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Re: Hmmmmm...Hi Jon

Posted by Jon Risch (B) on September 25, 2003 at 21:09:01

In Reply to: Hmmmmm...Hi Jon posted by jneutron on September 23, 2003 at 18:24:36:

Doing better thank you, but still not so great overall.

[ The rate of change of current causes internal eddy currents, which force re-distribution of the current density..If strand to strand contact is compromised, those eddy currents will be reduced, and the current will drive FURTHER into the bundle..As if the bulk resistivity of the conductor were reduced. ]

Of course, your statement asimes significant impairment of strabnd to strrand contact, but the real world has it5 sonmewhere in between, with the potential consequenes I point out.

[ Strands weaving in and out of the bundle suffer current redistribution as a result of differing time rate of change magnetic fields seen by the individual conductors...NOT SKIN EFFECTS.... ]

You are saying that strand jumping is going to be initiated by the self-inductance of the wire?
You see, that is the conundrum to me, I have reviewed my notes, reviewed the basic underlying principles of the skin effect and of self-inductance, and come to the tentative conclusion that they are not the same exact thing (they were certainly treated as two diferent effects in school), and that self-inductance effects tend to exist more or less equally throughout the wire, while skin effect is responsible for the current being crowded toward the surface of the conductor.

I could be wrong on this, but I am explaining things as I see them, to my curent level of understanding (translated into laymans terms).

[ OH, by the way, so far everybody I've seen has been using the incorrect equations for skin effect when the conductor approaches the physical size of the skin effect..WHY CAN'T ANYBODY GET THAT RIGHT???? ]

Again perusing my notes, and all available formulae's on the subject, none of them correct for the very small (less than 5 skin depths for a radius) conductors.

[ Which would mean that this sentence::

"Note that at 20 kHz, a 12 ga. wire (diameter of approx. 2.4 mm) etc., etc. ..."

...is totally blown outta the water..as it's 2.6 skin depths is modelled inaccurately by the planar equations you are citing.. ]

Yep. But the maun point is that a larger wire, like teh 12 ga., vs. the much smaller wires, like the 20 ga., will have more driving force behind the strand jumping, and therefore, more potential deleterious effect from any such strand jumping.

I note for the record, that these equations were also used by AH, in an article which yiou proof read, and ostensibly approved and gave yiour blessing to. I never saw one comment along these lines then. I still say yougo out of your way to questuion pro=-cable physics, and deliberately ignore the HUGE amoubnt of questionable science touted by the naysayers. Perhaps it is a true blind spot, and you can not even see you are doing this.

[ As I've explained, poor wire to wire contact causes the current to go deeper into the wire..so that explanation is incorrect...In point of fact, larger wires will have a lower drop in conductance overall than smaller ones to a point, until saturation occurs.. ]

I have never been one to try and relate skin effect issues to HF amplitude losses, which is all your concern about conductance is.

All I have ever said about skin effect (or if you prefer, self-inductance) is that it makes the surface of the wire more critical with regard to platings, finish, etc., as well as providing a potential mechanism for strand jumpingm, and why I think that the larger stranded wires ar going to get into more trouble than the smaller ones.

[ I would recommend not following the audioquest writeup, as it is wrought with incorrect analysis, such as assuming the validity of "classical skin equations" for small wires. ]

Then I would hope that you would also not recommend the Audioholics articles that have the very same skin effect equations in them, and atempt to cite skin depths, hard numbers and draw conclusions from them.

The Audioquest site article has some basic explanation of teh theory of strand jumping, and a nice graphic to help illustrate the situation, and this is why I point folks there, not for the worlds greatest physics lessson.

Come up with a nicely worded explanation/description, a nice graphic, and I will use it from now on.

Jon Risch

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