1

I recently purchased a new set of speakers only to find they hum when connected to my PC.

I have tried these speakers on multiple other devices and there is never a hum.

On stripping down my PC to only the motherboard and power supply I have found that as soon as the power supply is plugged in the speakers start to hum.

This happens even when the power supply is turned off either at the mains or on the supply. The only way to stop the hum is to unplug the power supply from the mains.

I have a few questions:

1) Is the hum more likely to be caused by the power supply or motherboard? (I'm assuming that the power supply is causing some kind of loop, though it seems strange it would do it when switched off)

2) If I don't fix this issue now, any new audio device could suffer the same problem?

3) Is there a way to fix this without buying a new power supply/motherboard/speakers? (I have no problem with upgrading either of the parts, just would like to know my options)

Improve this question
7
  • 1
    Based on the information you shared there really is no way for us to say either way. Both the power supply and the motherboard have components that could cause RF noise.
    – Ramhound
    Commented Dec 2, 2016 at 15:02
  • @Ramhound is there any further testing I can do to try and find out which it is?
    – stuart194
    Commented Dec 2, 2016 at 15:10
  • This is a ground loop. the first thing to do is ensure you are plugging your speakers into the same outlet as the PSU.
    – Yorik
    Commented Dec 2, 2016 at 15:19
  • @Yorik, yes they are plugged into the same outlet
    – stuart194
    Commented Dec 2, 2016 at 15:23
  • One trick for diagnosing this is to make a second ground connection from the two devices: attach a piece of speaker wire to a ground point of the speakers, and then touch the other end to the case, the psu external housing. (with the psu turned off). You might find that the hum lessens a little. then decide what to do.
    – Yorik
    Commented Dec 2, 2016 at 15:56

3 Answers 3

Reset to default
0

This is a fairly common phenomenon with laptops (but it happens with phones often enough). If your audio device works digitally, you'll likely never notice an issue, some USB devices with bad design may generate hum.

Any device you plug in could "suffer" the same problem.

You don't need a new mobo, just have the audio processed and output in a different way. If you're looking at analog solutions, find a low-pass filter that can cut out 60hz to 50hz range before you hit your speakers of course.

If you're the spendy type grab a DAC and use that as your audio interface instead of a direct connection to your computer. They're often designed specifically to avoid line-in or line-out hum.

Improve this answer
5
  • would that be the same this as a ground loop isolator?
    – stuart194
    Commented Dec 2, 2016 at 15:34
  • That's more on the nose, that might actually work.
    – TheUnknownGeek
    Commented Dec 2, 2016 at 15:53
  • If you were talking about a DAC (a digital to analog converter), it's an external audio device usually used by audio professionals. It's effectively an external sound card sometimes w/ their own power supply.
    – TheUnknownGeek
    Commented Dec 2, 2016 at 16:21
  • Following your comments about filters, I ended up searching for a speaker hum filter, which in turn led me to a ground loop isolator. Hopefully that does that trick!
    – stuart194
    Commented Dec 2, 2016 at 17:03
  • I was wondering about the sudden hop to ground loop isolator, because a ground loop is the classic culprit for noise in a lot of electronics. If it doesn't fix the issue, I'd take a shot at a DAC.
    – TheUnknownGeek
    Commented Dec 2, 2016 at 17:23
1

Hum doesn't come only from ground loops. A bad filter input electrolytic capacitor in the power supply, the one that comes after the rectifier, can introduce lots of hum that could affect the internal audio chip. So this hum can be mounted over the audio signal. Not 100% guaranteed, but replacing the PSU, the capacitor or the motherboard itself could be the solution.

Improve this answer
0

From Google (Ground Loop): "NORTH AMERICAN an unwanted electric current path in a circuit resulting in stray signals or interference, occurring, e.g., when two earthed points in the same circuit have different potentials."

So, plug them into DIFFERENT Circuits and it should be solved.

Improve this answer
5
  • Unfortunately I have already tried plugging the speakers into a different ground and that does not solve the problem
    – stuart194
    Commented Dec 2, 2016 at 15:42
  • Are you certain that the different outlets are actually on different circuits?
    – Xavierjazz
    Commented Dec 2, 2016 at 15:45
  • You are interpreting this wrong: the "circuit" is the computer and the speaker system interconnected by the audio cable. The "two earthed points" are the ground connections at the two different wall outlets.
    – Yorik
    Commented Dec 2, 2016 at 15:52
  • I suppose it is possible they are not, but I only have 6 sockets to chose from and I've chosen the two least likely to be connected.
    – stuart194
    Commented Dec 2, 2016 at 15:55
  • in that case plugging them into different circuits wouldn't really solve anything as I'm trying to get audio from the computer
    – stuart194
    Commented Dec 2, 2016 at 15:57

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .