What is the science behind audiophile fuses?

Certain things (at least at this point) cannot be measured in order to provide data that can be interpreted by independent observers demonstrating ironclad proof of an effect or lack thereof.  It doesn't mean there is no effect.  A foolproof test simply does not currently exist.

@orthomead , is this your learned opinion or are you spit-balling?  I think there are several ways to provide pretty ironclad proof. Not only several ways but they are not even very hard. One does wonder why they are not done.

Just as I wrote earlier, these types of discussions were much less common when audio stores were more prevalent.

When audio stores were prevalent I don't remember anyone even discussing fuses.

Don't be so pedantic.  Nearly every topic on these forums are assaulted by naysayers who refuse to believe any value is gained in higher end hifi let alone the clever and often times inexpensive tweaks and tricks of the trade- based on no experience.

What I am also saying is that people may sometimes be comparing two equivalent products thinking that one should be superior to the other because it cost 10% or 20% more.  For example, they might test drive a Ford and a Chevy and like one over the other.  But no one is going to compare a Ford to a Lamborghini, for example or claim that the Rabbit GTI is a giant killer.  The Rabbit GTI is a great car in its own right but not the same class as a Lambo.

I learned this years ago with phono cartridges.  I wore out a Koetsu Black phono cartridge.  I enjoyed it very much.  I bought a new "giant killer" cartridge for a few hundred dollars.  It sounded good but it was not in the same league at all as the Koetsu.  I quickly moved on to a much better phono cartridge.

Yes, high end hifi gets into the subtleties and nuances of music reproduction.  Most don't hear it and don't care.  Some people look at a painting and are moved in a profound way.  I spent about a minute gazing at the Mona Lisa and moved on.  (Hey, her eyes do follow me.  Cool.)

Your post needs some of this  

Am I a little dry?  Sorry.  I’m getting old and crotchety, I guess.

I'm no closer to understanding how audio grade fuses work but I got my new Hifi Tuning fuses earlier today for my amps and DAC.  I installed the fuse in my DAC.  The change in sound was immediate and apparent.  Deeper 3D imaging.  A little more clarity and crispness.  Images have an even more defined body to them.  And this is listening in the middle of the day, in the heat with the A/C running.  Can't wait until tonight to see how it sounds.  This audio hobby is just like a drug addiction- always looking for the next big fix.

Now the other part of this story is a sad and tragic tale.  A tale of woe.  A costly and tragic tale of woe.  I ordered two fast blo Hifi Tuning fuses for my mono bloc amps.  I originally intended to test the fuses in the amps first and then in a day or two try the other fuse in the DAC.  But alas, ignorance can be costly.  My amps require slo blo fuses.  When I pulled them out to check the ratings I saw a single filament in the fuse tube and assumed fast blo.  All I had to do was 1) Look on the back of the amp where it said slo blo or 2) Know and understand that the letter "T" on the end of the fuse stands for slo blo.  And so my amps powered up with the new fuses for just the briefest of moments and then poof.  The fuses are toast.  An expensive lesson but now I know; and a word of wisdom for others who read these woeful words.  (Good thing I didn't start out with those $400 brands).  These Hifi Tuning fuses are much less than $100 right now on sale.  It still hurts.

After hearing the change the new fuse made to the DAC, I mustered up some intestinal fortitude and reordered the proper fuses, this time for my Amps.

But now I have a couple of audio grade fuses to cut open and see what's inside for myself.  It's either that or try to sell them on eBay as used fuses.  Any takers?  :)