My attempt to compare an Outlaw 7500 and a Parasound A51

[RichB]

All you need to do is conduct a properly done bias controlled test to find out. Personally, I wouldn't go through the hassle, having gone through it years ago but that's the way to find out. Pesonally, I'd rather just listen to the music rather than obssess about whether some artifacts are audible or not. Let me know if you need some advice on how you should conduct the test.

I think I will need that to Gene

There are problems with DBT testing as well.
Ear fatigue, room acoustics, speakers (bookshelf or towers), too litte alcohol, then too much.
It is fraught with peril

- Rich

 

[fmw]

I think I will need that to Gene

There are problems with DBT testing as well.
Ear fatigue, room acoustics, speakers (bookshelf or towers), too litte alcohol, then too much.
It is fraught with peril

- Rich

Yes and it is also fraught with truth which wouldn't be of much interest to a subjectivist.

 

[RichB]

Yes and it is also fraught with truth which wouldn't be of much interest to a subjectivist.

… Or someone who has made up their mind.
Sure some Audiophiles have a need to imbue qualities on their purchases that simply do not exist.
Also, some people need refute audible differences exist so they can also justify their choices.
A non-biased person understands that both biases exist.

I do not think that John Curl is a fool or cunningly designed his amps to differentiate them in ways that are simply unnecessary.
I applaud Parasound for encasing their toroidal transformers in epoxy.
I do not believe that Morris Kessler</SPAN> is a fool for his design choices and the point at which he determined there were diminishing returns.

We KNOW that amp measure differently when driven within their limits.
We know that some types of distortion are more objectionable than others; specifically those that produce harmonics not in the original signal.
We know that some amps are not as linear as others and that this is not often measured and is not recognized as distortion in audio terms (although I think it should be).</SPAN>
Ideally, and amp is a cable with a small signal at one end a bigger one at the other end.</SPAN>

Let’s say, ACME designed a new $100 Nutrino Cable AMP. I will call this NCAM technology
ACME would commission DBT tests proving their amp sounds as good or better than all SS amps.</SPAN>
I know what I would do.</SPAN>
I would buy the damn thing and try it in my home with my speakers in my room.
If it sounds as good as or better than my A51, I would then sell my A51 on eBay for those who refuse to believe. </SPAN>
If it did not sound as good, I would sell the NCAM amp with overseas shipping and sell it folks who cannot buy NCAM amps in their country

- Rich</SPAN>

 

[fmw]

You will just have to do the bias controlled tests to find out. No point in trying to talk me out of it. I've actually done the bias controlled tests. When you've done them, come back and we'll talk about it. Until then I can only question what you say for good reason. If you won't accept the science, then I won't accept the bias and preference.

 

[RichB]

You will just have to do the bias controlled tests to find out. No point in trying to talk me out of it. I've actually done the bias controlled tests. When you've done them, come back and we'll talk about it. Until then I can only question what you say for good reason. If you won't accept the science, then I won't accept the bias and preference.

I experienced a difference and posted them here: "My attempt to compare an Outlaw 7500 and a Parasound A51" (Take note of the thread title).
I did my best to explain it what I did, my equipment, my methodology, and what I heard.
No claim was made that this was indicative of any larger truth.
Nor am I attempting to create a settled science.
Honestly, I was not convince you of anything.

Why don't you start a thread called something like "My findings indicate that all amps sound the same"?
Clearly you feel this way and you have proof.
Please post your equipment, signal path, the amps, the types of attendees, and the seating.
Also, it would be helpful to include a room measurements as this is also critical to the validity of your results.
Also recommended is the list of music selections, volume levels, and duration.

I fully accept science and I am uninterested in amp measurements and improving them.
You position seems to be, I did a DBT and I have determined that all amps sound the same.
Maybe there is a place for a site DBTs.COm. Amps are reviewed with measurements power into load;
Nothing else matters than DBT.com
The DBT motto: If our panel cannot hear it, it does not matter.

Last time I checked Audioholics.com include measurements and subjective reviews.
Should they remove their subjective reviews because they are flawed and misleading to the public at large

- Rich

 

[fmw]

I did bias controlled tests and discovered that not all amps sound the same. However, solid state amps of hi fi quality all proved to sound the same as long as they weren't being overdriven or used improperly. I'm all for measurements. I just understand that not all differences in measurements are audible differences.

I don't know what subjective reviews you refer to. Perhaps I haven't read them. If subjectivity is "I like the look of this amp" or "I feel confident that the power in this amp handles such and such requirements" or something of that nature, then I have no problem with it at all. If it says "I decided this high quality solid state amp sounds better than that one" in a subjective listening test, then I would simply ignore the statement as being misleading. So you need to define the subjectivity for me.

My problem arises when someone tries to influence a buying decision based on subjective audible differences when the preponderance of scientific evidence points to a lack of audible differences in that area. Incidentally, I don't think Audioholics does that. I rather like their reviews. I think TAS and Stereophile do that and I have no respect for their subjective reviews as a result. I think Stereophile does an excellent job with the reporting of their measurements and I do respect those.

There many reasons to choose one amp over another. I only hope that people do it for the right reasons and I don't like seeing people trying to motivate those choices for the wrong reasons.

 

[RichB]

I appreciate your efforts and information, but there are many factors even in a DBT that affect audibility.

Here is the some information from the Audioholics Review of the Parasound A51

To sum up my listening sessions the Parasound A 21 amp was very close in sound to the Acurus A250. The Parasound had tighter bass which is probably attributed to a better damping factor. The sound stage was a little lower than the Acurus which is a minor difference to many people. But wait, that is for the unbalanced listening. The balanced inputs added a whole new dimension of sound compared with the Acurus. The A 21 seems to be designed more for balanced inputs than unbalanced. Sure, it sounds good with unbalanced but it really bloomed with the balanced inputs.

It is very common for a reviewer to compare the amp under review with their "reference" amp.
While they did not say buy the A51 amp over the Acurus, I do not think that it was far off.

I understand that your experience nor your deeply held belief that SS amps sound the same.
Of course, company reputation, service, and build quality enter a buying decision.

But ignoring measured differences and some personal experiences (however flawed) are a tall order when buying a product primarily for its sound quality


- Rich

 

[fmw]

I appreciate your efforts and information, but there are many factors even in a DBT that affect audibility.

Here is the some information from the Audioholics Review of the Parasound A51



It is very common for a reviewer to compare the amp under review with their "reference" amp.
While they did not say buy the A51 amp over the Acurus, I do not think that it was far off.

I understand that your experience nor your deeply held belief that SS amps sound the same.
Of course, company reputation, service, and build quality enter a buying decision.

But ignoring measured differences and some personal experiences (however flawed) are a tall order when buying a product primarily for its sound quality


- Rich

I have to admit I don't like what Audioholics said in your quote. That is something I would put on my ignore list. There is no question in my mind that that statement results from a meaningless subjective listening session filled with bias from head to toe. Reviewers suffer from hearing bias just like you and I and everybody else.

I don't have a deeply held belief that SS amps sound the same. I have years of bias controlled testing to prove it to myself. It isn't a belief at all. It is a testing result. Nobody has ignored measured differences. Some measured differences are audible and some are not. The fact that there are measurable differences is no indication of audible differences at all. None. You may recall discussing one inaudible distortion spec being ten times larger than another inaudible one.

Like I said. Go do the tests and then come back and we will talk. Otherwise you don't have the credibility or experience even to discuss it.

 

[RichB]

I have to admit I don't like what Audioholics said in your quote. That is something I would put on my ignore list. There is no question in my mind that that statement results from a meaningless subjective listening session filled with bias from head to toe. Reviewers suffer from hearing bias just like you and I and everybody else.

I don't have a deeply held belief that SS amps sound the same. I have years of bias controlled testing to prove it to myself. It isn't a belief at all. It is a testing result. Nobody has ignored measured differences. Some measured differences are audible and some are not. The fact that there are measurable differences is no indication of audible differences at all. None. You may recall discussing one inaudible distortion spec being ten times larger than another inaudible one.

Like I said. Go do the tests and then come back and we will talk. Otherwise you don't have the credibility or experience even to discuss it.

I get an assignment

Post your results and methodology and findings here that I and other might understand and benefit from your work. Then we'll talk

I do recall that I did some research to see if amps perform differently under load.
And, they do. The XPR-1 is an exceptional beast and it is not likely indicative of the performance of all amps. That amp performs differently under a real load, although still excellent, it may not be true of all amps. It may be true of all amps that you tested. What amps were those?

Also, non-linearity is not considered distortion in the audio world.
So an amp that is less linear will not be distorting in the strictest sense, but we all know that even a minor volume difference will greatly affect perceptions. I believe you "told" me that at least once.

- Rich

 

[fmw]

I get an assignment

Post your results and methodology and findings here that I and other might understand and benefit from your work. Then we'll talk

I do recall that I did some research to see if amps perform differently under load.
And, they do. The XPR-1 is an exceptional beast and it is not likely indicative of the performance of all amps. That amp performs differently under a real load, although still excellent, it may not be true of all amps. It may be true of all amps that you tested. What amps were those?

Also, non-linearity is not considered distortion in the audio world.
So an amp that is less linear will not be distorting in the strictest sense, but we all know that even a minor volume difference will greatly affect perceptions. I believe you "told" me that at least once.

- Rich

I'll give you a brief summary from memory. Our audiophile club put together a bias controlled testing project that involved 10 members. For the amplifier tests we used a system that had a pair of B&W 801 matrix speakers, an Audio Research CD player and I honestly don't even remember the preamp we used. It was similar to the other components in terms of audiophile approval. Rather than building a switch box, we handled the X part of ABX by putting everything but the speakers behind a screen and we allowed no commentary during the tests. Not perfect but we got similar results to other bias controlled tests. There were 10 amps in the test. High end ones included products from Audio Research, Krell, Parasound. We had a pioneer stereo receiver, a Pioneer integrated and a Crown pro audio amp. I can't remember the others. We calibrated level on each pair by placing marks on stickers we affixed to the preamp volume control based on reading the voltage across one of the speaker's terminals and playing a 1khz tone. We allowed each member to bring their favorite tracks. We then made a random A/B list on a computer with a total of 100 items on the list. The process was to play the first 20 seconds of the member's track on each amplifier, identifiying which amplifier it was by calling out A or B. Then we did 10 iterations of the first 20 seconds blind, using the random list and had the listener ID the amp by calling out A or B for each iteration. We swapped the cables from the preamp to the amp manually between iterations. If the list called for having the same amp go twice in a row, we still unplugged and replugged the cables to be sure there were no clues for the listener. We did this for each of the 10 members - a total of 100 iterations. The results were 49 incorrect and 51 correct. Statistically, the listeners were guessing and those results included an Audio Research tube amp - low enough in distortion that it competed head to head with the solid state units. I can tell you the owners of the Krell and the Audio Research (which incidentally was me) sold those products soon after the test. I replaced my Audio Research tube amp with the Pioneer integrated. The Krell owner bought a Parasound as a replacement.

That's about how it went. It is a fussy process and a boring one. It is a completely different experience from a sighted test. What this did along with similar tests we completed with cables, DACs and other products was to reduce my expectation bias by a lot. If we expect a Krell amp to sound better than a Pioneer integrated, then it certainly will in a subjective listening test. Only by eliminating the bias can you get to the amazing fact that the Krell amp doesn't sound better, and I would no longer expect it to. The Krell amp may be able deal better with low impedances and it may provide more SPL than the Pioneer integrated but it doesn't actually sound any different when driving a pair of B&W 801 matrix speakers. That's what we discovered. Try it. It is fussy and time consuming but it isn't difficult in any way. You have a pair of high quality speakers. You just need some people to help you with the switching and scoring. Just do a test of a single pair of amps. If that piques your interest you can try another pair.

 

[Irvrobinson]

Like I said. Go do the tests and then come back and we will talk. Otherwise you don't have the credibility or experience even to discuss it.

I've done blind tests. I have several issues with listening comparison tests as being proof of anything:

1. Listening tests measure perception, not actual differences.

2. Humans cannot compare two sounds directly, like two images can be viewed side by side.

3. Aural memory is so imperfect as to be useless for judging fine details.

4. Differences in hearing acuity and test-taking abilities vary significantly.

5. Test subjects are often just guessing, except for cases of differences so gross that sighted tests usually suffice.

I think most electronics probably do sound similarly because they measure similarly, and that's all there is to it.

I think that comparative listening tests, blind ones included, are so flawed for detecting subtle differences that using them as evidence of audibility is poorly founded. Blind tests produce the results people who claim there are no differences want to find, just as sighted, subjective tests produce results that people who claim there are differences want to find. The epiphany I came to after participating in blind testing was that blinded tests and sighted tests are equally invalid, because in the end it is still human hearing perception and memory that's being tested, and the basic concept of doing so is what's flawed.

 

[PENG]

Blind tests are valid tests for proving whether there are night and day differences that are often claimed in sighted and/or uncontrolled (such as level matching) tests. I can agree to the argument that blind test cannot prove amps sound the same, but it does prove one cannot not easily hear the difference and if they go by such tests they could the amp that in a sighted test he would not pick. Another thing, if blind test is just as flaw as sighted test, then we should be telling people to go and listen for themselves before making their purchasing decision, they may as well just pick one base on specs and/or lab test data.

 

[PENG]

… Or someone who has made up their mind.
Sure some Audiophiles have a need to imbue qualities on their purchases that simply do not exist.
Also, some people need refute audible differences exist so they can also justify their choices.
A non-biased person understands that both biases exist.

I do not think that John Curl is a fool or cunningly designed his amps to differentiate them in ways that are simply unnecessary.
I applaud Parasound for encasing their toroidal transformers in epoxy.
I do not believe that Morris Kessler is a fool for his design choices and the point at which he determined there were diminishing returns.

I have no doubt in what you are saying, but then behind everyone's dream amp there is always a guru engineer/designer, and they all have their own say about certain controverial tops. Just two more I can think of:

Bob Carver:
[/COLOR]http://thecarversite.com/yetanotherforum/default.aspx?g=posts&t=4481

Roger Russel:
Roger Russell's Audio Distortions Truth and Humor

The first article has a paragraph on crossover distortion. Apparently they only use crossover distortion for their listening test in the belief that if you cannot hear x% of crossover distortion you have no chance of hearing the same % of other harmonic distortions and intermodulation distortion. If we can believe in those guys in the first article, we wouldn't have to worry about THD and TIMD of below 0.1%. Even my oldest AVR has less than 0.05% THD+N (actually much lower than that in lab tests) from 1W to rated output of THD and IMD, I really have no reason to believe THD and IMD contribute to audible difference, that is, to my ears. By the same token, I think the A51 sounds better to you than your 7500 not because of their class A bia, but because of something else. I find it hard to believe the 7500 don't use the class A bias. I believe the A51 probably run up to higher output in class A whereas the 7500 may only do so up to just a few watts, but I guess we have to ask Outlaw that question. To be clear, I read the article you linked and recognize the A51 has a cleaner harmonic distortion spectrum than other amps similarly tested, but from my research reading, such as those linked above and many others, that does not mean the amps with lesser measurements necessarily sound worse, or better. So at the end of the day, I would pay to participate in blind listening session and then I may have better time picking out my next amp. At the moment it is the H300, one that I think I can afford but I don't want to make a 4 to 5K mistake.

By the way, you mentioned linear distortions a couple of time, I would think most mid to high end amps have wide enough bandwidth such that linear distortions will be well below the point of audibility.

 

[fmw]

I've done blind tests. I have several issues with listening comparison tests as being proof of anything:

1. Listening tests measure perception, not actual differences.

2. Humans cannot compare two sounds directly, like two images can be viewed side by side.

3. Aural memory is so imperfect as to be useless for judging fine details.

4. Differences in hearing acuity and test-taking abilities vary significantly.

5. Test subjects are often just guessing, except for cases of differences so gross that sighted tests usually suffice.

I think most electronics probably do sound similarly because they measure similarly, and that's all there is to it.

I think that comparative listening tests, blind ones included, are so flawed for detecting subtle differences that using them as evidence of audibility is poorly founded. Blind tests produce the results people who claim there are no differences want to find, just as sighted, subjective tests produce results that people who claim there are differences want to find. The epiphany I came to after participating in blind testing was that blinded tests and sighted tests are equally invalid, because in the end it is still human hearing perception and memory that's being tested, and the basic concept of doing so is what's flawed.

So your position is that amplifiers neither sound alike nor sound different because listening tests of any sort are invalid? At least that covers everything, I guess.

 

[Irvrobinson]

So your position is that amplifiers neither sound alike nor sound different because listening tests of any sort are invalid? At least that covers everything, I guess.

No, my position is that amplifiers generally sound alike under many circumstances because they measure alike under many circumstances, and that both blind comparative listening tests and sighted comparative listening tests are flawed for detecting differences.

 

[3db]

No, my position is that amplifiers generally sound alike under many circumstances because they measure alike under many circumstances, and that both blind comparative listening tests and sighted comparative listening tests are flawed for detecting differences.

I've been stating that amps will sound the same if the amps compared are driving the same load and are both well within their intended design limits. Approach the limits and things will begin to differ and are most likely measureable. Hearing tests are flawed for detecting subtle differences only.

 

[RichB]

I've been stating that amps will sound the same if the amps compared are driving the same load and are both well within their intended design limits. Approach the limits and things will begin to differ and are most likely measureable. Hearing tests are flawed for detecting subtle differences only.

I sort of agree but I believe that amps may not sound the same driving the same speakers load.

- Rich

 

[Irvrobinson]

I've been stating that amps will sound the same if the amps compared are driving the same load and are both well within their intended design limits. Approach the limits and things will begin to differ and are most likely measureable. Hearing tests are flawed for detecting subtle differences only.

Good, we're in agreement. Two down, seven billion to go...

 

[3db]

Good, we're in agreement. Two down, seven billion to go...

I try to play "well" with others

 

[mtrycrafts]

... and that both blind comparative listening tests and sighted comparative listening tests are flawed for detecting differences.

I wonder why respected names in various fields of acoustics and research facilities use blind listening testing to arrive at thresholds of detection, JND levels, etc, and publish peer reviewed journal papers on their research. To make a blanket statement that listening tests are flawed, blind or sighted to detect differences is total nonsense not based in facts.