Wasn't the time Rupert left the company he sold the year before ? I believe it was at a moment where everybody in the company does not wanted to take any risks with NDAs near their new group?
I found Rupert open minded and curious enough to anything able to bring improvements to his products
. Did they had invented flying faders at this time ?Phase shift with skin depth -
Why coax was 'invented' and its characteristics has been thoroughly studied. Which ever model you choose, the skin effect is well known and why and how explained in many books. Then, because of skin depth at very high freq lead to no need for a conductor at all in the middle -- waveguides.
Using a simple electrical model - regarding skin depth - as the currents of frequency penitrate deeper into a wire, the phase changes as well. The inductance at different skin depths changes and thus the phase along with it. So in one sense, there is a time delay occuring thru the core's depth which affect waveform fidelity -- esp important in long cables and data or sq waves and pulses or transients. To be continued -- Thx-RNMarsh
Why coax was 'invented' and its characteristics has been thoroughly studied. Which ever model you choose, the skin effect is well known and why and how explained in many books. Then, because of skin depth at very high freq lead to no need for a conductor at all in the middle -- waveguides.
Using a simple electrical model - regarding skin depth - as the currents of frequency penitrate deeper into a wire, the phase changes as well. The inductance at different skin depths changes and thus the phase along with it. So in one sense, there is a time delay occuring thru the core's depth which affect waveform fidelity -- esp important in long cables and data or sq waves and pulses or transients. To be continued -- Thx-RNMarsh
I assume you realise that this should be understood as a tongue-in-cheek comment.RNMarsh said:
True.
Untrue? Dispersion in long cables may be made worse by skin effect increasing conductor resistance, but skin effect is not the cause of cable dispersion. Resistance is the cause of dispersion.
Thta is what skin effect does, yes.... increases impedance (R+X) -- the inductance change (X) at various depths is a contributor to dispersion. -RNM
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Scott,
Yes thanks, but my problem is relating this with the data that Ed Simon presented. It appeared that most accepted the slight increase in 2nd as being consistent with the R dependence on dI/dT proposal.
Thanks
-Antonio
A nice compact book was published "Inductance Calculations: Working Formulas and Tables" by Fred. W. Grover in 1946. I have a 1962 edition. 280 pages of math on every conceivable wire shape/form... with 97 worked out examples. Skin effect, and proximity included. Good stuff in there .... Thx-RNMarsh
High power high frequency RF coils are often made from copper tube, you can also cool them easier. Heres a guide to make your own, hollow tube inductors liquid colled in your crossovers
Coil Construction Techniques - HAMwaves.com
Coil Construction Techniques - HAMwaves.com
the local controversy is jneutron's insistence that proximity effect causes distortion by “modulating” a distributed resistance near a current carrying wire
and Ed Simon measuring ~ -152 dB 2nd harmonic with one arm of RN55 bridge wrapped with a drive wire
leaving some confused
especially those of us believing Maxwell's equations are linear and pretty certain the linear proximity effect is quite a few orders higher than the measurement
I'm actually fine with the measurement (except for having lots of questions about how Ed gets those numbers even with a AP analyser)
materials aren't infinitely linear, that low several confounding effects could explain such a small number
but some want to leap on it as proof of jneutron's assertion without putting any numbers from the equations on the table
the examples of where proximity effect occurs, is large, and yet the systems are't corrupted by 2nd harmonic are meant as counter examples to jneutron's claims
Leg pulling.
With waveguides the second conductor has no meaning.
EM waves have already been generated (e.g. by an antenna, a klystron tube) just before the entrance of the wave guide.
We tap the wave’s EM energy after (or just at) the end of the guide through an EM sensor (e.g. antenna)
The wave guide just confines the wave to propagation. Waves are confined inside the wave guide due to total (should) reflection from the wave guide walls.
Cross sectional shape of the guide has to match polarisation mode of the already generated wave. Cross sectional dimensions have to match wavelength.
Electric field is (should be) perpendicular to the wall.
Magnetic field is (should be) parallel to the wall.
These last two could and do happen within a coaxial cable as well.
The similarities stop when we think of the way we feed energy to and tap energy from in the case of the cable .
We apply an electrical potential difference between the inner and outer conductor.
We tap another potential difference between the inner and outer conductor at the far end of the cable.
What happens in between –how to explain the energy propagation- is the puzzle of my late life. The chicken and egg problem.
That’s why I refered to it.
Charge diffusion (ha, ha we can't get away with that so easy), eddy currents generation, counter magnetic action, finally leading to skin effect. All dynamically influenced by time. I agree.
The (many) nonlinearities observed all these years are due to materials variables.
Our recent problem as it seems is not the skin effect’s effects but how the proximity effect’s effects indicate an inherent (theoretical derived) frequency distortion.
Does Fred. W. Grover's book says anything about this distortion?
George
No confusion here. Maxwell's equations are linear, and the skin/proximity effect depends only on frequency.jcx said:
The measured 2nd harmonic, if it is really present, is due to something else. What we should be doing is thinking about what could cause it. I suggested movement of the wires, but I now think that might cause 3rd instead. 2nd requires some asymmetry between polarities. A DC bias could do it, as that would skew the thermal effects or any resistor non-linearity. A temperature gradient might do it, if there is an accidental thermocouple in the wiring.
That all the irony of all this passionating discussion: The distortion levels we are talking about are so low that we can doubt of their exixtance, and there is hundred places in all our systems, where we can improve distortions of 100X this levels.
Yes it is funny, obscure and mad. In some amplifiers (SE tube power amps e.g.), the same people would not care about 5% (-26dB) distortion and will say they sound the best. In resistors etc., the fight will be about -140dB. This proves the only thing - non existent engineering method to support results of subjective evaluation and crazy attempts to explain it by non-linear distortion.
The same is for 1m of signal cable and "phase delays" in audio band - again extraordinary nonsense of 1st class ranking.
The same is for 1m of signal cable and "phase delays" in audio band - again extraordinary nonsense of 1st class ranking.
I had a smile, reading "Obscure and mad". So true.
With age, i try to stay reasonably scientific, objective and weighted in my 'subjective evaluations'. If not, you can turn mad, indeed.
Well, those kind of explorations can save time for future designs. I understand the John Curl position. Why not use the things you know they WORK, even if it do not change a lot
I try to instant *compare*, with some kind of 'no focus' listening approach. Looking for obvious differences more than absolute "good sound".
I tried some changes of feedback resistances quality in one of my amps... well, how to say... Always the same amp, the same records, real difference ? Less than differences due to humidity level, i will not worry too much about missing 'Resista' . : -)
About pots, i compared, some time ago, against a passive fixed level attenuator, an ALPS pot and a PGA23XX.
Both, indeed have a signature. All the 2 solutions worked well ( dynamic, separation, micro details etc...)
After some various tries with the charge of the PGA, i found it was not so far from the resistance attenuator. With the ease it provide, i do not worry any more to suffer bad contacts and wear of conventional potentiometers. But i do not have the John's allergy to electronic parts hidden in a little plastic package designed by other's dirty fingers like Scott Wurcer's ones.
On the contrary, i'm so happy when i think to all the work (and money) they save to me and, sometimes, graceful to their talent.
With age, i try to stay reasonably scientific, objective and weighted in my 'subjective evaluations'. If not, you can turn mad, indeed.
Well, those kind of explorations can save time for future designs. I understand the John Curl position. Why not use the things you know they WORK, even if it do not change a lot
I try to instant *compare*, with some kind of 'no focus' listening approach. Looking for obvious differences more than absolute "good sound".
I tried some changes of feedback resistances quality in one of my amps... well, how to say... Always the same amp, the same records, real difference ? Less than differences due to humidity level, i will not worry too much about missing 'Resista' . : -)
About pots, i compared, some time ago, against a passive fixed level attenuator, an ALPS pot and a PGA23XX.
Both, indeed have a signature. All the 2 solutions worked well ( dynamic, separation, micro details etc...)
After some various tries with the charge of the PGA, i found it was not so far from the resistance attenuator. With the ease it provide, i do not worry any more to suffer bad contacts and wear of conventional potentiometers. But i do not have the John's allergy to electronic parts hidden in a little plastic package designed by other's dirty fingers like Scott Wurcer's ones.
On the contrary, i'm so happy when i think to all the work (and money) they save to me and, sometimes, graceful to their talent.
OH, I want to save money too! I have hundreds, if not thousands of IC's in my lab. I would LOVE to know what to do with them and put them to meaningful work.
My last two designs, one a power amp, the other a phono preamp (JC-3) are almost entirely made of IC's. I ultimately avoided using Scott's AD797 in the JC-3, because I found a much less expensive, yet the same sound quality IC from TI. I don't like getting 'ripped off' either from extra expensive IC's that are only priced to make extra profit.
Scott Wurcer and I have known each other for more than 25 years. I think very highly of his IC designs I tried to put his IC, the AD712, into an early Parasound power amp, based on the fact that I trusted his design, was already using it for servos, and although it would be directly in the audio path, it would be an 'easy' location, with light loading. Unfortunately, after the reviewers got through with it, I had to design it out, and then I was able to achieve success with the design. Was it the IC? I am pretty sure it was. Would any other IC do better at the time? I don't think so, but maybe a Harris mil grade device could have passed muster, I am not sure.
I designed out the IC, switched to a jfet follower to replace it, and I have lived with the solution, even as to today, in an number of successful audio amp designs.
My last two designs, one a power amp, the other a phono preamp (JC-3) are almost entirely made of IC's. I ultimately avoided using Scott's AD797 in the JC-3, because I found a much less expensive, yet the same sound quality IC from TI. I don't like getting 'ripped off' either from extra expensive IC's that are only priced to make extra profit.
Scott Wurcer and I have known each other for more than 25 years. I think very highly of his IC designs I tried to put his IC, the AD712, into an early Parasound power amp, based on the fact that I trusted his design, was already using it for servos, and although it would be directly in the audio path, it would be an 'easy' location, with light loading. Unfortunately, after the reviewers got through with it, I had to design it out, and then I was able to achieve success with the design. Was it the IC? I am pretty sure it was. Would any other IC do better at the time? I don't think so, but maybe a Harris mil grade device could have passed muster, I am not sure.
I designed out the IC, switched to a jfet follower to replace it, and I have lived with the solution, even as to today, in an number of successful audio amp designs.
My criticisms of IC's is much like I might criticize American or French automobiles. From my experience, too many compromises at the factory level to make them the best driving or performing vehicles, (and reliable, in the case of autos.)
I'll take German or Japanese cars almost every time, and I give thanks every time I drive one.
I'll take German or Japanese cars almost every time, and I give thanks every time I drive one.
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