The new Synergistic Research BLUE fuses ....

Jafreeman 10-27-2017
How do they work? They are better conductors than the tiny filaments in glass---question is, how much are they part of the circuit? ... Perhaps Al can define the various positions of fuses and their part in signal conduction. I know if I remove the fuses from the AC main inputs, the equipment won’t work at all. I believe the fuses in my Maggie 3.6 tweeter and midrange fuse bank are part of the final signal pathway. Are they the complete pathway, or are they a shunt to receive an overload? How about the AC position--and the rail fuse?

Aside perhaps for some unusual circuit configurations that may exist in a few designs, a fuse will always be in series with what it is protecting, rather than in shunt (i.e., in parallel). Otherwise the fuse wouldn’t be able to interrupt the current drawn by the equipment that is being protected, when a fault in the equipment makes that necessary.

Regarding upgraded fuses being better conductors, I’ve indicated in some previous fuse-related threads that when the resistance numbers that are available for various fuse types are looked at quantitatively the bottom line generally appears to be that they are small enough to at most be marginally significant in some applications, but not in most applications. And in the case of mains fuses the voltage drops corresponding to those resistances would certainly be vastly smaller than the +/- 6 volt tolerance we have in the USA on our incoming 120 volt AC. IMO what stands a greater chance of being significant more often are the **fluctuations** in fuse resistance that occur in applications where the the amount of current being conducted by the fuse fluctuates widely. Which in turn could very conceivably result in modulation or intermodulation effects on the signal. That would apply to speaker applications (as you’ve found with your Maggies), and to many power amplifier applications. Most preamps and source components, though, draw essentially the same amount of current all the time.

Nonoise 10-27-2017
As I pointed out on (I think) a different post, there are 3 levels of fuses out there with the first two for commercial use. The 1st level is the cheap, standard fuse that varies more than it should concerning it’s rating and the next level up are the boutique fuses which melt exactly when they should.

If you’re device is drawing more current than what it should, maybe you need to take a long, hard look at your component and find out why it’s doing what it shouldn’t be doing.

I recall that you’ve mentioned the statements in the first paragraph were told to you by a seller of boutique fuses. Is there any other basis that you are aware of for these statements? I am not aware of any other basis.

And I can recall that at least 8 different members have reported here in the past year or two that boutique fuses blew in their equipment, which in most or all cases had presumably been operating without issue for a considerable amount of time with the stock fuses. In most of those cases the fuse which blew had the same current rating as the stock fuse, but in at least one case I can recall the upgraded fuse blew even though it had a significantly higher current rating than the stock fuse.

Also, it’s perhaps relevant that the technical data supplied by Littelfuse and Cooper Bussmann for their fuses is vastly more comprehensive than data I’ve ever seen for any boutique fuse. And included in the data provided by Littelfuse and Cooper Bussmann is a melting point specification, measured in amps squared x seconds, which I’ve never seen provided for a boutique fuse. Admittedly, though, that particular spec is just provided in the form of a nominal value, without a +/- tolerance.

Finally, my perception and my own experience has been that with very rare exceptions stock fuses in audio equipment tend to blow when and only when a fault in the equipment makes it necessary.

So if I’m correct in interpreting the second paragraph I quoted from your post as implying that the equipment should be blamed when a boutique fuse blows and there is no evidence of an outright fault in the equipment, I would have to respectfully disagree.

Best regards,
-- Al

@lalitk   Who sells the HiFi Tuning Supreme Cardas fuses? All I'm finding are the Supreme silvers from the usual players..

@1markr ,

Please contact Chris at Chrisvh@vhaudio.com. 

@lalitk  Thanks!

@almarg , yes, it was a rep from The Cable Co. who told me he researched as best he could how and where fuses are made and told me there are basically three types or grades of fuses and the applications used for each. 

He also went on to say that the lowest grade of fuses can vary in performance despite the specs and the next two levels adhere better to the specs. The mid level fuses, which is what the boutique audio fuses are based on, have been around a long time for use in other, more critical applications. 

One would think that since this has been known for awhile, the more knowledgeable folk around here who are more versed in this would have said something sooner. Something like, "all those fuses are are rebranded, higher quality fuses that have been used in ...." and the conversation wouldn't have been so heated.

In my simple googling of high rupturing fuses and their uses, there are plenty of sites explaining them by highly degreed engineers so there is no mystery to these boutique fuses other than why they charge so much but that is another matter. 

Hearsay, yes. But I'm of a mind after researching what I could that it all makes sense without any need to strain credulity. That, and what my ears tell me. As for my last paragraph, there was a bit of snark in it. Not all the equipment should be considered faulty or poorly designed but who's to say that some of it isn't? We only have their word to go on, like mine and others who do hear a difference. The statement I made was to make people think before decrying aftermarket fuses.

All the best,
Nonoise