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Emulating car battery output through home power?

  1. Jul 20, 2015 #1
    I'm setting up an amplifier which is intended for use in a car, and I'm not using it in one. I'm trying to power it through a typical DC 250 volt wall outlet. What kind of transformer should I use? (I'm also trying to power a car stereo with it as well)
     
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  3. Jul 20, 2015 #2

    NascentOxygen

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    You mean 250v AC, I assume?

    How many pins does your wall outlet accommodate?
     
  4. Jul 20, 2015 #3
    3 pins. 2 regular and the optional ground.
     
  5. Jul 20, 2015 #4

    berkeman

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    You buy a power supply module that is already safety approved for the 240 (not 250) Vrms wall AC Mains output, and provides you with the output voltage required by the stereo or other load. What is the input power for the stereo specified for?
     
  6. Jul 20, 2015 #5

    NascentOxygen

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    You need a lot more than a transformer. You need a heavy duty 12v DC regulated power supply; this is a box containing not only a transformer but also transistors, ICs, large capacitors, and more.

    If you indicate how many watts your amplfier can put out, I'm sure someone here will be able to say what amp rating the regulated supply will need. If you plan to simultaneously power a second power-hungry device, its power needs must also be included in your calculations before deciding exactly what you need to buy.
     
  7. Jul 20, 2015 #6
    On the page in which I'm buying the stereo from, it doesn't specify what the input power is. It just takes whatever the car battery gives it, hence why I'm wondering to just make a wall output act like a battery.
     
  8. Jul 20, 2015 #7

    berkeman

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    So the input voltage is 12V. What is the power output specification of the amp?
     
  9. Jul 20, 2015 #8
    The amp is 1,500 watts.
     
  10. Jul 20, 2015 #9

    berkeman

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    Holy crap that's a lot of power. I = P/V, so that gives you the specification for the output current from an equivalent DC power supply.
     
  11. Jul 20, 2015 #10

    Averagesupernova

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    Be careful with amp manufacturers specs. There are plenty of ways they can inflate the spec to more than it actually is. If it truly is able to drive 1500 watts into a load then it is unlikely you will be able to find a 12 volt power supply capable of running this amp. If the amp were 100% efficient (it's not) you would need a power source capable of supplying 125 amps.
     
  12. Jul 21, 2015 #11

    jim hardy

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    Last edited by a moderator: May 7, 2017
  13. Jul 21, 2015 #12

    anorlunda

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    A 12v auto battery charger may also provide what you need, and they are relatively inexpensive.

    I agree that 1500 watts sounds excessive. Your car would have a hard time supplying so much current.
     
  14. Jul 21, 2015 #13

    jim hardy

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    The transformer type charger is not "filtered" so he'd want to add a "supercapacitor" at charger's output. That's available in any car radio shop, even Walmart.
     
  15. Jul 21, 2015 #14

    anorlunda

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    I would try it first without the filter Jim. The auto 12v environment is very noisy so the amp may have lots of it's own filtering. If it doesn't work well, the capacitor could be added.
     
  16. Jul 21, 2015 #15

    jim hardy

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    Indeed.
    Transformer type chargers hum, too.
    Inverter type is quieter both electrically and acoustically
     
  17. Jul 21, 2015 #16
    P = E^2/R, to deliver 1500W RMS using a 12V supply voltage, the resistance (impedance) of the connected speakers would have to be about 0.1 Ohm. With a more practical 2 Ohm speaker impedance, you would need more than 55V to deliver 1500W.
     
  18. Jul 21, 2015 #17

    Averagesupernova

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    This really isn't relevant. Car audio amplifiers in this range have built in switch-mode power supplies to step the voltage up to appropriately drive 2 and 4 ohm speakers. I suspect the amp in question is a single channel class D designed to drive a subwoofer.
     
  19. Jul 21, 2015 #18
    Ah - The OP is "setting up" an amplifier. Thanks for pointing this out.
     
  20. Jul 21, 2015 #19
    Well as a low cost solution why not connect a 60 amp battery charger to a car battery and use that . The battery should provide enough filtering.
     
  21. Jul 21, 2015 #20

    sophiecentaur

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    That would be the cheapest solution by far and, as long as you use fat enough supply leads, it would be truly representative of how that amp is going to work in the car.
    Does the amp manufacturer have any recommendations about how to supply the amp when mounted in the car? If they don't then their quoted Peak Power value is pretty suspect.
     
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