Static noise from speakers when computer is off

Solution 1:

Typically that noise happens when computer and speakers have different ground levels, explained here. Are you sure that you did not also change anything in that regard, different outlets, etc? Is your pc connected to other devices, antennas, network switches, etc? Try connecting your speakers and computer at the same power outlet, with an extension cord.

edit:

• 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.

very odd behavior, looks like there is something wrong with the cable or the speaker system itself. Is it a hissing noise or a deep hum?

Solution 2:

Sounds to me like your new cable is acting like an antenna and you're picking up the static from there. Try a cable with thicker shielding / insulation and see if that helps.

(Every time I've had a problem like this, this is what it turned out to be.)

Solution 3:

Actually, when you turn a computer off, it's not always completely off, just more in some kind of "standby" modus. Ever had an USB light connected to your computer? Did it go out when you turned your computer off? How about the lights at the back for your network card? (Some have lights there!) Are they off too, or does it support a wake-up call from the network? Keep the cable connected to your speaker, but plug them out of your computer. If you still get noise, the cable is the problem. Otherwise, the computer still generates noise even though it's supposedly off.

Solution 4:

Since you've added more comments to your question, a second answer... As you say, when you connect the cable to your speaker only, it starts to generate more noise than usual. That seems to suggest to me that the cable is working like an antenna, picking up random signals and sending these to your speaker. If your mother uses the same speakers and cable, and she lives in the same area as you do, then there might be something in the area that is causing those signals that are picked up by your speakers. Connecting the cable to the speaker is actually reducing this signal since it's now divided by the computer and speaker.

Maybe you need a cable with better isolation from those external signals. I'm not that big of an expert with this since I never had much problems like this. It could be that you're close to a GSM broadcast antenna and the cable is picking up random noise from it. To check this, try wrapping the cable in single layer of aluminium foil and check if the noise goes down a bit. Or connect the cable to a speaker in another room. If it does, you'll need a newer cable with better isolation. (No, you don't want to keep that cable wrapped in foil!) Such a newer cable might be expensive, though. And it's no guarantee that it will work better, so turning off the boxes with the computer might be a better option.

At home, I have a power button next to the outlet which turns on/off the outlets power. I prefer to use that power button to turn off my computer since it also turns off the power to the other devices on my desk. (Monitor, boxes, external harddisk, printer.) It might be the easiest solution in your case. :-)