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发表于 2009-6-7 00:06:07
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他在论坛里还有几篇教程，关于“集肤效应”，“采样理论”，”数字音频“，”失真”等。
关于集肤效应的影响和信号线方向问题
Hello Jose,
Your first question is:
“I noticed inyour article you wrote skin effect does not alters the timing relationshipbetween harmonics, but it alters the ratio between harmonics, are we talkingabout “cables coloring the signal”?”
When we talk about engineering, it is veryimportant to QUANTIFY matters. Quantifying often tells us the differencebetween what is practical and what is not. For example, stir a tablespoon ofsalt in a cup of water, and you will be able to taste salt. But stir a singlegrain of salt in an Olympic size fresh water swimming pool, and the water willbe salt free, for all practical purposes.
Skin effect impact on relative lowfrequencies, such as audio is negligible, even for hundreds of feet of cablerun. It is analogous to a grain of salt in a huge pool.
The effect is there, the question is howmuch of it do you get at audio frequencies. The answer is – the effect is sovery small that it can be completely ignored. I do not believe a human can heara .01dB loss at 20KHz. Skin effect causes much less than .01dB at 20KHz…
Your second question is:
“I have workedwith some audio cables offered by a well known company, where a nice arrowshows the correct signal flow direction, what are we talking about here?”
Whatever the intent and the motive, the endresult is consumer deception. The audio cables are made of material that doesnot have directionality to it. But to “add insult to injury”, the signal itselfis by directional. The electrons in the cable flow back and forth from thesource to the destination and back. That arrow is a big lie, nothing less.
The audio industry has a large number ofsuch crocks and deceptions, and the common method to sell such lies is to findsomeone(s) willing to state that they heard a difference. Such statements arethen used for advertising.
The proper way to screen subjective orfalse claims is to conduct a double blind ABX test (and that means keeping awaypeople that may have any commercial interests from the test site).
Other sales “methods” involve technicalclaims that go against science and technology. The marketing of such falseproducts take advantage of the fact that a large majority of people lackscientific and engineering fundamentals; therefore can not separate technicalfacts from complete fabrications, such as in the case of printing an arrow on aspeaker cable.
Regards
Dan Lavry
大概意思：从工程角度，集肤效应的影响很小，可以忽略。打比方：一勺盐会影响一杯水的味道，一粒盐的影响微乎其微。
很多知名厂商信号线或音箱线上标方向，是厂商“骗术”。
当然，个人听感认为，换线材对声音的一定改变是可闻的，改变信号线方向也有非常细微的变化。当然这种变化相对于声音全局，影响确实是很微小的。如果有较大幅度变化的话，应该是引入了较大“失真”。
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发表于 2009-6-6 16:59:12
发表于 2009-6-6 17:16:24
