Question Amps, Power and Fuses

[LiveAudio911 10+ year member]

There is a few topics to these nature around here but never really answer my specific question...

Just for grins and gigles I hope you guys can shed some light on this.. cus when it comes to this I have no clue..

So Not to long ago I thought I blew out an amp because I kept blowing my main fuse.. so when i put in my new amp, I only put an 80 amp fuse in so i would not keep blowing my premium fuses @ 150amp...

So I've been running all this time with only 80 amp fuse.. I've always had a power issue, but absolutely no difference between having the 80 in and the recommend in..

So My question:

1. Does the amp's on the fuse rating play any role in the amount of power provided? If so how?

 

2. My understanding of a fuse is once it hits a certain amperage, anything over that amperage or "Spike" would cause the amp to blow as a protection method.. so my question here is.. if amp running normally with no short circuits and so on.. is pulling lets say "140 amps" during musical peeks on a wire with only an 80 amp fuse, would it not technically blow the fuse, or is my understanding as backwards as a hillbilly marrying his sister?

And I suppose the reason for all these questions is kind this weird notion if all stated above was in some way true than I am not pushing as much RMS power as what i should be.. or.. that my power system is not even pushing the amount of power needed to even get close.. does any of this make any kind of seance at all guys?

Thanks.

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[LiveAudio911 10+ year member]

Anyone? ROFL

 

[n2audio 5,000+ posts]

I think you're kind of right.

An 80A fuse is designed to pass 80A indefinitely. it would pass 90A almost indefinitely. 100A for several minutes and so on.

Even at 2x rated current of 160A it would take a few seconds to blow. It would require a massive surge to blow instantly.

I've only blown on-board fuses on two amps personally. One was already torched by the time the fuses "protected" it.

With running a much lower fuse than suggested you may be getting slightly more voltage drop so a bit less voltage getting to the amp. I would guess this would be no more than a tenth of a volt or so - almost certainly an inaudible difference.

I assume you have at least a 4 gauge power wire? An amp with a recommended fuse size of 150A should PROBABLY be on 2 awg or 1/0 wire. It is really pushing the limit of 4 gauge and possible dropping another tenth or 2 of a volt which could begin effecting the amp's output close to something you could hear.

 

[keep_hope_alive Premium Member]

^agreed.

you'd be surprised how little power is required for normal listening volumes.

the amps fuse does not affect the power delivered, other than possible voltage drop from the fuse as stated above.

If you're not blowing the 80A fuse, that shows you that you're not needing as much power as you thought. Amplifier impedance loads, gain settings, and volume settings determine power output.

 

[Suicide Bobb 5,000+ posts]

Weird...cuz I switched from an 80a fuse to a 150a fuse, and there was definitely an audible difference. Not just my ears, but how much the car rattled. I'm not trying to sound like a doucher, but really, it did make a difference.

 

[keep_hope_alive Premium Member]

Weird...cuz I switched from an 80a fuse to a 150a fuse, and there was definitely an audible difference. Not just my ears, but how much the car rattled. I'm not trying to sound like a doucher, but really, it did make a difference.

are you saying it was louder with the 150A fuse? a 80A fuse has more resistance, thus more voltage drop, thus less power at the amp. But it shouldn't be that noticeable. Most likely, something was inadvertently changed when you inserted the new fuse - like a connection issue.

 

[Suicide Bobb 5,000+ posts]

Most likely, something was inadvertently changed when you inserted the new fuse - like a connection issue.

That may well have been the issue. The only thing is that the amperage of fuses at the amp was 150, while my power wire fuse was 80, so it could well have been the fuse...I guess we will never know for sure!