Nsgarch
BTW, were both of the ceramic fuses you tried sand-filled?
I don't know if the HiFi-Tuning fuse is sand-filled. Perhaps others know the answer to that question.
The reason for my interest in mechanically isolating conductors is I've have been working with Purist cables for some time now (including a pair of their new, solid core Provectus speaker cables, Albert Porter kindly lent me to audition.) And I am absolutely convinced that a properly chosen shock-absorbing material around the conductors is essential to achieving the "blackest" possible background in the final sonics.
I have observed this as well when auditioning cables. For instance, I think one of the reasons that the Nordost flatline series of cables "lean" toward the upper registers is that they are more prone to vibrations than other cables where vibration control has been part of the design requirements.
In the case of my fuse comparisons, the difference between the glass and ceramic fuses was quite pronounced. I think that the ceramic body + sand-filling + the little "bubble", if you will, on the filament, help to explain why the sound is cleaner with the Buss fuse in particular.
I should also mention that on the Maggies 3.6R, the fuses are easily accessible and can be changed in seconds without powering off anything. Of course, I made sure there was nothing playing.
One factor to take into account when trying fuses on a power amp or preamp is that, for safety reasons, the unit has to be powered off. Depending on the design and topology, the unit may need some time to fully perform at its best again. IMO, this can be an obstacle when doing A/B comparisons because there is always going to be a longer time delay between tries. Therefore, one may be hearing the difference between a "warm" and "cold" unit, as well as the difference between fuses.