It seems passive IM was the keyword here to find some reading, and it does indeed seem to be a real phenomenon causing increasing concern in microwave applications, according to some of the papers Google found. Although connectors are, not surprisingly, the focus of the Amphenol paper, even that paper, as well as others, mention also cables as potentially casuing passive IM.
So this seems to have been known but not of much concern until recently, when mobile phone base stations have made the problems appear more commonly. However, all papers seem to be concerned about microwave applications only, so could this be relevant for audio? I don't know, let me just quote this from one of the articles:
"Intermodulation distortion is most pronounced in systems where the high power transmission and low power receiver signals are carried simultaneously in the same transmission line, such as in the cable between the duplexer and the antenna in GSM base stations and in certain space applications. For low power levels, the effects of Intermodulation distortion are significantly less."
So this seems to have been known but not of much concern until recently, when mobile phone base stations have made the problems appear more commonly. However, all papers seem to be concerned about microwave applications only, so could this be relevant for audio? I don't know, let me just quote this from one of the articles:
"Intermodulation distortion is most pronounced in systems where the high power transmission and low power receiver signals are carried simultaneously in the same transmission line, such as in the cable between the duplexer and the antenna in GSM base stations and in certain space applications. For low power levels, the effects of Intermodulation distortion are significantly less."
There are safer ways of experimenting with CCIM. A good method is to buy ONE girl a pair of diamond earrings and then observe the resulting electrochemical effects that ensue in the volume immediatley between the crystals once installed. Of note, is that the effect can be rather long lasting. Of particular note, the effect may continue when the crystals are removed entirely from the test subject. Of further note, is the fact that after a sufficiently long period of time, no effect will be observed at all... regardless of crystal location. On a final, the effect can usually be reproduced when the crystals are placed on a new specimen.
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And here is a more scientific paper on passive IM, containing a list of references to academic, and other, publications, for those who want to go deeper into this.
http://conferences.esa.int/03C26/papers/a022.pdf
I honestly didn't read the paper, except for the abstract and a quick scan of the reference list, but it seems clear that the phenomenon has been known for quite long at least for microwave applications, and that it is considered important in space applications. To what extent this might matter for audio, I leave to others to judge.
http://conferences.esa.int/03C26/papers/a022.pdf
I honestly didn't read the paper, except for the abstract and a quick scan of the reference list, but it seems clear that the phenomenon has been known for quite long at least for microwave applications, and that it is considered important in space applications. To what extent this might matter for audio, I leave to others to judge.
For some reason, when I say 'cable' nobody thinks that it has RCA or BNC connectors on each end. Usually, this is a necessary addition to the cable to make it useful. It could well be the wire-connector interface. I am testing commercial products that have connectors previously installed.
The metallic interface stuff is most interesting and valuable.
I guess I laugh when $100 RCAs made from metals with little to no elasticity, silver, pure copper, etc... are touted as "premium".
The RCA is a poor design at best.
🙂
I guess I laugh when $100 RCAs made from metals with little to no elasticity, silver, pure copper, etc... are touted as "premium".
The RCA is a poor design at best.
🙂
Wouldn't the 1/4" phone plug be rated as the worse jack and plug style? It's used for speaker connections too.
-Chris
-Chris
Initially, before WW2, the phone jack was used. After WW2 the RCA plug was invented, apparently to use up scrap metal that was available, since it could be bent and pressed into shape. For several decades, pro audio used XLR and phone jacks, consumer audio used RCA jacks. About 30 years ago, when we started making better (and more expensive) audio products, we started experimenting with gold plating some of the 'better' cast RCA connectors. Levinson finally gave up on RCA, and changed to Lemo connectors, which, while much better, were completely incompatable with every other connecting cable. Lemo, however, has set a very high standard for connectors, but they are NOT cheap! In the late '70's the Japanese made the 'Tiffany' RCA connector. Vampire apparently copied their basic design and now makes the majority of connectors that we use today. Quality RCA connectors work very well, and probably even better than Lemo, today, for reasons that you would probably not believe at this time, so I will not go into it. There are different levels of premium connectors and they compare in price with Lemo connectors, which are also very expensive.
poobah said:
You are a naughty naughty wookie. If our knowledge of this phenomenon is uncovered and fully understood by the other side then all humanity will blame you. A naughty wookie indeed.
Re: Just for Poobah
begging your pardon sir, a girl is made of sweets and spice and everything nice!!!
😀 😀 😀
rpapps said:
begging your pardon sir, a girl is made of sweets and spice and everything nice!!!
😀 😀 😀
Hi rpapps,
Good show!
I removed the label from mine and kept it for reference. I've heard stories of unscrupulous dealers removing these warning labels to market them as RoHS compliant on top of that.
-Chris
Good show!
I removed the label from mine and kept it for reference. I've heard stories of unscrupulous dealers removing these warning labels to market them as RoHS compliant on top of that.
-Chris
john curl said:
Why Dr. VandenHul did not subject his work to peer review is quite clear. It would never have been published. In the intervening years, none of it has been reproduced..It is clear that the methods were not adequate, therefore the conclusions were incorrect. Time always clears out the errors..
Why are you wrong, John? So far, you've presented nothing in the way of a working mechanism.
john curl said:
Allegations...incorrect wording I think... hypothesis maybe.
While his work was indeed ahead of it's time with respect to pushing the envelope, he got bit by measurement errors..it happens..
Cheers, John
Christer said:
The paper clearly states what is going on.
Quote: ""These models are based on the assumption, validated by experiment, that the single major source of non-linearity in coaxial cables is due to contact resistance in the RF connectors.""
The entire premise for this distortion mechanism is the disruption of the characteristic impedance of the transmission line by three things..Constriction resistance, tunnel resistance, and contact capacitance. Note they discuss the forward and reverse issues, that being reflection coeff based..
NONE of those things occur in the middle of a wire, this is a connector thing.
Cheers, John.
john curl said:
Give what a break?
If you fabricate explanations, you will be called to the table.
If you spout other's erroneous explanations as being correct, you will be called to the table.
If you present out of context erroneous explanations as being scientific, you will be called to the table.
Don't take it personally. If I do such, I demand to be taken to task by others...that is how it works..peer review.
If you wish to present van de's "research", you must expect it to be called to task..because it over-reached.. It was incorrect...wrong, bad experimental method...
I have lauded your use of and modification of your ST1700 in the attempt at measuring that which was not within reach when designed. I've no problem with that. That was good, and I've stated such in the past.
But when it comes to using other's hairbrained explanations which are not founded upon any scientific basis, that is not doing anybody any favor.
If you are truly interested in advancing our understandings, do so....engage in the technical discussion..
Don't cop out with "give it a break"...I believe you are capable of far more..please discuss.
Cheers, John
Folks, I recommend to anyone interested to read the Amphenol (RF) paper on this subject. It is more inclusive as it talks about whole cable assemblies, rather than just switches or contacts, which, while important, are only part of the equation. I do not know exactly what Dr. VandenHul measured. When I personally spoke to him at the CES in January of this year, I learned that his initial measurements were made at a much lower level than mine, which are now limited to about 30mV. He used even better equipment, that he got surplus from Phillips Research Labs, about 20 years ago, or so. I initially presumed that I was measuring what he was initially referring to, but now I think it is Passive IM that I measure with my test equipment, in the ground return (shield) of various prefabricated audio cables, as well as perhaps some connector interface was well, as several 'better measuring' cables have more expensive connectors that are non-magnetic and generally better made.
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