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post #31 of 48
Thread Starter 
Quote:
Originally Posted by Real Man of Genius View Post
What you are referring to here would be "warm-up" rather than "burn-in" I believe. Burn-in being a semi-permanent (or at least gradually reducing) effect on *NEW* equipment.

Right?
yeah..i know. I didn't refer to the warm up as burn-in, i just give it as another example. in fact I stated that i can't comment on burn-in becasue i personally never noticed any changes in my own equipment.
post #32 of 48
Quote:
Originally Posted by Real Man of Genius View Post
My take on burn-in:
Given the absence of any real scientific explanation, I think the most logical theory is the brain acclimatization model that Koyaan discussed. I have experienced it as well. The brain does indeed like patterns.
What are your thoughts on what Happy Camper posted regarding capacitors, oxidation, etc.?
post #33 of 48
there are sometimes measureable changes in electronic circuits/components with extended operation - just not obviously audible because of their tiny effect on audio frequency signal response:

Quote:
Originally Posted by jcx View Post
wet electrolytics have very well known issues with the electrolyte/oxide dielectric "forming" process being somewhat reversable
without correct polarizing V the oxide partially "dissolves"

some time at operating V is required for Al electros to reform full strength oxide layer after long storage at 0 V

Hi-temp/Long life types with generous V derating are a good idea if Al electrolytic have to be used in the signal path

doped Si is also fairly piezo-resistive - packaging&assembly stress can cause op amp Vos shifts, high grade DC instrumentation should be stress relieved by slow thermal cycling of the assembled board

and I think moisture absorbtion could be a larger factor than most appreciate - with a dielectric constant of ~80 the fractional % water absorbtion of most plastic PCB substrate, part packages and some cap dielectrics causes measurable differences in dielectric loss - the heat of continuous on Class A circuits will cook out some of the equilibrium moisture

I still doubt that with all above taken together the response variation would often be audible in controlled testing

"acoustic memory" is just too plastic, combinined with accomodation and expectation effects leads me discount any "I heard it" "just listen" ancedotes - real ABX controlled, blinded tests would be needed to convince me any of the likely electronic burn in phenom rise to audible thresholds


the best mechanical "burn in" story I've heard was about a "hot" piano mod, the professional player waxed nostalgic over his recorded performance and then regretfuly pointed out he would be unable to repeat the performance - the modded piano action had gone from "fast and fluid" to loose and unplayable as the mod "wore in" over a few months of playing

the component ageing effects I am aware of are much smaller than the initial tolerance so even ABX with 2 amps could be difficult - you'd have to "blueprint" the amps to get the initial component matching better than the expected change on burn in
post #34 of 48
I've had problems with every new amp I've bought. It definitely sounded different thand the one I was used to, superior in certain aspects but also somewhat disharmonic over-all. That was again the case with the change from the Opera to the Symphony. I couldn't tell which I liked better, but they didn't sound the same.

I think this contradicts the purely psychological explanation from an objectivist point of view with the opinion that amps that measure the same sound the same: Given the different looks, the newness and the investment one would expect a positive impression.

After about 240 hours the Symphony was beginning to sound undisputedly better than the Opera. And these days (after more than a year of living with it) the case is absolutely clear.

Now it's easier to argue with the psychological effect of getting used to a new sonic characteristic (a possibility I don't absolutely exclude). But from the objectivist point of view there's a decision to be made: Either there is a difference in the first place – so there's a need for acclimatization –, or there's none, and every sonic difference is imagined. In the latter case it's not logical to hear a difference without a clear improvement based on high expectations (the motivation to buy a new amp); in the former case acclimatizing to an imagined alteration isn't a logical scenario.

Moreover there's the question of the allegedly limited acoustic memory. It's impractical or impossible to ABX two different headphone amps. So the capability of the acoustic memory to really remember the former characteristic can be disputed, and the pretension that it's all in the listener's mind sounds somewhat plausible. It's just that in the latter case there would be no need for acclimatization to a new characteristic.

There are a lot of inconsistencies in a strictly objectivist approach when it comes to amps and burn in. So in my book real differences and real burn-in effects are just as likely as placebo effects even or precisely from an open-minded objectivist perspective.

As to the OP's request: Unfortunately I'm not technically knowledgeable enough to give any useful information.
.
post #35 of 48
Thread Starter 
Quote:
Originally Posted by JaZZ View Post
I've had problems with every new amp I've bought. It definitely sounded different thand the one I was used to, superior in certain aspects but also somewhat disharmonic over-all. That was again the case with the change from the Opera to the Symphony. I couldn't tell which I liked better, but they didn't sound the same.

I think this contradicts the purely psychological explanation from an objectivist point of view with the opinion that amps that measure the same sound the same: Given the different looks, the newness and the investment one would expect a positive impression.

After about 240 hours the Symphony was beginning to sound undisputedly better than the Opera. And these days (after more than a year of living with it) the case is absolutely clear.

Now it's easier to argue with the psychological effect of getting used to a new sonic characteristic (a possibility I don't absolutely exclude). But from the objectivist point of view there's a decision to be made: Either there is a difference in the first place – so there's a need for acclimatization –, or there's none, and every sonic difference is imagined. In the latter case it's not logical to hear a difference without a clear improvement based on high expectations (the motivation to buy a new amp); in the former case acclimatizing to an imagined alteration isn't a logical scenario.

Moreover there's the question of the allegedly limited acoustic memory. It's impractical or impossible to ABX two different headphone amps. So the capability of the acoustic memory to really remember the former characteristic can be disputed, and the pretension that it's all in the listener's mind sounds somewhat plausible. It's just that in the latter case there would be no need for acclimatization to a new characteristic.

There are a lot of inconsistencies in a strictly objectivist approach when it comes to amps and burn in. So in my book real differences and real burn-in effects are just as likely as placebo effects even or precisely from an open-minded objectivist perspective.

As to the OP's request: Unfortunately I'm not technically knowledgeable enough to give any useful information.
.
interesting post Jazz, thanks for your comments.
post #36 of 48
Quote:
Originally Posted by PhilS View Post
What are your thoughts on what Happy Camper posted regarding capacitors, oxidation, etc.?
I think it is unlikely that the mere flow of a signal changes the properties of those components.
Heat and oxidation are intriguing, however. These could very well change the materials. Whether the change is sufficient enough to alter the sound signature (enough to be audible) is another matter but I believe it is certainly possible, if unproven at present.
EDIT: It still leaves the question of how it is possible that the changes are always for the better unanswered.
post #37 of 48
Quote:
Originally Posted by plonter View Post
yeah..i know. I didn't refer to the warm up as burn-in, i just give it as another example. in fact I stated that i can't comment on burn-in becasue i personally never noticed any changes in my own equipment.
Ahh... misread that, sorry.
post #38 of 48
Quote:
Originally Posted by JaZZ View Post

Now it's easier to argue with the psychological effect of getting used to a new sonic characteristic (a possibility I don't absolutely exclude). But from the objectivist point of view there's a decision to be made: Either there is a difference in the first place – so there's a need for acclimatization –, or there's none, and every sonic difference is imagined. In the latter case it's not logical to hear a difference without a clear improvement based on high expectations (the motivation to buy a new amp); in the former case acclimatizing to an imagined alteration isn't a logical scenario.

Moreover there's the question of the allegedly limited acoustic memory. It's impractical or impossible to ABX two different headphone amps. So the capability of the acoustic memory to really remember the former characteristic can be disputed, and the pretension that it's all in the listener's mind sounds somewhat plausible. It's just that in the latter case there would be no need for acclimatization to a new characteristic.
What you're saying is true (a strictly 'objectivist' position is contradictory with mental acclimating) if and only if the two components are volume matched. This is almost never the case. If someone compares amps without any level balancing, they're likely to mistake a different volume level for a difference in detail, etc. Furthermore, most amplifiers' potentiometers work over different ranges and provide different levels of attenuation based on the specific amplifier's gain, so changing volume would also not be a constant affair. Finally, whatever mental predispositions the listener has can also change over time (similar changes happen with medical placebos) and even imagined details can seem more familiar over time. I don't think that the two positions (components not making an audible difference and the theory of mental acclimating) are contradictory at all, especially when taking into account the dozens of variables present in uncontrolled settings.

OP: by definition, a scientific explanation is a (scientific) theory. Those theories have to be backed by some form of empirical evidence in order to be called a scientific theory instead of mere speculation. Without empirical data that fits the theory, you just have a "Just-so story." That said, you probably would have better luck posting in the misc. cables thread.
post #39 of 48
Quote:
Originally Posted by Real Man of Genius View Post
EDIT: It still leaves the question of how it is possible that the changes are always for the better unanswered.
I have my doubts on some claimed burn in issues as well, but with respect to your question above, I'd offer two thoughts, sort of playing devil's advocate given my own doubts on certain aspects of this issue:

1. I have seen several instances where people claimed, not that a component sound worse when it was finally "broken in," but that it did sound worse for a time and then got better. I'm not sure I accept that, but there are also instances where people claimed to be happy with an amp when they first got it, but after a time with it, they decided they didn't like it. Maybe they just didn't like it; OTOH, maybe the burn in had negative effects, but they did not attribute it to burn in.

2. I'm not sure it's totally illogical to conclude that an amp designer/manufacturer who is trying to achieve a certain sound would not be working primarily with components that are burned in. Hence, if things like capacitors do change over time (and assuming for the sake of argument it's audible), it would make some sense that the amp would sound better when it reaches the stage that mirrors what the amp designer was experiencing with his prototype.

Anyway, it would be interesting to hear what a guy like Ray Samuels would say on this subject. He always recommends substantial burn in time for his amps, and it would be interesting to see what his explanation would be.
post #40 of 48
Quote:
Originally Posted by PhilS View Post
I'm more than happy to have both comments deleted. Why don't you report the threads and ask the mods to edit it.
Because I'm happy to let the last word on your side, and the off-topic has been short enough not to disturb the discussion.

Quote:
Originally Posted by PhilS View Post
It's not inconsistent at all. It's only inconsistent if you feel compelled to advance a particular point of view,
That's quite right : if there is burn-in, a proof can be given without discussing the existence of the phenomenon first, but in the other case, no proof can be given.

Quote:
Originally Posted by PhilS View Post
Go back and read the other threads like this in the past. Here's what you find:
Too true... but two differences may appear in this thread. First, the rescriction to scientific explanations rules out the influence of Shakti stones, Langevin's heavy ions, Manta and other Hallographs.
Second, in the caricatural example that you gave, the "objectivist" side was not willing to explain at all.

Quote:
Originally Posted by plonter View Post
now,i want to make clear that although i am a "believer" i am also a thinking human being and willing to hear some comments about "burn-in" not true, not just comments that "Burn in" is true.
Actually, the burn-in problem is masked by another, more important problem, that is the sound of amplifiers.
Currently, it is admitted that a perfect amplifier is possible, exists, and that its street price should be around 200 or 400 euros for less than 100 watts stereo. Some candidates models : Behringer A500, InterM M300. I don't know measurments performed on them, but they have been compared to high-end audiophile amplifiers in good conditions, and showed similar sonic qualities.

The problem is that if an amplifier is perfect, how can it burn-in ? It is already quite difficult to distinguish between the sound of two different models, let alone the sound of the same model before and after burn-in.

The usual answer is that differences between amplifiers exist and are easily audible (except in ABX). Ok, but these differences can't be explained !

How can we expect to explain the différence between a burned-in amplifier and a brand new one, while we currently cannot explain why two different amplifiers sound different (except tube) ? We must begin with the easy questions before going on with the difficult ones.

Here are three aspects of the problem with amplifier sound :

First, the measured performances. Often enough, noise, output power, frequency response, phase response, harmonic distorsion, and intermodulation distorsion are all below the audible threshold. And it is very difficult to imagine any other kind of distorsion. The most probable that I can see would be intermodulation distorsion at frequencies different than the ones used in the usual tests. But they are sometimes performed without interesting results.
Any other measurment, like square wave or impulse response, should be perfect if the above are all perfect.

Second, the cancellation test. Douglas Self talks about it in his article about amplifiers ( Douglas Self Site ).
Here is how it works : we use an attenuator in order to decrease the output of the amplifier, until its level is the same as the input signal. Then this signal's polarity is inverted, and it is summed with a copy of the input signal.
This way, the output is substracted from the input, and we can see what's left. According to D Self : zero !
This measurment encompasses any possible characteristics of the sound. The complete musical signal is compared to the original in real time, and the experiment shows that it consists in a strictly identical copy of it, with a bigger amplitude, even while speakers are connected to the output.

That's what Douglas Self says. But in another discussion, (here : diyAudio Forums - Blind Listening Tests & Amplifiers - Page 1 ) a forumer gives more accurate figures. Actually, the result of the substraction is not null. Its amplitude is 60 dB below the original with cheap amplifiers (250 $), and 70 dB below with better amplifiers.

We must also note that these kind of measurments should be extremely difficult, because if the cable lenght of the original signal is not exactly the same as all the paths that takes the amplified one into the amplifier, at the speed of electricity (about 200 000 km/s), a difference of one meter would be enough to explain the -70 dB noise, because the two copies of the signal would not arrive exactly at the same time.

The third approach is blind testing. It is well known (is it ?) that tube amplifiers can be distinguished from transistor ones in ABX tests because of their high output impedance, that adds a coloration to the sound.
Example : http://www.soundandvisionmag.com/ass...rInterface.pdf

But between transistor amplifiers, ABX usually fail. Recently in France, a small group of forumers called the Kangourous (Kangaroos) began investigating the sound of amplifiers. There have been 5 meetings so far (I was at the first one). Here are all the links :
homecinema-fr.com • Voir le sujet - Kangourou : Les liens, les produits écoutés.

Currently, some interesting points have been found :
-Not even listening blind, a very cheap InterM M300 pro amplifier (around 150 euros) seemed to deliver the same sonic quality as a Mimetism 15.2 amplifier (4500 euros), on high end speakers ( JMR Euterpe or JMR Concorde Signature, I don't remember at what moment we switched).
In the same comparison, we noticed a bigger difference with another high end amplifier, the Atoll In100, than with the cheap InterM, that sounded closer to the Mimetism.
The blind test between the Atoll and the mimetism failed (actually, the listener scored 12/15, which gives a probability of false success of 1.8 %, but we agreed before the test that 14/15 was a minimum).
However, the distorsion was obvious for two other listeners. We did not have the time to repeat the test with them, nor to measure the distorsion, that was plainly audible on a 1 kHz sine. We think that a success is possible.

Second interesting point, while it seems confirmed that "any properly designed amplifers sound the same", it seems on the other hand that finding a "properly designed amplifier" is not easy at all !
In our first test, an expensive audiophile and a cheap pro one seemed to fit in that category, but not the other expensive audiophile one.
In further tests, they found that some AV receivers have conception problems. One of them did not shut down the low frequency management for subwoofer when setup accordingly ! Which resulted in a completely wrong bass response.

GrandX, the person who launched the idea, now follows the same path as Mike here : he wants to refine the blind protocol until he finds why he can hear some differences in usual conditions, and not anymore in ABX. Many improvement have been suggested for the next listening sessions :
-letting the listened adjust the volume with a CD player that has a variable output.
-testing in XY instead of ABX (an idea that would please Wavoman !).
-performing no more than one comparison in a day.
-Performing usual comparisons (not blind) with volume and balance equalized within 0.1 dB.
-Looking for correlations in subjective comments of different listeners instead of yes/no answers, and for this purpose, let the listeners agre on a limited list of adjectives before the test.

As we can see, we know little about real-world amplifiers because manufacturers don't publish measurments anymore, because scientific studies never cite any brand or model and use to work on abstract "well-designed" amplifiers, and because blind tests are extremely difficult to perform (just think about equalizing the volumes, that must be done with speakers working (because they suck current and this might change the volume), and while plugging anything in the amplifier output may cause it to burn instantly).

In these conditions, we can see what it is that seriously studying the burn-in of amplifiers !

Oh, and about the variations of the capacity in capacitors, I've read from some DIYers that in "well designed" (again ! ) circuits, small variations of the values of capacitors have no effect on the output signal of the amplifier.
post #41 of 48
Quote:
Originally Posted by royalcrown View Post
(a strictly 'objectivist' position is contradictory with mental acclimating)
Interesting. Could the same be said for placebo then?

Quote:
Originally Posted by PhilS View Post
2. I'm not sure it's totally illogical to conclude that an amp designer/manufacturer who is trying to achieve a certain sound would not be working primarily with components that are burned in. Hence, if things like capacitors do change over time (and assuming for the sake of argument it's audible), it would make some sense that the amp would sound better when it reaches the stage that mirrors what the amp designer was experiencing with his prototype.
Good points. I would think if that was the case the manufacturer would "pre-burn-in".

Quote:
Originally Posted by PhilS View Post
Anyway, it would be interesting to hear what a guy like Ray Samuels would say on this subject. He always recommends substantial burn in time for his amps, and it would be interesting to see what his explanation would be.
I would rather hear someone like Justin's opinion but yes, it would be interesting. Has it never been addressed by a manufacturer before as to the reasons for burn-in?


EDIT: Great frikkin post pio!!!
post #42 of 48
Quote:
Originally Posted by Real Man of Genius View Post
Interesting. Could the same be said for placebo then?
What do you mean?
post #43 of 48
Quote:
Originally Posted by Real Man of Genius View Post
Has it never been addressed by a manufacturer before as to the reasons for burn-in?
I seem to recall that from time to time, some of the headphone amp manufacturers have offered some information on this, but it's usually in other types of threads (e.g., a thread pertaining to a particular amp). They tend to stay out of sound science-type discussions; they have more sense than a lot of us, I guess.
post #44 of 48
Burn-in is sometimes explained away as simply getting used to a new sound. But is that really what is happening? this involves not only what we are hearing, but how we are reacting to it.

i have never met anyone who liked their first taste of beer, and who didn't "get sick" to some degree or other from their first cigarette. lots of people drink beer and/or smoke cigarettes however. the question is -- do they taste different now than when they were first tried/ brand(s) aside?

how we judge things has a lot to do with our state of mind, and our past experience with comparable experiences. as a former teacher, i have run across students who had test anxiety, such that they could not give the correct aanswers under the pressure of the exam, but could answer them all in calmer settings. music is an emotion-inducing affective art form, and it is much harder to perceive subtle differences under pressure. Nor are all people's acuities equal. a proper test would use subjects with proven abilities to pick out differences-- whether any particular person can hear a differences has nothing to do with whether such differences actually exist.

food for thought. maybe burn-in is a form of warm-up. spec sheets certainly show performance differences relative to temperature. i think there is more to it than mere habituation-- not sure what it would take to prove it.
post #45 of 48
Just want to give the a semiconductor manufacturer's perspective. We do not like change after burn in. Predictable and deterministic behavior is key. What if after 100 hours of use certain parameter change and cause plane to crash and telecom equipment to malfunction.

To make sure things are consistent, there is a qulaification process. Devices are burn in for 1000 hours at 125 deg C junction temperature to see if there is any gross number of failure or deviation. If not, then the chip is deemed production worthy. If not, usually there is some design error or manufacturing process at fault.

Can't tell you must about capacitor, but crystal and LED go through the same testing.
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