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Benchmark AHB2 / Class D Purifi Eigentakt / Mark Levinson 333 - Listening impression & Conclusion

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Thanks for sharing.
Last night, I invited my son friend (not an audiophile) to listen.
We used the telerac 1812 overture SACD, playing the songs 2 times and ask him to focus on the dynamic and details.
He was able to detect difference between AHB2 and Purifi.
But when I used my old entry surround speakers as test, none of us could tell the difference. So high resolution speakers matter.

I believe we need to develop new measurement method that explains WHAT we HEAR
Current measurement of freq response , IMD, THD based on sinewave and dummy load is single dimension and do NOT fully explain what we hear.

The speakers certainly matter, I heard the Purifi on Dynaudio Confidence speakers first, where this trait was barely noticeable: those are quite inefficient, and use soft dome tweeters. But on a very efficient JBL speaker with titanium tweeter, this character became quite obvious (relatively speaking).

As for measurements, the current measurements correspond just fine to make known audible characteristics, Bruno himeself mentions this in some of his presentations - however in most of their cases, at this point we've "solved" those measurable traits to a point where they by generally accepted standards should not be an audible issue or trait anymore - it would be interesting to double test this, but that would both be troublesome, and I suspect they'd be proven correct.
However there are also some things/phenomena we don't yet have conclusive methodology for describing, even if very visible within current measurements. Though I don't think this current matter falls into that category.
I'm entirely confident that, assuming what we're hearing is real (which of course it might not be, as some have not very subtly eluded to), then the explanation is likely to be found in some known measurement. Exactly where though is less clear. Amplifiers are extremely complex, and based on what I've heard explained, just by studying Bruno's work alone, there are numerous factors which could theoretically explain different amplifier's inherent sound characters that some purport to be able to hear. But at the same time, as said, they're often in modern amps at a level where they should theoretically not be audible characteristics in most properly designed amps.

I suspect it would require someone of quite lofty engineering caliber to build an amp to the best of their ability, and then mess with every little aspect of it, whilst simultaneously measuring and doing controlled blind tests, to have any hope of identifying is properly - given the current lack of meaningful conclusions on the topic... Short of on one hand subjective anecdotes, and the other mostly mockery.
 

SIY

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The speakers certainly matter, I heard the Purifi on Dynaudio Confidence speakers first, where this trait was barely noticeable: those are quite inefficient, and use soft dome tweeters. But on a very efficient JBL speaker with titanium tweeter, this character became quite obvious (relatively speaking).

As for measurements, the current measurements correspond just fine to make known audible characteristics, Bruno himeself mentions this in some of his presentations - however in most of their cases, at this point we've "solved" those measurable traits to a point where they by generally accepted standards should not be an audible issue or trait anymore - it would be interesting to double test this, but that would both be troublesome, and I suspect they'd be proven correct.
However there are also some things/phenomena we don't yet have conclusive methodology for describing, even if very visible within current measurements. Though I don't think this current matter falls into that category.
I'm entirely confident that, assuming what we're hearing is real (which of course it might not be, as some have not very subtly eluded to), then the explanation is likely to be found in some known measurement. Exactly where though is less clear. Amplifiers are extremely complex, and based on what I've heard explained, just by studying Bruno's work alone, there are numerous factors which could theoretically explain different amplifier's inherent sound characters that some purport to be able to hear. But at the same time, as said, they're often in modern amps at a level where they should theoretically not be audible characteristics in most properly designed amps.

I suspect it would require someone of quite lofty engineering caliber to build an amp to the best of their ability, and then mess with every little aspect of it, whilst simultaneously measuring and doing controlled blind tests, to have any hope of identifying is properly - given the current lack of meaningful conclusions on the topic... Short of on one hand subjective anecdotes, and the other mostly mockery.
Wordiness is no substitute for basic controls. Put your energy there instead of scribbling word salads.
 

BlackTalon

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I'll still not so sure that what you hear as a fault in the Purifi is not actually due to the speakers or room dampening. Only testing these in one system would seem to make it difficult to conclude anything except how each amp sounds in the system and room you have right now. Which is fine, but just means absolute judgments should not be made.
 

Lord Victor

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I'll still not so sure that what you hear as a fault in the Purifi is not actually due to the speakers or room dampening. Only testing these in one system would seem to make it difficult to conclude anything except how each amp sounds in the system and room you have right now. Which is fine, but just means absolute judgments should not be made.
I've tried the Purifi amp in multiple systems and rooms, and had similar results in all of them, comparing it to a Pascal amplifier primarily. Made a thread about it, which predictably went awry. But I stand by the listening impressions listed in it.
 

Wes

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that's fine, but I will stand by while you do a blind test
 
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Lord Victor

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that's fine, but I will stand by while you do a blind test
I already did twice, along with a handful of other people, with very consistent results. In this case I find it most likely to be the 'fault' of the pascal, as its specs are good, but far less ideal than the purifi - though I don't know. That was the reason for me making that thread: trying to figure out what might cause an audible difference so notable that multiple people in multiple systems/rooms described the same differences, without communicating.

But I've been down this road, I don't expect to change anyone's mind. I know there are people who firmly refuse to entertain anything that doesn't alight with their views. I'm just here to have a casual conversation about the matter, sharing ideas/possible explanations, not to prove anything on an academic level, because I don't currently have the necessary equipment to do that.
 

Matias

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'fault' of the pascal, as its specs are good
I disagree. Pascals have much higher distortion on the treble than mids and bass, typical of first generation class D amps. Which model did you test?
 

SIY

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I already did twice, along with a handful of other people, with very consistent results. In this case I find it most likely to be the 'fault' of the pascal, as its specs are good, but far less ideal than the purifi - though I don't know. That was the reason for me making that thread: trying to figure out what might cause an audible difference so notable that multiple people in multiple systems/rooms described the same differences, without communicating.

But I've been down this road, I don't expect to change anyone's mind. I know there are people who firmly refuse to entertain anything that doesn't alight with their views. I'm just here to have a casual conversation about the matter, sharing ideas/possible explanations, not to prove anything on an academic level, because I don't currently have the necessary equipment to do that.
It doesn’t take fancy equipment to run a properly controlled listening test. Only a sense of actual curiosity, open mindedness, and trust in your ears. For something like this, it’s particularly simple, only requiring a decent interface and some freeware like DetaWave.
 

Lord Victor

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I disagree. Pascals have much higher distortion on the treble than mids and bass, typical of first generation class D amps. Which model did you test?
That could certainly explain it - it was the L-Pro2s. It generally sounded brighter/more sterile than the purifi. Gave my Ti10K speakers a similar sort of sound character to B&W's 800 series, where the treble is accentuated, giving the perception of clearer details/transients/more dry sound, if you know what I mean.
Certainly sounded more along the lines of what I've been told in the past Class D could sound like, by people who disliked class D. Though it did give the perception of better precision/detail and more controlled bass, compared to the Purifi. I'm trying to identify the cause of that. Some sort of distortion artefact or non-linearity in the treble could certainly explain what I and the others heard. I'd be very interested if you have inklings as to what specific issue might be the cause.

Edit: Going back and looking, the closest to a solid answer was BoXeM Audio's bet, that it might be the Pascals output impedance, which might interact with the speaker, causing a shift up to 0.3dB in the treble with a 4ohm speaker, by his calculations. Its not much, but that could be it.
 
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MasterApex

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I'll still not so sure that what you hear as a fault in the Purifi is not actually due to the speakers or room dampening. Only testing these in one system would seem to make it difficult to conclude anything except how each amp sounds in the system and room you have right now. Which is fine, but just means absolute judgments should not be made.

I own them so there is no fault to any of my amps :)
As I said, they sound good and neutral on their own.

Yes, I am highlight the contrast among them in my environment (same room. electronics) , just swapping amps.
 

SIY

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That could certainly explain it - it was the L-Pro2s. It generally sounded brighter/more sterile than the purifi. Gave my Ti10K speakers a similar sort of sound character to B&W's 800 series, where the treble is accentuated, giving the perception of clearer details/transients/more dry sound, if you know what I mean.
Certainly sounded more along the lines of what I've been told in the past Class D could sound like, by people who disliked class D. Though it did give the perception of better precision/detail and more controlled bass, compared to the Purifi. I'm trying to identify the cause of that. Some sort of distortion artefact or non-linearity in the treble could certainly explain what I and the others heard. I'd be very interested if you have inklings as to what specific issue might be the cause.

Edit: Going back and looking, the closest to a solid answer was BoXeM Audio's bet, that it might be the Pascals output impedance, which might interact with the speaker, causing a shift up to 0.3dB in the treble with a 4ohm speaker, by his calculations. Its not much, but that could be it.
Or… it could be that it’s because of the most likely explanation. Maybe put your effort there.
 

Inner Space

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I'm just here to have a casual conversation about the matter, sharing ideas/possible explanations, not to prove anything on an academic level ...

I would love to have such a conversation. But surely you would agree that first we need to know there's something real to have a conversation about. I bet if you had some solid blind-test data, the subsequent sharing of ideas and explanations would run for a hundred pages. Maybe a thousand. It would be great. But we need somewhere to start, and anecdata is not a worthwhile point of departure, however sincere. I know that sounds critical and dismissive, but it's crucial.
 
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Lord Victor

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I would love to have such a conversation. But surely you would agree that first we need to know there's something real to have a conversation about. I bet if you had some solid blind-test data, the subsequent sharing of ideas and explanations would run for a hundred pages. Maybe a thousand. It would be great. But we need somewhere to start, and anecdata is not a worthwhile point of departure, however sincere. I know that sounds critical and dismissive, but it's crucial.
I’ve done/tried to do that before, but it’s my experience at this point that no standard is high enough, if the experiment would prove something that goes against the current convention.
I’d absolutely love to try again (though I don’t currently have access to the amps), but so far have been unable to get a sure fire way I would be able to do it that would not immediately be dismissible by some measure anyway, short of the critics performing the entire thing themselves instead...
If I were to do it in a way I’d consider bulletproof it would require equipment I don’t currently have - and my experience with some people’s attitude (you seem reasonable and civil enough mind you) on these things does not inspire much hope that even the most perfectly executed test would suffice, which leaves little motivation to try, in all honesty...
 
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MasterApex

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I'm trying to identify the cause of that. .

Me too...we need new measurement that explains what we heard.

In science, we can not use Newton laws to explain quantum physics phenomena.
I am hopeful that someone will produce measurement standards (beyond today freq response, SINAD, THD, IMD with dummy load) that will explain what we heard.
 

Matias

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That could certainly explain it - it was the L-Pro2s. It generally sounded brighter/more sterile than the purifi. Gave my Ti10K speakers a similar sort of sound character to B&W's 800 series, where the treble is accentuated, giving the perception of clearer details/transients/more dry sound, if you know what I mean.
Certainly sounded more along the lines of what I've been told in the past Class D could sound like, by people who disliked class D. Though it did give the perception of better precision/detail and more controlled bass, compared to the Purifi. I'm trying to identify the cause of that. Some sort of distortion artefact or non-linearity in the treble could certainly explain what I and the others heard. I'd be very interested if you have inklings as to what specific issue might be the cause.

Edit: Going back and looking, the closest to a solid answer was BoXeM Audio's bet, that it might be the Pascals output impedance, which might interact with the speaker, causing a shift up to 0.3dB in the treble with a 4ohm speaker, by his calculations. Its not much, but that could be it.
My bet would be 6.67 kHz distortion rising with power, so that the treble becomes "harsh" in dynamic passages. Typical of old tech, and what gave class D a bad reputation...

Screenshot_2021-06-03-18-43-14-709_com.google.android.apps.docs.jpg
 
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Lord Victor

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My bet would be 6.67 kHz distortion rising with power, so that the treble becomes "harsh" in dynamic passages. Typical of old tech, and what gave class D a bad reputation...

View attachment 133622
Huh, don’t know how we missed that, but yea... that'd probably do it. That and the output dependency, the entire thing actually starts to make sense - and confirms the suspicion I had that the Pascal was artificially sounding more precise, due to some non linear behavior...
Thank you so much for actually taking a serious approach to this! More people like that could have saved me a lot of grief - much appreciated!
 

SIY

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Me too...we need new measurement that explains what we heard.

In science, we can not use Newton laws to explain quantum physics phenomena.
I am hopeful that someone will produce measurement standards (beyond today freq response, SINAD, THD, IMD with dummy load) that will explain what we heard.
Terrible excuse to avoid basic controls, followed by a horribly inapt analogy, with a straw man thrown in at the end for good measure.

If you have no curiosity about what’s real and what isn’t, a science site is not the best place for you to be. If you are, do an actual experiment.
 

Lord Victor

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Me too...we need new measurement that explains what we heard.

In science, we can not use Newton laws to explain quantum physics phenomena.
I am hopeful that someone will produce measurement standards (beyond today freq response, SINAD, THD, IMD with dummy load) that will explain what we heard.
I’m fairly sure the measurements we have can describe what we hear just fine for the most part - it’s just a matter of figuring out how, or what to look for - as @Matias just proved, case in point, with part of the equation in my case simply being non linear distortion, adding quite solidly to explaining why the amp I was comparing the Purifi to, sounded brighter.
Proving that at least in my case the Purifi was the correct one, in spite of the subjective experience/preference. Can’t speak to yours or other experiences by this point, without comparing the Purifi to more amps - I certainly doubt the Benchmark has as obvious a flaw as the pascal did, explaining the experience. But I guess we’ll see.
 
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