Romex to your amp?

THHN = Thermoplastic High Heat NYLON.


THHN is not Teflon. Teflon is used for wires 99% of the time or more for temperature rating. A small amount of time for chemical resistance. It is also used for very high frequency cables (>several GHz) and even then not always.


Long 50/60Hz runs have long been multi stranded due to skin effect. There is no magic. Big difference between 100km and 2 meters though. I am sure Siemens is well aware of why in some instances stranded matters or does not. Guess what ... The transformer wire that the expensive cable hooks up in your equipment to is not stranded, is not 6 nines copper, is not directional, is not silver, is not single crystal, is not teflon coated.


Normally for AC cables we want to limit high frequencies somewhat not encourage them.

Oh yeah, "I meant", to talk about the almost always overlooked importance of correctly, "Grounding", your entire system. "To the earths theoretical electrical potential value", OR, "0-Ohm". 
First, you'll need to locate a fairly large, underground, "Moving, water source". apply your grounding electrode here and always "Oversize" your electrode conductor by at least 28%.
 Of course, this need to be completed "before", the home is built. Because this will dictate, "Where" the home is built.
"See, (Nikola Tesla)'s, notes", in Colorado.

Just to be clear. Everything that skipskip posted above is completely correct and I agree with it 100%. 
My OP was questioning the aspect of whether my friend would have a valid point. 
If we take this scenario one step further, and agree ( or not?) that Romex is the material/cable that is the limiting factor in the power supply SQ to our gear ( particularly our amps) then the question becomes how does a different kind of cable from the wall to the amp ( or other gear) better the sound of the cable in the wall. Maybe the answer is that it doesn't actually better the limitation of the cable in the wall, but that the connectors to our after market cabling are what makes the only real difference....thoughts on this?

I'm grateful that jollygreen did not get into "Physics" today. ;-)

Ground connection between equipment can be critical. That is not covered by in wall Romex.