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.








128x128jazzonthehudson
Mapman, you probably didn’t get the memo. Fuses are not only directional in DC circuits, they’re directional in AC circuits, too. You know, when the alternating current is moving in the correct direction the voltage drop is measured as lower across the fuse than when the current is moving in the other direction. Capish? Yes, I know you wish only to learn, Grasshopper.  But first you have to put on your thinking cap.
IMHO Ted at SR puts out a disclaimer and I think it is more likely that a manufacturer keeps the same process (why change?). AMR produced fuses en masse as did Isoclean and for the aforementioned brand, they are, so far, consistent IME (same as HiFi). Another indicator is that HiFiTuning users have consistently reported the direction in the same way as some SR users. Thanks Charles1dad and others for sharing this. It is people like you that has made this hobby more fun and trustworthy for me as I have made most of my purchases based on comments on the Gon. People like GK, though a bit overzealous in postings for my liking, seems to be genuinely interested to find out/help out. He may know that nerdy people can at times put off people (polarizing is only good for electric components) and sympathy counts when buying gear, hel-loo :-). May I also suggest using PMs (e.g. to mapman) instead of a public shout out? Thank you!

As for the circuitry, I know what upstream is as I have the schematics of the amp. Before submitting this dreaded thread, I have the following strategy: try first the fuses on L+R channels with open cover, assuming the fuses are labeled in the same way and proceed from there. Now I will resort to making sure that the 3 main channels (L, R, C) sound coherent. I simply don’t have time for the other channels and will assume that the labeling process is less random that I hoped for. This should be a 1-month project, included bypassing some caps, not a lifetime trial and error. I dread of the amp surviving me.

Again I would like to stump on the example of coupling caps (in tube amps, etc) where most manufacturers don’t care to implement it the correct way (aka polarity/direction), leaving improvements to modding shops and aware DIYphiles (wait, do I smell a conspiracy?).

Lesson learned, early adopters (we should have been over that for fuses but obviously we’re not) pay the price/scrutiny.

I sensed that the fire on my stake seems to fizzle out, you all have my gratitude for that!

Jazz, sorry for intruding on your soapbox.   Good luck with your endeavors.
Geoff,
I didn't intend to imply that the SR fuse lettering suggested current flow,  rather that this is the orientation providing the best sound quality consistently in my components. 
Charles,