|
Posts: 1002
Location: Texas
Joined: December 6, 2009
|
Up to a point, I think you are making some reasonable observations. However: "I think this is your gap in understanding. The human ear/brain, once trained, is a very subtle and sensitive sensor. There is plenty of evidence to support this.
Is a scope more sensitive, yes but the mistake is that the meter reader is making prejudgment on how low is too low to hear." I don't see a gap in understanding here. We all agree that there has to exist some threshold below which the human ear will not be able to perceive a sound. There is in fact a lot of research done on where these thresholds lie, how they change with age, etc., etc. Actually what is more relevant for the "breaking-in of components" discussion is not so much the absolute threshold of hearing, but the ability to hear a tiny change superimposed on a large background signal. And, what is more, to be able to remember how it sounded a few weeks previously, prior to the "breaking in." There can be no doubt, and I think probably you are not disputing this, that the sensitivity of precision measuring instruments exceeds the relevant thresholds of audibility. This brings us to another key point, which you alluded to when you said "However, I don't think you or anyone else can PREDICT what the impact on sound will be because no one has done any kind of correlation study." I absolutely agree with this, and I am always careful to distinguish between two totally different issues in discussions like this. I strongly maintain that a claim of an audible difference, resulting from some particular change of component, is logically capable of being disproved by means of electronic measuring apparatus, if it can be shown that the change in the charactersitics of the audio signal is unambiguously below any conceivable threshold of audibility. (And we don't need to descend into the kind of hopeless, helpless viewpoint of someone who says that we can't ever know anything about anything here! A lot is known and well documented about what the ear can and cannot hear.) A *totally different* question, and one that I would certainly never make any claims about, is the question of whether one could *predict* from measurements how something would actually "sound" to the listening subject. That is a much more difficult question, and one that I would not want to get into. For the present discussion, I only want to emphasise the point that sometimes one may be able to disprove an assertion about a claimed audible change by demonstrating that the change in the output from the amplifier is so much below the threshold of audibility that one can unambiguously rule out the assertion of a real, as opposed to imagined, effect. I think that the alleged "breaking in" of a solder joint would almost certainly fall in this category. On the subject of solder joints, you said in defence of the claim that "A thin layer of oxide makes already a fairly good resistance." However, unless we are talking about a shoddy dry joint or something like that, in a properly done solder joint the oxidation would be taking place on the outside of the entire joint, and would not be interfering with the electrical flow through the joint itself. In any case, if somebody were able to demonstrate by means of measurements that the signal voltage did indeed change significantly (i.e. above the threshold of audibility) as the solder joint broke in, then I would (obviously) have no hesitation at all in accepting that the effect would be audible. My experience, and my deductions based on order-of-magnitude estimates using standard physical principles, leads me to conclude that the effects would be way too small. Thus, when confronted with someone who claims that they do hear the effects of breaking-in of solder joints, I think it is more reasonable that I treat it with the same kind of skepticism that I have about claims that crystals sprinkled on the coffee table will affect the sound. In each case, the person reporting the effect is probably being perfectly sincere, but the explanantion for their perception is overwhelmingly more likely to be based on imagined psycho-acoustic phenomena than on actual facts.
Chris
|
