Fuse Elements

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Waker

Fuse Elements
« on: 17 Nov 2010, 07:26 am »
What part of a fuse's construction and materials give the fuse its amperage rating?  Is the fuse element larger or smaller in relation to its ampacity, or is there some other material/variable in play? Also, what causes a fuse to fail faster or more slowly? I am using Hifi Tuning fuses in Maggie 3.6R speakers that call for a 2.5amp fuse for the tweeter and a 5 amp for the midrange. The Magnepan manual lists the stock fuses as normal blow, and they caution against using slow blow.  All HiFi Tuning fuses only come in slow or fast blow.  My question is, would slightly exceeding the recommended ratings offer more conductivity in the way of larger fuse elements? And would using slow blow vs fast blow offer any more conductivity, safety aside? Forgive me if my thinking about fuses is too simplistic, as I just don't know how they actually differ in order to do what they do.  I just wonder if pushing the envelope a bit would offer even more current across this part of the path.  Thanks to all for your advice.             

JohnR

Re: Fuse Elements
« Reply #1 on: 17 Nov 2010, 07:34 am »
Err... well,  you would want to use "fast blow" fuses then. And the fuses are presumably there for a reason, so use the closest available values to what's specified by Magnepan.

richidoo

Re: Fuse Elements
« Reply #2 on: 17 Nov 2010, 02:52 pm »
Exceeding the fuse rating will provide more current headroom. But you won't really notice the difference of a 10% bigger fuse because the fuse element is never going to have the current capacity of a thick copper wire and the temporary contacts holding the fuse are still there. Using some contact enhancer like Walker SST will stop micro arcing and reduce impedance of the temporary contact (fuse clips) and improve the sound with the fuse in place. Using the HiFi tuning fuse is the best you can do while staying safe.

Sloblo offers more conductivity, but only for a short period. The resistance of a conductor goes up with the temperature, so even if it lasts 1 second instead of 1mS it will be red hot and not really helping the SQ. A fuse is by nature a poor conductor.

The fuse ratings are the minimum current that could damage the speakers in the event of electronics failure or operator error. Music power will always be much less than that. So with a good quality silver fuse and contact enhancer for the fuse clips you shouldn't be leaving much on the table. If you want still more, there are safe modding opportunities in the crossover.

Waker

Re: Fuse Elements
« Reply #3 on: 18 Nov 2010, 02:22 am »
Thanks for your input.