# Calculation of RMS power of an amp by looking at the fuse/s



## frankmehta (Jan 20, 2009)

I wanted to know whether there exists a simple way to calculate the ACTUAL RMS power of the amplifier, by having a look at the fuses.

For eg. my DLS amp has 2*30A fuses. How can I calculate the RMS power developed by it???


PS: Tried searching for this here, but ended up with ZILCH.


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## fish (Jun 30, 2007)

http://www.diymobileaudio.com/forum...3-zed-audio-amplifier-group-buy-zedmanual.pdf

This was interesting... seems to go against the grain how I originally perceived it.  Not really sure which way to go now.


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## Oliver (Jun 25, 2007)

Just quote the biggest number the amp has printed on it:laugh:

Otherwise . . . there is Ohms Law, meters and tests that will tell U


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## Austin (Mar 12, 2009)

The fuses on the amp dont mean much...well atleast to tell you how much power the amp can make.

You have to have meters and scopes like a$$hole said. There is no actual "watt meter" out there that i know of.


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## Oliver (Jun 25, 2007)

quote>
Another good indication of an amplifier's true output is the size of the fuse used. True 200 watt amplifiers do not use a ten amp fuse. Use your head when buying and keep in mind the brand's reputation for quality. A quick and dirty way to check the true power output of an amplifier is to take the fuse value of the amplifier (or the sum for multiple fuses) and multiply it by 6 for class A/B amps or *10 for class D amps* (higher efficiency). *This is by no means an accurate way to judge power *but it will tell you if your amp is even close to it's specifications. For example, if a class A/B "1,200 watt" amplifier has a fuse value of 25 amps then you can take 25*6 and get 150. So this "1,200 watt" amplifier is more in the range of 150 watts.
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quote>
One thing to note is that doubling the amplifier power does not double the sound output. A doubling of system power adds only 3dB of SPL (volume) to the output. SPL works on a logarithmic scale so it takes a 10dB increase for the sound to be "doubled". This works out to a little over three "doublings" of power. So if you have 100 watts of power you would need to double that to 200 watts, double that to 400 watts and then double that to 800 watts. That would give you a 9dB increase. To truly get the 10dB increase you would need 1,000 watts or a ten fold increase in power.
quote>


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## Austin (Mar 12, 2009)

^^ good post. I always knew to check the fuses when buying an amp but never knew what i should multyply it by to check roughly the wattage of the amp.


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