John Curl's Blowtorch preamplifier part II - Page 3054 - diyAudio
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Old 30th November 2012, 08:08 PM   #30531
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That's OK esperado, if you cannot understand my explanation, then I can't help you.
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Old 30th November 2012, 08:11 PM   #30532
RNMarsh is offline RNMarsh  United States
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Another practice to avoid 60Hz ground loops while you still have rfi removed --

You can use a cable with double shields (braid/foil) which are insulated from each other; ground one shield at source and other shield at load. You can increase the C between the two with addded external cap between shields. The Z is high at 60Hz and low at RF. center would be twisted pair for audio.

If you use triax cable, you can have the audio on the two shields only and not use the center at all... this keeps the highest flux density in the middle where L is highest, out of the audio path. Then use individual parallel wires spiral wound at 90 degress to each other for the tube conductors (shields) to kill L there (Mogami). The outer (3rd) shield does the rfi shielding and gets grounded at one end (c at other end for rfi bypass, if cable C isnt high enough). Thx-RNM

Last edited by RNMarsh; 30th November 2012 at 08:38 PM.
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Old 30th November 2012, 08:15 PM   #30533
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Quote:
Originally Posted by Esperado View Post
Like a cat6 network cable ?
For cancellation of external fields, yes. The twist does wonders.

But I was speaking about an overall shield.

As DF96 mentioned, not being truly concentric means that currents will not fully cancel the field outside the shield, and at any one spot, external magnetic fields can act on the core wire slightly different than the shield. But twisted, they'll tend to integrate out.

Cat 6 is not star, nor napoleonic. More like Absolute..with 2 olives rather than 3.

jn
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Old 30th November 2012, 08:25 PM   #30534
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Originally Posted by RNMarsh View Post
If you use triax cable, you can have the audio on the two shields only and not use the center at all... this keeps the highest flux density in the middle where L is highest, out of the audio path.
Using both shields constrains the magnetic field of the audio signal to the space between the shields. There will be no magnetic field inside the inner shield, nor outside the outer one.

You've eliminated the 15 nH per foot component of internal inductance of the core wire by using a shield as core. By doing so, it will now have an internal inductance of 15nH times shield thickness/shield circumference. If the shield has 100 individual wires at 100% coverage, that would mean approximately 150 pH per foot inductance for the inner shield.

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Then use individual parallel wires spiral wound at 90 degress to each other for the tube conductors (shields) to kill L there (Mogami). The outer (3rd) shield does the rfi shielding and gets grounded at one end (c at other end for rfi bypass, if cable C isnt high enough). Thx-RNM
I've no idea what you just said. Mogami says that? Link?

jn
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Old 30th November 2012, 08:34 PM   #30535
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by jneutron View Post
Using both shields constrains the magnetic field of the audio signal to the space between the shields. There will be no magnetic field inside the inner shield, nor outside the outer one.

You've eliminated the 15 nH per foot component of internal inductance of the core wire by using a shield as core. By doing so, it will now have an internal inductance of 15nH times shield thickness/shield circumference. If the shield has 100 individual wires at 100% coverage, that would mean approximately 150 pH per foot inductance for the inner shield.


I've no idea what you just said. Mogami says that? Link?

jn
I describe how to make shield/conductor which will over-come what you just said would happen with typically made shields. Nil L from shields. Mogami (Japan) did it this way, also. [reread the part about 90 degrees to each other. Signal on each wire of opposite polarity traveling at 90 degrees to each other.] But with triax configuration that I suggest using is a variation for 60hz ground breaking/sheilding. can apply to quad config as well. Thx-RNMarsh

Last edited by RNMarsh; 30th November 2012 at 08:49 PM.
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Old 30th November 2012, 08:35 PM   #30536
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My ex-wife was always efficient, even when she divorced me. Her major saying was, "Let's face the problems the next day when they come, one by one". And I have to admit, it was a good strategy, to deal with the major problems. However, it is the very long and inefficient way to optimize the system as the whole, optimizing sub-systems, but it is the one good algorithm to go, especially in our modern computer era of 0/1 digital reality.
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Old 30th November 2012, 08:36 PM   #30537
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Originally Posted by Esperado View Post
Fas42, on my point of view, math is NOT esoteric. "Sound of cables" is.
Cambridge dictionary: esoteric - very unusual; understood or liked by only a small number of people, especially those with special knowledge.

So far the discussion of "understood" or "accepted in the context of audio" cable behaviours over the last day or so has fitted under that umbrella, I believe. Haven't had time to digest the content of that period, but every bone in my body says the the "weirdo" stuff, like triboelectric and microphonic, gets on board, is attending the party, also. And that will be harder to understand, and explain.

Put it this way. Numerous times the SQ of my system has dropped, and I scatch my head, trying to work out what's gone wrong. Finally, I find something that fits into the weirdo category of causes, and voila, sound is fixed. You only have to do that, say, a few dozen times before slowly but surely the penny starts to drop ...

Frank
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Old 30th November 2012, 08:40 PM   #30538
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Originally Posted by RNMarsh View Post
It describes how to make shield/conductor which will over-come what you just said would happen with typically made shields. Nil L from shields. Mogami (Japan) did it this way, also. But not with triax configuration that I suggest using. Only twin-axial config. Thx-RNMarsh
From what you wrote, I can't see how inductance is cancelled. Do you have a link that better describes the theory? Thanks.

edit: I've re-read your words multiple times, I've still no idea.

As an aside, for a coax, there is no contribution of inductance for the outer shield anyway. The inductance of the coax is a direct function of the spacing between inner conductor and outer shield. Two wires at 90 degrees cannot cancel magnetic fields, the fields will add as a vector. That is why I am confused.

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My ex-wife was always efficient, even when she divorced me. Her major saying was, "Let's face the problems the next day when they come, one by one". And I have to admit, it was a good strategy, to deal with the major problems. However, it is the very long and inefficient way to optimize the system as the whole, optimizing sub-systems, but it is the one good algorithm to go, especially in our modern computer era of 0/1 digital reality.
Um, are you on the right thread?

jn

Last edited by jneutron; 30th November 2012 at 08:48 PM.
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Old 30th November 2012, 08:49 PM   #30539
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Originally Posted by jneutron View Post
But I was speaking about an overall shield.
Cat 6 SSTP
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Last edited by Esperado; 30th November 2012 at 09:13 PM.
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Old 30th November 2012, 08:55 PM   #30540
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Originally Posted by fas42 View Post
Cambridge dictionary: esoteric - very unusual; understood or liked by only a small number of people, especially those with special knowledge.
Forgive my poor English, in French, the same word carry a notion of 'occultism', magic.
I don't understand why people, here, don't speak French like everybody.
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