Direction of aftermarket fuses (only for believers!)

This popped up during an Internet search. It’s written by Ted at Synergistic Research. What he’s saying here is that the lettering on the fuse is only a tool to show the direction of the fuse before you reverse it, so you won’t lose track and accidentally insert it the same way as before. I.e., The fuse lettering doesn’t really go in the direction of current. You have to try the fuse both ways. Hel-loo!

"In my experience nearly all fuses are directional including SR Quantum Fuses. I recommend you try them in one component at at time and experiment with directionality. You should immediately notice a preference for one direction or the other. If a component has more than one fuse use a DVM (Digital Volt Meter) to determine direction of current in the circuit. Once you know the direction of current in each fuse holder place all fuses in like direction paying attention to have the letters on the SR Quantum Fuses all in the same direction either reading in the direction of signal flow, or against. Next switch direction and the correct match to your component should be readily apparent. There are just too many variables for me to make a blanket recommendation for all components when such a simple and definitive test is available."

" If a component has more than one fuse use a DVM (Digital Volt Meter) to determine direction of current in the circuit. "

The problem with this of course as many have pointed out repeatedly in various threads is with alternating current direction switches many times per minute.

As I understand it it is possible to determine power flow direction in an AC line, for example with an overhead transmission line which way is the source (the power plant). With a circuit schematic perhaps it is possible to determine which way to the components power supply from any particular fuse location? That would be a question for Almarg or other EEs perhaps to answer.

The thing is assuming fuses are directional and that orientation is a significant factor for best sound, you would look for devices that have the directions clearly indicated somehow plus a fuse with the same so things can be done easily without an electronics background. If all that is true but no indicators, someone in design was asleep at the wheel and the customers are paying the price to have to figure it all out.

Could you imagine buying an expensive portable device using 19 batteries in 19 different locations and no indicators which way to place each? That is essentially the worst case scenario for teh NAD assuming fuse direction always matters.

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.