No.rayma said:
No shield is perfect. Coax is good enough.
. . would be another proper shielded cable.
I find that hard to believe. Coax quality difference comes mainly from thickness, not metal quality.AndrewT said:
Some of the cable might have been copperplated steel - fine for RF, but perhaps poor for video?
Uhm.... Over the years, I've been in contact with most of the standard types of coax, but I've never seen one like that..... thatdoesn't mean i t doesn't exist, though...😉
Just can't be very common......?
And - I've sent AF signals (like IRIG time codes)over 400m of coax with no particular loss......
I think it has something to do with the way the contaminants disrupt the crystal lattice.
If wire quality is such a minor concern then why not use wire that has been sitting around for 50 years and is of the fragile easily broken stranded quality that you get from a kids electronics project kit.
I also challenge anyone here to hookup their equipment to a heavily corroded steel spring just like I done as a teenager.
If you did find differences in two identical cables then I would question the age of one of them. Any mineral should have a certain level of corrosion caused by the surrounding air. Too much and the stranded wires inside of a flexible cable will (I believe) rub up against each other and cause any number of problems with the variation of its cable resistance and the resulting difference which is caused by this in the audio signal is therefore audible.
Hence why I went with coax, 1 copper core, no variations between one day or another if the cable is moved. For a very very long time until something else corrodes (like connection pins)
My point is is that you get to a point where the cable is good enough for RF and it isn't terrible for Audio and it creates a solid and stable connection which wont vary much over time. At that point the only thing left is lower signal levels/voltages in one channel vs another caused by voltage drop which can be cured by going with a thick copper cored cable. Hence why I use high quality RG6 Quad with BNC now for everything. Less voltage loss. It is so overkill for audio use that I don't even bother thinking about interconnects or the wires anymore.
As for the connection going from the rear BNC connector to a PCB board I will use PCB screw standoffs for prototyping and directly wire the copper to the board in the final project. If I could I would probably use copper solder. If there is a discernable difference between material types at the transition point between wire/solder/board trace then why not take that variation out of the equation? I'm not saying that I prefer the sound of copper.....
As for the sheild. I believe that in an ideal world each conductor would have a floating shield dedicated to the purpose of keeping out unwanted noise. But with coax that is impractical. I have yet to mess around with XLR and its many varied iterations.
Scientifically speaking If you were to do a true A-B comparison between a cable and a direct connection between two integrated circuits then you would need to shield both IC's from each other to prevent introduced noise (basically design it like you would an RF device) and then add a resistor in between each pin which you are connecting together in order to compensate for the voltage drop that you would get from using a cable to connect the two.
So setup A would have the two IC's in seperate boxes and connected with a cable.
And setup B would have the two IC's in close proximity and connected together at the pins only with a resistor with a shield between the two.
And both setups would have floating shields.
But then you would get the whole issue of resistors having a sound. However I think that this kind of setup would probably be able to let you tell the difference between no cable and a cable/different variations of one. If there is any.
If you asked me 14 years ago when my ears were in better condition I might be able to discern the difference between one or another. But I would have also been easily misled by the shinyness of the cable's outer exterior, Being a teenager and all. 😀
I also challenge anyone here to hookup their equipment to a heavily corroded steel spring just like I done as a teenager.
If you did find differences in two identical cables then I would question the age of one of them. Any mineral should have a certain level of corrosion caused by the surrounding air. Too much and the stranded wires inside of a flexible cable will (I believe) rub up against each other and cause any number of problems with the variation of its cable resistance and the resulting difference which is caused by this in the audio signal is therefore audible.
Hence why I went with coax, 1 copper core, no variations between one day or another if the cable is moved. For a very very long time until something else corrodes (like connection pins)
My point is is that you get to a point where the cable is good enough for RF and it isn't terrible for Audio and it creates a solid and stable connection which wont vary much over time. At that point the only thing left is lower signal levels/voltages in one channel vs another caused by voltage drop which can be cured by going with a thick copper cored cable. Hence why I use high quality RG6 Quad with BNC now for everything. Less voltage loss. It is so overkill for audio use that I don't even bother thinking about interconnects or the wires anymore.
As for the connection going from the rear BNC connector to a PCB board I will use PCB screw standoffs for prototyping and directly wire the copper to the board in the final project. If I could I would probably use copper solder. If there is a discernable difference between material types at the transition point between wire/solder/board trace then why not take that variation out of the equation? I'm not saying that I prefer the sound of copper.....
As for the sheild. I believe that in an ideal world each conductor would have a floating shield dedicated to the purpose of keeping out unwanted noise. But with coax that is impractical. I have yet to mess around with XLR and its many varied iterations.
Scientifically speaking If you were to do a true A-B comparison between a cable and a direct connection between two integrated circuits then you would need to shield both IC's from each other to prevent introduced noise (basically design it like you would an RF device) and then add a resistor in between each pin which you are connecting together in order to compensate for the voltage drop that you would get from using a cable to connect the two.
So setup A would have the two IC's in seperate boxes and connected with a cable.
And setup B would have the two IC's in close proximity and connected together at the pins only with a resistor with a shield between the two.
And both setups would have floating shields.
But then you would get the whole issue of resistors having a sound. However I think that this kind of setup would probably be able to let you tell the difference between no cable and a cable/different variations of one. If there is any.
If you asked me 14 years ago when my ears were in better condition I might be able to discern the difference between one or another. But I would have also been easily misled by the shinyness of the cable's outer exterior, Being a teenager and all. 😀
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The following scientific paper, by C.Y.Ho et al.
http://www.nist.gov/data/PDFfiles/jpcrd221.pdf
indicates that pure copper has a resistivity of 1.725 x 10-8 ohm.metres (at a temperature of 300K), whereas 99.5% Cu alloyed with 0.5% Al has a resistivity of 3.21 x 10-8 ohm.metres (also at 300K).
I was surprised that there is such a big difference.
http://www.nist.gov/data/PDFfiles/jpcrd221.pdf
indicates that pure copper has a resistivity of 1.725 x 10-8 ohm.metres (at a temperature of 300K), whereas 99.5% Cu alloyed with 0.5% Al has a resistivity of 3.21 x 10-8 ohm.metres (also at 300K).
I was surprised that there is such a big difference.
Less than a factor of 2. I am surprised that the change is so small, given how messed up the lattic will be. Still a good conductor, so fine for audio interconnects.
It's really not a big difference when you consider scale. Pretend you're Bill Gates and you're faced with spending 5 cents or 9 cents.
It is important to consider what the shield is being asked to do.
If the victim circuit is below 377 ohms, the shield will be called upon to prevent time varying magnetic fields generated by nearfield sources.
If the victim circuit is above 377 ohms, the shield will be called upon to prevent time varying electric fields generated by nearfield sources.
In both cases, the fact that signal current may be flowing on the braid shield does NOT preclude it from shielding from external sources. In fact, the coincident current centroids of a coax prevents the signal from generating an external magnetic field as well as receiving induced signals from time varying magfields.
The outer cylindrical conductor is a shield.
Nor is it a requirement for e field shielding.
For magfield shielding, concentricity is the primary issue. For efield shielding, it is the sheet resistivity of the outer braid or foil that is the issue.
A twisted pair by itself is also a very good "shielded" cable for magfield induction prevention, as long as the granularity of the magfield is far greater than the twist pitch of the pair.
jn
If the victim circuit is below 377 ohms, the shield will be called upon to prevent time varying magnetic fields generated by nearfield sources.
If the victim circuit is above 377 ohms, the shield will be called upon to prevent time varying electric fields generated by nearfield sources.
In both cases, the fact that signal current may be flowing on the braid shield does NOT preclude it from shielding from external sources. In fact, the coincident current centroids of a coax prevents the signal from generating an external magnetic field as well as receiving induced signals from time varying magfields.
The outer cylindrical conductor is a shield.
Equipotential is not a requirement for magnetic field shielding.
Nor is it a requirement for e field shielding.
For magfield shielding, concentricity is the primary issue. For efield shielding, it is the sheet resistivity of the outer braid or foil that is the issue.
That is also a good one as well.
A twisted pair by itself is also a very good "shielded" cable for magfield induction prevention, as long as the granularity of the magfield is far greater than the twist pitch of the pair.
jn
DOH--- of course.... Have even pulled/buried some kilometers of it myself ..... 😱
don't think I'd use that for audio, though... plenty of RG58,213,214,174 etc etc 🙂
don't think I'd use that for audio, though... plenty of RG58,213,214,174 etc etc 🙂
As a bass player, that can be true but, this is solely due the the way a cable might be connected to a plug and the wire its self has nothing to do with it of course. 🙂
FWIW...I still got got a couple of cables from my system from the '70s and compared them with a rather high end modern (read somewhat expensive) cable and a cheapo cable .
The were all the same a sonically and all have the same resistance properties
It's interesting that most expensive cable has the worst RCA connector.
I learned a long time ago to buy audio with you ears, not your eyes.. 🙂
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Helium is rarer and (I guess?) more expensive than nitrogen so it must be better for audio purposes, surely? Surely we should really be using Helium-3 - I hear that the Chinese are planning to mine it on the Moon. We will then be able to buy a bottle of Helium-3 with all the EMC components omitted and the valves lubricated with best axle grease.
Better for what?
It'll kill insulation and glass to metal seals a lot faster than LN2. Bent/stressed plastics are more inclined to crack and fail at 4.5K vs 77K.
LN2 at about 25 cents per liter, Helium 2 at about 50 dollars per liter.
Much of the expense due to carnot. Him and his darn cycle..
jn
It was a while ago, and I don't think I have bought any cheap cables since, but I did try to isolate the problem from the cable terminations. I made sure there were loose coils of cable, either side of where I was bending the cable. It had to be on a high gain channel to get enough sensitivity to hear the crackle.
As other folks here have explained, it is actually a well known phenomena (tribo-electric effect). Insulators in the cheap cable are rubbing against each other, creating a 'static electric' discharge. If the source impedance is relatively high, the charge creates a signal voltage.
and almost doubles the heat.
Thus reducing the current capability when current is a limiting factor.
eg transformer wire, DC power cabling & VHF cabling where the skin effect reduces the main current route to the very thin surface layer.
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