Speaker Amplifier Problem

Discussion in 'The Projects Forum' started by EgagDesigns, Aug 10, 2012.

  1. EgagDesigns

    Thread Starter New Member

    Aug 10, 2012
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    Hi,

    I'm currently working on a project that consists of taking a line level input from something like an iPod and play it out some speakers. I'm having a problem with the subwoofer and woofer, whenever there are really low notes they must short or something causing the power supply to current limit. I have concluded that it's the woofer/subwoofer because without them connected it works fine.

    As for the circuit, I have the line level input coming into 4 sallen-key active filters. For the subwoofer, there is a lowpass filter with a 3db cutoff point @ 200Hz, tweeter has a high pass filter with 3db @ 5KHz, Mid-Range has a band-pass (high pass + low pass in series), and woofer has a band-pass (high pass + low pass in series) with 3dB cutoffs @ 100Hz - 1KHz.

    The filters look very good when viewing through an o-scope and scanning through the frequencies. There is no distortion and the 3dB cutoff points are perfect.

    From the filters, the signal travels into a TDA7386 chip which is a 4 channel 45 Watt amplifier which then goes out to the 4 respective speakers. I'm not sure if I don't have enough decoupling caps or if I'm doing something wrong with the amplifier chip, but I followed their figure from their datasheet to the t and I'm having the problems.

    Any help or suggestions would be GREATLY appreciated.
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    What is the model # of the power supply?
    What is the voltage and current rating of the power supply?
    What are the power requirements of the amplifier?
     
  3. EgagDesigns

    Thread Starter New Member

    Aug 10, 2012
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    It's just a bench power supply for testing, don't know the specific model off hand. Can get a max of 5 amps out of it at the voltage the circuit is running at, 12V. When the speakers don't go crazy it runs nice at .5A at a more than reasonable volume.

    No amp power requirements per se, but all speakers are rated at 35W or less.
     
  4. crutschow

    Expert

    Mar 14, 2008
    12,988
    3,226
    A loud bass note from a subwoofer may require a peak current more than the limit of your power supply. Is the sound distorted otherwise? You may just need a higher current limit power supply.
     
  5. EgagDesigns

    Thread Starter New Member

    Aug 10, 2012
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    The sound is great. Would it make sense to have a peak current of higher than 5A when it runs normally at 0.5A?
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Yes, it does make sense.
     
  7. EgagDesigns

    Thread Starter New Member

    Aug 10, 2012
    6
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    Alright, let me get some more power supplies to put in parallel and I'll report back.
     
  8. EgagDesigns

    Thread Starter New Member

    Aug 10, 2012
    6
    0
    I have given the circuit over 10A and it is still doing the described problem.
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,741
    759
    Are they switch mode PSU's ?
     
  10. EgagDesigns

    Thread Starter New Member

    Aug 10, 2012
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    I believe so. I have quite a few decoupling caps that I thought would stop any noise. Next to the output amp there is a 2200uF and .1uF decoupling caps.
     
  11. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The output power per channel is 14W at clipping into a 4 ohm speaker with a 12V supply. The average current from the battery is about 2.1A per channel or 3A peak per channel. You need a power supply that can supply 12A.
     
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