that flute that you hear and how loud are the harmonic cues that tell you that it is a flute?

Zero crossing distortion produces many high-order harmonics and it is most audible when playing at low levels.

IMD is particularly problematic because it does not resemble the harmonics that are produced by musical instruments. With IMD, the distortion does not occur at harmonic frequencies and it may be well separated from any musical content that would mask it. Many class-D amplifiers have IMD problems. Class-AB amplifiers can produce significant IMD when they have zero-crossing distortion. They can also produce significant levels of IMD when presented with a pair of high-frequency tones.

The distortion produced by electronics is different than the distortion produced by speakers. The differences in the spectrum can be seen on an FFT. Electronics are more prone to creating high-order harmonics which are not well masked.

Electronics produce harmonic distortion at perfect integer-related frequency ratios. Musical instruments do not. For example, the piano produces harmonics that are a bit further apart than integer ratios. The tuning of a piano is normally stretched to compensate for this non-integer harmonic spacing. The overtones produced by a piano string will beat against the integer-ratio harmonic distortion produced by electronics. A "warm-sounding" amplifier will make a piano sound like it is out of tune.

Harmonic distortion may change the sound of a musical instrument long before we can recognize the fact that the music is distorted. The ratios of harmonics to the fundamental give each musical instrument its unique voice. Any time you add harmonic distortion, you make changes to this voicing.

A non-linear phase response may be more audible than a non-linear frequency response. Errors in the phase response may create the impression that the frequency response is different. The frequency response of the AHB2 extends down to 0.1 HZ and up to 500 kHz so that the phase response is linear within the 20 Hz to 20 kHz audible band.

Many amplifiers distort when driving the low-impedance portions of the speaker's impedance vs. frequency curve. This doesn't show up in steady-state 8-Ohm and 4-Ohm tests. It is important to look at the distortion when driving very low impedances. The AHB2 stays clean when driving difficult loads and phase angles. In contrast, most amplifiers do very poorly into these difficult loads.

Here is an application note about a double-blind ABX listening test that we did between the AHB2 and a typical class-AB amplifier with decent specifications. This test was examining the audibility of zero-crossing distortion when playing a single tone through loudspeakers at a low level (0.01 watt producing 67 dB SPL at the listening position). It was very easy to hear the difference between the two amplifiers. I scored 25 correct out of 25 trials on my first attempt.

ABX listening test:

https://benchmarkmedia.com/blogs/application_notes/power-amplifiers-the-importance-of-the-first-watt
https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-benchmark-ahb2-amp.7628/page-17#post-180468

There are valid reasons for these two amplifiers produce detectable differences.
In room sweep measurements are not going to expose phase and distortion when measured by the UMIK-1 (which has its own distortion).

- Rich
 
P

PENG

Audioholic Slumlord
For those interested in why amplifier distortion and phase can influence amplifier sound, there is this post by Benchmark's John Siau:



https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-benchmark-ahb2-amp.7628/page-17#post-180468

There are valid reasons for these two amplifiers produce detectable differences.
In room sweep measurements are not going to expose phase and distortion when measured by the UMIK-1 (which has its own distortion).

- Rich
Again, I can follow what you are saying, but there are no evidence such level of distortions are discernible while there are evidence (blind tests) that the opposite is more likely to be true. If John Siau is right about everything he said, I would definely buy a pair of the AHB2, but unless and until I see some proof, I won't.
 
RichB

RichB

Audioholic Field Marshall
Again, I can follow what you are saying, but there are no evidence such level of distortions are discernible while there are evidence (blind tests) that the opposite is more likely to be true. If John Siau is right about everything he said, I would definely buy a pair of the AHB2, but unless and until I see some proof, I won't.
I suspect there is insufficient data to provide the proof you are looking for.
Even if the proof existed with one pair of speakers, that may not hold true for your speaker and your ears.

Perhaps, you can find a Canadian dealer that can facilitate an in-home audition.

- Rich
 
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P

PENG

Audioholic Slumlord
Also for those interested, I would like to make one more point on distortions. If very low levels (say well below 0.1%) of THD, IMD, COD, TIM, Phase etc., are audible, or even easily discernible as some people claimed, I wonder why Audio Gurus Dr. Sean Olive, Floyd Toole, Harman International have not conducted studies of audibility of various audio amplifiers as they have done so much on loudspeakers. If I read between the lines, I think they clearly know where the focus should be on.

Another guru (more on the loudspeaker side) may be worth quoting, didn't seem to have much issues with even a lowly $200 receiver. Below are some of what he said in some old Audiocircle and Diyaudio threads.

https://www.audiocircle.com/index.php?topic=68889.msg942701;topicseen#new

"Nothing beats a receiver for value, and if you put electronics into the class of "it is not a significant factor" then why would I spend money unnecessarily? I can then buy more CD's and Blue-Ray's. As long as you realize that when you buy "seperates" its mostly for looks since the performance differences are not that great if at all. If you have enough cash to get your room perfect and have the best speakers and still want to spend some more money then go ahead. I'm not that wealthy."

https://www.diyaudio.com/forums/solid-state/109147-geddes-distortion-measurements-24.html
post#235

"The correlati0on would be between the specific design and sound quality but not the topology. In other words its possible to make a high quality design out of any topology. Maybe thats what you were missing?

For example class-A topology has an inherate advantage in crossover distortion because it doesn't have any. But that design has so many other problems that are just too hard to get arround.

Class-D is inherantly a disaster because of the complexity of making a broad band highly linear design. But that does not mean that it canoot be done, its just complicated.

Class-AB has many advantages, but crossover distortion is NOT one of them. Not properly handled crossover distortion can kill a class AB amp. However, just like anything else, proper design can make a class-AB amp as good as a class A in terms of sound quality."


The correlation is all with the implimentation and not with the topology.

And what he said about Golden ears (I agree with him on that, but would have not have put it so bluntly):

https://www.diyaudio.com/forums/solid-state/109147-geddes-distortion-measurements-24.html
Post#231

"First, the opinions of "Golden Ears" are about useless since they consistantly hear things that don't exist and cannot be heard in blind tests by them or anyone else. But yes, there are things in amplifiers that matter. Its mostly the nonlinearity at very low signal levels - something that no one publishes. So test your amps for the harmonic content as you reduce the signal level. The harmonics of a good amp will disapear into the noise. A bad map will have the higher orders actually grow in relative level as the signal level drops."

Notable amps and loudspeakers designers are going to have their strong opinions, but there is one constant, just like brand fan boys, they almost invariably praise their own design, or brands they own; and will of course do their best to convince you with all the reasons they can find or think of.
 
P

PENG

Audioholic Slumlord
I suspect there is insufficient data to provide the proof you are looking for.
Even if the proof existed with one pair of speakers, that may not hold true for your speaker and your ears.

Perhaps, you can find a Canadian dealer that can facilitate an in-home audition.

- Rich
I have done many serious audition, comparisons in high end dealers audition room, but in my own home it will be very difficult to set things up for a fair and square comparison. The best I managed was a comparison between my 4BSST and A21. I could not tell a difference but my much younger son in law who is an audiologist, thought he could hear a very slight difference. He did guess right a few times but that was clearly statistically meaningless. Given the little difference if at all, we didn't bother spending more time on the test.
 
RichB

RichB

Audioholic Field Marshall
Also for those interested, I would like to make one more point on distortions. If very low levels (say well below 0.1%) of THD, IMD, COD, TIM, Phase etc., are audible, or even easily discernible as some people claimed, I wonder why Audio Gurus Dr. Sean Olive, Floyd Toole, Harman International have not conducted studies of audibility of various audio amplifiers as they have done so much on loudspeakers. If I read between the lines, I think they clearly know where the focus should be on.

Another guru (more on the loudspeaker side) may be worth quoting, didn't seem to have much issues with even a lowly $200 receiver. Below are some of what he said in some old Audiocircle and Diyaudio threads.

https://www.audiocircle.com/index.php?topic=68889.msg942701;topicseen#new

"Nothing beats a receiver for value, and if you put electronics into the class of "it is not a significant factor" then why would I spend money unnecessarily? I can then buy more CD's and Blue-Ray's. As long as you realize that when you buy "seperates" its mostly for looks since the performance differences are not that great if at all. If you have enough cash to get your room perfect and have the best speakers and still want to spend some more money then go ahead. I'm not that wealthy."

https://www.diyaudio.com/forums/solid-state/109147-geddes-distortion-measurements-24.html
post#235

"The correlati0on would be between the specific design and sound quality but not the topology. In other words its possible to make a high quality design out of any topology. Maybe thats what you were missing?

For example class-A topology has an inherate advantage in crossover distortion because it doesn't have any. But that design has so many other problems that are just too hard to get arround.

Class-D is inherantly a disaster because of the complexity of making a broad band highly linear design. But that does not mean that it canoot be done, its just complicated.

Class-AB has many advantages, but crossover distortion is NOT one of them. Not properly handled crossover distortion can kill a class AB amp. However, just like anything else, proper design can make a class-AB amp as good as a class A in terms of sound quality."

The correlation is all with the implimentation and not with the topology.

And what he said about Golden ears (I agree with him on that, but would have not have put it so bluntly):

https://www.diyaudio.com/forums/solid-state/109147-geddes-distortion-measurements-24.html
Post#231

"First, the opinions of "Golden Ears" are about useless since they consistantly hear things that don't exist and cannot be heard in blind tests by them or anyone else. But yes, there are things in amplifiers that matter. Its mostly the nonlinearity at very low signal levels - something that no one publishes. So test your amps for the harmonic content as you reduce the signal level. The harmonics of a good amp will disapear into the noise. A bad map will have the higher orders actually grow in relative level as the signal level drops."

Notable amps and loudspeakers designers are going to have their strong opinions, but there is one constant, just like brand fan boys, they almost invariably praise their own design, or brands they own; and will of course do their best to convince you with all the reasons they can find or think of.
It's an interesting quote, but did you notice that the author has heard difference between class A/B and class D...?

Speaker designers make speakers.
I am not too surprised that they stay in their lane.
Other divisions of Harman make $10K mono-block amplifiers so there is that.

If you read the post above, John Siau also stated they did blind tests.
How many times on this forum have folks complained that manufactures, especially cable, won't do blind tests.

There is no convincing anyone of anything in audio, I think that is irrefutable.

- Rich
 
RichB

RichB

Audioholic Field Marshall
I have done many serious audition, comparisons in high end dealers audition room, but in my own home it will be very difficult to set things up for a fair and square comparison. The best I managed was a comparison between my 4BSST and A21. I could not tell a difference but my much younger son in law who is an audiologist, thought he could hear a very slight difference. He did guess right a few times but that was clearly statistically meaningless. Given the little difference if at all, we didn't bother spending more time on the test.
You might want to consider trying a couple of more amps that have taken different approaches to amplification and distortion.
I would class the A21 and AT6000 as similarly good but found the AT6000 quieter and also produced no 60Hz hum.

The AT6002 had transformer hum discernable from my listening position.
The A21 had no discernable transformer hum from my listening position.
The AT4002 and AT522NC had hum that could be heard inches away.
The AHB2s have no transformers and are utterly silent at my speakers and mechanically.

The AT522NC is very different, next to it, theAT6000/AT4000 sound dark.
The AHB2 is closer to the AT522NC but the AHB2 has more apparent resolution than all others.
The same sounds are present, of course, just more identifiable.
There is a reason that my signature has changed of late.

- Rich
 
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Out-Of-Phase

Out-Of-Phase

Audioholic General
"If you read the post above, John Siau also stated they did blind tests."

I want to see multiple independent DBTs of that amp.
 
RichB

RichB

Audioholic Field Marshall
"If you read the post above, John Siau also stated they did blind tests."

I want to see multiple independent DBTs of that amp.
So say we all. :p

They are not discounted, so in the states, anyone who is seriously interested can return them and you are out the shipping.
I am not saying everyone will like them but they are different.

- Rich
 

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