Help! Powering audio amp

Discussion in 'The Projects Forum' started by jippolito, Jan 8, 2014.

  1. jippolito

    Thread Starter New Member

    Jan 7, 2014
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    I am trying to power a car audio amp indoors using a 120-16v transformer (t113074( www.platt.com/platt-electric-supply...0-16-32/Acme/T-1-13074/Product.aspx?zpid=1324)) connected to a bridge rectifier rated for 40amp and a car audio amp rated at 4.4f. The transformer is putting out 16vac. After the bridge rectifier i am getting around 14.3 vdc. When I hook up the cap or amp (which is 5500w) my voltage jumps to around 20.7 causing my amp not to run and my cap to read high on its digital readout. I have tried using caps on each leg of vdc to ground to filter dc voltage ut i can not get the voltage to stay around 15vdc with the amp or cap hooked up. What am i doing wrong or what else should i ad to the circuit to lower the 20.7vdc to around 15vdc with being able to use 40amps? FYI i already had the transformer sitting around the house and thats why I am trying to use it.
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
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    428
    you will have to add a voltage regulator capable of handling the current. a 16 vac transformer goes to quite a bit more charging the filter cap to the peak of the voltage.
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    What are you doing that you need to #1 use a car radio and #2 need 6000 watts..
    "Marty McFly"
     
  4. tcmtech

    Well-Known Member

    Nov 4, 2013
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    You have the wrong transformer. :rolleyes:

    To get the proper DC voltage you would need a 12 VAC transformer.

    When you rectify AC into DC and add a capacitor you get a DC voltage nearly equal to the peak of the AC voltage which is 1.414 times the RMS AC voltage.

    For what you are doing at that power level I would highly recommend going with a commercial 12 volt battery charger with at least a 100 amp continuous rating charging a good sized 100 ah or larger deep cycle battery plus the 4.4 farads of capacitors.

    If your amplifiers do infact put out 5500 watts you need a power source capable of supplying that plus a good 20% more on the DC power side.

    (5500 x 1.2)/12 = 550 amps of current have to come from some place and clearly a 1500 VA transformer and 40 amp rectifier are no where close to being sufficient on their own.

    BTW a good source for a transformer that will work for your application would be a small wire feed welder that uses a simple multitap transformer. Most any cheap 200 amp rated MIG units have a lower output voltage range of around 12 - 15 volts DC.
     
  5. donpetru

    Active Member

    Nov 14, 2008
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    You can show me what model of car amplifier that you want to supply? That car audio amplifier eat 5500W from car battery ??? I doubt.
     
  6. jippolito

    Thread Starter New Member

    Jan 7, 2014
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    i will post a pic when i get home. it is a 5500w car amp. i dont expect to run the amp full....maybe not even 1/4.
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Why?
    Just buy a proper receiver/speaker set.
    For the money you spent on the transformer you could have just bought a full 5.1 surround sound kit.
     
  8. donpetru

    Active Member

    Nov 14, 2008
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    I understand but when you get home post a picture with all the amp and tell me what value does the speaker impedance (2 ohms, 4 ohms ...)?
     
  9. jippolito

    Thread Starter New Member

    Jan 7, 2014
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    I had the transformer sitting around the house. No money spent.
     
  10. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Surprisingly common capability with today power electronics. I have a pair of Audiobahn amplifiers that will easily do 2500 watts RMS into 1 ohm off of a 12 volt rated source.

    Amplifiers that will do double that RMS into 1/2 ohm are all over the place now.
     
  11. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    I can hear the neighbors now... "Turn that crap off... Its shaking my windows"... "Damn Kids"
     
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