# Amplifier distortions



## ajinfla (May 10, 2009)

TheHammer said:


> One study indicated that extremely low THD amps sounded bad due to the high levels of negative feedback used to achieve low THD.


Link?


----------



## TheHammer (Dec 16, 2012)

*Re: Best flagship A/V receiver?*



ajinfla said:


> Link?


In my post, I included the link:

https://passlabs.com/articles/audio-distortion-and-feedback

In that post, the author states:

"Negative loop feedback creates higher order distortion harmonics" and goes into a detailed discussion. 

There are some that feel otherwise:

http://www.edn.com/design/consumer/...fiers--Why-there-is-no-such-thing-as-too-much

What I liked about this article were some of the comments below that contradict the title.

I will do some more searching, but I remember distinctly that there were several studies back when there was a race to zero THD in early SS amps where this became an issue.


----------



## ajinfla (May 10, 2009)

*Re: Best flagship A/V receiver?*



TheHammer said:


> In that post, the author states:
> "Negative loop feedback creates higher order distortion harmonics" and goes into a detailed discussion.


Right. "States". Not, "Shows audibility listening tests data". Big difference. Nelson is a fine amp designer, entitled to his own statements, which should be taken as just that.



TheHammer said:


> I will do some more searching, but I remember distinctly that there were several studies back when there was a race to zero THD in early SS amps where this became an issue.


Yep, remember that also, but also zero listening data to support the purported "issues".
Fact is, competently applied feedback is good for inaudible amplification, i.e., voltage or current multiplication. It's bad when you want an amp to be a special effects box, with "sound".
It's a preference thing, no right or wrong. 
But largely irrelevant to flagship AVRs, as they will all fall into the feedback is good category. It will be a non-factor regarding their "sound".....other than when clipping.

cheers


----------



## Savjac (Apr 17, 2008)

*Re: Best flagship A/V receiver?*

Nelson is a brilliant designer of amps and speakers and quite successful at it, if he says it, consider it a technical fact.


----------



## ajinfla (May 10, 2009)

*Re: Best flagship A/V receiver?*



Savjac said:


> Nelson is a brilliant designer of amps and speakers and quite successful at it, if he says it, consider it a technical fact.


Right. As opposed to an "*audible*" fact. 
TheHammers post I responded to included the word "sound", which has a very specific meaning.
That's why I asked the rhetorical question about (_sound_ related) links for NFB, related to amps.
Mr Pass's paper had, plenty statements, but zero data on "sound". *Zero*. Thus categorized in relevance as such, appeal to authority notwithstanding.

cheers


----------



## TheHammer (Dec 16, 2012)

*Re: Best flagship A/V receiver?*



ajinfla said:


> Right. As opposed to an "*audible*" fact.
> TheHammers post I responded to included the word "sound", which has a very specific meaning.
> That's why I asked the rhetorical question about (_sound_ related) links for NFB, related to amps.
> Mr Pass's paper had, plenty statements, but zero data on "sound". *Zero*. Thus categorized in relevance as such, appeal to authority notwithstanding.
> ...


Though I tend to come from the 'all amps sound alike' camp (with the normal provisos), I also recall that back in the days before they made great solid state amps, that manufacturers went way overboard with negative feedback, in order to reduce THD specs to astonishingly low levels - all in the name of marketing. 

It was about that time people began to complain about transistor sound. Whether this was because they missed the 'warm' sound of tube amps filled with higher levels of harmonics, or if there was actually an audible characteristic from these high feedback transistor amps, we likely will never know. New measurements such as TIM / slew rate came into vogue. Designers cut back in the amount of negative feedback. The rest is history.

http://en.wikipedia.org/wiki/Tube_sound#Negative_feedback

http://www.nutshellhifi.com/library/tinyhistory2.html

"In the mid-Seventies, along came Matti Otala and the discovery of TIM (slewing) distortion. Our Number One engineer (the conservative old-timer who designed the PZ-3) was utterly horrified by Otala's first Audio Engineering Society paper and said it was unscientific bunk (well, his language was stronger than that). Our young Number Two engineer took Matti seriously, let "traditional values" go by the board, and tried a different approach.

Bob Sickler let the distortion rise up to the 0.1% level, by making very large decreases in feedback (feedback dropped from 40-50 dB to 20 dB) and using the most linear complementary-symmetry topology possible. The slew rate and power bandwidth improved by a factor of 10 to 50 times."


----------



## ajinfla (May 10, 2009)

*Re: Best flagship A/V receiver?*



TheHammer said:


> It was about that time people began to complain about transistor sound. Whether this was because they missed the 'warm' sound of tube amps filled with higher levels of harmonics, or if there was actually an audible characteristic from these high feedback transistor amps, we likely will never know.


Actually, that is determinable. 
I remember all that rumored audiophile stuff too and Otala, Crown amps, etc, etc.
Like I said, lots of "statements" about NFB, zero audibility data. It does affect recovery from clipping, which certainly affects "sound"...but then we fall right into the driven to "non-linear" caveat.
Once again, pulling us back to AVRs, NFB should be the least concern of the above. All will use it and thus have low output impedance and immunity from load variations. All will have issues to some degree with overload recovery when clipped (and that most certainly is audible!).
Elementary stuff in 2014.
If someone believes or is concerned their speaker load and dynamic output requirements might lead to non-linear behavior of an AVR, get an sufficiently capable external amp. They don't have to cost a fortune.

cheers


----------



## Savjac (Apr 17, 2008)

*Re: Best flagship A/V receiver?*



ajinfla said:


> Right. As opposed to an "*audible*" fact.
> TheHammers post I responded to included the word "sound", which has a very specific meaning.
> That's why I asked the rhetorical question about (_sound_ related) links for NFB, related to amps.
> Mr Pass's paper had, plenty statements, but zero data on "sound". *Zero*. Thus categorized in relevance as such, appeal to authority notwithstanding.
> ...


I honestly do hope we can meet one day Aj, I bet it would be a good conversation, I am sure I could learn much. Never the less, audible facts are hard to quantify and put into a technical paper without using the very words that techo junkies hate with a passion. Science and technology can only get us so far as we are humans and not computers, as such, we have to listen and voice each design that comes off the drawing board so to speak. I really have no idea of what NFB does to much of anything especially sound as each design that uses or does not use it will be different and as such cannot be quantified without knowing all that goes before it and after it. 

Back to the point at hand, yes I agree 100% with your thoughts on its relevancy to an AVR, I doubt 1 in a million consumers, myself included would even know what to listen for if any trace of itself is left behind.


----------



## lcaillo (May 2, 2006)

I have met AJ and assure you that you are correct on both points savjac. The conversation would be very interesting an you would learn something. That does not mean that he is more right than you are but that you both have interesting and different perspectives and are willing to converse honestly with civility.


----------



## TheHammer (Dec 16, 2012)

*Re: Best flagship A/V receiver?*



TheHammer said:


> It was about that time people began to complain about transistor sound. Whether this was because they missed the 'warm' sound of tube amps filled with higher levels of harmonics, or if there was actually an audible characteristic from these high feedback transistor amps, we likely will never know.





ajinfla said:


> Actually, that is determinable.


Yes. My point was that I am not aware of any ABX or otherwise double blind testing that has been done between early design high feedback amps and newer more sophisticated designs. There were tests done on early transistor amps, like Dynaco, but I think that it was compared to tube amps and other transistor amps of the day.

Just because an ABX test has not been performed does not prove that high levels of NFB would not be audible. 

Modern transistor amps 'seem' (qualitatively) to sound better than early transistor amps. But without controlled studies, we do not know if that is true.


----------



## ajinfla (May 10, 2009)

*Re: Best flagship A/V receiver?*



TheHammer said:


> My point was that I am not aware of any ABX or otherwise double blind testing that has been done between early design high feedback amps and newer more sophisticated designs.


Try this post in this very thread. First link. The 70s Pioneer uses oodles of NFB to achieve its ultra low distortion (see the curve). 
It won vs the newer designs (though that's _not_ what they were testing for specifically). And is highly prized by "audiophiles" (check some ebay prices). Go figure.



TheHammer said:


> Just because an ABX test has not been performed does not prove that high levels of NFB would not be audible.


"Argument from ignorance" (/negative proof) fallacy.



TheHammer said:


> Modern transistor amps 'seem' (qualitatively) to sound better than early transistor amps.


Seams split with time.



TheHammer said:


> But without controlled studies, we do not know if that is true.


Correct...and the onus of proof falls squarely on one side.

NFB dosage in 2014 should only be a concern amongst the "lack of" crowd (aka "audiophile") driving complex reactances. That eliminates AVRs entirely. 
Unless we are talking about clipping recovery. Which, _again_, falls into the "driven to non-linear" caveat.

cheers


----------



## TheHammer (Dec 16, 2012)

*Re: Best flagship A/V receiver?*



ajinfla said:


> Try this post in this very thread. First link. The 70s Pioneer uses oodles of NFB to achieve its ultra low distortion (see the curve).
> It won vs the newer designs (though that's _not_ what they were testing for specifically). And is highly prized by "audiophiles" (check some ebay prices). Go figure.


Good link. Can you show me where you get that the Pioneer uses "oodles of NFB", especially compared to earlier transistor amps? Somewhere around the mid-70's, by my failing memory, I began to feel that transistor amps sounded quite good. I was quite happy with my Soundcraftsman, for example, circa 1977. It bragged of exceedingly low TIM. It would be interesting to compare the NFB levels of earlier SS amps, with this late 70's vintage in the ABX test, with today's amps.



TheHammer said:


> Just because an ABX test has not been performed does not prove that high levels of NFB would not be audible.





ajinfla said:


> "Argument from ignorance" (/negative proof) fallacy.


My hypothesis is that early transistor amps sounded inferior. I have collected (qualitative) evidence to support that hypothesis. I do not know if that is true. That hypothesis cannot be proven or disproven until a test is performed. The next step of this process would be to develop an experiment to test the hypothesis, not dismiss it because there is no evidence to prove it. Whether those amp really did sound inferior, I do not know, but there is some subjective evidence that they did.

Tests never prove a hypothesis. They can only disprove a hypothesis. We generally accept a hypothesis as true when it is tested many times and not disproven. Every hypothesis or theory is just one test away from being disproven.



TheHammer said:


> Modern transistor amps 'seem' (qualitatively) to sound better than early transistor amps. But without controlled studies, we do not know if that is true.





ajinfla said:


> Seams split with time.


Perhaps. I do not have enough data to know. Several qualitative opinions that many (undefined) early 'solid state' amps sounded 'bad'. And if they did sound inferior, if it is undefined high levels of NFB, or some other design issue?

http://www.nutshellhifi.com/library/tinyhistory2.html

This is a link that I provided with an earlier post where the author stated:

"the first generation of transistor amps .... were so aggressive and harsh with Class AB crossover distortion and Transient Intermodulation Distortion (TIM) that an entire generation of "East Coast Sound" speakers became duller and duller to compensate."

The article goes on to say that Pioneer amps were better, so perhaps those tested in the ABX you quoted did not suffer from the "aggressive and harsh" sound of the other early transistor amps?

We would have to define which of these early amps suffered from this alleged inferior sound. The link quotes early "Scott, Fisher, Sherwood" as culprits. So that would be a good place to start. While this testing might prove interesting, it is of historical interest only.



TheHammer said:


> NFB dosage in 2014 should only be a concern amongst the "lack of" crowd (aka "audiophile") driving complex reactances. That eliminates AVRs entirely.
> Unless we are talking about clipping recovery. Which, _again_, falls into the "driven to non-linear" caveat.
> 
> cheers


Agreed. It is not an issue today. While I am of the opinion (or should I say 'hypothesis'? :nerd that modern amps are transparent on their effect of the sound, I think that may not have always been true.

And I agree with the opinions of some in this thread that the significant differences between these flagship receivers today are price, features, interface, and reliability.


----------



## ajinfla (May 10, 2009)

*Re: Best flagship A/V receiver?*



TheHammer said:


> Good link. Can you show me where you get that the Pioneer uses "oodles of NFB", especially compared to earlier transistor amps?


Nope, I made no such claim (vs earlier), nor chase wildly shifting goal posts. If you have an alternate explanation for the shown distortion curve, I'm all ears/eyes.
So now we need <1978 amplification with <0.005% THD, or...??



TheHammer said:


> It would be interesting to compare the NFB levels of earlier SS amps, with this late 70's vintage in the ABX test, with today's amps.


Even more interesting, would be _some_ ABX tests.
What has prevented that over the last 40 yrs?



TheHammer said:


> My hypothesis is that early transistor amps sounded inferior. I have collected (qualitative) evidence to support that hypothesis. I do not know if that is true. That hypothesis cannot be proven or disproven until a test is performed. The next step of this process would be to develop an experiment to test the hypothesis, not dismiss it because there is no evidence to prove it. Whether those amp really did sound inferior, I do not know, but there is some subjective evidence that they did.


Well, change "qualitative" and "subjective" "evidence" to "anecdote" and we're on the same page, scientifically.



TheHammer said:


> I do not have enough data to know.


Actually you don't have any. Anecdotes are not "data". Controlled listening tests of the purported maladies, with positives, would certainly constitute data.
That there is zero, despite many who seem quite motivated, is rather telling.



TheHammer said:


> http://www.nutshellhifi.com/library/tinyhistory2.html
> 
> This is a link that I provided with an earlier post where the author stated:


Right. "Stated".
If I had a dollar for every audiophile "statement" and "hypothesis"....



TheHammer said:


> Agreed. It is not an issue today. While I am of the opinion (or should I say 'hypothesis'? :nerd that modern amps are transparent on their effect of the sound, I think that may not have always been true.


Well, that is a testable hypothesis. Do share if this is finally ever done. 
Needless to say I have bigger fish to fry in 2014 than early 70s SS amp with large doses of NFB "sound" hypotheses, etc. 



TheHammer said:


> And I agree with the opinions of some in this thread that the significant differences between these flagship receivers today are price, features, interface, and reliability.


Right on.:T

cheers


----------



## chashint (Jan 12, 2011)

*Re: Best flagship A/V receiver?*

In the late 70's I had a Sansui G-7500 stereo receiver and my best friend had a Pioneer (I don't remember the model but it had some kind of Dolby quad feature on it).
Both of these receivers were fantastic.
I used mine for over 25 years, unfortunately my friend's Pioneer was lost in a house fire one year after he got out of the Navy.
There was a lot of very nice stereo equipment available at that time and every brand had a unique style.
I don't yearn for the good ol days of HiFi but I remember them fondly.
I seriously doubt the old Sansui or Pioneer would sound any different or be identifiable compared to any current generation AVR in a blind test (assuming the normal stipulations of level matching and linear operation).


----------



## TheHammer (Dec 16, 2012)

*Re: Best flagship A/V receiver?*

To recap, this side discussion started when I typed:
"While with THD, less is better has always been the mantra. And it comes from the days when amps produced high levels of distortion. However, as time went on and levels of distortion dropped, the question became, when is it low enough? One study indicated that extremely low THD amps sounded bad due to the high levels of negative feedback used to achieve low THD."

I do remember reporting in magazines (Stereo Review, Audio, High Fidelity, etc.) in the early to mid-70's where there were reports that high (qualitative) NFB resulted in audible distortion. Unfortunately, those articles do not seem to be on the web, which I guess is not surprising for 40+ year old research.



ajinfla said:


> Try this post in this very thread. First link. The 70s Pioneer uses oodles of NFB





TheHammer said:


> Good link. Can you show me where you get that the Pioneer uses "oodles of NFB", especially compared to earlier transistor amps?





ajinfla said:


> Nope, I made no such claim (vs earlier),


I thought your point was that the Pioneer used in that ABX has "oodles of NFB" and therefore, if high amounts NFB were audible, it would show up in that test? 



ajinfla said:


> nor chase wildly shifting goal posts.


Referring to my original comment above, the goal posts have not shifted. The link that I provided

http://www.nutshellhifi.com/library/tinyhistory2.html

speaks of "the early transistor amplifiers" manufactured by "Scott, Fisher, Sherwood".



TheHammer said:


> In my post, I included the link:
> 
> https://passlabs.com/articles/audio-distortion-and-feedback
> 
> ...





ajinfla said:


> Right. "States". Not, "Shows audibility listening tests data". Big difference.


I believe that we are both aware, that in that early era of amplifier design, that ABX tests were not routinely performed. It was more 'seat of the pants' era. I think that the differences between those early transistor amplifiers manufactured by "Scott, Fisher, Sherwood" and later ones manufactured by Soundcraftsmen, Pioneer, Yamaha and others may have been audible. 



ajinfla said:


> Even more interesting, would be _some_ ABX tests.
> What has prevented that over the last 40 yrs?


I guess the answer would be, why would they bother? Other than to satisfy our curiosity about a time long gone by, I cannot think of any reason to do so. My point is, just because someone has not performed the ABX tests does not mean that they do not exist. 

I think your comments means that you believe that early primitive transistor amps would sound the same as today's much more sophisticated amps. 



ajinfla said:


> Well, change "qualitative" and "subjective" "evidence" to "anecdote" and we're on the same page, scientifically.


Interesting that you would insist that anyone's observation has no relevance. Especially since it was a common opinion in the industry at the time.

http://www.nutshellhifi.com/library/tinyhistory2.html

"In the mid-Seventies, along came Matti Otala and the discovery of TIM (slewing) distortion."
"Bob Sickler let the distortion rise up to the 0.1% level, by making very large decreases in feedback (feedback dropped from 40-50 dB to 20 dB)" "The slew rate and power bandwidth improved by a factor of 10 to 50 times." "In 1976, Audionics introduced the CC-2, which was the first low-TIM amplifier sold in the US." "by now, though, nearly all transistor amps use the same design principles as the CC-2."

http://en.wikipedia.org/wiki/Audio_system_measurements

"Transient response 
A system may have low distortion for a steady-state signal, but not on sudden transients. In amplifiers, this problem can be traced to power supplies in some instances, to insufficient high frequency performance or to excessive negative feedback. Related measurements are slew rate and rise time. Distortion in transient response can be hard to measure. Many otherwise good power amplifier designs have been found to have inadequate slew rates, by modern standards."

http://www.tungsol.com/tungsol/html/faqs14.html

"Adding a 5th to a strong 3rd harmonic give the sound a metallic quality that gets annoying in character as the amplitude increases."

The following link displays data that shows higher feed back results in higher levels of 3rd, 5th (and other) harmonics.

https://passlabs.com/articles/audio-distortion-and-feedback



ajinfla said:


> Actually you don't have any. Anecdotes are not "data". Controlled listening tests of the purported maladies, with positives, would certainly constitute data.
> That there is zero, despite many who seem quite motivated, is rather telling.


I have presented a great deal of research that points to the possibility that higher NFB may be audible.

And with your comment, the lack of ABX data means that you dismiss the advances in solid state design that occurred during this era as meaningless.

I believe it is one thing to say: ABX tests have been performed on modern amps and there is no statistically significant difference in sound.

It is quite another thing to say: ABX have not been performed, therefore there is no difference in sound.




ajinfla said:


> Needless to say I have bigger fish to fry in 2014 than early 70s SS amp with large doses of NFB "sound" hypotheses, etc.


True. I think at this point, that we both agree that such a discussion is of academic interest since it does not affect today's much more sophisticated amplifiers. 

cheers to you also.


----------



## ajinfla (May 10, 2009)

*Re: Best flagship A/V receiver?*



TheHammer said:


> To recap, this side discussion...


....You have provide zero audibility data to back up the born from early 70s audiophile belief "more NFB is bad, early 70s amps prove this".



TheHammer said:


> I thought your point was that the Pioneer used in that ABX has "oodles of NFB" and therefore, if high amounts NFB were audible, it would show up in that test?


The 70s Pioneer with lots of NFB/very low THD audibly beat out more "modern" amps with higher THD in an ABX...though this was not the specific parameter under test.



TheHammer said:


> I think that the differences between those early transistor amplifiers manufactured by "Scott, Fisher, Sherwood" and later ones manufactured by Soundcraftsmen, Pioneer, Yamaha and others may have been audible.


Maybe. Maybe not. Still zero evidence of correlation to "excessive" NFB/low THD. Or cognizance that "other" physical factors, like for example, early transistor saturation may/may not have been the cause?



TheHammer said:


> I think your comments means that you believe that early primitive transistor amps would sound the same as today's much more sophisticated amps.


They might or they might not. And completely irrelevant today, except maybe for the nostalgic?



TheHammer said:


> Interesting that you would insist that anyone's observation has no relevance. Especially since it was a common opinion in the industry at the time.


Anecdotes and opinions are just that. I don't believe in power bracelets either, despite any popularity.



TheHammer said:


> http://www.nutshellhifi.com/library/tinyhistory2.html


http://www.cordellaudio.com/papers/another_view_of_tim.shtml



TheHammer said:


> I have presented a great deal of research that points to the possibility that higher NFB may be audible.


...and zero data that it is. That's the key to any audibility claim.



TheHammer said:


> And with your comment, the lack of ABX data means that you dismiss the advances in solid state design that occurred during this era as meaningless.


That's quite a stretch.



TheHammer said:


> It is quite another thing to say: ABX have not been performed, therefore there is no difference in sound.


Direct quote who said that?



TheHammer said:


> True. I think at this point, that we both agree that such a discussion is of academic interest since it does not affect today's much more sophisticated amplifiers.


There are examples of both lots of feedback all the way through no feedback designs today.
Unfortunately, NFB and its implementation still remain a mystery to some. Hopefully you read through Bob Cordells links above. He's got some great books too.
Or you could follow Lynn's path ditching SS altogether and end up with a glowing bulb zero NFB special EFX box. 
To each their own.....and really nothing whatsoever to do with "flagship AVRs".

cheers


----------



## Savjac (Apr 17, 2008)

*Re: Best flagship A/V receiver?*

Interesting continued discussion albeit one with no purpose as the gentleman already bought an AVR. Not sure what is being accomplished any longer.


----------



## TheHammer (Dec 16, 2012)

*Re: Best flagship A/V receiver?*



ajinfla said:


> ....You have provide zero audibility data to back up the born from early 70s audiophile belief "more NFB is bad, early 70s amps prove this".


True. Lack of ABX testing does not disprove my hypothesis. 



ajinfla said:


> The 70s Pioneer with lots of NFB/very low THD audibly beat out more "modern" amps with higher THD in an ABX...though this was not the specific parameter under test.


The links I provided indicated that even the early Pioneers were superior to the "Scott, Fisher, Sherwood" that were the early SS amps. And I agree that it might be impossible to isolate NFB as the sole parameter of an ABX test.



ajinfla said:


> They might or they might not. And completely irrelevant today, except maybe for the nostalgic?


We both agree on this point. :clap:



TheHammer said:


> Interesting that you would insist that anyone's observation has no relevance. Especially since it was a common opinion in the industry at the time.





ajinfla said:


> ...and zero data that it is. That's the key to any audibility claim. Anecdotes and opinions are just that.


I think that is where we have our disagreement. I do not disregard the opinions of respected engineers, designers and reviewers of the day, nor the research that I provided to you - without any evidence to refute it.

I believe that ABX testing is a powerful tool, but not the only tool at our disposal. And like all scientific tools, it cannot prove anything. And it is useless when not applied, as in this case.



ajinfla said:


> I don't believe in power bracelets either, despite any popularity.





ajinfla said:


> you could follow Lynn's path ditching SS altogether and end up with a glowing bulb zero NFB special EFX box.


At what point did I give you the impression that I am a fan of tubes and zero NFB? 

It is interesting that you are introducing "power bracelets" and "glowing bulbs" into this discussion.


----------



## ajinfla (May 10, 2009)

TheHammer said:


> True. Lack of ABX testing does not disprove my hypothesis.


Once again: http://en.wikipedia.org/wiki/Argument_from_ignorance
Your hypothesis is not supported by any evidence. When evidence suggesting otherwise (Pioneer ABX) is presented, it is rejected.
Once more: http://www.cordellaudio.com/papers/another_view_of_tim.shtml




TheHammer said:


> The links I provided indicated that even the early Pioneers were superior to the "Scott, Fisher, Sherwood" that were the early SS amps.


Anecdotally. Even if assumed valid, exactly how would the high NFB/low THD Pioneers being "superior", support your hypothesis? Why are any other possibilities (_assuming_ the inferior/superior part) , like (early) transistor saturation, conveniently ignored?



TheHammer said:


> And I agree that it might be impossible to isolate NFB as the sole parameter of an ABX test.


Is the hypothesis NFB by itself is bad, or...??



TheHammer said:


> I think that is where we have our disagreement. I do not disregard the opinions of respected engineers, designers and reviewers of the day, nor the research that I provided to you - without any evidence to refute it.


http://en.wikipedia.org/wiki/Argument_from_ignorance
http://en.wikipedia.org/wiki/Argument_from_authority
No "evidence" is required to refute an opinion. Opinions and conjecture, etc...are just that.



TheHammer said:


> I believe that ABX testing is a powerful tool, but not the only tool at our disposal. And like all scientific tools, it cannot prove anything. And it is useless when not applied, as in this case.


Scientific evidence (ABX et al) will never supplant belief. Once again, lack of proof: http://en.wikipedia.org/wiki/Argument_from_ignorance



TheHammer said:


> At what point did I give you the impression that I am a fan of tubes and zero NFB?


Your "highly respected" designer whom you cite as evidence for your hypothesis. http://www.nutshellhifi.com/triode2.html
Folks who have misconceptions about the nature of NFB/THD often end there (like Lynn et al). Perhaps you are an exception?



TheHammer said:


> It is interesting that you are introducing "power bracelets" and "glowing bulbs" into this discussion.


There might be many theories and hypotheses put forth by those reminiscing power bracelets 40yrs from now...but never any evidence of efficacy. 
I did not introduce Lynn's opinions and preferences into the discussion.

cheers,


----------



## fmw (Aug 11, 2013)

AJ is completely correct. Not everything measurable is audible. The only way to determine without question if it is audible or not is to conduct a bias controlled listening test. The industry is loaded to the gills with examples of companies and audiophiles using meaningless measurements to make audibility claims. Just look at the high end cable industry.


----------

