[Sgt. Ear Ache]

Amps SHOULD perform better than the published specs - those are only the minimum performance figures. And most do just that - they get better.

And, most of them do need about those 300 hours to really settle down and remain constant in performance - at least when operated at intended temperature. I hope no one will dispute the fact that amplifier from the stone cold after non operation for a considerable amount of time sounds exactly the same as after having reached its optimum operating temperature.

Reaching published specs zealots have been perhaps best answered by Bob Carver; after one of his tested amps failed to reach published power output by a few watts ( at 100 or 200 W spec IIRC ) due to a few too little turns of wire in the secondary of the transformer in the first batch, both competition and specsomaniacs had a field day. After that, he spec'd all of his amps as 101 + 101 Watts, 201 +201 Watts, 401 + 401 Watts, etc - and seeing to that that even with AC voltage lower than normal, that " one more watt " has been available.

Have any published data you can point me to comparing any amps specs out of the box and after 300 hours use and revealing the audible differences?

I'd also be interested in seeing the numbers after 100 and 200 hours as well. I always wonder how these burn-in numbers are arrived at. Why does something need 300 hours of burn in? What could happen between 200 and 300 hours? And why does the process then stop at 300 hours? lol. What if measurements are taken at 400 hours (assuming such measurements are ever taken, and I don't think they ever are) and its now appreciably WORSE than it was at 300 hours?

And while the Bob Carver story is mildly amusing I suppose, it really has nothing to do with what we're talking about since we are actually talking about IMPROVING on published specs (via burn in) rather than simply reaching those specs.

 

[analogsurviver]

Have any published data you can point me to comparing any amps specs out of the box and after 300 hours use and revealing the audible differences?

None that I am aware of.

The degree of precision of AD/DA soundcards ( or whatever you want to call them ) capable of ACTUALLY documenting such minuteae has not been around for long - there is at least one from China that is "roughly" an order of magnitude better than Audio Precision and can measure speaker level power outputs directly. The price is - very roughly IIRC - about 1k plus shipping/customs .

Although I know this will be dismissed as anecdotal evidence, I have seen and heard many cases importers have been forced to demo fresh from the box units at audio shows - sometimes even resorting to " whatever it takes to clear the customs by date/hour D" - in order to have that hot component at - usually yearly - show.

And in most cases, it DID backfire - badly so. Because people have been commenting actually on the sound of burning in of the said component - with appropriately different audible impressions scattered all over the place. If heard early on, it was usually poor ... - and few "poors" from known and well respected listeners will stuck and suffocate any later more positive impressions. No prizes for guessing what that means for sales.

My advice in such a pinch ? DO NOT make active demo - static display only. Burn in the damn thing properly - and AFTER that invite audio press or whoever/whatever to take a real listen. I have seen and heard too many mistakes, made with all the best intentions, in this way - no need to repeat that one over and over again.

 

[Sgt. Ear Ache]

None that I am aware of.

The degree of precision of AD/DA soundcards ( or whatever you want to call them ) capable of ACTUALLY documenting such minuteae has not been around for long - there is at least one from China that is "roughly" an order of magnitude better than Audio Precision and can measure speaker level power outputs directly. The price is - very roughly IIRC - about 1k plus shipping/customs .

I'm not interested in changes that can't be measured by the gear used to arrive at the amps original performance specs. I'm interested in changes that might be heard by human ears.

Although I know this will be dismissed as anecdotal evidence...

yes. It will.


(y'know, the utter lunacy of this burn-in stuff is just mind blowing! So here I'm being told that the equipment doesn't exist yet that can measure the minute changes that occur via the process of burning an amp in, BUT sales guys setting up displays at audioshows and random passing listeners can easily note that amps sound bad ootb due to not having been properly burned in! I mean come on! )

 

[KeithEmo]

In the situation of "how fast can the fastest human run a mile".....

1) We have a very simple and well defined metric. (We all agree on what a mile is, what a minute is, and what running is.)
2) We have a system in place that encourages people to compete. (So we can reasonably hope than anyone likely to be the fastest human has been tested.)
3) We have a system with at least a pretty good test methodology. (Although we might see slightly different results at a different temperature, or altitude, or humidity... we do also know that most tracks at least have hard dry surfaces.)
4) We have a lot of data about how fast a LOT of humans can run. (I'm sure that, in aggregate, and over history, we have millions, or even billions, of "mile/times".)
5) Nobody is asking me to buy something, or avoid buying something, based on the number I'm reading.

So, based on all of that, I would say that it's reasonably likely that nobody can run a mile in two minutes.
However, a lot depends on what you mean by "hedge your bets", and what standard you use.
I don't personally pay extra for "meteorite insurance" on my car - because I feel the likelihood of my car being struck by a meteorite is unlikely - and so unlikely that I'm prepared to take that chance.
(However, in fact, it is NOT impossible - there is at least one documented case of a car that was struck and destroyed by a meteorite while parked in its owner's garage in recent history.)

So, yes, I feel quite safe saying that "I'm pretty sure that no human can run a mile in two minutes."
(However, notice how, even then, I did not say "I am absolutely sure.")
(And, no, I don't mind a bit admitting that phrasing it that way is a form of hedging that bet.)

how bout 2 minutes? You figure it's safe to say nobody on the planet can run a 2 minute mile, or do we need to hedge our bets on the possibility that there's someone out there who can?

 

[bigshot]

The technique here is obvious...

1) Throw in an irrelevant analogy
2) Ignore direct questions about the topic being discussed
3) Try to divert the argument to the details of the analogy instead of the real topic.

We are talking about Stereo Review's test where they determined that amps of various price ranges and designs all sounded the same. If you don't have any comments on that subject, then we'll mark it as mutually agreed upon and move on.

In case the conclusion of Stereo Review has slipped your mind, here it is again, along with a handy link so you can read about all the details of the test.

"...the evidence would seem to suggest that distinctive amplifier sounds, if they exist at all, are so minute that they form a poor basis for choosing one amplifier over another. Certainly there are differences between amps, but we are unlikely to hear them." -Stereo Review January 1987 Pg 78 https://www.americanradiohistory.com/Archive-HiFI-Stereo/80s/HiFi-Stereo-Review-1987-01.pdf

 

[analogsurviver]

I'm not interested in changes that can't be measured by the gear used to arrive at the amps original performance specs. I'm interested in changes that might be heard by human ears.

Human ear is a very sensitive instrument. It is not ALWAYS reliable - but, over longer periods of time, it can discern what is good and what is better. ABX 30 or so seconds can never replicate that - as borne out by so many tests, Stereo Review's January 1987 included. You are never going to see a musician playing one instrument for 30 seconds, swap it as fast as possible with another, play the same passage of 30 seconds as played on the first instrument, etc, etc. No - they will play say one movement with one instrument, the second with another, or even repeat the same movement, but played with another instrument. But never 30 seconds ...

I have simply cited the possibility to measure with a machine that has an order of magnitude better performance ( lower distortion primarily ).One can't measure a 0.01% THD amp with a 0.1%THD measuring device - hope that is clear and understood. There is a great deal more zeroes involved in this case, though. Still, this measuring device operates only at 192kHz sampling rate ( enabling analysis to max 96 kHz ) - something at least two times faster might well give us even more meaningful results.

yes. It will.
I expected such reply.

(y'know, the utter lunacy of this burn-in stuff is just mind blowing! So here I'm being told that the equipment doesn't exist yet that can measure the minute changes that occur via the process of burning an amp in, BUT sales guys setting up displays at audioshows and random passing listeners can easily note that amps sound bad ootb due to not having been properly burned in! I mean come on! )

You can laugh as much as you please - but it is true. Eventually, we will arrive at equipment capable of measuring "beyond the wildest imagination of audibility". It is just we are not there yet. Up to that point - and even beyond - human ears/brain combo, regardless how imperfect it might be, will remain relevant.

If an amp A and amp B both have performance figures WELL past accepted audibility thresholds, but A makes you play recording after recording and B makes you switching the system off due to listening fatigue, there is (yet...) no instrumentation that can decipher WHY - but ear/brain CAN discern at least that the difference does exist and can state preference. But not in 30 seconds intervals ....

Understanding the principles behind the ability of the ear to over longer periods of time relatively easy discern such differences where best measuring equipment (yet... ) can't is the next great step towards achieving perfection in reproduction of the recorded sound. I believe in co-operation and learning - not entrenching firmly on either of the banks of the same river.

 

[analogsurviver]

The technique here is obvious...

1) Throw in an irrelevant analogy
2) Ignore direct questions about the topic being discussed
3) Try to divert the argument to the details of the analogy instead of the real topic.

We are talking about Stereo Review's test where they determined that amps of various price ranges and designs all sounded the same. If you don't have any comments on that subject, then we'll mark it as mutually agreed upon and move on.

In case the conclusion of Stereo Review has slipped your mind, here it is again, along with a handy link so you can read about all the details of the test.

"...the evidence would seem to suggest that distinctive amplifier sounds, if they exist at all, are so minute that they form a poor basis for choosing one amplifier over another. Certainly there are differences between amps, but we are unlikely to hear them." -Stereo Review January 1987 Pg 78 https://www.americanradiohistory.com/Archive-HiFI-Stereo/80s/HiFi-Stereo-Review-1987-01.pdf

No, SR 1987 test did not slip my mind - actually, I am going to re-read (particularly the result charts ) it within 24 hours. I was familiar with it from the date of publishing - plus the usual month or so to reach my shores. All I can say it was a well meant and well conceived test - using tone arm I still have in daily use and cartridge I am also familiar with that spawned a lot of offsprings, some of which I still own and use - about as representative of then SOTA level as possible and still quite viable today.

There is one, VERY important aspect of the test that has NOT been reported. How or where each respective listener has been sitting during these tests. If the PRECISE - and by that, I do mean precise - positioning of the listener's head/ear has not been maintained during listening to both A and B amps, this test is meaningless. Just one seat removed in any given acoustic venue will most likely result in greater difference than any two properly functioning amps.

0:45 am here, TBC later in the day after sleep.

 

[GearMe]

I think there is some literal truth to it, but I changed it by your request.

Thanks!

 

[TheSonicTruth]

here, TBC later in the day after sleep.

"TBC"?

 

[GearMe]

An interesting side bar to the amp discussion...

Would be curious to hear the group's thoughts

 

[bigshot]

There's no reason to worry about if a listener was sitting straight up or slumped back in his chair. If that makes a difference, it has absolutely nothing to do with the amp.

If an amp A and amp B both have performance figures WELL past accepted audibility thresholds, but A makes you play recording after recording and B makes you switching the system off due to listening fatigue, there is (yet...) no instrumentation that can decipher WHY

Where did you see a blind test where a specific amp consistently received statistically meaningful reports of listening fatigue compared to another amp? What make and model of amp is proven to have identifiable levels of listening fatigue? Or are you just making stuff up again?

There are documented reasons why one might experience listening fatigue. Foremost among them would be a narrow frequency response spike, which would be measurable. People can also experience fatigue from wearing headphones too long, getting tired of the music they are listening to, and because they have other things that they would rather do. None of these things are measurable, and none of them have anything at all to do with the amp. In fact, I think the amp is just about the least likely culprit if you are experiencing listening fatigue. I would look to the transducers first.

 

[TheSonicTruth]

fact, I think the amp is just about the least likely culprit if you are experiencing listening fatigue. I would look to the transducers first.

Or the mastering engineer for the album being listened to..!

 

[bigshot]

And listening to a better kind of music too!

 

[Steve999]

As to @bigshot's last point, how about this kind of music?

 

[castleofargh]

why are we doing this again?

"all amps sounds the same" is false. it's easy to disprove as we just need one case where 2 amps do not sound the same within all existing amps and all existing conditions. on the top of my head I can think of a few ways to get my own amps to become audibly different so "all amps sound the same" is not the position of science or whatever, it's just another false claim.
of course that fact doesn't in any way legitimize random empty claims about 2 specific amps sounding audibly different under very specific listening conditions. a proper listening test or significant differences in measurements are needed for that.