I have a rather old set of Creative speakers called Inspire 2.1 2400.
The original cable that connects them to the computer was of poor quality, and at some point I had to replace it. The original cable had an external volume control (you can see it in the photo). I replaced it with a normal cable.
Since then, I get static noise when the computer is off, so I have to turn off the speakers together with the computer, which is a hassle.
I tend to blame the new cable, but I don't know how to choose a cable that won't cause this noise.
Edit: following the replies and comments here I did some more tests.
- When I disconnect the audio cable from the speakers, there's no noise.
- When I connect the audio cable to the speakers only (not to the computer), they are very noisy.
- When I connect the audio cable both to the computer and the speakers, and the computer is off, there's noise. But it's less loud than when the cable isn't connected to the computer.
- It doesn't matter if the computer is connected to the power source or not. The noise persists when I disconnect the power cable.
- Finally, the noise doesn't stop when I turn the computer on, only sometime during the operating system start-up.
BTW, my mom has an identical set of speakers and she has the same noise problem.
Edit2: the noise may be described as hum. It's very similar to the 50Hz example.