Help with Audio Amp Filter

Discussion in 'The Projects Forum' started by RyanTAkers, Nov 19, 2013.

  1. RyanTAkers

    Thread Starter New Member

    Nov 18, 2013
    2
    0
    Hi All,

    I'm after a little help with sorting out an annoying amplifier problem.
    As part of a larger project, I need to output a voice message from an Arduino. I have got myself the sparkfun MP3 player shield, and have that running fine through headphones on the 3.5mm jack. The problems come when I try to run the output through an amplifier and subsequently a speaker.
    I have built a 0.5Watt amplifier from Jaycar (KC5152) and am using this as my amp.
    If I try to power the amp from the Arduino 5v output, I get a lot of high frequency white noise. If I power the amp from a separate 9v battery, I get the result I am after, however I need to run this system off a single DC power supply.
    I have also tried the "finesse voltage regulator noise" method here: http://www.wenzel.com/documents/finesse.html
    I also experimented with an optocoupler, but had no success there.
    I have a feeling that the answer is widely available, but I don't know the correct search parameters.

    I don't deal with audio circuits much, so any help in this area would be greatly appreciated. Even if it's just a pointer to some sort of reference (or some other example would be great)


    Thanks in advance.
    Ryan
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,446
    3,362
    Try filtering the power supply into the audio amp.
    Use a ferrite bead inline with the power feed followed by a 100μF electrolytic capacitor.
     
    RyanTAkers likes this.
  3. RyanTAkers

    Thread Starter New Member

    Nov 18, 2013
    2
    0
    Thanks MrChips, I'll give it a try. Sorry for the late reply, I got despatched OS for work and have only just arrived home.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    On page 15 of the following PDF, there is a drawing on how to use the ferrite bead in the schematic:
    rf_proto-1.pdf

    Bertus
     
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