Hum Problems and AC Grounding


  Sometimes one can run into hum problems if you have several pieces of equipment connected together with audio cables and the 120 volt power is coming from different receptacles to feed these components. This can cause a small difference in ground voltages between the components and this small voltage is now placed across the audio cables and can induce hum into them. So it is very important that all equipment that is connected together with audio signal cables be powered by the same receptacle and that all receptacles are in fact properly grounded.

  It should be no problem to have a TV and an amplifier on the same receptacle. Again it is important to ensure that all receptacles are wired correctly, with the hot, neutral and ground wires appropriately connected to the receptacle. Most TV's likely have a two wire polarized plug that can be inserted in only one direction into the receptacle. If this TV plug was reversed (either by a defective TV plug itself, or an improperly wired receptacle) it may cause hum problems in an amp.

  Most importantly, if you are not certain that a receptacle is properly wired and grounded, have it checked by a certified, licensed electrician. Never attempt this yourself.