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Old 22nd January 2013, 04:24 PM   #33321
PMA is offline PMA  Europe
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I might open another item and ask for real results again. The power supplies, regulated power supplies. I would be very interested to see both low frequency and HF FFT spectra measured at the rails of different regulated power supply designs. This would prove or demystify claims about efficiency of different designs regarding both noise in audio band and suppression of high and very high frequencies.
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Old 22nd January 2013, 04:27 PM   #33322
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Originally Posted by RNMarsh View Post
I agree also with the inductance vs freq....goes to path of least resistance... towards the surface of the conductor where the L is lowest.
Do not agree on your explaination regarding the fields. Perhaps just a different view of the same thing? -RNM
http://www.phys.uri.edu/~gerhard/PHY204/tsl243.pdf

jn

ps..Becker had the same text, I was actually looking for a drawing online which shows it. For now, the calculations from some code I wrote. Top is the wire, bottom is B. Note it rises linearly from wire center to wire surface, then as 1/R out of the conductor.

pps. Found some with supporting pictures, all ya hafta do is google "magnetic field inside wire", the nj ppt link is an AP physics course for high school. Page 8 has the equations, 9 has the drawing. I won't copy the drawing and paste it here, but it basically duplicates the drawing I posted.
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Old 22nd January 2013, 04:30 PM   #33323
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Originally Posted by jneutron View Post
WOW!
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Old 22nd January 2013, 04:45 PM   #33324
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I think I see part of what you are talking about but still don't recognize most of what you are asserting - rather than citing sources - what's so hard about pointing us to the names, equations?

Hall effect is considered the beginning of quantum effects - not classical EM, which describes purely linear conductors, infinitesimally divisible charges, currents - ultimately put together, described by Maxwell's equations

at any point where DF6, I or others talked about Classical EM, Maxwell's equations, linear conductors you could have said whether the effect you are describing is a quantum effect

I suppose we could argue over whether “ordinary magnetoresistance” is purely classical

Magnetoresistance - Wikipedia, the free encyclopedia

if we're getting close to whatever effect you still haven't referenced - we can look at the equations, put some numbers on carrier mobility in metals, resistive films, under the influence of magnetic fields that may be encountered in home audio on boards already designed to avoid inductive coupling to nonlinear PS rail, Class AB stage currents

for a start the field at the center of a 1 cm loop carrying 1 Adc is ~ 6 uT,

single digit Amps of current in reasonably sized Cu wires gives average electron velocity <mm/s

the (way) sub ppm level effects of “ordinary magnetoresistance” for ordinary circuit design seems easy to miss in the much larger % level effects of linear partial mutual inductance proximity effect
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Old 22nd January 2013, 04:54 PM   #33325
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Originally Posted by john curl View Post
Please give it a break, PMA. 7th harmonic is STILL very important.
What is the level where it is no more important ?
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Old 22nd January 2013, 04:57 PM   #33326
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I think about -110dB down at 5KHz. That is what I measure for.
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Old 22nd January 2013, 05:01 PM   #33327
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I think I see part of what you are talking about but still don't recognize most of what you are asserting - rather than citing sources - what's so hard about pointing us to the names, equations?
Skin...

File:Skineffect reason.svg - Wikipedia, the free encyclopedia

note the explanation...

The current redistributes because the eddies are opposite in the center, they cancel there but reinforce on the surface.

Now, consider an external source and a cylindrical sheet of current such as a metal film resistor. the eddy currents will cause a redistribution on the cylindrical sheet. Since the current on the sheet is what is causeing the external magnetic field, the current tries to redistribute as close to the external wire as it can because it's the path of least reactance.

With a copper conductor, the variation in resistance is not very large. With a cylindrical sheet of resistive material, it is not.

It's not a quantum effect..

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Old 22nd January 2013, 05:13 PM   #33328
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Thanks very much to PMA for the excellent comparative measurements and for the striking conclusion, that despite these tiny numbers an ordering of sound qualities is still possible.

One possible explanation is that the devices' intrinic (pre-feedback) linearity is important, but not ordinarily measured. Another is that the devices' monotonicity, or lack thereof, of linearity with signal level is important, but not ordinarily measured. Crossover distortion is one example of a well understood imperfection that is poorly tested for conventionally.

Thanks again,
Chris
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Old 22nd January 2013, 05:19 PM   #33329
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Thanks Chris, for bringing that up. I usually estimate what something will sound like by its open loop transfer function as well, but I did not want to incur further criticism by bringing that up here.
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Old 22nd January 2013, 05:23 PM   #33330
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For the record, the IC op amp that I use in place of the AD797 has to amplify over 30 dB or 40 times and has a final load of 800 ohms above 2KHz. Not so easy as some might guess.
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