Subwoofer hum

Discussion in 'General Electronics Chat' started by pyler, Apr 23, 2015.

  1. pyler

    Thread Starter New Member

    Oct 9, 2012
    Whenever I plug the power cord and the speaker cable in my laptop there's a hum that can be heard in the subwoofer. However, when I take out the power cable, it goes away. It also goes away whenever I plug in a VGA cord into the laptop (with the power cable plugged in as well.)

    Why does this happen?
  2. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
    Ok, this is merely a 'shot in the dark'... It seems as the hum is introduced by the PS (60Hz crosstalk 'through' the SMPS...) --- Perhaps capacitance in the VGA cable (or VGA display if connected) filters off or cancels said noise...

    Responses to the following would be helpful:

    1) Is the hum present when the the power cable is attached to the laptop but disconnected from the mains?
    2) Is the VGA cable 'open'? -OR- Is 'the other end' connected to a VGA device?

    Best regards
    Last edited: Apr 23, 2015