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In Reply to: Re: would it be a real (something (I can hear) if the hook-up wires inside the amp are not teflon? or maybe... posted by Cura on March 25, 2007 at 00:31:25:
The best i've hear is Cotton- I find it sounds less grainy than teflon.
Follow Ups:
Hi.Cotton will be decomposed when getting too hot (300F or 149C) &
deteriated by ultra violet rays (direct or indirect sunlight).Its resistivity is 1,000R/cm, or 1 ohm per mm. Theoretically, it can't handle any voltage at all !!!!
It may be OK for signal wires with no voltage is involved. Otherwise...
c-J
Its resistivity is 1,000R/cm, or 1 ohm per mm. Theoretically, it can't handle any voltage at all !!!!It may be OK for signal wires with no voltage is involved. Otherwise...
Where did you get that figure from? According to the data on the Swicofil site that Cpk referenced, it's electrical resistivity is given as on the order of 10 9 ohm/cm 3 .
se
Hi.1,000,000,000R/cm3=1,000R/cm=100R/mm. (Not 1R/mm, sorry wrong typing).
Taking the example of a #18 16 strands hook up wire with extruded PVC jacket, commonly used for HV PS for tube amps. Its wall thickness is 0.925mm (UL/CSA rating). So if it were cotton wrapp insulation, its dielectric resistance would be 0.925x100R=92.5R ASSUMING the cotton wrap get the same EVEN thickness of a #18 hook-up wire designed for 600V UL/CSA rating.
So if the hook-up wire of same gauge size but with cotton wrap of same thickness instead of extruded PVC were used to carry say 350V typical tube plates HV PS, there would be a leakage DC current running from the copper conductor to the chassis neutral ground via the cotton wrap (350V/92.5=3.78mA) !!!! This would be totally unacceptable.
This would be an ideal situation ONLY if we ASSUMED even insulation thickness throughout the cotton wrap wire. Since cotton wrapp is NOT extruded like rigid PVC or Teflon materials, the current leakage would be very severe if the thickness of the cotton wrap at the contact point were futher squeezed down due to the weight of the wire itself & for whatever reasons.
Hence my statement: for signal path wiring is OK, but I would never use cotton wires for HV, period. Even for signal path use, I would make it damn sure it would NOT get close to any HV wires let alone its high dielectric constant e.
But if some find cotton wires sound better disregarding its sticky physical & electrical properties, it is their call.
c-J
DCC (Double cotton covered) copper wire was all there was in the days before varnishing and plastic extrusion.I have some interesting old radio books showing how to wind 500V coils with DCC wire. ETC.
You may do what you wish, of course, but it doesn't help others to make questionable claims, and your 1 ohm figure is nonsense!
Hi.In the good old days, before the National Board of Fire Underwriters
(NBFU), UL & CSA stepped in with the electrical standards, you could use whatever you wanted. Who would give a damn?But if you use anything electrical, not rated by UL or NBFU or CSA (in Canada) today, you are asking for trouble in case of fire.
c-J
The answer is a value in ohms, perhaps with a explanation of measurement method.My example of how cotton WAS used simply illustrates that it cannot have a inherent low resistance.
Your lecture on fire hazards etc is not releavant and just a diversion.
Your lecture on fire hazards etc is not releavant and just a diversion.
Yup. He originally said "Its resistivity is 1,000R/cm, or 1 ohm per mm. Theoretically, it can't handle any voltage at all !!!!" Now he's just doing a lot of dancing around. Not worth the time.
se
Hi.Basing on 1,000,000,000R/cm3, I deduce electrical resistance per linear mm is 100R (cube root of the above figure).
You said I was wrong. So what is the correct insulation resistance per mm thickness of cotton ???
c-J
Basing on 1,000,000,000R/cm3, I deduce electrical resistance per linear mm is 100R (cube root of the above figure).
Uh, 100 is the cube root of 1,000,000,000? I think you need new batteries for your calculator.
se
Hi.My calculation based on cotton's 100 million ohms/cm3 is 100R/mm.
You said it was "nonsense".Now you come up with less than half of my calculated value, only 42R.
So your's a "Double Nonsense".I got the impression neither of both insulation resistance numbers is correct.
Insulation resistance is in the range of mega ohms. Under a test voltage 250VDC, min. insulation resistance is 250KR. For 500VDC, 500KR, & for 1KV, 1MegaR. If a cotton wire could handle up to 500VDC,
its insulation resistance got to be in maga ohm range.So how you arrived this lowly 42R?
c-J
So how you arrived this lowly 42R?
I didn't. Deep Thought did. And it's not 42R, it's simply, forty-two.
se
.
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1,000,000,000R/cm3=1,000R/cm=100R/mm. (Not 1R/mm, sorry wrong typing).
Your numbers make absolutely no sense whatsoever.
You go from 10 9 ohms/cm 3 to 1,000 ohms/cm. What the hell's that supposed to mean? It's obviously not a cubic centimeter, but it can't be a square centimeter because then you have no thickness. You've divided the original number by one million. Where does that number come from?
It's nonsense.
If you want to scale it, you need to stick with three dimensions. One cubic centimeter is made up of 1,000 cubic millimeters. So you can also state the resistivity for cotton as 10 6 ohms/mm 3 .
So if the thickness of the cotton insulation is 1mm, then the resistance through an area of 1 square millimeter would be 1,000,000 ohms, not 100 ohms.
se
Hi.The insulation resitance of an insulated conductor is the electrical resistance offerd by its insulation to an impressed direct current potential tending to produce a leakage of current through the same.
For wire usually measured in megaohms per 1,000 feet.
So where come in volume & area?
c-J
Hi.Define 'electrical insulation resistance'.
c-J
Good day.se
On the link below you can check the dielectric constant of insulatorsVacuum: 1
Cotton: 1.3-1.4
Teflon: 2.0
Polyvinyl Chloride 3.4
Epoxy Resin (Cast ) 3.6
http://www.clippercontrols.com/info/dielectric_constants.html
And you can check the definition of dielectric constant
http://en.wikipedia.org/wiki/Dielectric_constant
The 1.3-1.4 figure for cotton is rather misleading unless you're going to make your cables by simply stringing the wires through cotton balls. In textile form, the figure is rather higher due to there being much less air for a given volume compared to cotton in its raw form.se
That gives a much higher number for DC.
That gives a much higher number for DC.
Yes, thanks. I recall your posting that link on some other forum not long ago.
se
that it was a posting of yours I saw (not on AA) that caused me research to subject a little more. So actually thank you.
that it was a posting of yours I saw (not on AA) that caused me research to subject a little more. So actually thank you.
Ah. Well, you're welcome. :)
se
another example of what your saying is... kraft paper... which may be listed generically as having a dielectric constant of say approx 2.5.
But this really depends on how much calendaring the kraft paper has had done to it--- calendar it a lot and you decrease the amount of air captured in the paper and the constant goes up. Also--- keep in mind that if the material in question is relatively "porous" and it is going to be impregnated then the dielectric qualities of the impgrenant are perhaps dominant.Another excellent example of this phenomenon is Goretex... which is from the teflon family--- and depending on which GT your talking about--- has dielectric constants as low as say 1.3--- but largely from injecting a lot of air into the teflon--- making it a not very good mechanical platform.
MSL
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