We Need A Separate Forum for Fuses

Hi Elizabeth,

While others here disagree, IMO the most plausible explanation that has been offered regarding fuse directionality was provided in this thread by Atmasphere (Ralph). As you’ll see it recognizes the legitimacy of the many observations of fuse directionality that have been reported, but at the same time does not mean that a fuse is **inherently** directional. And note that he has performed actual measurements which support his explanation. Some excerpts from his posts in that thread:

Atmasphere 5-23-2016
If y’all are interested, I think I’ve sorted out what this reversal phenomena is all about.

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
... 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.

While Ralph’s explanation may strike some as being at least somewhat implausible, even though he has performed measurements supporting it, to me and I believe to most others having electronic design backgrounds it is far less implausible than the notion that a fuse would be intrinsically directional.

Also, as far as I am aware exactly one member here besides Ralph has reported inserting and re-inserting a fuse with differing rotational orientations and comparing sonics, a member by the name of SGordon1. Like Ralph he found that significant sonic differences resulted, and encouraged others to try this.

Regarding your thoughtful hypothesis about magnetic fields, the magnetic field surrounding a fuse would have a magnitude and be in a direction corresponding to the current flowing through the fuse, which I would not expect to differ as a function of which way the fuse is inserted.  Aside, that is, from the small effects on magnitude of the phenomenon Ralph has described.

Best regards,
-- Al

There is no doubt magnetic fields are bad for the sound. That’s why there are low frequency high permeability metal absorbers for large transformers and similar high frequency high permeability metal shields/absorbers for speaker magnets. Fuses themselves can be shielded greatly reducing magnetic field effects on the fuse/sound, but you would undoubtedly find the fuse was still directional so it’s very unlikely magnetism causes directionality in fuses in particular and wire generally. I don’t even have to bring up the self induced magnetic field.

All of the wire in the component is directional, not just the fuse. Cable manufacturers control directionality of cables and power cords for a reason. To remove all the guesswork and to improve the sound. Whereas cables are controlled for directionality and are marked with directional arrows, fuses usually must be tried both ways even when they are marked with a symbol or arrow.

Perhaps fuse holders should be manufactured better, who knows, in any case rotating the fuse in a fuse holder would produce random results so the fuse holder theory cannot be the overriding one. The sonic results are also quite peculiar and notable for fuse directionality and cannot be attributed to the imperfections of fuse holders. In other words there are recognizable and repeatable distortions in the sound of fuses in the wrong direction, unlike a “weak” connection in a fuse holder.

I've posted this link on connector tests where it was determined that connectors are the villain. The author would measure and leave and came back and measure again only to get a different result, all the time. Nothing was touched or changed. Bare ends were determined to be the best way to connect a wire. This was in a military application where it was crucial to have consistency in reconnecting equipment which happens to operate in the same range as audio equipment. 

So can a fuse holder be considered a connector? If so, is it as unreliable in being consistent as other connectors? Could that account for the differences when measured after rotating a fuse in it's holder? If so, it wouldn't account for sounding different when reversed. Just a thought, which I'm sure will be shot down.

All the best,
Nonoise

The key phrase in Al's reprint of Ralph Karsten's post is "fuses are inherently incapable of having directionality in any way whatsoever". THAT'S what sticks in the craw of believers.