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What exactly does an amp do?

  1. Jul 24, 2007 #1
    I know that in car audio systems amps are used to increase power to the speakers especially the subwoofers but how exactly does it do that? If an amp is 1000 watts and watts is volts times amps than what is the amp doing to make the 1000 watts? Also in some cars that have systems that are sometimes 4000 watts or more how is the cars electrical system able to handle that kind of power? Any enlightenment will be much appreciated. Thank you.
     
  2. jcsd
  3. Jul 24, 2007 #2
    Think in terms of energy. A watt is a measure of energy flow per unit time. Unit of energy is a joule (J), so a watt is a joule per second J/s. (watt is also Volt Amp same thing)

    To give you an idea, a fully charged car battery can hold up to 6 million joules of energy. If you want to dump it at a rate of 1000 J/s (1000 watts) into an amp, it will take 6000 seconds or 2 1/2 hours to fully expend its energy.

    A car's battery is recharged of course, by an alternator. The energy to recharge the battery comes from gas. To give you an idea 1 gallon of gas has about 130 million joules of energy. Most of that energy is converted into motion of the car, and some is used for everything else, including running the alternating.

    An amp is composed of transistors that actually do the amplifying. It is a very broad subject to explain all in a single thread. But you can read up about them here,

    http://en.wikipedia.org/wiki/Transistor
     
  4. Jul 24, 2007 #3

    chroot

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    An amplifier takes in a signal with a small amplitude (a couple of volts from your head unit) and outputs a similar signal with a much, much larger amplitude (even as high as a hundred volts for large speakers). It creates this large version of the signal by consuming power that ultimately comes from the car's alternator.

    - Warren
     
  5. Jul 24, 2007 #4

    Danger

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    In the simplest terms, you can think of an amp as a relay. The low side of it reacts to a low-power signal and uses it to control a high-power source that goes to the load (speakers). Most vehicles pumping high decibels have auxilliary batteries that are specifically dedicated to running the sound systems. The most powerful ones have auxilliary alternators as well, also driven by the engine.
     
  6. Jul 25, 2007 #5
    So an amp works by increasing voltage to the speakers?
     
  7. Jul 25, 2007 #6

    Danger

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    No. It doesn't actually increase the voltage in the way that a transformer does; rather, it modulates a high-power source to follow the pattern of the original signal. Any automotive sound system that I've seen still uses 12 volts (or 24 in some special cases); it's the available amperage that gets boosted.
     
  8. Jul 25, 2007 #7

    chroot

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    An amplifier takes a small signal, and outputs a similar, yet much larger signal. In that sense, yes, the amplifier ultimately makes sounds lounder by enabling you to apply a larger voltage to your speakers.

    - Warren
     
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