LM386 sounds like whispering...Help..!!

Discussion in 'The Projects Forum' started by utilityhacker, Jan 10, 2015.

  1. utilityhacker

    Thread Starter Member

    May 1, 2014
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    so i have the lm386 and i built the same circiut shown in datasheet on a bread board 20% gain. The only difference is i didnt find the 0.005uF cap and im using a 0.04uf ceramic cap instead. The input voltage is provided from a 9v battery Im using a mobile phone as an input. The problem is the output sounds like whispers. Also there is lot of distortion. I additionaly added a 220uf electrolytic cap(25v) across the pin 6 and 4 and a 100uf electrolytic cap (25v) from the 10k pot to pin 3. I dont know what im doing wrong . Pls help guys..!!
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Do you mean this 20X circuit:

    [​IMG]

    A 9 Volts battery can be to small to power the amplifier.
    Better use a block of AA or larger batteries.

    Bertus
     
  3. tracecom

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    Apr 16, 2010
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  4. Alec_t

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    Sep 17, 2013
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    Try without the cap on pin 3.
     
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  5. GopherT

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    Nov 23, 2012
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    On the input, your 100uF cap should not be connected between the pot and PIN 3! Connect your pot directly to PIN 3 as shown. Then put your CAP between your audio source (phone) and the POT where it is labelled input.

    Your present configuration has no DC path to ground where the Cap connects to the non-inverting (+) input and all signal will be greatly attenuated that way.
     
  6. utilityhacker

    Thread Starter Member

    May 1, 2014
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    4
    that helped a lot but still there is still lot of distortion in the circuit.
    i mean before it was horrible but now i can recognize the song and is much louder.
    i also checked the circuit on another breadboard and the distortion was still there.
    pls help..!!



    that was helpful
     
  7. GopherT

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    Nov 23, 2012
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    Lower the volume of your pot on the input. The distortion should go down.
     
  8. utilityhacker

    Thread Starter Member

    May 1, 2014
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    whe
    when i lower the pot volume the distortion does goes down but the speakers volume decreases like whispering and i need it to be loud :(
     
  9. GopherT

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    Nov 23, 2012
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    @utilityhacker
    This is only a 1 watt amplifier. At 1 watt, the datasheet says you will have 10% distortion. So, what do you want, loud OR low distortion? You don't get both with this chip. (And you barely get loud).

    There are other chips out there that do more than 1 watt.
     
  10. djsfantasi

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    Apr 11, 2010
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    And is the pot a linear or logarithmic one? The pot number should end in 'A', for audio. Linear pots cannot control audio signals.

    Edit: it was just pointed out to me that this designation isn't standard. What you should take away is you need a pot with a logarithmic taper.
     
  11. djsfantasi

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    Oops. See my edited post.
     
  12. GopherT

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    You may need a small input buffer. Try something like this...

    [​IMG]
     
  13. tracecom

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    Apr 16, 2010
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    If you are powering the circuit with less than 9V, or with a weak 9V battery, it will not function well. And neither will it function well built on a solderless breadboard.
     
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  14. Alec_t

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    Sep 17, 2013
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    Are you using screened cable between the phone and the amp to cut out noise pickup?
    If your battery is still a little PP3 its voltage may drop under load to the point where the amp distorts.
     
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  15. utilityhacker

    Thread Starter Member

    May 1, 2014
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    its just an ordinary 3.5mm jack and ordinary jumper wires
     
    Last edited: Jan 11, 2015
  16. GopherT

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    Nov 23, 2012
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    It sounds like you have several possible opportunities to improve.


    - your two leads could be acting as an antenna. Any open space in the loop between the leads captures radio and other signals. Your LM386 is fast enough to amplify radio waves and cause distortion in the audio. Some possible solutions...
    --- mount to a Circuit board
    --- twist your two input leads tightly to avoid gaps "used in Internet cable known as 'twisted pair'".
    --- reduce gain (your input signal may be too high for a gain of 20 without clipping (distorting)
    --- mount everything onto a well-designed circuit board to avoid radio interference.
    --- add two 1k resistor between (one between your input (+) and phone and one between ground and phone ground)
     
  17. djsfantasi

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    Apr 11, 2010
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    -- And check the type of pot used for volume control
     
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