First, a point of information: Some of the responses which followed my previous post lead me to believe that references to "fuse rotation" are being interpreted differently by different people. To clarify, I believe that what was done by the three gentlemen I referred to in my previous post who have **actually tried** rotating fuses did NOT necessarily involve, or at least require, rotating the fuses while they were in their holders, which as has been said above would often be hard to do. As I understood it, removing the fuse from its holder and then reinserting it with differing rotational orientations would suffice, which of course would be no more difficult to do than reversing the fuse’s direction a corresponding number of times.
Also, the underlying cause of the rotational effects Ralph (Atmasphere) observed in his experiments was NOT stated to involve removal of oxidation or other impurities from the contact surfaces. I’ll quote his explanation of the phenomenon directly, as stated in
this thread:
Atmasphere 5-23-2016 4:52pm EDT
It has to do with the fact that the connections on fuse holders are not perfect. The act of reversing the fuse sometimes gets you a better connection. However, directionality really isn’t the issue. Similar to a power switch, the contact area of the fuse holder that is actually doing the work is a fraction of the total contact area. As a result, if you simply rotate the fuse in its holder, you will find that there is a best position where more of the fuse holder contact area is touching the fuse contacts. When the fuse was reversed, on occasion you got better contact or worse contact, which appears initially to be a directional issue, but that is really an illusion.
Interestingly, this effect is measurable as a voltage drop across the fuse holder. As you might expect, the less voltage drop the better. So it is possible to adjust (rotate) the fuse in the holder for minimum voltage drop and thus the best performance. A side benefit is the fuse will last a little longer as the operating temperature is reduced.
Atmasphere 5-26-2016 12:31pm EDT
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. The improvement is measurable and audible; descriptions others have made on this thread of what happens when you get the direction right accurately describe what happens when the contact area is maximized.
Occam’s Razor has something to say here! Given that a fuse has to be used in AC circuits and given that people report differences by reversing the fuse, and also understanding how fuses are inherently incapable of having directionality in any way whatsoever, the explanation that they somehow have an effect by reversing them in the holder is a fairly complex explanation: some sort of unknowable, unmeasurable quality of the fuse itself.
A simpler explanation is that the 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.
Does all of that sound at least somewhat implausible, even though Ralph’s claims are based on actual experiments? It would not be unreasonable to think so, IMO. However, I feel safe in saying that to most of those having an extensive background in electronic design (such as myself) the notion that a fuse would have **inherent** directional characteristics to an audibly significant degree is substantially MORE implausible.
And as I have said in a number of past threads, in audio it is often extremely easy to attribute a perceived effect to the wrong variable.
Regards,
-- Al
