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I have arduino UNO hooked up with wtv020-sd-16p and it works fine, playing audio files - speaker is connected right to the WTV020's pin #4 and #5. However, volume is rather low. So I have ordered LM386 amplifier module. I have wired it's IN pin with WTV020's pin #2 AUDIO-L. But no sound comes out of speaker. I can hear only some scratches from the speaker while arduino is running.

LM386 is pretty easy, only VCC, IN and GND pins, so there is nothing much to screw up. I am wondering, what could be the problem ?

Thanks for any help or hints in advance.

EDIT: Only to note, when WTV020 is playing sound, speaker goes completely mute. When it doesn't play sound, little scratchy sounds can be heard from speaker. Maybe it could help with analysis ?

  • Where does the Vcc plugged into the lm386 come from? This one should be at least 1A I think. – jfpoilpret Aug 11 '14 at 14:03
  • Oh, I am powering LM386 from Arduino 5V. So it might be the problem ? – Frodik Aug 11 '14 at 14:43
  • @jfpoilpret But here is shown LM386 taking power directly from Arduino's VCC as I am using, so it should be fine then ? arduino.cc/en/Tutorial/SimpleAudioPlayer – Frodik Aug 11 '14 at 14:50
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    Try feeding your input to the module via a series capacitor to remove any DC offset. – Chris Stratton Aug 11 '14 at 16:11
  • @ChrisStratton You've nailed it. Please add your comment as answer, I will accept it. Thank you. – Frodik Aug 11 '14 at 16:41
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when WTV020 is playing sound, speaker goes completely mute. When it doesn't play sound, little scratchy sounds can be heard from speaker. Maybe it could help with analysis

Indeed - what you are describing sounds like the DC component of the Arduino's output is outside the workable range of the amplifier, effectively cutting it off. When there is no output, the voltage is within range and little bits of noise are able to be amplified.

You should be able to fix the cutoff problem with a series capacitor to block the DC component of the input, allowing only the AC signal through - a common technique for coupling between stages in Audio and RF systems.

The value of the capacitor will depend on the impedance of the circuit it is driving. A bare input to many chips could use a quite small value, while a circuit with feedback or a voltage-divider volume control might require a larger or carefully chosen one.

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