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Direction of aftermarket fuses (only for believers!)

It is with reluctance that I start another thread on this topic with the ONLY GOAL for believers to share their experience about aftermarket fuses.
To others: you can call us snobs, emperors w/o clothes,... etc but I hope you refrain posting just your opinion here. If you did not hear any difference, great, maybe there isn’t.

The main driver for this new post is that I am starting a project to mod my NAD M25 7 ch amp for my home theater. It has 19 fuses (2 per channel, 4 on the power supply board, 1 main AC) and I will try a mix of AMR Gold, SR Black and Audio Magic Platinum (anyway that is the plan, I may try out some other brands/models). As it is reasonably difficult to change them, esp the ones on each channel module that requires complete disassembly, I would like to know what the direction is for these models mentioned and of course, others who HAVE HEARD there is a difference please share your experience on any fuse model you have tried.

Fuses are IME directional:
Isoclean is one of the first to indicate the direction (2008/2009) on their fuses. Users of HiFi Tuning (when the awareness rose quite a bit amongst audiophiles) have mostly heard the difference.

As an IEEE engineer, I was highly skeptical of cabling decades ago (I like the speaker design of John Dunlavy but he said on many occasions that cables nor footers matter at all, WRONG!). Luckily, my curiosity proved me wrong as well. I see the same skepticism that I and many others had about the need for aftermarket cables many, many years ago now on fuses and esp on the direction on fuses.

Another example is the direction of capacitors (I do not mean electrolytic types). Even some manufacturers now and certainly many in the past did not believe it can make a difference sonically. Maybe some do but it takes time in the assembly to sort and put them in the right direction/order (esp as some of the cap manufacturers still do not indicate "polarity") so that maybe is one argument why this is not universally implemented.








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danvignau's avatar
danvignau
935 posts
 
Since my head amp inverts the signal, should I just rotate the fuses in my amp and drill a hole to attach my volume knob backwards on the shaft, or maybe just do one of the above? TeeHee
jazzonthehudson's avatar
jazzonthehudson OP
277 posts
 
Look, another flatearther!
polyglot
77 posts
 
danvignau, have you tried after market fuses at all? You may want to try some and do more about power conditioning. Referring to your post there, big caps is just quantity, not quality.  
atmasphere's avatar
atmasphere
11,632 posts
 
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.


almarg's avatar
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almarg
9,670 posts
 
Sounds right to me, Ralph (Atmasphere). I’ve made similar points in some of the other fuse-related threads. I’ve also suggested at times that before reaching conclusions about the matter that people reverse and re-reverse the direction of the fuse a couple of times or more, to verify that their findings are repeatable. While also assuring that the equipment is in equal states of warmup as the comparisons are made.

Not sure if anyone here has been that thorough, but it seems to me that the less likely and the less explainable a perceived effect would seem to be, the greater the degree of thoroughness that is called for before reaching a conclusion as to its cause.

One additional point that occurs to me, though, is that if the AC voltage at a particular location is significantly on the high side, and therefore presumably higher than the voltage that was assumed and used in the design and test of a component, minimum voltage drop across the fuse holder could conceivably degrade the sound to a slight degree, rather than enhancing it. Depending on the specific design, of course.

Best regards,
-- Al

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