High pitched whine from speakers/Mobo

12characters

Greetings,
hopefully my narrative can give you enough clues as to my problem.

I have an ASUS mobo with onboard sound. I used to use a soundblaster without any problems. The speaker out comes in the form of a single 1/8" jack.

For a few weeks I had a mono 1/8" split to two RCA which ran to my home stereo reciever. I was noticing a high pitched whine coming from the PC box. When I would unplug the 1/8" from the jack it would almost eliminate the whine (not entirely). At this point I realized my 1/8" was a mono (I intended for a stereo).

So now that I have my stereo 1/8" Y-Split to RCA the whine is coming both from the mobo AND through the audio on the speakers. It is the same pitch and everything. I tried switching the speakers to my studio monitors and I get the same thing.

HOWEVER the whine from the mobo has decreased. Its almost like there is X amount of whine to go around and now its split between the mobo and the audio chain so its less present from the Mobo.

Another set of points is when I turn off the PC I can still hear the whine. When I switch off the PSU the pitch climbs really high for a second and then cuts out.


I dunno . . any ideas?

Tipstaff

That right there is a dead giveaway. Either you've got a bad PSU, or your motherboard isn't handling the power coming in properly, which could mean it's bad. Right now the best advice I can give you is to try a different power supply out. If the same thing happens then it's most likely your board.

There is something else to consider (but it may not be something critical). How do you have your PC conected to the power? Does it connect directly to a wall outlet, or is it connected to surge/power bar? As a test you may want to try using a power bar, or if you are using one, switch it with another.

12characters

Do you mean just a standard one, or something with a conditioner? I live in an older house, so the wiring may not be sound as sound can be.

After some more compartive listening ive decided not to rule out the PSU. Can a bad capacitor or poorly wapped coil in the psu send audio interference through the speaker line? I mean the jack is right next to it . . .but I dont know.

Tipstaff

Pretty much any type of power bar that has surge protection. The higher the protection the better, however, if you access to one, a UPS backup that has some sort of voltage regulation or line conditioner would be better. The idea is rule out the power coming into the system. An even simpler way to rule out the power coming in would be to try the computer a friends house. If the same issue occurs there, then you know that the issue is isolated to the computer.

As for the PSU, since everything in your system is connected to something powered by that PSU any interference will be passed along to other components. Onboard audio chips are very susceptible to this type of interference, more so due to them being mounted directly to the motherboard. Because the motherboard is making the same whining this is a good indication that the PSU could be bad, however as I mentioned before, it could also be that your motherboard is bad, and is the one creating the interference. In most cases it's easier (and cheaper) to try a new PSU to see if that's the cause, and then work your way in from there.

Here's something to try. If there is a computer shop near you try taking your computer to them, and ask to try a new PSU. Let them know the issue you are having, that you just want to be sure it's the PSU giving you issues before you buy a new one, and if it is then you "might" buy one from them. Most times they'll be more than willing to help as it's a possible sale for them. 'Course, you don't necessarily have to buy anything from them, but it's one way to try a new PSU without having to fork over any money.