All of the quantitative specifications I have seen in my examinations of technical datasheets for garden variety fast blow and slow blow fuses support the conclusion that for the kinds of fuse ratings that are used in audio components the voltage losses and current limiting that may be introduced by the resistance of garden variety fuses are so low as to be negligible, and to leave little or no room for improvement. And even if that were not so, at least in the case of mains fuses any such losses would be completely swamped by differences in AC voltage among various locations, and probably even among different outlets at the same location. And it seems safe to assume that the limiting effects of whatever infinitesimal amount of inductance a fuse may have on abrupt changes in demand for current would also be negligible.... the fuse design can only have 3 possible outcomes:
Allow the unit to operate as designed;
Starve it of current or voltage lowering its performance;
Raise the amount of current that can pass through the fuse, which would damage the unit if an internal short were to occur (but have NO effect otherwise, as an electrical circuit operating normally will only draw the amount of current the circuit uses, no matter how much might be available).
As someone who knows his way around a circuit board, to use your words, I have no idea how these fuses may work their magic, although I remain open-minded given the overwhelmingly positive results that have been reported by members I consider to be particularly credible.
Best regards,
-- Al