Humming in speakers

[fixit7]

A humming started in my speakers.

I use a Logitech external speaker system.

If I turn it's volume down, the humming volume goes down.

If I unplug/plug its power source the humming goes away for a while.

[Brumby]

What happens if you unplug/plug the signal input jack?

[fixit7]

I found out that the speaker output plug was not all the way plugged in.

[Brumby]

Do you mean the connection between your computer and the speakers?

[radiolistener]

Probably you're need to replace electrolyte capacitors in your speakers. This is the most weak elements and often this is a root of cause of malfunction due to low quality.

[Brumby]

I went for the low tech idea that a plug wasn't inserted properly.  Looks like I was right - and if the "speaker output" the op mentions is the socket on the computer they're using, then I was exactly right.

An improperly fitted plug is the easiest way to get hum in your audio.

Re-capping the amp in the speakers is not a bad idea - but it would appear to be rather unnecessary in this case.

[fixit7]

Do you mean the connection between your computer and the speakers?

Yes.

When I pulled it out halfway, the hum came back.

[Brumby]

Exactly what I thought - and super easy to fix!

Sometimes you can get the same problem even when the plug is fully inserted - especially if it has been plugged in for a long time.  Contamination build up and/or oxidation/corrosion (which may not even be visible) can interfere with the connections.  Just unplug/replug (maybe a few times) to wipe the contacts clean enough for another period of hum free sound.