Help with lm386 audio amp.

Discussion in 'The Projects Forum' started by TIP31, Feb 1, 2014.

  1. TIP31

    Thread Starter New Member

    Aug 17, 2013
    25
    0
    I need help with a lm386n audio amp. I had it on my bread board and it had a lot of static. I followed the Minimum Parts Diagram that is in the datasheet, but to no prevail. Can someone help me?

    [​IMG]

    The circuit on my breadboard. The blue wire represents the 8
    Ω speaker, and the power supply isn't plugged in, in this picture.

    Here is the diagram:


    [​IMG]
     
    Last edited: Feb 1, 2014
  2. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    I do not see any picture of the breadboard.
    I get an broken image.
    When I try to look at it,I get asked to login on gmail, wich I do not have.

    Please upload the picture to the forum.

    Bertus
     
  3. TIP31

    Thread Starter New Member

    Aug 17, 2013
    25
    0
    The picture should show up now.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    Can you tell us what the problems are?

    I made some remarks in the photo:

    [​IMG]

    Bertus
     
  5. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
    The resistor that is supposed to be 10Ω looks to be 100kΩ. The audio input shield may be shorted to the inner conductor; it's hard to tell, but there is evidence of high heat at the end of the white wire. And, as Bertus said, you need to ground the other side of the pot.

    I also don't see any wire connecting the ground rail on the top of the breadboard to the ground rail on the bottom, nor any any wire connecting the power rail on the top of the breadboard to the power rail on the bottom.
     
  6. TIP31

    Thread Starter New Member

    Aug 17, 2013
    25
    0
    @ Bertus

    Yes the terminals from the capacitors are free from each other and I put one of my problems in the post, but it is having a lot of static and the quality is awful.


    @Tracecom

    The resistor is 10Ω I can assure you, and the red wire on the side is connecting the ground of both sides. The positive rail of both sides would be unnecessary, because I have nothing connected to the bottom one. The white wire is the really thin and quite annoying headphones wire; I had to solder it to a solid core wire, but it is connected to ground.
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    The color code of the resistor marked 10 Ohms, would be brown,black,black.

    [​IMG]

    This table comes from the following page:
    http://www.diyaudioandvideo.com/Electronics/Color/

    The colors on the picture are brown,black,yellow wich would be 100 k Ohms as tracecom remarked.

    It could be that the LM386 is having trouble with a high DC on the input.
    Put a capacitor of 10 μF between the audio-line and the potentiometer.

    Bertus
     
    TIP31 likes this.
  8. TANDBERGEREN

    Member

    Jan 20, 2014
    74
    4
    You need a 10uF capasitor between pin 1 and 8
    The gain with the components shown will only have a gain of 20.

    With the capasitor it will be at 200.

    What signal input do you have?

    What is the problem actually, not to provail is a very subtile description of what You experience.
     
  9. TIP31

    Thread Starter New Member

    Aug 17, 2013
    25
    0
    Oops grabbed the wrong resistor, and it works really well now. Thanks for your help.
     
  10. TIP31

    Thread Starter New Member

    Aug 17, 2013
    25
    0
    I only want a gain of twenty for this, or I will have too much distortion.
     
  11. TANDBERGEREN

    Member

    Jan 20, 2014
    74
    4
    OK.
    Still, I don't really understand what the problem is.
    The value of the resistor shouldn't have any significant effect on this amp's performance.
    I have used it for years, and never had any trouble setting it up.
     
  12. TIP31

    Thread Starter New Member

    Aug 17, 2013
    25
    0
    Well, I switched the audio ground to the other ground rail and that's what mainly fixed it.
     
  13. wayneh

    Expert

    Sep 9, 2010
    12,106
    3,038
    I've had that problem, and now use at least 2 wires to connect the 2 ground rails on my breadboard. It's too easy to have a dicey connection.
     
Loading...