[Heidegger]

Don't want to pile up posts, but when I left here I went searching for more info on amp burn-in and found an interesting and highly technical post about this at at
 
http://www.hifivision.com/introductions/4939-amplifier-burn-2.html
 
The post by venkatcr concludes:
 
"So what does happen that make people say that their amplifiers sound better after usage? There is one possibility and this relates more to the power unit.

There is a lot of copper used in the power unit for flow of current. Asit [one of the posters over there at hifivision] had once explained that the conductivity of copper increases after current flows through it for some time. Essentially the molecules inside the copper align themselves in the direction of flow. This reduces internal resistance within the copper and aids in the smoother flow of current. The power unit will, thus, after some usage, be able to deliver marginally higher current, and more important, the higher current faster. This will affect the amplifier circuit in two ways. One, the amplifier’s slew rate will improve enabling the amplifier to match the input signal’s speed better. Two, the power unit will be able to replenish the capacitors faster, thus enabling the amplifier to attack the next rush requirement with equal gusto. The net effect will be that, to our human ears, the music will sound smoother.

A well designed amplifier, in my opinion, will, with usage, not have any positive change in tonality, headroom, dynamics, or other similar and important characteristics of the sound signal. The only possible positive change is the increase in the slew rate and the resultant ‘attack’ speed of the amplifier."
 
This really caught my eye since, above all, the black cube linear when first listened to had a very slow attack speed, making the music sound quite dull. (I can't tell you how often I yawned those first few days.) Venkatcr could be wrong, of course, but it really accords with my experience. Moreover, if you read his/her post s/he really seems to have done some homework. If correct, then all I have to say to you nay-sayers on this thread is: Keep your minds open. There might be things you don't know about. And don't assume that "subjective" experiences are always wrong. Sometimes our ears can hear things that are really there. (Imagine that!)

 

[khaos974]

I didn't exactly bother to check my chemistry book but it seems to me that conductivity only depends on the nature of the material and its temperature, it seems strange that a non permanent electrical current would be able to change the metalic bond of the conduction electrons in the metal, if someone point me to a paper or an excerpt saying the contrary I'll gladly retract this statement. Besides, the atomic mesh of copper and silver, at room temperature, essentially is essentially static, again, please give me a paper saying otherwise.
 
Typical propagation speed of the electromagnetic wave in a coax cable is about 2/3 speed of light, that's 2e8 m.s-1, I doubt that even dividing that speed by ten could have any audible impact.
 
I think that you imagine the displacement of electrons in a cable as water pushing out of a tube, this is a very flawed image, let's replace it by a still imperfect but less flawed one: imagine a tube filled with water, with 2 discs plugging both end of the water filled section (water cannot escape the tube).
Push on one end, the other en moves, pull on one end, the other end moves, any current you have in an audio system is essentially a succession of push/pull motions on one disc, the delay (if, as the guy on hifivision says, the speed of electricity varies) needed for it to propagate to the other disc is inconsequential, the other end will still make the same pull/push movement. And it is, considering the 2/3 speed of light figure, for all intent and purpose instantaneous in the audio realm.

 

[jcx]

yes electromigration is BS in room temp copper, wires with the dimensions of parts leads, amp internal wiring

 

[Prog Rock Man]

It would be worth starting another post on burn in, the above just gets lost here.

 

[EthanWiner]

Quote:

1. Because I would then have to accept the "fact" that my amp is a piece of garbage, and that I have grown accustomed to listening to garbage. Not only that, but I would have to accept the "fact" that garbage now sounds great to me. Because garbage is exactly what this amp sounded like when I first got it. The other possibility would be that the amp really sounded great when I first got it, but that I only thought it sounded like garbage.

I don't get your point about garbage. But unless you measured your amp, or at least made two recordings that you and maybe others here can compare, you really are just guessing. It makes no sense that a solid state amplifier will change sound over time. At least it makes no sense to people who understand how amplifiers actually work. This remind me of a great quote made years ago by a very smart person:
 
"When you can measure what you are speaking about, and express it in numbers, you know something about it. But when you cannot ... your knowledge is ... meager and unsatisfactory." --Lord Kelvin, 19th century physicist
 
--Ethan

 

[Heidegger]

 
Quote:

1. I don't get your point about garbage.
 
2. But unless you measured your amp, or at least made two recordings that you and maybe others here can compare, you really are just guessing. It makes no sense that a solid state amplifier will change sound over time. At least it makes no sense to people who understand how amplifiers actually work.
 
3. "When you can measure what you are speaking about, and express it in numbers, you know something about it. But when you cannot ... your knowledge is ... meager and unsatisfactory." --Lord Kelvin, 19th century physicist
 
--Ethan

1. What's not to get? The amp sounded like a piece of junk at first. I wouldn't have paid $5 for it unless I was planning to resell it at a profit. In contrast, now it sounds fantastic, like a whole different amp.
 
2. You say it makes no sense to people who understand how amplifiers work? Guess what? I think the people who built the amplifier should know then, and I sent them an e-mail asking about it. This is what Lehmannaudio wrote back: "[size=small]Typically, a new unbroken-in piece of equipment will sound a bit thin or dry, with a lacking of bass weight. . . . I don’t think what you are hearing is anything other than break-in." -- Stirling Trayle, Lehmannaudio. Now, who knows more about amps -- you or the people who build them?[/size]
 
[size=small]3. Your appeal to numbers is rather pointless here, as neither one of us could make those calculations.[/size]
 
 

 

[tmars78]

 
1. What's not to get? The amp sounded like a piece of junk at first. I wouldn't have paid $5 for it unless I was planning to resell it at a profit. In contrast, now it sounds fantastic, like a whole different amp.
 
2. You say it makes no sense to people who understand how amplifiers work? Guess what? I think the people who built the amplifier should know then, and I sent them an e-mail asking about it. This is what Lehmannaudio wrote back: "[size=small]Typically, a new unbroken-in piece of equipment will sound a bit thin or dry, with a lacking of bass weight. . . . I don’t think what you are hearing is anything other than break-in." -- Stirling Trayle, Lehmannaudio. Now, who knows more about amps -- you or the people who build them?[/size]
 
[size=small]3. Your appeal to numbers is rather pointless here, as neither one of us could make those calculations.[/size]
 
 

Your point about what the maker of amp said, is rather pointless. Of course he is going to say that. He is in the business of making money too, and people looking to turn a profit, will say ANYTHING to make a buck. Sad? Yes, unfortunately.

 

[nick_charles]

 
Quote:

 
[size=small]3. Your appeal to numbers is rather pointless here, as neither one of us could make those calculations.[/size]
 
 
A good proxy for the numbers is to take the analog outputs and make recordings from them before and after a period of time, too late now of course, then you can scope out the FR and convert it into numbers which you can then plot so you get a graphical representation of a before and after...

 

 

[upstateguy]

 
Quote:

The day before yesterday I played some SACDs and it seemed that the amp was emphasizing the treble too much. The music sounded a little too bright and somewhat unpleasant. I couldn't make out the mids that well. I played the exact discs yesterday and they sounded GREAT. Go figure.
 
 

Had you replaced your cables or performed some other tweak when you heard the treble emphasis, you would now be crediting the improvement to the cables or the tweak.
 
What you have just described is a good example of what happens when people report the difference cables and tweaks make.
 
USG
 

 

[Mkubota1]

Quote:

Had you replaced your cables or performed some other tweak when you heard the treble emphasis, you would now be crediting the improvement to the cables or the tweak.
 
What you have just described is a good example of what happens when people report the difference cables and tweaks make.

Reminds me of the numerous blind tests where nothing is changed; yet listeners are able to describe IN GREAT DETAIL the differences of A vs. A. 

  Is there someone out there who can explain this?  I would especially like to hear an explanation from someone opposed to blind or DBT.  It's one thing to not be able to tell between A and B.  But when they start to describe something that is the same as totally different, it sounds like they're just making stuff up- don't know any other way to put it.
 

 

[upstateguy]

Quote:

Originally Posted by Mkubota1 /img/forum/go_quote.gif

Reminds me of the numerous blind tests where nothing is changed; yet listeners are able to describe IN GREAT DETAIL the differences of A vs. A. 

  Is there someone out there who can explain this?  I would especially like to hear an explanation from someone opposed to blind or DBT.  It's one thing to not be able to tell between A and B.  But when they start to describe something that is the same as totally different, it sounds like they're just making stuff up- don't know any other way to put it.
 

My guess is that expectation plays a big part in that.  They expected to hear something different, and so they did.
 
USG
 

 

[tmars78]

Reminds me of the numerous blind tests where nothing is changed; yet listeners are able to describe IN GREAT DETAIL the differences of A vs. A. 

  Is there someone out there who can explain this?  I would especially like to hear an explanation from someone opposed to blind or DBT.  It's one thing to not be able to tell between A and B.  But when they start to describe something that is the same as totally different, it sounds like they're just making stuff up- don't know any other way to put it.
 

I wouldn't say they are making it up. They really could be hearing what they are describing. The human mind is a powerful thing, and we can make ourselves believe almost anything, especially when we are expecting to hear something. Its called Expectation bias.

From Wiki:

Experimenter's or Expectation bias – the tendency for experimenters to believe, certify, and publish data that agree with their expectations for the outcome of an experiment, and to disbelieve, discard, or downgrade the corresponding weightings for data that appear to conflict with those expectations.[8]

 

[Mkubota1]

Quote:

Quote:

... it sounds like they're just making stuff up- don't know any other way to put it.
 

I wouldn't say they are making it up. They really could be hearing what they are describing. The human mind is a powerful thing, and we can make ourselves believe almost anything, especially when we are expecting to hear something. Its called Expectation bias.

Right... poor choice of words on my part.  What I meant was that they are describing what they perceive the sound is as it passes through all of the effects of cognitive bias.
 
I was just reading up on an article about ABX testing (by Robert Harley no less) and all of the valid criticisms of it.  It seems like the main ones are length of listening time and system quality or familiarity.  So I thought to myself:  Aside from the obvious time constraints, why not do a DBT where the tested component is blindly inserted into the reference system for say a period of one or two weeks.  And then that component is switched out (or not!) and the tester gets to listen for another week or so.  You wouldn't be able to do a number of trials like you could in a traditional ABX test.  But it seems like this sort of method would appease those who say they can hear the difference.  Going back to my original question:  So what if you did a test like this with a person who says they can hear the difference between cable A and B, and at the end of say 3-4 trials they describe to you the differences (in great detail of course).  But then they find out that the cables were never switched.  What would they say?  Or would this never ever happen?
 
I'm certainly not saying that ABX is the perfect test and I know there are people who have really excellent hearing (though not nearly as many that make the claim).  Blind testing is like chemotherapy.  It's not without its drawbacks; but the alternative(s) are usually far worse.

 

[tmars78]

Right... poor choice of words on my part.  What I meant was that they are describing what they perceive the sound is as it passes through all of the effects of cognitive bias.
 
I was just reading up on an article about ABX testing (by Robert Harley no less) and all of the valid criticisms of it.  It seems like the main ones are length of listening time and system quality or familiarity.  So I thought to myself:  Aside from the obvious time constraints, why not do a DBT where the tested component is blindly inserted into the reference system for say a period of one or two weeks.  And then that component is switched out (or not!) and the tester gets to listen for another week or so.  You wouldn't be able to do a number of trials like you could in a traditional ABX test.  But it seems like this sort of method would appease those who say they can hear the difference.  Going back to my original question:  So what if you did a test like this with a person who says they can hear the difference between cable A and B, and at the end of say 3-4 trials they describe to you the differences (in great detail of course).  But then they find out that the cables were never switched.  What would they say?  Or would this never ever happen?
 
I'm certainly not saying that ABX is the perfect test and I know there are people who have really excellent hearing (though not nearly as many that make the claim).  Blind testing is like chemotherapy.  It's not without its drawbacks; but the alternative(s) are usually far worse.

What you say is all well and good, and those types of tests have been proposed here numerous times, but no one has taken the plunge. Even if someone does take the plunge, if they fail, they will only blame the test. It seems to be what they usually do. From all of the reading I have done here at head-fi, what I have learned is, the skeptics want to be proved wrong, and the believers egos are too big, and are afraid to be proved wrong. They say they can hear differences, swear up and down they are there, but won't put their money where their mouth is, and find all kinds of excuses to not do a blind test.

 

[Steve Eddy]

Quote:

 
I was just reading up on an article about ABX testing (by Robert Harley no less) and all of the valid criticisms of it.  It seems like the main ones are length of listening time and system quality or familiarity.  So I thought to myself:  Aside from the obvious time constraints, why not do a DBT where the tested component is blindly inserted into the reference system for say a period of one or two weeks.

That's been done before.
 
Tom Nousaine had installed ABX switchers into a number of people's home systems where they could do the tests at their leisure, taking as long as they like to listen or switch, etc. Some of these people had the ABX switcher in their system for months and even years.
 
None of them ever turned up a positive result.
 
se