Three Down...?

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AR-cap4.jpgSo you know how it goes; there's the HiFi Crazies on one side, who say that cables DO make a difference; that that difference is clear and obvious; and that anybody who can't (or WON'T) hear it must be either deaf, have his head up his butt (If you put it up far enough, your ears get dirty and you can't hear very well), or must be some kind of damn fool or troll.

And on the other side, there's the damn fools and trolls who say that HiFi Crazies are crazy; that they believe in snake oil, voodoo, and other batsh*t nonsense, and that they should all finally wise-up and accept that, regardless of what they THINK they hear, cables depend not at all on exotic designs and exotic materials; are affected by nothing other than resistance ("R"), capacitance ("C"), inductance ("L"), and characteristic impedance ("ZO"); and ― if they're "properly" designed and built ― don't affect the sound at all.

I've already written two articles ("One Down" and "Two Down") on the "fab four" - the conventional cable parameters, R, C, L, and ZO - and have shown, at least to the satisfaction of some goodly portion of my readers, that, for audio purposes, resistance and characteristic impedance are either of little consequence, are easily dealt with, or are utterly irrelevant. Capacitance, though, is a different matter, entirely: It really IS of great consequence, to cable performance as to so many other areas of electronics, and its nature is such that it might very well provide the perfect proof to those out there who so gleefully brandish pitchforks and cry "Voodoo!" that there's more to how cables work than they've ever imagined or been willing to admit.

For one thing, cables don't just HAVE capacitance; for all practical purposes, they actually ARE capacitors and, depending on their specific design, might actually be as many as several different capacitors in a single deceptively simple-seeming structure.

AR-cap3.jpgTo understand how that's possible, consider this: In the final analysis, all any capacitor is is a system of two conductors (the "plates") separated by a non-conductor (the "dielectric"), such that when a voltage is applied to the plates, it stores or releases energy. When more conductors are added - each separated from the others by a dielectric, and each with its own separate charge source (in short, NOT just more wires of the same circuit) more capacitors will be created, one for each possible combination. (two wires can only make one capacitor [A+B]; three wires can make three capacitors [A+B, A+C, C+B], four wires can make six capacitors [A+B, A+C, A+D, B+C, B+D, D+C], and so on, with the perfect three-wire example being a two-conductor shielded cable, which really DOES [Go ahead and COUNT 'em] have all three capacitors present and even has the possibility of a fourth one that I may touch on in some future article.

In the most basic complete cable, just two conductors ― one "hot" and one "ground" ― allow the completion of a circuit and, because we know that's true, we can be certain that the conductors never touch, either each other or any common conductor anywhere along their length. (If they did, a "short" in the circuit would prevent the passage of signal.) Not touching means that there's a non-conductive (or at least effectively non-conductive) distance between them, and that distance ― whether or not there's anything in it ― acts, in every case, as a dielectric to (voila!) create a capacitor!

If that cable just mentioned were out in space, in a satellite, for example, or on the outside of the International Space Station, and if its wires were just two bare wires, the dielectric - the stuff occupying the space between them - would be "hard" vacuum and would, as the dielectric material LEAST able to store energy, be said to have a dielectric constant of "1". Any other material would have a greater energy storage capacity for any identical volume of material and its dielectric constant would be the number indicating how much greater that capacity was. A material that could store 4.7 times as much energy as an equal volume of vacuum would, for example, have a dielectric constant (commonly written as the letter "K") of 4.7.

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