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    Amplifier efficiency question

    When an amplifier is said to have a given power output, is that number a measure of it's total output, or the actual power that is being converted into music?

    For example, if I have an amp that is rated at 100wRMS x 2 channels, does that mean that the total output of the amp is 100wRMS x 2 channels before inefficiency is considered? So if the amp is 70% efficient then only 70 of those 100w per channel will be converted into music? Or does the rating measure the actual watts that will be used for music power after inefficiency is considered?

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    natem33 is offline Senior VIP Member



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    Good question. Although I don't have deffinate answer for that, I know that Rockford fostgate measures the actual amount of watts that an amp is putting out with the gains turned all the way up.




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    Amplifier output is measured as electrical energy at the load (speaker). The amount of acoustic energy you get depends on the efficiency of the speakers (converting electrical power to sound), not the amp.

    Amp efficiency comes to play on the INPUT side. A typical power amplifier running class AB1 is only 50% efficient. That means a 500 watt output amp draws 1000 watts from the battery, and loses 500 watts of heat to the heatsink.

    Newer technologies are more efficient, but I'm not sure by how much.

    drc, EE



    dave
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    Another thing to concider in all of this is the fact that "stated" power does not have a specification. Each amp manufacturer is allowed to put anything they want on the specs to sell the amp. We have all see the flea market 700 watt amps for sale for $19.

    We, as a nation of consumers, do not have a accurate way to measure amplifier output. There are some companies that measure the watts as the total amount of power the amplifier can produce into a resistive load. Read this RESISTIVE LOAD, not a speaker necessarily. So, you have amp A who runs as much freakin' distorted crap power as they can through a huge bank of ceramic resistors until they flame, and they say thier amp puts out 1,000 watts RMS. Big deal, this tells you absolutely nothing about how it sounds.

    Listen to many amps and listen to them with your speakers sets...the good will always come through.




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    Efficiency is just how effective the amp is at turning voltage into the wattage needed by the speaker. A low effectincy, say like 40 or 50% will only be able to use that much power that it recieves to turn into usable energy for the sub. An amp with a low efficiency will produce more heat. Sorry I don't know how to spell that word.




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    A normal Class A/B amp is like everyone else said 40 to 50% efficent but a class D is anywhere from 65 to 88% efficent sometimes more depending on the make. Crossfire is around 87% percent wich is really good. Take a normal amp say rockford 1000.1 and a crossfire 1000.1D and run them at full power for a while. Put your hand on both and you'll get the jist of effeciency. The class D will be alot cooler meaning it turned the voltage into power basically instead of turning it into heat. An A/B amp can't handle the voltage as well and has to do something with it. The class D has a little higher distortion but for subs you'll never hear it. Now for highs and mids my personal expeirence in to run a highly efficent class A/B with low distortion for crisp clear highs. Rockford doesn't make amps like they use to but awhile ago I would have said them now I say Harrison labs or JL. Hope that helps.




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