Hello, I am a DJ and frequently come up with this issue. Thank you for your help. I am getting ground loop noise from my PA system when my laptop is plugged in, when I unplug it, and only use battery power, no noise. I heard you could use a three to two pronged cheater power adapter, tried it connecting my computer cord to the grounded power strip and it works. I understand this could be dangerous though. My question is: If I connect the computer to a grounded power strip and not directly into the "wall" will this be a safe solution?
Happy Thanksgiving,
MrPickles
The power brick, assuming it is working properly, provides isolation between the incoming line wires (hot and neutral) and the DC wires going to the computer. As long as the brick does not fail there is no shock hazard as a result, whether the grounding conductor is carried through or not.
Even with a simple failure of the brick there would be no harmful voltages on the DC leads to the computer.
But there may be filter components between the incoming AC leads and the grounding wire (EGC) to keep the switching power supply from radiating RF noise back into the house wiring. And if the EGC is not connected it may cause there to be a leakage voltage and current on the grounded side of the DC supply.
Bottom line, I personally would use either a three to two adapter or a more formal box designed for sound equipment that "lifts" the ground, but I cannot recommend that you do the same.
To avoid problems or even hazards with other equipment that might be plugged into the power strip, I would not put the adapter on the line cord of the power strip. I would only use it on the end of the AC cord to the power brick.
The "right" design to deal with the problem, IMHO, would be to use an audio isolation transformer between the computer audio output and the mixer or other equipment.
A direct box should be able to do this, or just a length of three wire mic cable (XLR connector on each end) with a transformer balanced-to-unbalanced adapter plugged onto each end.
That way you do not have to mess with the AC configuration in any way.
