Originally Posted by drez
So for the same purity level, am I understanding that ETP copper is more conductive than OFC? Pretty interesting, I never knew that (then again this is not really my field.)
Not quite. What I said was that ETP copper, which is less inherently pure than OFHC copper, is AS conductive as OFHC.
If you just leave the impurities in suspension, it would have a lower conductivity. But if you add a precisely controlled amount of oxygen during the smelt, the oxygen reacts with the impurities and takes them out of solution. And this results in a conductivity that's the same as OFHC which has a higher intrinsic purity.
In other words, there's really no difference between the two as far as conductivity is concerned.
The reason OFHC copper was developed was for situations where the copper may be heated in a reducing atmosphere such as hydrogen. Since ETP copper contains oxygen, it can react with the hydrogen which can cause the copper to become brittle. Since OFHC copper can't have any appreciable oxygen content, it has to have a higher intrinsic purity in order to be as conductive as ETP copper.
Bottom line, with regard to audio applications, OFHC copper is just a marketing buzzword. I mean, Oxygen Free High Conductivity copper sounds sexier than Electrolytic Tough Pitch copper.