30w,4 ohm speaker driving IC

Discussion in 'General Electronics Chat' started by wenn32, Mar 21, 2011.

  1. wenn32

    Thread Starter Member

    Nov 9, 2010
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    Hello, i want to drive my car speaker which is sony's 30w,4ohm speaker.so i have left & right channels.here i am going to concentrate on one channel (cause as you know i can duplicate the circuit if i know one of the channel).i need an ic that can drive this 30w,4w speaker.can you please tell me an ic that can do this job for me.
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    There are about 120 car radio amplifier ICs available. Most advertise an output with severe clipping distortion with a 14.4V supply of 20W per channel or 30W peak per channel.

    When the car battery is 13.2V and the amplifier is barely clipping then the power into 4 ohms is 14W.

    These amplifiers are actually two amplifiers in a bridge. They drive each end of a 4 ohm speaker. One example is a TDA7240A. A pcb design is in its datasheet.
     
  3. wenn32

    Thread Starter Member

    Nov 9, 2010
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    Thanks for the reply i am really new with audio circuits and i wanted to know if i have a 30w speaker & if i supply 14w will that reduce volume(ie music) or will it increase noise?? & should i connect a voltage amplifer before the power amp since i have a very few volts coming from my input device (which is my mobile(nokia) itself i am going to use audio out).i also found this ic KIA6221AH which is a 30w x 2 amp which i think is cool for my purpose do you recommended me using this ic.Thanks!
     
  4. Audioguru

    New Member

    Dec 20, 2007
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    Your speaker is designed to be driven from a car radio that has a phoney "peak" power rating of 30W or a real power of 14W.
    The difference in volume between 30W and 15W is just a little. 10 times the power sounds twice as loud.

    Most power amplifiers are very sensitive so a preamp is not needed.

    The Korean amplifier IC has the same power as most other car amplifier ICs.
    It produces 30W per channel when the battery voltage is very high with severe clipping distortion and with a 2 ohm speaker.
    It produces about 14W when the battery voltage is normal when it is barely clipping with low distortion into a 4 ohm speaker.

    Its noise level is fairly low like all other car amplifier ICs.
     
  5. wenn32

    Thread Starter Member

    Nov 9, 2010
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    Thanks!suppose if i connect 2ohm speaker to 4 ohm ic what will be the effect? And what happens if i connect 8 ohm speaker to 4 ohm ic? How can i control volume?does that mean i will somehow have to control power right? & its your call sir should i go with korean or TDA IC.
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    And what happens if i connect 8 ohm speaker to 4 ohm ic?[/quote]
    The IC will probably blow up (fail).

    With a volume control pot.

     
  7. wenn32

    Thread Starter Member

    Nov 9, 2010
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    Thank you very much for helping me with much details & PCB.Since you have said TDA i am gonna go with it since it also gives me the operation i need. Thanks again for the help.can i make the ic to work with 8 ohm or 2 ohm speaker?if so what parameter should i change??
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    You said your speakers are 4 ohms, not 2 ohms and not 8 ohms.
    The Korean car amplifier IC is the only stereo amplifier IC that I have seen that can drive 2 ohm speakers. There are two quad amplifier ICs that can drive 2 ohm speakers available but they have many pins and need a special heatsink. Any car amplifier IC can drive 8 ohm speakers but since the current is less than with 4 ohm speakers then the power is less (a little more than half the power).

    The TDA7240A power amplifier IC cannot drive 2 ohm speakers because the current and heating will be too high.
     
  9. wenn32

    Thread Starter Member

    Nov 9, 2010
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    ok now its clear.i have seen data sheet but you have given me the answer.Thanks!
     
  10. dha

    New Member

    Dec 25, 2008
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    Here is a little factoid that might interest you. Power is computed as voltage squared over resistance. If you are limited to 12 volts and 4 ohms, even with straight DC your output is limited to 144 over 4 or about 36 watts. If you are talking RMS ac your going to be limited to a lot less, as in your case. That's why the lower the impedance of the speaker, the more power you can get out of your 12 volt radio.
     
  11. wenn32

    Thread Starter Member

    Nov 9, 2010
    37
    0
    thanks for the info
     
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