More Metaling in Cable Design

In the last part (Part 2) of this occasional series on weird stuff about cables, I wrote about the actual metal that the cables are made of, and about how -- although there's broad disagreement about what that metal ought to be (mostly an ongoing war over what's better, copper or silver) -- most people agree that "purer is better." I also wrote that, while a great many cable companies declare the metal they use to be hyper-pure, my company (XLO) -- which paid ultra-premium prices to buy copper claiming ultra-premium purity -- was never able to find any testing laboratory, either commercial or university-related, anywhere in the United States that would (could?) certify any level of purity higher than 99.99% [four nines], despite the copper manufacturer's claim of purity 100 times greater than that.

welder.jpgEvery time a "nine" is added to a purity claim, because ours is a decimal system of numbering, that's a claim of 10 times greater purity, so "five nines" -- a claim sometimes made for silver -- would, if true, actually be 10 times as pure as the "four nines" purity that the laboratories claimed to be willing or able to certify. "Six nines" would be 10 times purer than that; a total of 100 times greater than the claimed capability of any testing laboratory we contacted at the time that we were looking for confirmation of the quality of the copper that we had spent so much money to buy.

Although I mentioned this inability to get independent verification of the purity claims of the copper manufacturers (or of some other cable manufacturers, who were claiming as much as eight nines of purity) as unfortunate, I also said that: "... just because nobody else can test it, doesn't mean that they (the manufacturer) can't, and just the need to test initial results and to maintain their product's ongoing quality control would strongly indicate that they need to and probably (can)."

I finally went on to ask "...even if it really is that pure, so what?" I pointed out that the differences in conductivity or resistance (the other side of that same coin) between the cheapest and the most expensive copper grades (or even silver) are tiny; that changes in resistance caused by changes in temperature can be just as significant, and that there are a goodly number of cheap and easy ways to reduce resistance. I declared that just lowering resistance couldn't possibly be the only reason why purer metals make for better sound; that there must be something other than just resistance that the purity of the metal affects; and I promised that that would be my subject for next time.

Well, here it is, "next time," and I'm going to do exactly that. Before I do, though, let's take a quick look at the whole concept of purity, and what it means as applied to metals:

Do you know what brass is? Or solder? Both of them are alloys; the result of mixing two or more metals (and possibly some other ingredients) to produce a new metal with different properties. It's like mixing flour, water and other ingredients to make bread. The bread is made of, but has significantly different characteristics than, any of its ingredients. The mixing and baking of the ingredients has produced a new thing entirely.

How about copper? Nice impure copper. Even though the copper has other things in it -- even if those other things are metals -- does that make the copper an alloy? Maybe. but also maybe not, and possibly even both!

One easy way to understand this uses another food analogy, but instead of bread, this time let's consider the difference between a chocolate cookie and a chocolate chip cookie: A chocolate cookie is a uniform brown because the chocolate (or, more likely, the cocoa) in it is (at least for purposes of this example) completely mixed with and inseparable from the other ingredients in the cookie. In essence, it forms a chocolate "alloy." A chocolate chip cookie, on the other hand, has discrete pieces of chocolate mixed in with and surrounded by a matrix of "pure" cookie. That's not an alloy, but what scientists would call a "conglomerate."  (Google defines a conglomerate as "a number of different things or parts that are put or grouped together to form a whole but remain distinct entities.")

Although there are copper alloys (brass and bronze being two of them), at least most of them are produced on purpose by metallurgists seeking a solution to a particular problem. Most of what is sold just as "copper," however, instead of by some alloy name or number (Tellurium copper or Brush-Wellman Alloy 174, to give just two examples) is not such an alloy at all, but, for the most part, a conglomerate of copper and some number of other materials.

To whatever extent it is a natural alloy, the major alloying elements in copper may include sulfur, silver and gold, which are likely to be present in very minor proportions. These additional metals are sufficiently unlikely to produce any negative effect that in most IACS standards, silver and gold impurities are simply counted as part of the copper component, and not treated as impurities at all.

The impurities more likely to produce problems are, like the chocolate chips in cookies, non-alloying, and instead of becoming part of the copper itself, become conglomerated intrusions between the pure (or alloyed to whatever degree) copper crystals at their "junctures" -- the points where they join to make up the metal structures that are the wires we deal with. These non-alloying impurities include two major components or component groups: copper oxide (CuO) and the "iron triad" elements (Iron [Fe], Nickel [Ni], and Cobalt [Co]), all of which can have a deleterious effect on signal transmission, regardless of any degree of wire resistivity.

As I've written before, CuO, in very thin films (as it's certain to be, between the individual crystals of a copper wire), is a semiconductor, and acts like a tiny diode to resist the flow of electrons in one direction. Consider that there are thousands of crystal junctures (and thus thousands of diodes) in even a short length of wire. Consider that in all of those tiny diodes may be aligned so that they all (or significantly all) resist positive or negative signal flow. They may block all signal below a certain level, or they may even be "mixed aligned-and-random" at different points in the wire. Thus, it should be apparent that wide variations in low-level signal transmission and in the resultant "sound" of the wire they're part of are both entirely possible and not at all uncommon.

It's a very similar thing with the iron triad metals. Iron, nickel and cobalt will also take a strong magnetic charge that will affect low-level electron flow and will hold their charge until it either naturally dissipates or they are re-charged to a lesser or the opposite polarity by the signal passing through the wire. This, too, will have a clear and obvious effect on the sound of a wire or cable, and is why some audiophiles will regularly de-magnetize their cables or their entire system by the use of a demagnetizing device like a bulk tape eraser, or by playing a "de-mag" track like the ones found on the XLO/Reference Recordings Test and Burn-In Disc and some other recordings.

There are still other weird things about how the metals used in wires and cables (and in the connectors fitted to them) can affect their "sound," regardless of their total resistance. These include one that is -- even to me -- utterly baffling. I'm out of space for now, but I promise I'll write about all of them next time, in Part 4 of this series.

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