What is the science behind audiophile fuses?

as scientists we always stay on the shoulders of giants (Feynman citation, I believe)

This predates Feynman by quite a few years.  From Wikipedia:

[The] metaphor of dwarfs standing on the shoulders of giants(Latin: nanos gigantum humeris insidentes) … expresses the meaning of "discovering truth by building on previous discoveries".^[2]This concept has been dated to the 12th century and, according to John of Salisbury, is attributed to Bernard of Chartres. But its most familiar and popular expression occurs in a 1675 letter by Isaac Newton: "if I have seen further [than others], it is by standing on the shoulders of giants."

https://en.wikipedia.org/wiki/Standing_on_the_shoulders_of_giants

@reimarc -

     If your ears and system could determine/resolve the difference in presentation, between the mentioned XLRs; I'll bet that you'd appreciate what better fuses provide.

      As I mentioned: some come with a 30 day, satisfaction guarantee.

      Were you to feel them not worth the $$, you'd lose nothing but the time and postage expended, to return them/it.

       As an inquisitive scientist, isn't your interest piqued (that much)?

       If there's a Hi-Fi Tuning Gold fuse that fits your amp: $49.95* is all it would cost to sate any curiosity.

                 *ie, scroll down this page: https://www.vhaudio.com/fuses.html

        more: https://highend-electronics.com/collections/audiophile-tuning-fuses

@tksteingraber realize that the fuse replacement is just a short piece of conductor adjacent to the power cable.  I don't think you'll ever hear a significant effect fro different coppers on such a short piece of conductor, just so it is heavy (not thinwalled tube).  Now often the fuse holder is not great--it can't be soft copper or it will relax and not clamp the fuse.  Often they are .....clears throat....whispers....steel.  so a good fuse holder would be where to focus your interest. 

That said, I'm as audiophile geek as anybody so I buy high conductivity copper 5mm bar from McMaster car, cut it into fuse lengths on my lathe, and polish with scotchbrite.  I'll be glad to send you one if you want one.

Jerry

@carlsbad2...when you mentioned 'slug', 1st thought 'metal bar, low gauge copper'; 2nd, a diy from an earlier 'confounded fused flail' that 'appeared' (not sounded, yet) worth spending less time on than you do...

But I applaud your efforts to fab and take a Good Slug @ it... aesthetics do count even for a lowly slug... ; ) 👍

3urd was 'homeless snail', soon to be ' budget escargot' ='d *bleah*🙄

@reimarc ....If 'lectric exotic at the super bunting autopsychoic sounds like fun:

0>60 under 2, 0>100>0 under 8 ; seconds, street version pending if not out already... 

The budget 2 wheel version:

...all it lacks is 110db air horns....  My 1st personal diy option...; )

@reimarc The power supply doesn’t merely allow proper operation, it is that which is the source of the actual music. Simply put, the amplifier circuitry modulates the flow of that power through the speakers. Ceteris paribus, the better the power supply, the better the sound.

not the signal circuit itself but the part that supplies the power for proper operation.