All power amps “good ones” sound the same.

[user 37518]

@user 37518, are you sure you are not letting your own bias influence your objectivity?  You misread bluebird's post thinking it "proved your point" but missed the very important distinction between converters and amps. And the link you provided doesn't actually support things either. It is perhaps surprising that many people preferred the cheaper amp setup. Maybe it shows that expensive gear isn't always preferable.  But the fact that most people had subjective preferences implies that there ARE audible differences, which was the subject of this thread.

Statistically, there wasn't a real preference, there was a slight tendency towards the cheap amp but it was not statistically relevant.

 

[user 37518]

I guess I should have read the paper. I didn't know they gave out PhD's at community college.

What is that supposed to even mean?

 

[user 37518]

I would love to see this test conducted. I am not qualified to set up a Double Blind Whoopee Ha Ha. user 37518 is not qualified to set up a Double Blind Whoopee Ha Ha. We would need someone who is competent to set it up. There doesn't seem to be much curiosity in finding out the answer. I guess an engineering student could be forgiven for not having the curiosity of a scientist.

What do you know about my qualifications? when you talk about the engineering student, are you refering to me? Im not an engineering student, I have an engineering degree and a masters in engineering, I am an engineer, I am also a PhD candidate, which is different. What are your qualifications ?

 

[Gold]

What is that supposed to even mean?

It means telling someone they have to run a test that is impossible for them to run is idiotic.

 

[user 37518]

It means telling someone they have to run a test that is impossible for them to run is idiotic.

Who said it was impossible? you said it, I didn't

 

[Gold]

Who said it was impossible? you said it, I didn't

I want to do the test. I just can’t do any of the academic busywork. If you are into doing that stuff by all means let’s do it.

 

[john12ax7]

Statistically, there wasn't a real preference, there was a slight tendency towards the cheap amp but it was not statistically relevant.

14 people preferred A
10 people preferred B
14 couldn't tell a difference

So 24 of 38 people heard a difference and had a preference.  63% would qualify as statiscally significant.

 

[ruairioflaherty]

I've been lucky enough to run many many experiments with power amps over the years and there most definitely are differences. Do they matter? Well, like everything that depends on what you are trying to achieve...

One example of a test I ran over many months was having all of the following amps all available in my mastering room to drive a pair of PMC IB2S passive speakers (about $20k worth - decently revealing and not a terrible load)

Parasound JC1 Class A monoblocks (John Curl design)
Bryston 4B SST2
Bryston 7B SST2 mono blocks (same basic topology but with significantly more power available)
Hypex UCD 400 Class D
Hypex nCore 400 Class D

I owned or could easily own everything listed, there was no incentive for me to prefer any over any other.  I was going to keep the ones I liked the best regardless.

I was in a position to switch quickly, have others switch (single blind) and also just work on one set of amps for weeks at a time and then switch.  I did all of the above many times over on every genre, at the end of the day and first thing, in the middle of the day of work etc.

They all sounded different. Subtly so but definitely different.

I could and did work with any of them with the same basic results.

 

[user 37518]

14 people preferred A
10 people preferred B
14 couldn't tell a difference

So 24 of 38 people heard a difference and had a preference.  63% would qualify as statiscally significant.

Don't be fooled by the data, couldn't tell a difference is also a preference, you are grouping the data to suit your best, of those who prefered A or B basically 58% prefered A and 42% prefered B, that is almost a coin toss. What is important here is that out of the 3 options, out of the total,  36.8% prefered A, 26.3% prefered B and 36.8% couldn't tell, which means that you can see that the 100% is roughly divided in 3 equal parts, not exactly but roughly.

It is not the only study, I can cite similar studies in which no statistically relevant difference was detected, A long time ago I remember a study which basically concluded that if the amps are not clipping or near clipping, people couldn't tell, I'll look it up.

 

[john12ax7]

you are grouping the data to suit your best

This is exactly what you are doing. I'm not suggesting the study as proof of audible differences, that was not the question asked and it is important to be precise in these things. It may,  however,  suggest that.

What I am saying is that it is most definitely NOT proof that there are no audible differences, the subject of this thread.  I've spent a good part of my career at research universities,  so no stranger to scientific methods. If you are of a similar background then there needs to be more rigor in your arguments and conclusions.  I would hope it apparent that "do you hear a difference" vs "do you have a preference" are vastly different questions.

Note: for the group choosing X it is unclear how many heard a difference with no preference vs couldn't hear a difference. Given that it is even more incorrect to conclude "no audible difference"

 

[user 37518]

This is exactly what you are doing. I'm not suggesting the study as proof of audible differences, that was not the question asked and it is important to be precise in these things. It may,  however,  suggest that.

What I am saying is that it is most definitely NOT proof that there are no audible differences, the subject of this thread.  I've spent a good part of my career at research universities,  so no stranger to scientific methods. If you are of a similar background then there needs to be more rigor in your arguments and conclusions.  I would hope it apparent that "do you hear a difference" vs "do you have a preference" are vastly different questions.

Note: for the group choosing X it is unclear how many heard a difference with no preference vs couldn't hear a difference. Given that it is even more incorrect to conclude "no audible difference"

There is also NOT proof that there are audible differences. That study did not mean to test if people could hear a difference or not, but if an expensive amp sounded better than a cheap one, I will find a better study to exemplify what I've been saying since there are plenty.

 

[john12ax7]

There is also NOT proof that there are audible differences.

I'm not suggesting the study as proof of audible differences

It seems you are not carefully reading what is being written by me and others.

That study did not mean to test if people could hear a difference or not,

Agreed.  But all the more curious then as to why it was originally presented as evidence of such.

 

[john12ax7]

Performing proper tests like these are not difficult but are rather time consuming with very little reward.  In the end one group will say "so what I already knew that,"  another group will question methodology if they don''t like the results.

It's already off on the wrong footing since no one has defined the parameters of what makes a power amp "good enough". It's really a question of threshold of audilbility. There needs to be consensus on minimum specs required.  There also needs to be clearly defined parameters of what you are testing for,  for example "which is best " vs "is there a difference"

From a technical standpoint there is another interesting challenge due to amp / speaker interaction.  What is the best power amp? A standalone needs to drive a variety of loads,  good universally but sub-optimal individually. If B&W are difficult they are likely highly reactive. Do you use a generic amp,  lots of feedback for ultra low output impedance? Theory suggests instead that optimal power transfer will be by complex conjugate match,  which is very speaker specific.  This is why it is best to match amp to speaker and almost self evident that amps will inevitably sound different under certain conditions.

 

[user 37518]

Agreed.  But all the more curious then as to why it was originally presented as evidence of such.

What I tried to prove is that when people are not looking and are not biased, they didn't prefer the more expensive amp.

Performing proper tests like these are not difficult but are rather time consuming with very little reward.  In the end one group will say "so what I already knew that,"  another group will question methodology if they don''t like the results.

It's already off on the wrong footing since no one has defined the parameters of what makes a power amp "good enough". It's really a question of threshold of audilbility. There needs to be consensus on minimum specs required.  There also needs to be clearly defined parameters of what you are testing for,  for example "which is best " vs "is there a difference"

I agree with you that performing these tests are not difficult or insanely expensive as Gold believes, but yes they are time consuming.

What makes a good amp? technically to almost every (sane) manufacturer, its the amp that offers the least ammount of THD and IMD, with the flattest frequency response over a specified bandwith. That is something we can measure.

Let me be clearer about what I have been arguing all along: two amps with very low THD, IMD and flat frequency response over a specified bandwidth are virtually the same in a double blind test, which I think is what the thread title means "All power amps “good ones” sound the same", like I mentioned in a previous post, if we compare a homemade single ended tube amp from the 30s and a modern solid state amp I bet you can hear a difference, that is no question, otherwise it wouldn't matter how you design an amplifier. What I am saying, and im repeating myself, is that two amps that meet the criteria of low THD, IMD and flat frequency response are indistinguishable in a double blind test.

 

[Gold]

I agree with you that performing these tests are not difficult or insanely expensive as Gold believes, but yes they are time consuming.

I would have to hire a private company to perform the tests so they conform to academic standards. Unless I can con a grad student into doing it.

 

[user 37518]

I found this article from the 90s which can be considered old, but this debate we are doing is old aswell, in that article the author reviewed the result of 22 (although 23 are reported?) blind and double blind trials which tested if there was a difference between two amplifiers, I can't post the entire article because its copyrighted, I have access to the AES library and had a chance to see the full article.

https://www.aes.org/e-lib/browse.cfm?elib=5426

To summarize, at the end of the article there is a table with the results of all the tests of which 18 of the 23 have a result of around 50%, meaning random result or not statistically significant, the ones that did have a statistical relevance have notes attached to them like "Misbiased tube", "Ignored 25% of the data", "Oscillating Amplifier", etc...

The paper concludes with the following statement, and I quote: "...This does not suggest that amplifiers are perfect and they will never be found to sound different. It does suggest to purcharsers of today's audio amplifiers that as long as the product in question meets basic traditional measured performance standards, has enough output capability, and adequate quality of construction, it will be sonically indistinguishable from all others meeting those criteria."

Q.E.D.

 

[Gold]

There is another AES paper from I think 1972 that draws the same conclusion.

 

[john12ax7]

Not difficult does not necessarily mean not expensive.

Speaker technology and acoustics have also both advanced over the decades.

 

[john12ax7]

I've been lucky enough to run many many experiments with power amps over the years and there most definitely are differences. Do they matter? Well, like everything that depends on what you are trying to achieve...

One example of a test I ran over many months was having all of the following amps all available in my mastering room to drive a pair of PMC IB2S passive speakers (about $20k worth - decently revealing and not a terrible load)

Parasound JC1 Class A monoblocks (John Curl design)
Bryston 4B SST2
Bryston 7B SST2 mono blocks (same basic topology but with significantly more power available)
Hypex UCD 400 Class D
Hypex nCore 400 Class D

I owned or could easily own everything listed, there was no incentive for me to prefer any over any other.  I was going to keep the ones I liked the best regardless.

I was in a position to switch quickly, have others switch (single blind) and also just work on one set of amps for weeks at a time and then switch.  I did all of the above many times over on every genre, at the end of the day and first thing, in the middle of the day of work etc.

They all sounded different. Subtly so but definitely different.

I could and did work with any of them with the same basic results.

You left out the important part,  what did  you end up with? I'm also curious if you had different opinions based on criteria,  like one may be more refined but you prefer working on another?

I did a blind scotch tasting years ago with interesting results.  It's not my favorite alcohol and I don't drink it often. Ranking in terms of taste my favorite was not the most expensive.  But there was also ranking in terms of quality / cost.  On that I scored a perfect 100% ranking  them highest to lowest cost (there were at least 5).

When seeking answers it's important to ask the right questions.

 

[pucho812]

I got 5 on it

Out of how many?