AC hum, also known as ground loop hum, is a very common problem in audio recording, live performances and home theatre systems. It is identifiable by a low hum or sometimes buzzing sound coming from each of the speakers at a frequency of 50 or 60 Hz, depending on national power standards. Eliminating AC hum can occasionally be time-consuming but the process itself is very simple.
- Skill level:
Things you need
- Surge protector
- Grounding adaptor or pliers
Consolidate all of the connected units in your system into one surge protector. For example, in a desktop computer recording system, this would include the recording interface, computer speakers, monitor, the computer itself and any connected peripherals, such as an external hard drive.
Remove any units that are not connected to your system from the surge protector and find a different socket to plug them into or plug them into their own surge protector. This includes lamps, phones, desk fans or musical amplifiers (that are not plugged into your system).
Isolate the source of the AC hum (if it is still there) by removing each of the units from your system, one at a time, and testing whether or not the hum remains. As soon as removing one of the units also removes the hum, then you have found the source. If you find that you are unable to remove the hum, then the source is probably the speakers.
Insert a grounding adaptor between the source's plug and the socket or use your pliers to remove the ground pin from the source's plug and plug it back into the surge protector. If the hum remains, try plugging the now nongrounded unit into a separate wall socket. If the hum still remains, then the unit is probably defective, so it may be worthwhile searching for fixes particular to that unit or even returning it for a different one.
Tips and warnings
- Removing the ground pin plug or using a grounding adaptor may remove the hum but it also puts your unit at increased risk. Consider purchasing an AC hum filter if you are worried about your unit.
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