One reason it’s not really fair to discuss High Fidelity Cables in the context of magnetic fields and using magnets or demagnetizers in audio systems is because High Fidelity Cables use magnets for the actual conduction of the signal (I.e., magnetic conduction, his term) as opposed to trying to “manipulate the signal.”
Also it should be pointed out that the conductive element in HFC is not copper or silver but a high permeability alloy, you know, for absorbing/shielding magnetic fields. I suspect a pretty good cable or power cord could be made using that same high perm alloy in lieu of copper or silver and just skip the magnets. You know, since the current flowing through the conductor produces a magnetic field, one that is most likely not too good for the sound. Yes, I know what you’re thinking, well, what about all the other wire and cabling in the system, including the internal speaker wire and transformers? Bingo! 😛