I suppose it would be totally out of bounds at this point to say that I have gone beyond AC power cords, and found that even in straight flat DC power, I can hear differences in the types of chemical compositions of the batteries being used. Not only does the wire matter, but whether there is a Ni-Cad, Lead Acid, Alkaline, or whatever kind of battery being used. I use DC power for most of my system, and have experimented with different battery types, and believe me, they are audibly different. So, is 12v simply 12v, or is there a difference?
Science is to be used to explain why things happen, not to be used to say that they can't happen because the scientist can't measure them. A real scientist would expand his study and abilities to find out why there is a sonic difference, and not stand on previous ideas that cannot explain the phenomenon. Science is learning, not the refusal to learn.