Amp Noise

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

  1. dkester13

    Thread Starter New Member

    Aug 14, 2013
    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


    Apr 5, 2008
    dkester13 likes this.
  3. jerluwoo

    New Member

    May 17, 2014
    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.
    dkester13 likes this.
  4. dkester13

    Thread Starter New Member

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


    Nov 30, 2010
    Pretty much, yes.

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