Amp Noise

Discussion in 'The Projects Forum' started by dkester13, May 18, 2014.

  1. dkester13

    Thread Starter New Member

    Aug 14, 2013
    7
    0
    Hey, i soldered the velleman k4001 amp. when a play music though it, it sounds pretty clear and nice, for such a cheap amp. The problem is when i remove the input, the noise is huge!!!

    Can someone help me? it should be something with ground, but i have no idea, since when connected to the pc the noise disappears. Maybe because it is grounded with the pc ground??

    I need to remove this problem because i want the amp to be mobile, so plugging and unplugging wil happen a lot. And i don't want that noise.

    Thank you
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    dkester13 likes this.
  3. jerluwoo

    New Member

    May 17, 2014
    6
    1
    With the input disconnected the input trace of the pc board acts as a sort of antennae conveying all electrical noise into the amplifier. The high gain setting of this kit, only 40mV in for full output, makes it worse than most. Adding a volume potentiometer to the input will help considerably and help make the amp more compatible with different input sources such as direct line in from a cd player with no volume control. Choose a dual 10kohm logarithmic type potentiometer.
     
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  4. dkester13

    Thread Starter New Member

    Aug 14, 2013
    7
    0
    Thanks, i used a potmeter and the noise is drastically reduced. So the noise is now dissipated though the resistance?
     
  5. #12

    Expert

    Nov 30, 2010
    16,310
    6,817
    Pretty much, yes.

    Radiated noise doesn't have much power, so a resistor to ground loads down the voltage quite a bit.
     
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