Geoff’s statement above is correct. See the first of my posts dated 10-28-2016 in the long running
"Synergistic Red Fuse" thread, in which I quote posts that have been made here by Ralph and several other designers of well regarded audio electronics on the subject of fuse directionality. I quoted Ralph’s comment (which had originally appeared in another fuse-related thread) as follows:
Ralph Karsten of Atma-Sphere:
… Fuses are inherently incapable of having directionality in any way whatsoever.
… I joined this thread recently with some results on testing. Those results are that the directionality appears out of coincidence and that actually greater improvement can be had by rotating the fuse in the holder for best contact…. Reversal is improving the contact area because fuse and holder are not dimensionally perfect and the fuse might sit better in the holder in one direction. By rotating the fuse in the holder without reversing it gets the same effect only more profoundly.
Also, in the numerous fuse-related threads that have appeared here over the years I can recall exactly two members who have reported experimenting with fuse rotation: Ralph, and a member named SGordon1, who posted in the Red Fuse thread on 5-3-2016 about having done that. Both gentlemen reported that significant differences resulted.
Also, as far as I can recall none of the many people who have reported hearing differences as a result of reversing the direction of a fuse have ever indicated that they went back and forth between the two directions multiple times, reinserting the fuse each time with randomly varying rotational orientation, to verify that their results were repeatable and that they were unrelated to rotational orientation.
Now, does it seem unlikely that rotating a fuse in its holder would have a reasonable likelihood of making an audibly significant difference? In the absence of empirical evidence, such as Ralph has provided, my technically-based instinct would be to consider it as being unlikely although possible. However, I would think it to be vastly more unlikely, and in fact impossible, for a fuse to have **inherent** directional characteristics, to an audibly significant degree. And as I mentioned, several other designers of respected audio electronics whom I quoted in the post I referred to above agree with me.
Regards,
-- Al