Because you did not offer any new path to promoting sales, Mr. Hawksford did. A story as old as science.
I would think Mr. Simon means the voltage drop across the cable (presumable coiled), not the voltage across the 1Meg load.
Which opens a can of worms about the coiled cable reactance, return path, instrument grounding, etc... Measuring 1nV is nowhere trivial or easy to reproduce.
"Because there are changes when you insert and remove the connectors, so after a few repeats it seems to smooth out. You certainly can do more. But at a single forward and reverse it could be anything from random chance to dirt."
Might be thermoelectric effect. 1 or two degrees K will be enough if you are trying to resolve nV.
In my younger days I was in a small team that developed high performance panel indicator(1988-1989) for industrial applications. 16 bit resolution with a 4 bit front end gain ranging amp. We bought a very expensive HP meter for testing and development. I could never get a repeatable reading off my panel indicator from one hour to the next until one of the more experienced engineers pointed out the problem. Once the measurement set-up was sorted out, I got the repeatability required.
Might be thermoelectric effect. 1 or two degrees K will be enough if you are trying to resolve nV.
In my younger days I was in a small team that developed high performance panel indicator(1988-1989) for industrial applications. 16 bit resolution with a 4 bit front end gain ranging amp. We bought a very expensive HP meter for testing and development. I could never get a repeatable reading off my panel indicator from one hour to the next until one of the more experienced engineers pointed out the problem. Once the measurement set-up was sorted out, I got the repeatability required.
No, try for the truth for a change.
With respect to his theory:
I detailed why the planar exponential skin depth approximation cannot be used for cylindrical conductors for that diameter and that frequency.
I detailed why his "laminar flow" explanation and diagram were incorrect.
I detailed how the source of the internal magnetic field of the wire was caused by the current within the wire, which is NOT the same thing as an impinging e/m wave.
With respect to his test fixture:
I detailed why a meter long twisted pair of wires shorted at the end is so difficult to measure v drop, especially when using truncated signals and high bandwidth edges.
I detailed why distinguishing the inductive kick of a meter of twisted pair with respect to the resistive drop of that length of wire was so difficult.
I detailed why the use of a magnetic conductor increases the internal inductance of the wire by the factor of the relative permeability.
I detailed how, if he expects a twisted wire pair of thinly insulated wires to have an inductance of 150 nH per foot externally and 15 nH per foot internally for a total of 165 nH per foot. Then the substitution of a magnetic conductor of mu 100 will make the internal inductance 1500 nH per foot, for a total of 1650 nH per foot.
Designing the test setup to cancel out 165 nH per foot, swapping out the copper for iron with the resultant 1650 nH per foot, yet not even considering the difference...and then, when spotting an inductive kick and calling it "the return of residual energy from the wire" is not science.
I offered to help him.
Offer denied.
I do this stuff for a living. Spotting his errors was trivial.
John
Ed do you propose reversal literally, unconnecting and reconnecting the ends? I certainly hope you don't mean using clips. One would also think AC stimulus has built in reversal of electron drift, or are we challenging superposition?
EDIT - I might be wrong but I doubt you are prepared to categorically eliminate all possible false signals/confounders from your experimental set up. jn might be able to help.
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MH's claims do seem rather suspect in terms of the amount of effect he claims. I'm not going to go over all his calculations with a fine tooth comb, but for most twin-lead and coax cable you typically see pretty fast propagation velocities, relative to audio frequencies. For a lot of coax its about 2ns/ft. So, sure if you send a fast rise time step down a piece of cable you can measure the delay, or reflection time if you intentionally mismatch it. And, yes, you get some frequency dispersion.
Anyway, the disagreement between MH and JN seems to be about the exact degree of transmission line effects, not as to whether or not they exist at all.
That being the case, JN seems to be maintaining that the effects are much too small to hear. If MH were right in any way at all, despite any errors in his articles, then the effects might be big enough to hear. This brings us back to the question of whether or not anybody can be shown to be able to reliably hear such effects? I gather the answer is no.
That could be for other reasons than theoretical E&M reasons, but the end result is still the same. If you can't hear it, why bother worrying about it?
Also, I would just point out that most audio systems are to play back recordings or used for sound reinforcement. In those cases, often rather long mic cables are or have been used, and often with multiple interconnections and patch panels involved. So, garbage in, garbage out? If something was recorded with 100ft mic cables, it seems hard to imagine that a couple more feet of speaker cable would make much difference even if someone could demonstrate that a hearable wire effect existed.
So, it would seem at this point the burden of proof is in the court of those who think wire effects are audibly significant. Such folks need to figure out how to demonstrate to others that the claimed effect is real in the sense of being hearable by at least one human test subject in a fair test that can not be easily gamed. If somebody can in fact hear it, then such a demonstration should not be too difficult to arrange.
We are fortunate to have you as a contributor to this forum.
Hawksford has impressed me as a man who took to academia with gusto and has had a great time. In some areas (not sure which) I suspect he knows his stuff. In others I fear he has a serious case of PhDitis, which leads him to suppose that he can be imaginative and speak and write authoritatively on about everything under the sun.
For him to disregard your comments and refuse your assistance is the height of arrogance. Such an attitude is all too common in academia.
No, it's not, it's more fundamental. See jn's post above. Bad analysis giving incorrect results, followed up by even worse experiments to try to cover up the embarrassing mistakes.
I will give you 'debate points' JN, but I was lead to believe that the 6dB increase was cancelled out, and the 3dB/oct component remained. Also, the nominal test result was verified by a computer simulation that showed a similar shape of the added distortion waveform when compared to the measured test.
Markw4, these debates have gone on for a LONG TIME and there is much supporting evidence not put up here. It is best to keep an open mind about this subject, before committing yourself one way or another. The short form Stereophile version is a good start, if anybody wants to verify or refute MH's work, but there is more, perhaps on MH's website.
Markw4, these debates have gone on for a LONG TIME and there is much supporting evidence not put up here. It is best to keep an open mind about this subject, before committing yourself one way or another. The short form Stereophile version is a good start, if anybody wants to verify or refute MH's work, but there is more, perhaps on MH's website.
Ok, but the incorrect results amount to exaggerations to the effect that transmission line behavior of audio wires would be of sufficient magnitude to be hearable. All wires have associated E&M fields and behave like transmission lines to some degree other, its just that the effects are often negligible, particularly at low frequencies and over short distances.
John, it is not about debate points.
He starts with theory which was valid, but then used the planar exponential skin depth approximation where it was not valid. He calculated a specific result, did not find that result when using copper wire, substituted a very high inductance conductor without consideration of that higher inductance, got an inductive kick that he did not understand, and called it residual energy returning from the wire.
Anybody with experience at actually testing low impedance high slew rate setups would have understood the error.
The fact that he didn't know how to actually design a high speed test setup is of NO significance. It is NOT a simple thing to do.
The big failure was the rush to print without actually verifying the result with someone with experience. In '85, I was already 4 years into sub nanosecond 100 milliohm testing using microwave resistors, I had already learned a lot of the errors the newbies make at these slew rates and impedances (I made a lot of them). But I was in industry, so I couldn't give it away anywhoo.
John
Probably closer to at least a significant fraction of 1/4 wavelength, since 1/4 is sufficient for resonance. Here again, the issue raised by MH is his claim that the propagation velocity in the wires he was talking about was so slow that the the wavelengths were far, far shorter than free space wavelengths would be, and therefore cable length was sufficient to be significant. However, using iron wire as MH apparently did, changes things drastically.
I believe you are missing the point.
He claims that since the propagation velocity of e/m fields within a conductive media like copper is slow (in fact, I can actually jog faster than a 50 hz planar wave through copper, look at the article), that the energy drives into the wire towards the wire center, the is released when the signal is stopped,
In fact, what he presents is actually the waveform of an inductor with a truncated signal. He had calculated the inductance of his twisted pair using copper wire, but when he substituted iron, neglected the inductive contribution of the iron's permeability which was significantly larger than the actual twisted pair's external field.
So, while he presents "something" which he claims may explain audibility, that something is simply the inductance he neglected to consider when he swapped wire material.
John
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