audio power amplifier ratings

Discussion in 'General Electronics Chat' started by guitars13339, Jun 13, 2012.

  1. guitars13339

    Thread Starter New Member

    Jun 13, 2012
    1
    0
    How is it possible for any amplifier to put out more wattage to the speakers than what it pulls from the wall outlet?
    How can amp companies claim these impossible wattages?
     
  2. KASSIMSAMJI

    New Member

    Dec 30, 2011
    5
    0
    the chief basic building block of amplifier is a transistor whatever the type implying that u have what we call DC current gain the one thats behind the wattage amplification tho most power comes from the batter particular amplifier is connected to
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,002
    3,232
    It has nothing to do with whatever KASSIMSAMJI said. :confused: It's call specmanship (lies). You can't get more continuous power from all channels than drawn from the mains. But they often rate the power from only one or two channels at a time putting out maximum power. That way the maximum audio output will be no more than the mains power. Another trick is to use peak power which uses the energy stored in the power supply filter capacitors to provide a momentary large power peak in excess of what the amp can continuously deliver. Caveat Emptor. ;)
     
    endolith likes this.
  4. WBahn

    Moderator

    Mar 31, 2012
    17,737
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    Are they still calling it "peak music power" or some such crap?

    They do it the same way that air compressor manufacturers are able to put stickers claiming 6HP on the side of a compressor with a 120VAC/15A plug on it.

    They lie.

    It's pure specsmanship in which marketing people, who seldom know a damn thing about engineering even if they have an engineering degree, come up with the most absurd measurement they can think of that will result in a high number with the right units (and they aren't too picky there, either) and plaster on all the advertisements whether they know that they are misrepresenting the real case wildly or not (and most of the time they damn well do).
     
    endolith likes this.
  5. wmodavis

    Well-Known Member

    Oct 23, 2010
    737
    150
    First off it is NOT possible to "put out more wattage to the speakers than what it pulls from the wall outlet". That would require a breaking of the law of conservation of energy and result in an efficiency of greater then 100%. Just not possible.

    UNLESS... the method of measuring the supply power and the output power are different, as several have intimated. I.E. rms power vs peak power. Not the same animal. And back in my day there were even some who rated amplifier output in the super bogus "peak-to-peak music power". That doubles the value of 'peak music power'.

    But as stated the advertised specs are usually written by the marketing person - not the engineering group. You do not need to be a liar to be in marketing but it sure helps. It make the sales go up and the company bottom line to look better and the marketing guy's career to advance. And that whole string of events is also made possible by the mostly unknowing public who purchases the produce. And more power is better - right?

    Power output specs should ALWAYS be suspect unless there is clear indication of how that power was measured/calculated or what standard was follower. And even then you should measure it yourself to be sure.
     
    endolith likes this.
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    I recently bought some low cost powered speakers that sound fantastic. They are rated at 150W or 75W. Those ratings are for WHATS!

    The small power transformer is labelled "9VAC/1.1A" (9.9W). The amplifiers are probably 60% efficient so only a total of 6W goes to the two satellite stereo speakers and the sub-woofer.
     
  7. wmodavis

    Well-Known Member

    Oct 23, 2010
    737
    150
    Do not try to put 150 watts of average power into them or you'll be sorry.
     
  8. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The rating of 150W is the actual output of 6W times the age (25) of the marketing idiot.
    Peak power (sometimes called Maximum power) is phoney baloney.
     
    endolith likes this.
  9. bertus

    Administrator

    Apr 5, 2008
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  10. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Close, the real formula is;
    WHATS = (Watts * BSF)

    The BSF varies from manufacturer to manufacturer. :D
     
    endolith likes this.
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