In Reply to: Re: Resonances in interconnects posted by jneutron on November 9, 2004 at 07:45:43:
Hi John,I agree with your statements.
Skin effect most definitely does not simply occur at higher frequencies, and then suddenly drop to zero at a certain cutoff point. It continues to decrease as frequency decreases, and does not decrease in a linear fashion. You're correct in that 15 nh/ft is not discernable.
Here's a terrific overview of skin effect at audio frequencies, using speaker cable as the example. Very well done, and simple to follow, if you ignore the equations! Reminds me of how much I hated calculus.
http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/skineffect/page2.html
A brief excerpt:
"Figure 3 shows the power loss in the cable as a function of frequency. The solid (blue) line shows the loss when the wire’s internal impedance is taken into account. The broken (red) line shows the loss that would occur if we ignored the internal impedance. Hence the difference between the two shows the results in this case of ‘skin effect’. In principle, the broken line shows what we might expect when using wires of ‘Litz’ construction with a fill factor approaching unity. The solid line shows what we might expect from either a solid wire or a multistranded wire of closely packed thin strands.For the example chosen, at low frequencies the bulk resistance of the copper wire causes a power loss of around 0·008dB. At 10kHz the loss rises to 0·009dB if the internal impedance were absent, and 0·016dB with the internal impedance taken into account. At 25kHz these values rise to 0·012dB and 0·028dB respectively. Hence the change in relative signal level from near-d.c. to 25kHz, with internal effects taken into account is around 0·020dB. This is quite a small change so it is not obvious that it would be noticed in a practical audio system."
I think I'd have to put 0.020 dB loss in the same class as 15 nh/ft.!
Unfortunately, you've made a huge error in judgement by disclosing that temperature also plays a part in skin effect due to changing temperature (outside normal ambient ranges). I can see it coming: a completely new line of audiophile speaker cables and interconnects, superheated to just below the melting point of copper so as to increase resistance in order to reduce skin effect.
Oh, wait...
Clay ;)
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Excellent post... - Fisherdude 08:49:25 11/09/04 (4)
- You guys are outrageous. Thanks. We need a Leno/Letterman forum (nt) - free.ranger 15:55:57 11/09/04 (0)
- Re: Excellent post... - Steve Eddy 09:27:08 11/09/04 (2)
- Re: Excellent post... - jneutron 09:52:08 11/09/04 (1)
- Re: Excellent post... - Steve Eddy 11:29:28 11/09/04 (0)