# What is the relationship between fuse rating and amp power?



## silent1 (Jun 2, 2005)

Would amps times voltage be max power possible ever? Or could there still be substantial peaks beyond this? 

For Instance... a 60x4 at 4ohm or 100x4 at 2 ohm amp with a 40 amp fuse would be 480 watts at 12 volts. Im guessing that would be 120 watts a channel. Is this the most amount of power it will ever make at any given load? Is it possible for the amp to run at 100 watts a channel and still have a 200 watt peak? Is this amp overrated?


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## mikey7182 (Jan 16, 2008)

I think it has just as much to do with efficiency/current draw as it does output... I'm still learning though.


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## haibane (Sep 29, 2005)

Fuse rating is merely a number figured out to protect the amp from dying. The amp might be able to take a current of 40amps, but has a fuse that cuts it off at 20amps. Its hard to say the output from it because P=VI, but also V=IR = 4 x 40 = 160v. 160v^2/4ohms and that gives us 6400 watts. I am sure it does that all night. The thing is your input voltage doesn't mean anything either because you are going through either a series of Mosfets or BJTs and therefore unless you took apart the amplifier you wouldn't know what the different effects would be because you don't know the internals of the amplifier. There are way too many variables to say fuse gives you this much power in other words.


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## silent1 (Jun 2, 2005)

That makes sense.


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## phatredpt (Feb 22, 2006)

14.4 volts x 40 amps = 576
576 x .7 (70% efficient amp) = 403.2 watts
Looks like this might explain your rating


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## silent1 (Jun 2, 2005)

Ok, you got 403 at 70%. Is this peak or rms?


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## annoyingrob (Aug 24, 2007)

silent1 said:


> Ok, you got 403 at 70%. Is this peak or rms?


RMS. It's what the amp can draw continuously.

I usually go by a general rule of thumb, fuse rating x10 = continuous output power.


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## haibane (Sep 29, 2005)

AVERAGE power dang it. No such thing as RMS power... ugh...


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## annoyingrob (Aug 24, 2007)

haibane said:


> AVERAGE power dang it. No such thing as RMS power... ugh...


How about continuous power


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## phatredpt (Feb 22, 2006)

haibane said:


> AVERAGE power dang it. No such thing as RMS power... ugh...


And to think...
They have been using the wrong term to rate amplifiers for all these years!


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## haibane (Sep 29, 2005)

phatredpt said:


> And to think...
> They have been using the wrong term to rate amplifiers for all these years!


EE... here if you really want to get in to it lol


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## phatredpt (Feb 22, 2006)

EE here also...
For over 25 years 
thanks though!


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## haibane (Sep 29, 2005)

phatredpt said:


> EE here also...
> For over 25 years
> thanks though!


So I guess you were only kidding?


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## phatredpt (Feb 22, 2006)

P average = V rms x I rms

For those that want to get technical


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## phatredpt (Feb 22, 2006)

haibane said:


> So I guess you were only kidding?


RMS is the "term" that seems to have been settled on by the industry to keep the definition short and sweet IMHO

the real questions are:

With what input voltage?
At what frequency or range?
Continuous or Burst (i.e. IHF 202)
At what distortion %?

The CEA rating method was a nice thought to create a level standard, but the issues that it makes amps look "better" by using high distortion ratings, and high input voltage levels to inflate the output ratings in the interest of the manufacturers left a "stigma" over it.

And of course all of these measurements are done using resistive loads (as they must be to keep things comparable) but in the real application (reactive loads) your "mileage may vary"
 

So yes... I WAS kidding


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## Pseudonym (Apr 17, 2006)

*NERRRRRD FIGHHHHHT!!!!*


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