Audibility of Audio Power Amplifier Distortions

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Audibility of Audio Power Amplifier Distortions

Reply #100 – 2014-12-01 11:39:52

Quote from: amirm on 2014-11-30 21:06:46

As I promised Steven earlier, here are some additional quotes from the Meyer amplifier test.

One of the key requirements for a correct listening test is critical test signals/music tracks. We need content that is revealing of the differences we like to find. This is stipulated strongly in ITU BS1116 and is standard practice in research/industry. It is abundantly easy to use tracks that don't bring out the difference and proceed to declare there is no audible difference.

When a distortion is not uniformly apparent, finding the difference becomes a statistical effort. If I suck out 43 Hz out of the system, but you play content that has little in that frequency, then you won't hear the difference before and after I do that. I think we all agree that a system that has big hole at 43 Hz is broken. Yet we can trivially create results from double blind tests that say there is no problem at all. We may get lucky and throw music at the system that does have 43 Hz content, or the opposite. What are the odds?

Well, just like gambling, we like to improve our odds. We do that by using trained listeners who know what to listen for and find them easier than average listeners. And we help them further with critical music segments that makes the job easier and less subject to errors/nocebo, etc.

Let's put this knowledge to practice. Here are the results of the double blind tests that Meyer ran in his stereo review article:

Look at the difference the type of signal makes. I have highlighted Pink Noise. See how that is revealing in all three test cases. Now look at the rest of the outcomes in test #2. All would be dismissed as not being good enough and equiv. declared in the two amplifiers.

In this case we have objective proof that the pink noise data is correct. We know that the frequency response varied between the two amplifiers. So there was no need to throw music at the system. The job was done the moment pink noise showed revealing difference in amplifiers.

Depends on what one is trying to prove. The pink noise tests do, as you suggest provide reliable evidence that there was probably a frequency response difference.

However, is that enough?

Quote

Unfortunately the audio test field is littered with people who throw random tracks of music at a system and proceed to declare equivalence. No attempt is made at determining what the potential problems are, and what kind of content best exercises it. This is my #1 beef with many listening tests. I hope the above data shows why.

How do we know that the selections that Meyer used were not carefully chosen to be diagnostic where there are other kinds of audible differences to be heard?

Given that sighted evaluations are generally known to be highly prone to false positives, how do we know that they are using diagnostic content?

In your Levinson #53 amplifier test, what do we know about the musical selections that were used in the evaluation?

Since all listening tests of the #53 are per your own admission sighted, how do we know that your claims about it are based on anything but false positives?

See, here's the problem Amir. you seem to use tough standards with the people that you disagree with and in this case have insulted vigorously on this forum, and another far easier one for you and your other subjectivist buddies.

I my case I wrote up an experiment on HA that I believe most knowledgeable people would instantly know was based on objective tests, and you claimed vigorously and repeatedly that I used sighted evaluations. Needless to say your pistol seems to get half-cocked long before you determine there is even anything to aim at. ;-)

Audibility of Audio Power Amplifier Distortions

Reply #101 – 2014-12-01 14:53:16

Quote from: Arnold B. Krueger on 2014-12-01 11:19:55

Whether you know it or not Amir the Levinson 53 article contains claims of audibility and technical claims that are controversial if not outright wrong. There is no evidence there to support the conclusions given. That is actually good because the claims are so wrong that support would violate the laws of physics.

Unless Amir ends his dancing evasion of his own Listening Tests for Audibility of Audio Power Amplifier Distortions, I see no point in answering a single diversionary question he asks about any other test, since these are all smokescreens for him to hide behind. I encourage all to steer him back to his own unanswered claimed tests.
If he is truly interested in Listening Tests for Audibility of Audio Power Amplifier Distortions, then his own purported tests, where he claims positive results, are all that are needed to demonstrate the validity of the thread topic.
Of course, if it's yet another complete farce like his DAC distortion "+/- 10% volume" listening tests I have linked numerous times, then he has ample reason to run form these amp distortion listening test claims of his.
He claims positives, not nulls for the thread topic. Let's see them....and how.

cheers,

AJ

Audibility of Audio Power Amplifier Distortions

Reply #102 – 2014-12-01 16:27:56

Nothing is more sobering than to miss an audible difference in blind tests that can be shown to objectively be there and audible. Yes, I speak from embarrassing experience here .

Here is the best example of that in Meyer's test:

The frequency response of a tube amp is compared to a transistor one. There is clear variation in response in the tube amplifier. Pink noise confirmed conclusively that it was audible. Yet, yet.... testing with the music selections did not reveal the difference!

Here are the scores again from the test #2:

Pink noise garnered 99.9% confident result of difference between amps. In sharp contrast, combined music trials rendered only 34% confidence.

Had someone just presented the music trials at 34% confidence, we would all say that the two amps are equivalent. Yet that would be completely wrong conclusion.

This is why two things are critical in listening tests of this sort:

1. Was critical test content used that would bring out the differences. In this case the difference was frequency response variations and hence we needed content that would have content in the region of interest that would make it as easy as possible to detect the difference.

2. Were trained listeners used so that they could find the differences if not abundantly audible?

In this test with music, the issue could have been #1, #2 or both.

Lesson here is if the results of a listening test are negative, you need to establish that it is not due to #1 and #2. If you cannot, then the results are not reliable. This is why I am like a broken record when it comes to these two issues. If you don't know how to find the right material or have the critical listening abilities to hear non-obvious differences, then you have no business running such tests.

Edit:errrrrrr... typo as usual.

Audibility of Audio Power Amplifier Distortions

Reply #103 – 2014-12-01 16:46:50

Are you trying to tell us that a negative result does not prove the null hypothesis? We already knew that!

Audibility of Audio Power Amplifier Distortions

Reply #104 – 2014-12-01 16:53:07

Is there a reason you posted this pointlessly cantankerous 'spin' on Meyer's 1991 results *twice* now, Amir?

You aren't teaching anyone here anything with this. We know that type of probe signal matters. We know that training matters.

Meyer himself noted the difference between pink noise and music, and he himself does not claim these as be-all and end-all results. You conveniently neglect to post relevant text from the article.

e.g.

Quote

I did two sets of trials, one with a steady signal called pink noise that makes it easy to hear response differences and another with music.

Quote

Because of the relatively small number of trials in these tests, the results should be taken primarily as an indication of where to look and how to proceed with more thorough tests in the future.

Audibility of Audio Power Amplifier Distortions

Reply #105 – 2014-12-01 16:58:42

Quote from: pdq on 2014-12-01 16:46:50

Are you trying to tell us that a negative result does not prove the null hypothesis? We already knew that!

No. I am telling you exactly what I said: *how* to run such tests as to generate reliable results. The importance of revealing content. The importance of using trained listeners. And ignoring test data that doesn't do that.

If a test is not proper, you ignore it and don't look to it to have done anything for the null hypothesis one way or the other.

If you were looking to see if my gas tank is empty and hence the reason my car did not start, and proceeded to check the radiator instead, we don't get to make any judgement about what is wrong with my car. We throw out the tester's data as the person not being qualified to run such diagnosis.

Audibility of Audio Power Amplifier Distortions

Reply #106 – 2014-12-01 17:19:52

I'm not sure what you mean by a "proper" test. Is a "proper" test one that gives the result that you wanted? And is an "improper" test one that gives results that you don't like?

Audibility of Audio Power Amplifier Distortions

Reply #107 – 2014-12-01 17:31:07

Quote from: pdq on 2014-12-01 17:19:52

I'm not sure what you mean by a "proper" test. Is a "proper" test one that gives the result that you wanted? And is an "improper" test one that gives results that you don't like?

Not at all. I thought I already explained what is proper and improper. A proper test has Proper content. And Proper listeners. Violated those two principals and I don't care what the outcome is. The results are unreliable.

Of course my views are shared by the international standards for finding small differences: ITU Recommendation Broadcast Standard 1116:

3.1 Expert listeners
It is important that data from listening tests assessing small impairments in audio systems should come exclusively from
subjects who have expertise in detecting these small impairments. The higher the quality reached by the systems to be
tested, the more important it is to have expert listeners.

6 Programme material
Only critical material is to be used in order to reveal differences among systems under test. Critical material is that which
stresses the systems under test.

These are the first things you look for. If they are not there, the outcome whether you agree with it or not is not material.

Audibility of Audio Power Amplifier Distortions

Reply #108 – 2014-12-01 17:51:37

Here is another insight from the test notes:

Notice what great thing about pink noise: it keeps repeating so when you switch back and forth, you hear the "same" thing. Why is that important? It is because of how our hearing works.

The first part of our perception is a "tape recorder" that captures everything that is being delivered by the ear. Think of this as a lossless recorder. This is the short-term memory and highly reliable. Ever ask someone to repeat something only to remember exactly what they said? That is short term memory recall.

As you can imagine, the volume of such data can be huge. Estimates are in many megabytes in computer terms. There would be no way to keep recording and recording everything that comes in. To get around this problem, the short term memory has strict limits on it measured in seconds. Different research gives different numbers for this but it is "short few seconds" before the data is overwritten.

What happens next is smart filtering. The cognitive part of the brain kicks in to extract useful information. Was that your loved one talking? Female voice? Piano playing? Etc. This is your longer term memory and is based on characteristics extracted from the short term memory. Now you in kilobits order of magnitude so a lot can be saved and recalled.

When the differences are huge, like a male person talking instead of female, we can use our long term memory. But when differences get small where brain classification would ignore, then we must rely on short term memory.

Back to the test, the pink noise keeps repeating with the same characteristic. So we can switch and instantly hear the difference.

With music, that was not so in his testing. The music kept playing linearly. Going "back" to the previous source did not give you the same content as was just heard. This means that you must rely on the much less accurate longer term memory classification.

They tried to deploy a useful technique which is to pick something like a long note that lasts for a bit. This way when you switch inputs you are still hearing something similar. But similar is not the same as what was heard. When differences get small, you want to re-hear the exact same thing.

As such, it is critical to be able to give the user the ability to loop and re-hear the same segment as was just heard. From countless listening tests I have performed I can tell you with 100% confidence that the reliability of the test suffers and suffers big time when all that is provided is linear playback. I want to hear that one piano reverb trail that may be 1 or 1.5 seconds. I want to focus on that detail. I don't want to hear one note for one input and another note for the other input.

When we don't provide such tools to the listener, the last part of the quote comes true. It becomes very frustrating to perform the test. You think you heard something but when you try to go "back" to it, the music has already gone forward. So you have to re-listen and that quickly becomes tedious. And tiredness means more mistakes. Listeners start to vote randomly or just vote "A" which the latter explaining why we don't always land at 50-50 negative outcome.

Easy segment selection and looping is essential to finding small differences. Give me a good tool for that and the job becomes hugely simpler. You can see that in my double blind ABX test results. I am able to finish these tests with lightning speed when I have that ability. I give Foobar ABX plug-in pretty poor ratings in this regard by the way. Segment selection is painful due to poor user interface implementation. The new one unfortunately does not fix that and piles on more problems on top of that.

Audibility of Audio Power Amplifier Distortions

Reply #109 – 2014-12-01 19:29:12

Quote from: amirm on 2014-12-01 17:31:07

6 Programme material
Only critical material is to be used in order to reveal differences among systems under test. Critical material is that which
stresses the systems under test.[/color][/i]

Surely one needs to use some common sense here. The critical material must still be testing the thing that is to be determined. I could test how these amplifiers perform into an inductive load but then all I am testing is how they perform into an inductive load.

Until you can show me how testing with pink noise (which I never listen to) relates to listening to music (which I DO listen to) I am unconvinced.

Audibility of Audio Power Amplifier Distortions

Reply #110 – 2014-12-01 20:55:11

Quote from: pdq on 2014-12-01 19:29:12

Until you can show me how testing with pink noise (which I never listen to) relates to listening to music (which I DO listen to) I am unconvinced.

That's easily shown .

Here are the test results again. Please focus on test case #2:

Would you say the results of those two tracks are more representative of the experience you have when you listen to your full collection of music? I.e. you won't reliably hear any coloration?

Audibility of Audio Power Amplifier Distortions

Reply #111 – 2014-12-01 21:09:58

What you have shown is that in at least one case the pink noise test does not correlate to testing with music.

Audibility of Audio Power Amplifier Distortions

Reply #112 – 2014-12-01 21:21:40

Quote from: pdq on 2014-12-01 21:09:58

What you have shown is that in at least one case the pink noise test does not correlate to testing with music.

No. The data shows that the two music clips, just those two, don't correlate with the results of the pink noise.

The pink noise however, 100% correlated with objective differences that we know create coloration. It told the truth. The two music samples did not.

There are some 10,000,000 commercial music tracks. We would be lucky to perform a listening test with just 10 of them. How would we claim that those 10 clips represent 10 million tracks people may listen to? We can't, right?

Now, you are right that the pink noise is unlikely to be one of those 10 million tracks . However, to the extent it is the most difficult track and we use that to find a transparent system, then we have very, very high assurance that across those 10,000,000 tracks (and millions of listeners) we have a transparent system.

Now, if no system can pass the test then sure, we have picked too difficult of a test signal. But to the extent we can find transparent gear, then the clip is very appropriate to use for testing. And what we must do if we want to represent equality between systems from negative outcomes.

Audibility of Audio Power Amplifier Distortions

Reply #113 – 2014-12-01 22:10:33

Quote from: amirm on 2014-12-01 21:21:40

Now, if no system can pass the test then sure, we have picked too difficult of a test signal.

What test signal did you use here to get these positives?
http://www.madronadigital.com/Library/Mark...3Amplifier.html

Quote

But How Does it Sound?, by Amir Majidimehr
In comparison testing I have done, switching amplifiers using the classic class D configuration always sport incredible low frequency control and power. They beat out linear class AB amplifiers almost regardless of price. What they give up though is high frequency fidelity which I find somewhat harsh. The distortion is highly non-linear and challenging to spot but it is there. The Mark Levinson No 53 is the first switching amplifier I have heard which does not have this compromise. Its bass is amazingly authoritative: tight and powerful. Yet the rest of the response is absolutely neutral and pleasant.

Pink noise?

Audibility of Audio Power Amplifier Distortions

Reply #114 – 2014-12-01 22:21:14

Quote from: krabapple on 2014-12-01 16:53:07

Is there a reason you posted this pointlessly cantankerous 'spin' on Meyer's 1991 results *twice* now, Amir?

Yes, to avoid answering anything about this Audibility of Audio Power Amplifier Distortions Listening Test he claims to have done: http://www.madronadigital.com/Library/Mark...3Amplifier.html
No test material listed....or anything, yet claiming positives and some other ridiculous nonsense about Class D vs AB power supplies and "bass".
Btw, your Inbox is full.

cheers,

AJ

Audibility of Audio Power Amplifier Distortions

Reply #115 – 2014-12-02 00:09:42

Quote from: amirm on 2014-12-01 21:21:40

Quote from: pdq on 2014-12-01 21:09:58
What you have shown is that in at least one case the pink noise test does not correlate to testing with music.

No. The data shows that the two music clips, just those two, don't correlate with the results of the pink noise.

The pink noise however, 100% correlated with objective differences that we know create coloration. It told the truth. The two music samples did not.

Amir, if you were more honest you'd note that Meyer himself wrote that when he used speakers that did not present a difficult load for the amps, the small measured FR differences was "faintly audible with pink noise" and not at all to him, with music. He ascribed the differences to the 0.25dB difference in the 'vocal' range to which we are very sensitive (300-500Hz).

A 0.25dB difference, faintly audible to him, only when pink noise is used. And even in the more robust case where both pink noise *and* music revealed a difference, it was only when the systems were not biamped. Many more systems today *are*, of course, biamped, than they were back in 1991....thanks to the popularity of active subwoofers

So I'd say that your 'truth' here is, at best, a piddling one. Under most conditions -- listening to music via non pathological speaker/amp combos -- the difference is *in practice* likely to be inaudible, as it was even between this tube amp and this SS amp under 2 out of 3 conditions. THAT is the important truth.

Since the start of the "Great Debate", hi end amps have been promised to routinely yield big, obvious difference for the music lover. Neil Young and the hi rez cheerleading squad promises that 'high resolution' audio will do the same.

In fact, neither of them do.

Readers, you need not take Amir's quote-mining (or my responses) of the Meyer 1991 Stereo Review article as gospel. You can read it for yourself:

https://dl.dropboxusercontent.com/u/2605734...erInterface.pdf

Audibility of Audio Power Amplifier Distortions

Reply #116 – 2014-12-02 01:55:56

Quote from: amirm on 2014-12-01 23:48:28

I am not a girl. It was blue noise.

Or imaginary noises in your head that sounded "harsh" and "bassy". Since there is zero evidence showing any test actually took place.

Quote from: amirm on 2014-12-01 23:48:28

You said it AJ.

No Amir, that's your name on this subjectivist audiophile tale, see:
http://www.madronadigital.com/Library/Mark...3Amplifier.html

Quote

But How Does it Sound?, by Amir Majidimehr
In comparison testing I have done, switching amplifiers using the classic class D configuration always sport incredible low frequency control and power. They beat out linear class AB amplifiers almost regardless of price. What they give up though is high frequency fidelity which I find somewhat harsh. The distortion is highly non-linear and challenging to spot but it is there. The Mark Levinson No 53 is the first switching amplifier I have heard which does not have this compromise. Its bass is amazingly authoritative: tight and powerful. Yet the rest of the response is absolutely neutral and pleasant.

That's you making multiple absurd claims about Audibility of Audio Power Amplifier Distortions Listening Tests. Now you hide from it. Nothing about listener training, program material, level matching (+/- 10% ??), etc, etc.....while demanding info about every one of those, in other tests. Pot, meet kettle.

Quote from: amirm on 2014-12-01 23:48:28

For you it always is....

That's ok Amir. I'll continue to ask about your claimed amplifier listening tests, in the Audibility of Audio Power Amplifier Distortions thread, out here in the open for all to see.
We appreciate you starting a thread, on a topic that you claim to have done tests of, yourself.
Literally.

cheers,

AJ

Audibility of Audio Power Amplifier Distortions

Reply #117 – 2014-12-02 02:30:02

Quote from: amirm on 2014-12-02 01:22:06

Quote from: krabapple on 2014-12-02 00:09:42
So I'd say that your 'truth' here is, at best, a piddling one. Under most conditions -- listening to music via non pathological speaker/amp combos -- the difference is *in practice* likely to be inaudible, as it was even between this tube amp and this SS amp under 2 out of 3 conditions. THAT is the important truth.

No, there is no such "truth" in the article. You are giving us your opinion devoid of what is said there. This is what is in the article, word for word:

It says it sounded better. It says it added warmth that was pleasing with most material. It says it softened upper midrange hardness. It said it gave vocals more natural sound. These are benefits/characteristics that audiophiles cherish. Have you not ever listened to a tube amplifier Steven?

How can you twist this into "in practice likely to be inaudible." You have to be kidding us.

Quote
Since the start of the "Great Debate", hi end amps have been promised to routinely yield big, obvious difference for the music lover.

And the above direct quote from Meyer absolutely confirms that. Well designed tube amps absolutely sound delicious and nice. I have no use for them because I like power and don't care for their maintenance. But don't take the position that they don't have better subjective sound. Your own reference says they do in no uncertain terms.

Whatever sound tube amps have or impart depends upon the impedance profile of both the amp and the speaker. The impdedance profile of the tube amp as well as the distortion isn't constant as power goes up. Throw in the different favors of tube amps like SET and OTL along with different taps and it may well add warmth or make things sound boomy or just act like a SS amp. I agree with the maintenance part but they sure can be works of art.

Audibility of Audio Power Amplifier Distortions

Reply #118 – 2014-12-02 17:20:52

Quote from: amirm on 2014-11-30 02:26:26

I am good with that coming from you. Are we done or will you change your mind and re-post the same thing again?

If we are going to impose a moratorium on 'posting the same thing again', please let's not be selective in applying it, OK?

Audibility of Audio Power Amplifier Distortions

Reply #119 – 2014-12-02 17:30:22

Quote from: amirm on 2014-12-02 01:22:06

Quote from: krabapple on 2014-12-02 00:09:42
So I'd say that your 'truth' here is, at best, a piddling one. Under most conditions -- listening to music via non pathological speaker/amp combos -- the difference is *in practice* likely to be inaudible, as it was even between this tube amp and this SS amp under 2 out of 3 conditions. THAT is the important truth.

No, there is no such "truth" in the article. You are giving us your opinion devoid of what is said there. This is what is in the article, word for word:

It says it sounded better. It says it added warmth that was pleasing with most material. It says it softened upper midrange hardness. It said it gave vocals more natural sound. These are benefits/characteristics that audiophiles cherish. Have you not ever listened to a tube amplifier Steven?

How can you twist this into "in practice likely to be inaudible." You have to be kidding us.

Hmm, does 'under most conditions', to you, include tube amps driving the top part of biamped systems ? Is that a vastly popular choice these days?

Meyer himself noted in his conclusion, which I have already quoted in full here (and which you failed a pop quiz on already) , that tube amps -- and SS amps designed to sound like tube amps -- are likely to 'behave differently' from SS amps. Whoop de do! There's your niche market, Amir, go for it.

Quote

Quote
Since the start of the "Great Debate", hi end amps have been promised to routinely yield big, obvious difference for the music lover.

And the above direct quote from Meyer absolutely confirms that. Well designed tube amps absolutely sound delicious and nice. I have no use for them because I like power and don't care for their maintenance. But don't take the position that they don't have better subjective sound. Your own reference says they do in no uncertain terms.
..

Whatever sound tube amps have or impart depends upon the impedance profile of both the amp and the speaker. The impdedance profile of the tube amp as well as the distortion isn't constant as power goes up. Throw in the different favors of tube amps like SET and OTL along with different taps and it may well add warmth or make things sound boomy or just act like a SS amp. I agree with the maintenance part but they sure can be works of art.

That warm tubey goodness (which I have heard) only was audible with music when the system was biamped. And only when he used speakers that were a tough load. You left that part out. IOW, you have to 'match' your tube amp to the 'right' system to get that sound*. Meyer talks about this too, in another part you didn't quote.

*I'd call that 'pathological' audio behaviour, but YMMV.

Audibility of Audio Power Amplifier Distortions

Reply #120 – 2014-12-02 22:47:52

Quote from: krabapple on 2014-12-02 17:30:22

That warm tubey goodness (which I have heard) only was audible with music when the system was biamped. And only when he used speakers that were a tough load. You left that part out. IOW, you have to 'match' your tube amp to the 'right' system to get that sound*. Meyer talks about this too, in another part you didn't quote.

No, I didn't leave anything out. I provided an exact cut out of the article with the complete answer. Here is the concluding paragraph for the whole article:

For solid-state amps he is providing his opinion that the likely sound the same but no back up is provided in the article. He also adds an undefined catch: within their power capability. As a user, you have no idea when that limit has been hit. Dynamic power limiting will cause coloration which can last just milliseconds.

For tube amplifiers, he is saying you basically need to expect different sound with different speakers without any of the qualifications you are trying to say on his behalf.

The conclusions as he states them is quite different than our marching orders in forums. Have someone say they replaced an AVR with a monoblock and heard a difference and hell will break lose. The person will be told that is an impossibility. Yet, above is your expert witness saying that could happen.

Audibility of Audio Power Amplifier Distortions

Reply #121 – 2014-12-02 22:55:55

And this is what he says above that concluding remark:

This torpedos any statement that amplifiers sound the same. That even if two amps have been shown to sound the same in blind tests, all you have to do is change the speaker and the sound will be different.

Audiophiles we hate talk about this all the time. They call it "synergy." Here is your expert witness saying that is 100% true.

Audibility of Audio Power Amplifier Distortions

Reply #122 – 2014-12-03 00:33:08

Quote from: amirm on 2014-12-02 22:47:52

For solid-state amps he is providing his opinion that the likely sound the same but no back up is provided in the article.

Amir, you say almost the exact same thing in yours, 3rd sentence, but no back up is provided in the article. Very sloppy.

Quote from: amirm on 2014-12-02 22:47:52

He also adds an undefined catch: within their power capability.

Amir, I've highlighted where you make similar claims about amplifier power limits, but provide zero data for these purely subjectivist claims. Highly unprofessional, hobbyist at best.

Quote from: amirm on 2014-12-02 22:47:52

The conclusions as he states them is quite different than our marching orders in forums. Have someone say they replaced an AVR with a monoblock and heard a difference and hell will break lose.

Amir, the conclusions you state about Class D HF harshness, super bass and various amp "sounds", are exactly the same as on subjectivist audiophile hive forums. Have a rational person say lets see some supporting honesty controls testing evidence and all hell will break loose. Not terribly objective at all.

cheers,

AJ

Audibility of Audio Power Amplifier Distortions

Reply #123 – 2014-12-03 01:51:52

Quote from: ajinfla on 2014-12-03 00:33:08

Amir, the conclusions you state about Class D HF harshness, super bass and various amp "sounds", are exactly the same as on subjectivist audiophile hive forums.

Don't know subjectivist audiophile forum members writing things like this: http://www.madronadigital.com/Library/Mark...3Amplifier.html

The so called “interleaving” method has a great advantage over traditional class D designs as the interleaving factor acts as a multiplier on the switching frequency. As an example an 8-way interleaved output stage run at 500 KHz, acts the same as a class D amplifier running at 4 MHz! This makes filter design much simpler as we have plenty of time to go from conducting the full audio response, say up to 50 KHz, to full reject of the 4 MHz effective signal. Indeed that is how the Mark Levinson No 53 works. Here is a comparison of the distortion prior to filtering for the traditional 2-way interleaving to 8-way method used in Mark Levinson No 53:

[...]

Being a “statement” product, the Mark Levinson No 53 sports a traditional linear power supply from the Mark Levinson Reference 532 amplifier. The temptation in class D designs is to use a switching mechanism in the power supply itself feeding the amplifier. While this provides improved efficiency it aggravates a weakness of switching amplifiers which is their very high sensitivity (compared to linear amplifiers) to power supply voltage variations and noise which unfortunately get worse with switching supplies. Copious amount of “negative feedback” can be used to compensate for this but that leads potentially to amplifier instability (and some would claim compromised audio fidelity).

Are you able to follow this kind of technical explanation Ammar?

Quote

Have a rational person say lets see some supporting honesty controls testing evidence and all hell will break loose. Not terribly objective at all.

Last time you and I talked about objectivity and double blind tests, you had an awful time admitting that you don't believe in it. Has anything changed?
-----

Quote:Originally Posted by AJinFLA
At least I'm honest about not blind testing my loudspeakers...

This is what it took for Ammar to be "honest:"
Quote:Originally Posted by amirm
We would only know that [form follows function of his speakers] if you had run a blind test against some other ones, now wouldn't we?

Quote:Originally Posted by AJinFLA
A blind test of "Form following function"???

Quote:Originally Posted by amirm
No need to be confused. You want me to listen to your speakers. I am asking what type of blind listening tests you have run on it. You do believe in blind testing of speakers, do you not?

Quote:Originally Posted by AJinFLA
To verify what claim? "Form follows function"???

HDMI audib....?..ooops, sorry

.

Quote:Originally Posted by amirm
You do believe in blind testing of speakers, do you not?

Quote:Originally Posted by AJinFLA
Sure do. And measuring audible difference sound waves.

Quote:Originally Posted by amirm
AJ, I can't follow your answer. Have you run any blind tests of your speakers against others to verify it performs better?

Quote:Originally Posted by AJinFLA
Perhaps you could have JJ..or someone high school, or anyone who isn't an audiophile...explain it, slowly, to you?

Performs better than....what?
Where did I make such a claim, that it performed better than X?

Quote:Originally Posted by amirm
So you designed a speaker with no goal for it to be better than anything? And think I should come and listen to it and be impressed with that goal in mind?

Quote:Originally Posted by AJinFLA
I designed it to be better than the last, at meeting known, scientifically established thresholds, such as smoothness of FR on and off axis, etc, etc.

Quote:Originally Posted by AJinFLA
I said blind tests for already established audibility thresholds (such as FR JNDs) are unnecessary, not what you just fabricated above.
============

"Blind tests are not necessary...AJ in Florida"

Audibility of Audio Power Amplifier Distortions

Reply #124 – 2014-12-03 02:46:14

Quote from: amirm on 2014-12-03 01:51:52

Don't know subjectivist audiophile forum members writing things like this:
Quote
But How Does it Sound by Amir Majidimehr
OK, lots of technical talk but does any of this impact the sound?
You may know that there are two schools of thought here. One that says all amplifiers more or less sound the same.

Actually, that's exactly what they write. First, some BS about amp "sound", immediately followed up by a strawman. Perfect, yes.
Here's more:

Quote

This usually translates into the amplifier sound becoming leaner at higher volumes, together with increased high frequency distortion, and less than impactful bass.

Notice how those subjectivist audiophile forum members posit their purely subjective perceptions as facts, with zero supporting evidence. No blind tests or anything about methods, setup, training, etc, etc.
Just purely subjectivist blathering.
More:

Quote

In comparison testing I have done, switching amplifiers using the classic class D configuration always sport incredible low frequency control and power. They beat out linear class AB amplifiers almost regardless of price. What they give up though is high frequency fidelity which I find somewhat harsh. The distortion is highly non-linear and challenging to spot but it is there. The Mark Levinson No 53 is the first switching amplifier I have heard which does not have this compromise. Its bass is amazingly authoritative: tight and powerful. Yet the rest of the response is absolutely neutral and pleasant.

Quote from: amirm on 2014-12-03 01:51:52

Are you able to follow this kind of technical explanation Ammar?

No, there is nothing "technical" to follow, just a bunch of subjectivist audiophile forum member tripe about "incredible low frequency control and power". What the heck does that mean? "They beat out linear class AB amplifiers almost regardless of price." Really? Talk about BS hyperbole. Where are the objective listening tests/data supporting such a preposterous claim? Nowhere, zero data, no blind tests or anything about methods, setup, training, material selection, pink noise?, music? etc, etc.

Quote from: amirm on 2014-12-03 01:51:52

Last time you and I talked about objectivity and double blind tests, you had an awful time admitting that you don't believe in it. Has anything changed?

If you are referring to this or this:

Quote from: amirm on 2014-12-02 16:57:58

If what I present doesn't meet some high bar, so be it....
The comparison I performed was using a Mark Levinson No360S against the on-board DACs in five to six DVD-A and SACD players, all playing the same time sync'ed CD. In other words, I would listen to the analog output of the player while its digital output would feed the ML DAC. All front panel lights were turned off in addition to video circuits (yes, all of that made a difference in fidelity).
The two sources were fed to the dual inputs of a Stax "earspeaker" electrostatic headphone amp. If you are not familiar with Stax, you can read learn more about them here: http://www.stax.co.jp/Export/ExportProducts.html. I have three of their units and results are consistent across the board although the highest end unit does make the job a bit easier. Using headphones allowed me to completely eliminate the room and take advantage of the amazing transparency of these headphones to listen for the slightest differences. To latter point, I would often listen to material at levels well above what I would use for listening to music, allowing me to hear detail that would otherwise be lost.
I then picked material that made it easier to detect differences between DACs. I am not going to disclose what constitutes such content. Without such material, the job can range from difficult to impossible. One has to know what could be damaged by a DAC and then use music that has such content. To give you an example, when you compress music, it is the transients that suffer. So something like guitar music is much more revealing than say, violin as the latter is much more harmonic than the sharp impulses of a guitar. Voices play the same role. None of these are useful for testing DACs though so don’t use that as a hint to the question posed . You can’t test the cornering of a car if you just drive it straight….
The comparison was then conducted without knowing which input is which, sitting in front of the headphone amp and toggling back and forth. When necessary, I would go back and re-listen. Once I found which one sounded worse, I would then repeat the exercise by randomizing the inputs and seeing if I could still identify which one was worse. My success rate was 100% in the second test (i.e. could always verify that the first result was not by chance). This testing was repeated a number of times comparing the different sources against each other and the ML.
I did not level match anything. However, once I found one source was worse than the other, I would then turn up the volume to counter any effect there. Indeed, doing so would close the gap some but it never changed the outcome. Note that the elevated level clearly made that source sound louder than the other. So the advantage was put on the losing side.
The results above were later objectively shown to be backed by some science in Stereophile magazine.

....Then yes, I don't believe your tests are either objective or blind, much less double. They reek of purely subjectivist tripe, so no, nothing has changed in at least 12 years (assuming the DAC distortion listening "test" was '02).
I bet they go well with subjectivist audiophile forum members on AA, WTF??, etc forums. They love that amp "sound" DAC "sound" stuff. Slurp it right up. Good "business understanding" I suppose.

cheers,

AJ