Agreed. But sometimes connectors superficially look like clean metal, but are still noisy. Sometimes people may look for explanations for what they think they are seeing that would seem to make sense to them. And they may be overconfident in their beliefs about cause and effect, as people often are. Confirmation bias occurs in all humans. They look for evidence that tends to confirm what they already believe and discount or ignore evidence to the contrary. Even if they are in the business of selling upscale connectors, that doesn't necessarily make them lying hucksters, although it is a possibility.
Absolutely.
Why mention length at all as in typical? It is not an issue at all for the audio band and frequency response. For long lengths, skinning can alter settling time, but that effect is so low, it's unimportant. Ed might have to worry about it if for kilofoot runs, but nobody else.
Wow, some real errors and oversights there, I expect better from Steve.
As we all know, skinning causes the current to concentrate on the surface. As a consequence, two things change.
1. Conductor effective resistance. At high frequencies, the effective R continues to increase, yet he considers the HF characteristic impedance without the steadily increasing R. He even states the R is only an issue for LF..
2. Conductor inductance decrease. At high frequencies, when the current is confined to the surface, there is NO internal inductance. As a consequence, the actual characteristic impedance will drop as the current goes from uniform DC 15nh/ft, to zero nh/ft at very high frequency. That term is neglected in the graphical representation, as well as the discussion.
Granted, the venue is not a very technical one, but one must be careful when citing such a glossy overview as justification for a technical position.
Actually, twisted pairs do indeed have an external magnetic field. An outer shield cannot stop it. The field dropoff will be on the order of about 5 times the conductor spacing. If a shielded wire like a mike cable is lying within conduit or tray, or even wrapped around a metallic structure, there will be eddy losses as a consequence.
What is important however, is how much loss. For low level, the line impedance is sufficiently high that there is little magnetic field. For speaker level, the losses are inconsequential.
Whoa. Where did 8 Khz come from?? That certainly does not happen.
Do you have any cites which say 8Khz?? I'd love to find out who claimed that.
Now, finally we're getting somewhere.
When a contact is so bad that a very small point is carrying all the current, there will be a non-linearity caused by the current density at the point and the spreading to the base materials. This is a common effect that occurred in the semiconductor wafer test industry. When a probe station is setup for die testing, the probe tip will wipe on the aluminum pad of the semiconductor to establish a good contact. However, it is still a very small point contact. When I push an ampere into the point contact, there will be a non-linear resistance at that contact, and it is entirely due to the current density at the point. No diodes, no skin effect, nothing that has been discussed here.
I suspect that if one googles enough, they will find industry literature which defines this, explains it, and discusses how to get around it.
For me, I would solve it like this:
To test a 4001 in chip form at 7 amperes, I used 8 probes on the surface, 7 carrying one ampere apiece spaced uniformly around the chip about 25 % from the edge, and a central probe to pickup the contact potential of the aluminum.
At DC, totally accurate. However, at sufficient frequency a core and shield can behave differently. A shield NEVER has 15 nH/ft inductance, this is a consequence of geometry. A non oxidized core will skin at frequency as a consequence of it's sectional conductivity. If that sectional conductivity is destroyed by oxidation between strands, then it will not generate the eddy currents which are responsible for "skin effect". Grossly oxidized multistrand core wire will behave differently from oxidized braid shield.
Total agreement. We use hypertac exclusively for anything that we need reliability for, from room temp to zero (kelvin).
John
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Interesting. Perhaps you could explain a little further. It seems like it is magnetic force that forces electrons towards the surface, given that skin effect, as I recall, is dependent on conductor permeability. So electrons end up where electric field repulsion force between them is in equilibrium with magnetic force pushing them away from the center of the conductor where the magnetic field is stronger?
It is easy to spot the difference, precious metal connectors with features to assure a good mechanical contact exist and are readily available at a small premium.
Then there are things like the Eichmann Bullet sold with flowing pseudo-scientific nonsense.
Eichmann Bulletplugs vs WBT Nextgen phono plugs - [English]
and of course...
At DC, the magnetic field within a cylindrical conductor is zero at the center, and peak at the surface. The lines of flux are circular around the center of the wire.
When the current is time varying, the magnetic field is trying to rise and fall in amplitude to match the current.
When the magnetic field is trying to change, faraday's law of induction occurs in the conductor material. This induction creates eddy currents which have a toroidal geometry, with the lops of current travelling in the same direction as the current in the wire closer to the outer surface of the wire, and in the direction opposite of the current closer to the center of the wire. So the toroidal currents cancel at the center, and reinforce at the surface. The net effect is that all the current goes to the surface.
And yes, it is indeed strongly impacted by the conductor permeability as well as the conductor resistivity.
As an aside, my avatar is that of the magnetic field intensity of a double braid coax.
John
Actually I misspoke there, thanks. I had meant that the notion was that the best topologies had the worst PSR.
I wrote that post before I'd been sent a client email that really p-oed me, someone concerned about having a gain trim on a phono preamp who added that he hadn't analyzed the circuit and probably wouldn't do so anytime soon. This was copied to the multitudes, many of whom are not expected to know anything about circuits but are certainly good at being concerned. My verbiage must have been precognitive
Wright I'm sorry has left us. He let me buy his OOP book and it has some reasonable information along with some not-so-reasonable---I recall a hybrid phono stage with an input single-ended JFET common-source stage feeding a cathode, where it is asserted that the gain follows the source resistor, which fails to account for the FET transconductance. But so it goes. We chatted once and he surmised that Harman companies must have had an unlimited budget for R&D. What a fantasy that was!
Steve Lampen said (see Understanding Skin Effect and Frequency)
I don't know who he is, but let us hope he has nothing to do with the actual cable design!
Maybe he should retitle his blog 'misunderstanding skin effect'?
True, but nothing whatsoever to do with skin effect. Strangely, the graph he shows contains the truth - its just that he hasn't understood his own graph. The Y axis, by the way, should be labelled 'magnitude of impedance' not impedance. The actual explanation is simple: take the full formula (which applies everywhere, not just the 'transition curve') and let R be much larger than wL.
I don't know who he is, but let us hope he has nothing to do with the actual cable design!
There are several ways to model skin effect --- the model i have seen is different from JNEUTRON's explanation. The inductance is the greatest at the wires center and lowest at the surface. Thus, the HF will travel the easiest path - that being the surface. The reason the L is greater in the center is because that is where the flux density is greatest.
THx-RNMarsh
THx-RNMarsh
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Because they are sadist pricks that sometimes don't know anything more than what's in the text books.
Ask Sync. He is in the midst of it right now.
Prof "All pots are the same. If you set them at mid point you get exactly half the resistance.
Sync " But what about log pots."
Prof " What the hell is that. There is only one kind."
Curiously inaccurate. Where did you get this??
Here, I googled it for you.
PhysicsLAB: Ampere's Law
Go down to the graph with the red line..roughly two pages down if there were page breaks..
Note that the flux density at center is ZERO.
The website equations and graph are entirely consistent with every EM text in my office, so I didn't bother taking a picture of a page and post it. The 30 seconds it took to google were just way easier.
Your statement that HF will travel the easiest path, that is a good one..it is entirely consistent with what is also being taught in EMC courses.
Edit: one thing to be wary of, they represent current into and out of the page as x's and o's. While this is proper nomenclature, the wire depiction included with the equations and graph of ampere's law applied to a conductor has two o's in the wire body. This is meant to represent current flowing in only one direction. Some people may confuse that as meaning two conductors. It is NOT.
John
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It's hard to find good teachers in electronics. The experience level is often lacking, for one, even if the basics of device, circuit, and system theory are present. If they have as well an attitude and wish to persuade the students that they are authoritative, then you are really in trouble.
Phil Anderson has written about the class he taught that included Brian Josephson. The latter was thoughtful enough to make his remarks to Anderson after the class sessions, and they often consisted of ways that Anderson could have explained things more clearly
Bear why do you run around in circles with questions of generality?
There are some circuits that benefit from super regulators and some that don't.
Not a wonder you can't get a straight answer.
But then that's not really what this thread is about is it.
I was at the other extreme. There are physics courses that are more practical than my engineering one, but when you are being lectured by someone working on single electron memory structures you forgive them. I was fed all the equations and no explanation of what possible use they were. Sadly all rusted away now and need relearning.
Now I really must work out what I want to do with my life when I grow up
Forget about the conclusions in the article - which if it is the one from I think earlier than edition 10 (haven't picked up the later ones) - I have read, albeit when it came out, and with great interest.
However, the question is not what the article said, the question is what YOU say about this topic. Audible or not audible, that is the question. Feel free to state under which conditions (generally speaking) it is or may be or not be. This is the question on the table.
I'm asking this of all the regular and irregular participants.
...all the while bangin' on the skins... daddy-O
_-_-
However, the question is not what the article said, the question is what YOU say about this topic. Audible or not audible, that is the question. Feel free to state under which conditions (generally speaking) it is or may be or not be. This is the question on the table.
I'm asking this of all the regular and irregular participants.
...all the while bangin' on the skins... daddy-O
_-_-
They have greatly improved the page. Back a few years, it was abysmal.
They now include bessels and when they are appropriate..nice.
I'm glad they included the toroidal eddies in the wire I spoke of. I posted that depiction about two years before H. Johnson included it in his book, now I see it everywhere. Good, that's as it should be.
I love the explanation of coax vs frequency..very good.
They should also include a depiction of a coax that has been deformed with core off center, to show how the current will redistribute as frequency increases to force the shield current to go back to common centroid.
They should also include the depiction I linked to a few posts back with the equation below and above the wire surface.
John
The theory behind that way of teaching, as I understand it, is that technology changes rapidly, so your limited time in school should be used to learn things with a long half-life, which is to say a lot mathematical theory. The other part of it is that you are much more likely to get through learning math if you keep up your momentum in school and keep learning and practicing (learning by rote) with it faster than you can forget it. Unlike learning the technology of the day, if you don't learn mathematical theory in school, its unlikely you will do it on your own later. But, yes, schools do graduate people who can do math problems from a book and are otherwise lost in the real world. And, yes as you describe, I can think of the physicists I know who made it through Jackson (electrodynamics) and can't remember much about it now.
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Not seeing how this is a generality.
The question is audibility, not a technical "benefit" which can be measured.
Does anyone here think that super regulators can produce an audibly better (or worse) result?
If the answer is specific to circumstance, please feel free to state this or discuss.
We're banging deep into contact effects and skin effect, as have other subjects of seemingly minute detail in the past. All the while a whole lot of discussion seems to also say that (for lack of a better way to put it) "very little of this stuff" is going to be audible.
All the blind tests seem to indicate that "next to nothing" shows an audible difference. Well, maybe a difference above some threshold/magnitude.
Each an every time that the question of where that threshold lies - be it a narrow band or a wide area - nobody steps up to say. Otoh, people regularly step up to say that X or Y or P can not possibly be heard - no difference. And then go on to cite various things.
This is a good point to start getting at some sort of definition, even if it is a narrowly focused one. Regulators in this case. Pretty easy to measure (per the Linear Audio article(s)) so seeing if there is ANY correlation to audibility given that there are SOLID 'numbers' to refer to would appear to be a valid point of discussion.
_-_-bear
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