why do hi-end fuses keep blowing, while std don't?

Modjeski doesn’t talk about the "sound" of fuses, only their electrical behavior. What the internal composition of the fuse does with the gas created when a fuse pops (if my memory serves me well. I haven’t read his Forum posts in in years), what’s it’s "high breaking capacity" (whatever the hell that is. The Hi Fi Tuning Fuse designer didn’t know either, Modjeski reported ;-), how it behaves in a DC circuit (what the power tubes in the RM-9 run on), those kinds of issues.

Yes, Modjeski is skeptical (to put it mildly) of the audible benefits of power cords, fuses, overly-expensive (define that as you wish) interconnects and speaker cables, etc. But one thing you can be sure of, even if you don’t consider him an audiophile: he is an expert at electronics, circuits, tubes, transformers (he winds his own), and, yes, fuses.

There is a great video on You Tube of Nelson Pass and Roger Modjeski giving back-to-back talks to DIY designers at the semi-annual Burning Amp Festival in the Bay Area a couple of years ago. Well worth your time to watch (and learn). Modjeski is now offering a new ESL loudspeaker of his own design and build, and a partnered direct-drive OTL tube amp that eschews the input transformer found in most other ESL designs, as well as, as it's title suggests, an output transformer. I'm dying to hear THAT combination! His little RM-10 amp is THE amp for the old Quad ESL.

You're missing my point, Mr. Kait. You are in fact making it without realizing it. Listening for the audible effects of a fuse, and evaluating it's electrical behavior, are two very different things. Modjeski approaches hi-fi evaluation first as an ee (as a purely intellectual activity), audiophiles don't.

A point worth making is that Modjeski investigated and reported his findings on only the original Hi Fi Tuning Fuse, not any other boutique brand or design. Each of those has it's own unique characteristics, and should be evaluated separately. The ARC LS16 I bought years ago came with a Hi Fi Tuning Fuse installed, and worked fine. After reading Modjeski's report on their use in his RM-9, I wouldn't dare install one in a power amp tube application (in a DC circuit). Knowing how audiophiles react to criticism of a product they own, I'll bet very, very few have read that report. Suit yourself!

As for RM being an electronic wizard, anyone who can watch his talks at The Burning Amp Festival (and those of Nelson Pass) and not come to the same conclusion is a better man that I. Or better yet, listen to one of his amps! Geoff, I'm going to take a wild guess and say I'll bet you have never heard one. The RM-9, the RM-10, the RM-200, any of his single-ended triode amps, or his OTL's? What amp do you listen to music through?

A.E.’s are more skeptical than E.E.’s. But more to the point A.E.’s investigate rather than proclaim some conclusion or another without a thorough and complete investigation. That is, after all, the scientific method. That’s how we progress. But RM is not alone, I know many high end amp designers who are cock sure they’re right about a lot of audiophile ideas that have been accepted over the past twenty years. Like fuses, directionality of fuses, directionality of wire, aftermarket power cords, directionality of power cords, stuff like that.

I repeat, of the approximately 90,000 aftermarket fuses sold there has not been a single component damaged by a fuse that has been documented and verified. So,I think it's safe to write off RM's "experience"  as a fluke and dismiss him as one would any outlier.