GEEK wrote:
By hitting it accidently with a Dremel and watching the sparks fly!
So I took some samples to my belt sander and half of them (the newer ones) threw sparks

Quote:
Then you have bootleg wire - probably repackaged copperweld (TM) wire that was bootlegged. Household wiring must be entirely virgin copper by code, and THHN wire is emphatically copper as described by the OP.
Yes there is something wrong if domestic mains has steel conductors. Some breaker boards used in the UK had a copper plated steel buss wire from the main breaker to the individual circuit breakers, the buss wire loosened with heat and cooling and caused the boards to set fire.
You can't clamp down very well on steel with copper/brass terminals (the steel is harder).
From a sonic point of view I like mains solid core for DC current in PSU's but I strip the PVC and replace with PTFE sleeve.
I prefer it to OFC, LCOFC is better..
NB just for interest Orange drop 715 have copper plated steel lead outs and actually sound better than the 716 which has copper, but that's just horses for courses

<<NB no oxen..LOL
What the effect is with this plating is a weird concept, cheaper? strange..Amtrans are playing with Gold plated OFC I have never tried it.
I have tried Nickle wire and it doesn't sound like copper. What a PITA to solder

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Obviously Steel wire armour is a different thing.
Regards
M. Gregg