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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 20th April 2012, 02:20 PM   #22541
jneutron is offline jneutron  United States
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Originally Posted by ThorstenL View Post
Perhaps. Perhaps not. I think it is warranted and I have discussed what constitutes in my eyes "organised scientific crime" on the side of this group, sufficient to warrant the appellation.
There is plenty of blame on both sides. I just happen to have a lower tolerance threshold for groups outside the law.
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Originally Posted by ThorstenL View Post
Let me put it as delicate as I can. As long as you do not protest when some call others snake oil merchants or even fraudsters or suggest that they are delusional, in public. And as long as you do not do so, in these cases insist people should stick discussing facts, I feel you lack the moral power to demand it when the shoe is on the other foot.
So your expectation is that everybody must be the content police, and that all who do not knee-jerk-react to such sillyness have no moral fortitude.

First, I have objected in the past to such descriptions on both sides. Obviously you are either unfamiliar with that or I've not done it enough to satisfy you. Since I do not live to satisfy you in this regard, I won't worry about it.

Second, I have defended parties on both sides of the fictional fence you choose to retain. Since you choose to retain this fence, that is your albatross, not mine.

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Originally Posted by ThorstenL View Post
Shall we agree that I will stick with facts and subjects (which I would by far prefer to wasting and lay off the name calling well, lets say about 48 Hours after the last use of "Snake Oil Merchant" or "Fraudster" or "Delusion" (or equivalent characterisations) on these boards, something you surely must agree is a fair request?
No, it is not a fair request. Since it would never come to pass that everybody exhibited restraint in this regard, your request (as you well know) is doomed to failure, and you would wish to claim a moral victory as a result...(see, I told ya so)...that kinda thing.

I would love it, but I am a realist.

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Originally Posted by ThorstenL View Post
They have been told enough times that they MUST KNOW this.
Telling them their wrong is insufficient. Telling then they are wrong a thousand times is still insufficient.

You need to detail scientifically WHY they are wrong, How they are wrong, WHAT they are wrong about, and provide a scientific model which explains in horrid equational and physics detail what is going on, and predictions that will arise from that model that are testable.

The ridiculously foolish phrase " I trust my ears even though I can't prove it", is an abysmal affront to intelligent and educated people. Telling them (audiophiles and scientists alike) they are wrong is foolish.

Detail why they are wrong and how to fix it. That has been my approach all along. Just ask about IC's, PC's, EMC, localization theory..that kinda goop. If any of your so called "scientists (or strawman scientists)" feels the desire to question the fact that IC's and PC's can indeed affect the sound of a system, I'd be more than happy to trash their assertions using derivations of Maxwell's theory, EMC theory, practical application and test, geometric considerations of trapped magnetic flux, amp chassis current control, whatever.. THAT is how you get your message across...detail in THEIR language exactly why they are wrong..reactions consistent with an 8 year old isn't working.

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Originally Posted by ThorstenL View Post
Despite knowing this they continue to promote their methods and they continue to present their results as the scientific gold standard.
Again, with this "OH YAH, well same to you" schtick. It doesn't work..

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Originally Posted by ThorstenL View Post
Do we need to go on?
Go on??? All I see is you beating your head against a wall. When will you realize it isn't working?

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Originally Posted by ThorstenL View Post
If in doubt I always go with funny...
Ciao T
Always good advice.

Look. You and I have much in common, and agree on quite a bit. You are foundering about using a people skills technique that hasn't worked for children for decades. And you misrepresent scientists... your message ain't working. In fact, it is counterproductive.

Please consider changing your techniques.

cheers, j

Last edited by jneutron; 20th April 2012 at 02:26 PM. Reason: wow, that cut and paste lost all the brackets..weird
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Old 20th April 2012, 02:21 PM   #22542
vacuphile is offline vacuphile  Netherlands
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Originally Posted by jneutron View Post
A material with a relative permeability greater than 1 will "attract" the flux lines in the area, and will change the reluctance of the path the flux lines take. (I am attempting to keep this simple, but may not succeed well, sorry).

Any cylindrical conductor carrying low frequency current will store magnetic energy within the conductor via it's internal inductance, roughly 15 nH per foot times the magnetic permeability of the conductor. If you use a magnetic material like the iron I use at work with permeability around 3000, the internal inductance will be 45 uH per foot per wire. Typically, I would expect a mu of 100 to 1000 for magnetic materials, so figure 150 nH per foot to 1.5 uH per foot.

Another problem is linearity of the material. Most typical magnetic materials also have a hysteresis curve, a non linear relationship between B and H (magnetic stimulus and response). For example, if you have a magnetic wire which stores energy via inductance, and you put it into a magnetic field which is also time varying, you will modulate the wire inductance. Using the previously exampled wire, at low signal levels, I'd expect 45 uH per foot...at 1 ampere, that stores 22.5 microjoules. If I subject it to a magnetic field that causes it's permeability to halve, the wire will give up 11.25 microjoules due to permeability drop.

If you use a magnetic plate to separate a low signal high sensitivity area from a high magnetic field area, and the high magnetic field modulates the wall permeability, the result can be a mixing of signals on the low level side.

Care must always be taken when materials which exhibit non linearities as a result of stimulus, are put into an environment which allows that stimulus.

j
I have been thinking a bit about this and I hope it would not be OT to come back to this with some technical questions, from the practical perspective of a guy soldering stuff together. But first: upon rereading I come to the conclusion that I might not understand the calculations as provided. If I multiply the 15nH internal inductance with the permeability figures you mentioned, I constistently get to results 10 times higher than the ones you provide (i.e., with a mu of 100 it would be 1.5uH and not the 150 nH you mention). Anyways, this is not the real question I have, which are just practical.

1) I have an assortment of very nice NGO t.t.h. caps. When I use them, I always take care to minimize path length and area within the path loop to keep the self resonance frequency as high as possible. Now, these rather expensive parts all have magnetic leads, which I just learned increase their inductance. Probably not a good thing, but to what extent is it relevant in real life?

2) some of the interconnect cable I use is the tan coloured Belden PTFE coax, which has very good screening and is pretty tough as long as you don't kink it. However, the inside cable is silver clad copper on steel. Does this imply that the inductance would be let's say a hundred times more than that of the same cable with a non-magnetic core? Is it a component to avoid for audio?

Vac
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Old 20th April 2012, 02:28 PM   #22543
PMA is offline PMA  Europe
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John Curl's Blowtorch preamplifier part II
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Originally Posted by vacuphile View Post
I.

1) I have an assortment of very nice NGO t.t.h. caps. When I use them, I always take care to minimize path length and area within the path loop to keep the self resonance frequency as high as possible. Now, these rather expensive parts all have magnetic leads, which I just learned increase their inductance. Probably not a good thing, but to what extent is it relevant in real life?

2) some of the interconnect cable I use is the tan coloured Belden PTFE coax, which has very good screening and is pretty tough as long as you don't kink it. However, the inside cable is silver clad copper on steel. Does this imply that the inductance would be let's say a hundred times more than that of the same cable with a non-magnetic core? Is it a component to avoid for audio?

Vac
ad1) you can quite easily measure the elcap inductance.

ad2) no, the inductance of the conductor would not be 100x higher.

A lot of fairy tales here.
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Old 20th April 2012, 02:42 PM   #22544
jneutron is offline jneutron  United States
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Originally Posted by vacuphile View Post
I have been thinking a bit about this and I hope it would not be OT to come back to this with some technical questions, from the practical perspective of a guy soldering stuff together. But first: upon rereading I come to the conclusion that I might not understand the calculations as provided. If I multiply the 15nH internal inductance with the permeability figures you mentioned, I constistently get to results 10 times higher than the ones you provide (i.e., with a mu of 100 it would be 1.5uH and not the 150 nH you mention).
Clearly my math skills need woik...your right of course...my error..
Quote:
Originally Posted by vacuphile View Post
1) I have an assortment of very nice NGO t.t.h. caps. When I use them, I always take care to minimize path length and area within the path loop to keep the self resonance frequency as high as possible. Now, these rather expensive parts all have magnetic leads, which I just learned increase their inductance. Probably not a good thing, but to what extent is it relevant in real life?
Depends on the frequency. I'm betting that the self resonance is well beyound the frequency where the skin depth causes the current to ignore the center of the wires. For rf, probably not relevant..
Quote:
Originally Posted by vacuphile View Post
2) some of the interconnect cable I use is the tan coloured Belden PTFE coax, which has very good screening and is pretty tough as long as you don't kink it. However, the inside cable is silver clad copper on steel. Does this imply that the inductance would be let's say a hundred times more than that of the same cable with a non-magnetic core? Is it a component to avoid for audio?

Vac
It most likely will have higher inductance at low frequencies. As to audibility, I cannot say..others here may be able to answer. You could experiment yourself, given it doesn't cost much. Me, I wouldn't worry, but that's just me.


The low frequency inductance of that coax is the sum of the inductance within the center conductor and the inductance between the center wire and the shield. As the frequency goes up, skin effect will cause the wire's current to move to the outer surface of the core wire. As the current skins more and more, the 15nH per foot time mu number will go down, getting close to zero at rf. Leaving only the inductance due to the spacing between the core and the shield.

Belen ignores the core wire internal inductance and gives only the core to shield number because that is what determines the characteristic impedance of the cable at RF. I've found over the years that Belden at least, has been providing fewer and fewer inductance per foot numbers in the wire product catalog, and I suspect it's because users like us would measure the inductance typically at 100 or 120 hz. That will give a higher inductance number that the rf one, so the user would calculate an incorrect cable impedance as a result.

Sorry bout the rant...thanks for correcting my math...I ran out of fingers...

j

ps..Sy, I hilited the answer to your concen in the next post.

Last edited by jneutron; 20th April 2012 at 02:54 PM.
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Old 20th April 2012, 02:42 PM   #22545
SY is offline SY  United States
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John Curl's Blowtorch preamplifier part II
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Originally Posted by PMA View Post

ad2) no, the inductance of the conductor would not be 100x higher.
Indeed, coax stubbornly continues to work at VHF.
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Old 20th April 2012, 02:49 PM   #22546
PMA is offline PMA  Europe
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John Curl's Blowtorch preamplifier part II
Someone has probably confused magnetic induction (B) with inductance (L)

B, of course, depends on permeability.
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Old 20th April 2012, 02:51 PM   #22547
jneutron is offline jneutron  United States
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Originally Posted by PMA View Post
ad2) no, the inductance of the conductor would not be 100x higher.

A lot of fairy tales here.
That is quite incorrect, caveat being..the core inductance is a smaller part of the overall inductance, so the full cable inductance does not go up two orders of magnitude.

At low frequency, the internal core wire inductance will be exactly mu times 15 nH per foot.

The actual low frequency impedance is Z = sqr[(L internal + L between)/C]

At high frequency, where cable Z is measured typically, the internal core wire inductance is essentially zero., so the equation becomes:

Z = sqr(L between/C)

If you wish to discuss the equations, speak up, I'll explain the equations more.

But don't expect me to do the math right...I'd have to take my shoes off above ten..

j
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Old 20th April 2012, 02:55 PM   #22548
PMA is offline PMA  Europe
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John Curl's Blowtorch preamplifier part II
Hi John, thanks, I am familiar with Maxwell. Just wanted to explain there is no simple multiplicative relation.
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Old 20th April 2012, 02:59 PM   #22549
jneutron is offline jneutron  United States
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Originally Posted by PMA View Post
Someone has probably confused magnetic induction (B) with inductance (L)

B, of course, depends on permeability.
Please review the math. I have not confused B and H.

The inductance internal to a cylindrical conductor is L = (muzero*murelative)/8 pi.

The inductance between the core wire and shield is L = (muzero/2 pi) times ln (b/a).. Note I've assumed the insulation mu relative is 1.

j
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Old 20th April 2012, 03:00 PM   #22550
jneutron is offline jneutron  United States
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Hi John, thanks, I am familiar with Maxwell. Just wanted to explain there is no simple multiplicative relation.
There is. The magnetic field within a cylindrical conductor is a linear function of radius. It is zero at center, maximum at surface, then drops as 1/r outside the conductor until the shield, where it becomes zero due to opposing field of the shield.

I believe we are speaking across each other. The core wire inductance does indeed scale with core mu, but the overall coax inductance doesn't go up like that because of the ln(b/a) term.

j

Last edited by jneutron; 20th April 2012 at 03:03 PM.
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