Your right ...but not as good as air !.....in fact not as good as air / ptfe if you use oversized ptfe tube the actual contact area of silver to ptfe is very small. much less in fact than a cotten silver interface as the cotten will tend to sag on to the conductor.
As to cables I've been there eaten the book and read the pie......I've made over a hundred IC cables using all manner of conductors and insulation types and topologies. though its not my style to tell people whats best or what they should be using I see no point in people reinventing the wheel. Just because some people attempt to make vast profits from relatively simple ideas......[take a look at RA for instance though there are many others ] for instance a simple twisted pair of good quality conductors, insulators and good quality plugs will go a long way towards sonicly excellent IC's.
This is starting to go rantish ....but if you see an advert that has all sorts of pseudo scientific gobble di gook the chances are your being mislead.
As to claims of metal purity many of these need to be taken with a pinch of salt to.....
I recently made enquries of a chap selling neotech cable as to the authenticity of the 6n silver ....his reply was he had just taken the data from the suppliers web page, with out further investigation ! Its a mute point if he was trying to deceive or was just lazy. I feel most of these claims also reffer to the ingot purity and not the finished wire. I can't substantuate this but when you consider that an assey test is quite likely to cost shy of £100 your not going to carry out many of them, and if you do it will be on the stock material rather than the finished product.
Maybe there are people out there that can put me right if I'm in error ?
Another thought has occured to me ......if you have a high purity metal does it have a greater propensity to suck up environmental polution SO,SO2,O3,NO2,NO3 or contaminents from the construction process Fe, Mn, Sn, Pb, etc plus their oxides and sulphides. Any of which will detract from the original purity.
If you have a substance that is 99.99999% [7n] what and how are you going to identify what the remaining 00.00001% is on a commercial scale ?
So I supose what I'm saying is how much relavence are you to place on advertising claims ? For me well its almost none but for others without the knowledge or the ability to find out I suspect they place a high reliance on the integrity of the copy writer/manufactor.
Oh yes there was this bloke who said his 99.9999% [6n] claim was a typo and should have read the industrial standard 99.99% [4n].......but then didn't bother to change the ad !
