Skin Effect: effects are negligible

3db

3db

Audioholic Slumlord
<font color='#000000'>As an electrical engineer, I have studied tramsmission line theory and I noticed the author didn't include distributive capacitance which is effected by  high frequency. The capacitance can be modelled as being connected in parallel to the ideal conductor so that as the frequency goes up, the impedance of the capacitor drops causing the voltage across the ideal conductors to drop.   Another hole I see in his description is the general terms of low and high frequency.
Skin effect becomes noticeable  with frequencies above 10 Mhz. Skin effect has no bearing at all in the audio world as the wavelengths in this frequency range are much to long to excite both the distributed capacitance and lumped inductances.

Bottom line is this, if you buy an audio cable that costs $$$$$ becasue it says on the package that skin effect is almost non existanct, than you are getting scammed.

Links to articles relating to this discussion:


Cable Face Off

Calculating Cable Inductance

[since 3dB began this discussion, I added the links to these articles to his original post, and to the front page under the daily dose. &nbsp;Many thanks to 3dB for begining this discussion that I should have opened prior to posting the article &nbsp;
]</font>
 
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G

Guest

Guest
<font color='#000000'>&quot;&quot;as the frequency goes up, the impedance of the capacitor drops&quot;&quot;

Yes..but the transmission line model includes both cap and inductance, so is accurate over a wide range of frequencies..

&quot;&quot;Skin effect becomes noticeable &nbsp;with frequencies above 10 Mhz&quot;&quot;

The power companies have to worry about skin effect at 60 Hz. &nbsp;They tend to limit the maximum conductor size to less than two inch wall thickness, as anything further than that from the surface adds weight while carrying little current..

&quot;Skin effect has no bearing at all in the audio world as the wavelengths in this frequency range are much to long to excite both the distributed capacitance and lumped inductances.&quot;&quot;

I'm not quite sure what you meant here..the wavelengths are too long to consider standard reflection coefficients and other standard t-line issues.

But, as can be seen in the recent cable face off article here, the skin effect is measureable, and begins to impact the inductive storage of the wires. One must be aware of the actual frequencies where that occurs, though..

The internal field collapse that occurs when an audio signal changes from lf to high slew is what still puzzles me, I'm not sure how the energy difference presents either as an amplitude modulation, or as a phase shift....So, at least for me, skin effect is not entirely a dead issue, and I've more work to be done..

From the detailed measurements Gene presented, skin effect has not been shown as a smoking gun for audio, and I've no proof otherwise..yet.

Cheers, John</font>
 
3db

3db

Audioholic Slumlord
<font color='#000000'><table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>
Guest : &quot;&quot;as the frequency goes up, the impedance of the capacitor drops&quot;&quot;

Yes..but the transmission line model includes both cap and inductance, so is accurate over a wide range of frequencies..

&quot;&quot;Skin effect becomes noticeable &nbsp;with frequencies above 10 Mhz&quot;&quot;

The power companies have to worry about skin effect at 60 Hz. &nbsp;They tend to limit the maximum conductor size to less than two inch wall thickness, as anything further than that from the surface adds weight while carrying little current..

&quot;Skin effect has no bearing at all in the audio world as the wavelengths in this frequency range are much to long to excite both the distributed capacitance and lumped inductances.&quot;&quot;

I'm not quite sure what you meant here..the wavelengths are too long to consider standard reflection coefficients and other standard t-line issues.

But, as can be seen in the recent cable face off article here, the skin effect is measureable, and begins to impact the inductive storage of the wires. One must be aware of the actual frequencies where that occurs, though..

The internal field collapse that occurs when an audio signal changes from lf to high slew is what still puzzles me, I'm not sure how the energy difference presents either as an amplitude modulation, or as a phase shift....So, at least for me, skin effect is not entirely a dead issue, and I've more work to be done..

From the detailed measurements Gene presented, skin effect has not been shown as a smoking gun for audio, and I've no proof otherwise..yet.

Cheers, John
The power companies have to worry about skin effect at 60 Hz. &nbsp;They tend to limit the maximum conductor size to less than two inch wall thickness, as anything further than that from the surface adds weight while carrying little current..

Agreed. But the &nbsp;&quot;average&quot; cable length run of speaker wire is negligible compared to that of hydro cable.


I'm not quite sure what you meant here..the wavelengths are too long to consider standard reflection coefficients and other standard t-line issues.

Yes, thats what I mean


But, as can be seen in the recent cable face off article here, the skin effect is measureable, and begins to impact the inductive storage of the wires. One must be aware of the actual frequencies where that occurs, though..

Everything (well almost everything) can be quantified thru models and measured but the question is, do they make an audiable difference. I&quot;m inclined to think no and is the &nbsp; reason that I posted this. &nbsp;Yes, differences can &nbsp;be measured but can we has humans pickup these subtle differences? &nbsp;


</font>
 
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gene

gene

Audioholics Master Chief
Administrator
<font color='#000000'>Hi 3dB;

I appreciate your feedback. &nbsp;I think you missed the points of my articles. &nbsp;In many places I explicitely state that skin effect is a non issue for audio frequencies, though it is barely measurable at 20kHz and starts being more noticeable above 50kHz. &nbsp;
SKin effect is responsible for increased Rs and decreases Ls (minimized internal inductance at very high F) as can bee seen here:

Calculating Cable Inductance

Transmission line effects for audio frequencies dealing with the cable lengths for typical audio applications is also a non issue. &nbsp;However as John points out, it becomes an issue for power due to the very long runs.


As for collapsing fields of audio affected by Skin, you got me, I will leave that for John to pursue as I don't personally see or agree that it can have an impact. &nbsp;Though given Johns background and expertise, if anyone can prove or disprove it, it will be him or his colleagues as the place he works contains some of the top scientists in the country.</font>
 
3db

3db

Audioholic Slumlord
<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>
gene : <font color='#000000'>Hi 3dB;

I appreciate your feedback. &nbsp;I think you missed the points of my articles. &nbsp;In many places I explicitely state that skin effect is a non issue for audio frequencies, though it is barely measurable at 20kHz and starts being more noticeable above 50kHz. &nbsp;
SKin effect is responsible for increased Rs and decreases Ls (minimized internal inductance at very high F) as can bee seen here:

Calculating Cable Inductance

Transmission line effects for audio frequencies dealing with the cable lengths for typical audio applications is also a non issue. &nbsp;However as John points out, it becomes an issue for power due to the very long runs.


As for collapsing fields of audio affected by Skin, you got me, I will leave that for John to pursue as I don't personally see or agree that it can have an impact. &nbsp;Though given Johns background and expertise, if anyone can prove or disprove it, it will be him or his colleagues as the place he works contains some of the top scientists in the country.</font>
<font color='#000000'>Hello Gene

I guess I did miss your point about the effects of skin effect being negligible &nbsp;in the audio realm. And as John pointed out, &nbsp;the effects can be measured. I was trying to point &nbsp;out (rather poorly) the &quot;practical effects&quot; (practical meaning audibly percertive) &nbsp;vs &nbsp;the theoretical effects.

But why wasn't the affects of distributive capacitance &nbsp;included in this model?</font>
 
G

Guest

Guest
<font color='#000000'>&quot;&quot;as the place he works contains some of the top scientists in the country.&quot;&quot;Gene

Yes, but a lot of them wear shorts and sandels, no socks, and wife beater t-shirts, while climbing over 29 inch snow drifts...

The two inch power company thing is more for cost, why pay for more copper that doesn't see the current. &nbsp;But, it really isn't a length thing.

&quot;&quot;Yes, differences can &nbsp;be measured but can we has humans pickup these subtle differences?&quot;&quot;3dB

Good question...I've no answer..

&quot;&quot;Everything (well almost everything) can be quantified thru models &quot;&quot;3db

The inductive collapse/slew rate dependent effect I &quot;rant&quot; about hasn't been modelled, to the best of my knowledge..So I don't know how to quantify it yet..

But our profession was built on being able to quantify, model, predict, and use...as you state..

Cheers, John</font>
 
gene

gene

Audioholics Master Chief
Administrator
<font color='#000000'>3dB;

I kept my modeling to simple lumped paramaters given the frequencies we were dealing with and made no attempt to do any transmission line or distributed modeling. &nbsp;Again, we are dealing with audio. &nbsp;I only extended my measurements past 100kHz to demonstrate drastic changes in Rs and Ls as a result of skin effect. &nbsp;

I am working with another audio guru named Rod Elliot on an article to study the RF implications of high C cables on amplifiers with high unity gain crossing to show how adding a zobel at the speaker side can reduce and/or eliminate this potential problem. &nbsp;Stay tuned....

so much to do, so little time. &nbsp;If I could only turn this website into my day job, than I will have 40+ more hrs/week of pure fun

</font>
 
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