Grounding an audio signal in DIY amp

Discussion in 'General Electronics Chat' started by hrs, Nov 15, 2014.

  1. hrs

    Thread Starter Member

    Jun 13, 2014

    I've built a simple chip amp. It has an RCA input at the rear panel. Here the grounds are floating i.e. the signal ground coming from my PC for example is not connected in any way to that of the amp. It just stops where the signal continues. This works.

    In the front panel I've put a 3-pole minijack socket. Here I've also left the ground floating. When I plug in a portable mp3-player the sound is very bad, as if a lot of the signal is filtered out. When I connect the mp3-player ground to the ground of the amp with alligator clips all is well. The intended use of the minijack socket is for portable devices, but ...

    Suppose I perminently connect the minijack ground to the amp and put the signal from my PC or any other device that has its own ground into that minijack socket, could that cause ground loops or other problems? If the PC is connected to a different mains circuit than the amp, could it be that the ground of the PC and the amp are at slightly different potentials?

    Supposedly the right thing to do would be to use balanced lines but I dont have enough experience points for that yet.
  2. Brownout

    Well-Known Member

    Jan 10, 2012
    I don't think that should cause a problem.
    hrs likes this.
  3. crutschow


    Mar 14, 2008
    You must have at least one common ground connection (typically through the audio cable) between all the devices for them to work properly. Ground loops are caused when you have more than one ground connection (such as one from the audio cable and one through the AC safety ground). Ground loops can cause hum in the audio signal.
    Last edited: Nov 16, 2014
    hrs likes this.