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Old 30th October 2017, 12:01 PM   #21
50AE is offline 50AE  Bulgaria
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Chassis wire
I probably slept during my physics classes, because I missed that part mentioned in the physics books. "The sound of wires", it must be an interesting subject for sure.
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Old 30th October 2017, 12:25 PM   #22
DF96 is offline DF96  England
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It would have been in first year electromagnetics, where circuit theory is shown to be the low frequency approximation of EM. Then you just have to know that an audio wire forms a trivial part of a potential divider, so any reasonable conductor (e.g. any metal, or a banana) surrounded by any reasonable insulator (typically, mostly air) will be sufficient.
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Old 30th October 2017, 07:16 PM   #23
DualTriode is offline DualTriode  United States
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Triboelectric effect is proposed as a plausible culprit in the conversation about Teflon insulated silver wire. Online there is conversation of triboelectric effect causing noise in cables; guitar cables as an example.

The claim regarding silver wire causing a bright harsh sound relates only to silver plated wire. I did not find any reference to similarly harsh sounding silver only wire.

Scratching my head about the bright harsh sound of silver plated copper wire, if it in fact happens, thermoelectric effect comes to mind. There may possibly be a bimetal effect as well. It could be all about the heat.

The silver plated copper conductor has a copper inner core and a silver outer layer. Silver has about 6% greater conductivity than copper. As AC flows in the composite conductor more current will pass through the silver than the copper. I see the potential for local voltage differences, heating rates, thermal expansion and stress all related to current and AC frequency.

Remember the primary mechanism for resistor distortion is heat and to lesser extent voltage.

Anyone with an Audio Precision APx555 that wants to test this? Just an idea.

DT
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Old 31st October 2017, 12:53 PM   #24
DF96 is offline DF96  England
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I don't think you will get much heating. Copper and silver are good heat conductors so the heat will be distributed fairly evenly. Thermoelectric effects, if significant, would be at bass or signal envelope frequencies, not mid-range or treble. I don't see a problem. There is no hard evidence that there is a problem.
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Old 31st October 2017, 08:57 PM   #25
DualTriode is offline DualTriode  United States
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Quote:
Originally Posted by DF96 View Post
... There is no hard evidence that there is a problem.
DF96, you are right, no solid evidence.

Only squishy subjective reports.
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Old 2nd November 2017, 10:58 AM   #26
Johnny2Bad is offline Johnny2Bad  Canada
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There are many other dielectrics you could use instead of PTFE, with excellent properties, and in many cases, very limp. Also you could look at foamed dielectrics (eg foamed PE) which incorporate air ( = 1 ) to result in dielectrics near or sometimes exceeding PTFE.

As I understand it, silver coated copper PTFE wire is used in aviation and aerospace to minimize corrosion and to tolerate extreme temperature conditions. Sometimes there are fires, explosions, etc in these vehicles and you want to minimize the impact ... a half-working sat is still worth millions per year to the owner, or a damaged aircraft benefits from minimal associated damage to get safely to the ground.

Not to be overlooked, these vehicles also must be able to tolerate very cold conditions as well; PTFE does well in that environment, or one where the temperature varies from very cold to hot in relatively short periods of time.

Some dielectrics cannot be used in passenger carrying vehicles (passenger also = crew only) due to toxic gases in fault conditions. PTFE is not an angel in this regard but apparently it's not bad enough; if you survive the fire you will survive the PTFE emissions. Rumours about space crews perishing in fires due to poisoning seem to be unfounded; the fire apparently did the damage itself.

Although I don't know if it's an issue, rocket fuel is generally highly corrosive stuff, as are some fuels used in aviation. Maybe small emissions during launch or operation could get into the payload or structure, thus the desire for corrosion resistance.

I hadn't considered the manufacturing process, but that does make sense.

PTFE also has the negative quality of migration; it doesn't stay in the manufactured shape forever, and can expose the bare conductor at pinch points, etc over time. So careful dressing / routing of the wire is recommended. (Many years ago the crew I hung with would machine Teflon "buttons" to serve as piston keepers in high performance internal combustion engines. They had to be replaced regularly as they would change shape over time).

Silver-coated PTFE wire is readily available as remnants because aviation / aerospace / NASA requirements are no more than one splice in a run of wire, so not all of a spool can be used in production.

As always, there are advantages and dis-advantages to any dielectric material.
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Old 2nd November 2017, 12:24 PM   #27
50AE is offline 50AE  Bulgaria
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It is true that PTFE and pinching do not go together. This kind of insulation is really gentle, and quite boringly elastic at the same time. Thin PTFE wires can really spring around with a.. character.
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Old 2nd November 2017, 02:51 PM   #28
Johnny2Bad is offline Johnny2Bad  Canada
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Quote:
Originally Posted by 50AE View Post
It is true that PTFE and pinching do not go together. This kind of insulation is really gentle, and quite boringly elastic at the same time. Thin PTFE wires can really spring around with a.. character.
I have also heard (but not experienced) that PTFE can migrate with twisted-pair assemblies; ie not manufactured wire which is machine-twisted but in hand-twisted pairs.
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Old 3rd November 2017, 11:48 PM   #29
Speedskater is offline Speedskater  United States
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While Silver has about 6% greater conductivity than copper, this only applies if the two wires have exactly the same cross-section area. Does a 100 inch long copper wire sound different than a 106 inch long copper wire? I don't think so.

It's unlikely that the end-to-end resistance/impedance of any chassis wire matters.
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Old 4th November 2017, 12:46 AM   #30
nigelwright7557 is offline nigelwright7557  United Kingdom
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For a CCTV project I was working on I investigated wire for running long wires to the camera. It was quite shocking the difference in resistance of the wire samples I bought in. I can only guess some were made of poor grade copper to be so bad.
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