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Old 23rd January 2013, 12:08 PM   #33391
gk7 is offline gk7
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Originally Posted by PMA View Post
... It is another card than yesterday, for it performs better in CCIF2 test.
May I ask which make this soundcard is, or more general with which soundcards
do you have good experiencies (when used for measurements) ?
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Old 23rd January 2013, 01:22 PM   #33392
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Originally Posted by gpapag View Post
Thanks for going into the trouble jn
Still in the dark but it’s not because of you.

http://www.google.com/url?sa=t&rct=j...41248874,d.dmg

Pay specific attention to the textual content within the first paragraph. (or, you could work the equations, your choice. Conceptually, eq 4 and 5 say it all, and note the text immediately following eq 11. Note also that the closed form solution for the resistor scaling ratio now has a form which includes lambda to the fourth power, never negative.

For a tubular resistor, the film conductivity will weigh heavily..high resistivity material will have a lower J2, whereas low resistivity will have a more significant j2.

Note that this is bog standard stuff for high speed switchmode supply coil design. High current slew rates directly impact conductor dissipation even if the switchmode supply is constant frequency. High current slews also tend to blow up 3 and 4 inch diameter hockey puck scr's if the external circuit allows too high a dI/dt, even with spiralling gate finger geometries. It blows them up underneath the gate wire pad.

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Originally Posted by RNMarsh View Post
This is also shown in text books, Like this one from my library - Elements of Engineering Electromagnetics by N.N. Rao. Though the effect isnt as straight line as in this theory.
Your first figure is electrostatic potential, not magnetic field density. Static B field in a cylindrical conductor is exactly straight line, zero at center max at surface. Once time varying is introduced, the straight line will be depressed at center, reinforced at surface, and certainly not straight..

Oh, while I'm at it. The current density of the core of a coax goes to the surface, we call that skin effect, think of it as the current redistributing to lower inductance, that being the 15 nH per foot inductance consistent with a cylindrical conductor. The current density of the shield goes to the inner surface...that is NOT skin effect, it is proximity effect as a consequence of the magfield being generated by the core wire. When asymmetrical core to shield occurs, this proximity effect will force the shield current to redistribute such that magfield outside the shield goes back to zero, and the current takes the path of lowest inductance (reactance).


jn
ps..excellent..I wasn't sure if the link would retain integrity. Let me know if the link doesn't work..here's the title..

SERBIAN JOURNAL OF ELECTRICAL ENGINEERING
Vol. 7, No. 1, May 2010, 13-20
13
A Closed Form Solution for the Proximity
Effect in a Thin Tubular Conductor
Influenced by a Parallel Filament
Dragan Filipović1, Tatijana Dlabač2

Last edited by jneutron; 23rd January 2013 at 01:28 PM.
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Old 23rd January 2013, 01:55 PM   #33393
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Chris, don't let them 'shake you up' for your personal convictions. What works, works.
Measurements can often predict that something will work well, BUT NOT ALWAYS.
For example, as an input stage device, I had tested a third device with similar specs to the other two. It DID NOT sound as good as the two others, so it was put aside. WHY? I don't know, and I don't have to go further to find out, because I have found 'successful' IC chips that sound darn good in the application with a gain of 40.
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Old 23rd January 2013, 02:42 PM   #33394
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Attache is the inverted Fletcher Munson type curve I showed yesterday. I have added another "curve" to it. So what does this represent?
Attached Images
File Type: jpg Inverted Fletcher Munson SP Filter.JPG (76.8 KB, 179 views)
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Old 23rd January 2013, 02:42 PM   #33395
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Old 23rd January 2013, 02:56 PM   #33396
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Quote:
Originally Posted by jneutron
SERBIAN JOURNAL OF ELECTRICAL ENGINEERING
Vol. 7, No. 1, May 2010, 13-20
13
A Closed Form Solution for the Proximity
Effect in a Thin Tubular Conductor
Influenced by a Parallel Filament
Dragan Filipović1, Tatijana Dlabač2
Thanks for finding that. It confirms what I have said all along: that proximity effect depends on frequency, not magnitude. Eq (11) shows that the distribution of currents depends on material properties, geometry, and frequency. Current does not appear.

To clear up one possible confusion: the Fourier series they use is a series in theta (angle around the conductor) not frequency. This of course fits nicely with the original pupose of Fourier theory: solving differential equations in heat conduction. No harmonic generation is implied!!

Another possible confusion (it temporarily confused me!): lambda is not wavelength, but a function of geometry, material properties and frequency given by eq (2).

I would like to thank jn for presenting evidence which disproves his theory. Many people would have quietly buried it.
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Old 23rd January 2013, 03:07 PM   #33397
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Originally Posted by simon7000 View Post
So what does this represent?
My bank account ?
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Old 23rd January 2013, 03:47 PM   #33398
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I would guess that it is the averaged curve of the harmonic components coming from the power supply caps.
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Old 23rd January 2013, 04:02 PM   #33399
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Originally Posted by DF96 View Post
Thanks for finding that. It confirms what I have said all along: that proximity effect depends on frequency, not magnitude. Eq (11) shows that the distribution of currents depends on material properties, geometry, and frequency. Current does not appear.
Actually, that is incorrect. I really expected you to see it, but am not suprised.. Lambda has current embedded, although the authors do not state it..sigma.

The final form for J2 they show as integrated, so they've already assumed a steady state current equivalent. Try looking at the sheet currents on the cylinder with no transport current..just the eddy currents.

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Originally Posted by DF96 View Post
To clear up one possible confusion: the Fourier series they use is a series in theta (angle around the conductor) not frequency.
Certainly a point worth mentioning. I can see others being confused by it.

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Originally Posted by DF96 View Post
Another possible confusion (it temporarily confused me!): lambda is not wavelength, but a function of geometry, material properties and frequency given by eq (2).
And sigma. That being current density.
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Originally Posted by DF96 View Post
I would like to thank jn for presenting evidence which disproves his theory. Many people would have quietly buried it.
While I always work that way, in this case you missed the current magnitude the authors casually forgot to mention embedded in that weird lambda. That is why I mentioned the fourth power of lambda, as current is in there.

jn

Last edited by jneutron; 23rd January 2013 at 04:16 PM.
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Old 23rd January 2013, 04:26 PM   #33400
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Ed Simon says it is a 6dB/octave curve to simulate what a single cap filters.
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