Why does your guitar amp hum when you plug in guitar?

Answer

It could be a number of things, but fluorescent lighting in or near the room will cause what's called a "60Hz hum." If this is the case you could try to reverse the polarity on the 'Mains Plug'. i.e the AC mains leading to the step down transformer.

Alternatively confirm the same by switching off circuits (Tubelights, television etc) one at a time, to see if this hum stops. Particularly if the hum stops when you switch of the television - have the TV repaired fopr faulty filter capacitor.

If the hum is caused by earthing or neighbouring tubelights check the shield of the amplifier.The shield is supposed to be grounded to effectively eliminate the electric fields surrounding the same.

If it's more like a buzzing sound, there may be a loose connection in either jack (the guitar's or the amp's) or the patch cable itself; there might be a poor solder somewhere; or you might just be picking up interference from a nearby electronic device. If it's really noticeable, you might consider taking the amplifier to a local repair shop and having them take a look at it.

It could also be a poor ground, which will require re-wiring of the outlet or possibly the entire electrical system in that area of the building. Try plugging the amp into different outlets and see if the hum subsides; if it doesn't, it's likely an issue with the amp or the guitar themselves.

First answer by Razorgrin. Last edit by Wayndsouza. Contributor trust: 5 [recommend contributor]. Question popularity: 14 [recommend question]