About TDA2004

Discussion in 'The Projects Forum' started by devgorkha, Jun 4, 2011.

  1. devgorkha

    Thread Starter New Member

    May 17, 2010
    This is the stereo power amplifier (class B) specially use in car radio. I use it in my project. I have to drive loud-speaker through it applying different type of input.

    1.Input from MIC

    2. input from mono audio source.

    3. input from stereo audio source.

    4. Both mono audio and MIC (mix audio signal.)

    there is no problem with mono input and stereo input but input from MIC doesn't work.

    I use electret MIC with preamp ( image 2) output of preamp is connected to buffer and then connected to the input of TDA 2004.

    next problem.....

    TDA2004 with 5Ω stereo speaker and input volume control 22k stereo pot ... when i increase volume to maximum sound distorted.
    may be supply problem or ... i used 18v supply.
  2. iONic

    AAC Fanatic!

    Nov 16, 2007
    If you are using 18V with the PreAmp, then I would expect distortion.
  3. devgorkha

    Thread Starter New Member

    May 17, 2010
    no no 18v is only for TDA 2004. 9V for preamp.
  4. Audioguru

    AAC Fanatic!

    Dec 20, 2007
    The output power of a TDA2004 with an 18V supply and a 5 ohm load is about 7.2W per channel at clipping. Of course it distorts with severe clipping distortion if the input to the TDA2004 is higher.

    The preamp transistor is wrongly biased so it is almost saturated which produces severe distortion if the input to the TDA2004 is at a fairly high level.
    The mic preamp has very little negative feedback because its circuit is cheap and simple so it will produce distortion on all loud sounds into the mic.

    Maybe the preamp doesn't work because the pins on the transistor are connected backwards. Look at its photo in the datasheet.

    Maybe you are confusing distortion with acoustic feedback howling where sound goes around and around because the mic can hear the speaker?

    AAC Fanatic!

    Jul 1, 2008
    Besides your bias issue that AG pointed out, C1 (.1uF) seems far to small. C2 may not be an issue though because the input Z of the power amp is fairly high. That said, a 10 to 20uf would be more appropriate.