Hi everyone, I have a little issue here. I have a projector up, an onkyo surround sound system and the works. I have a monitor cable going to the projector (vga) from my PC and a monstor audio cable from the sound card of the PC to the Onkyo. My problem is this. When I flip the audio/video to the PC, there is a low hummmm that I can't tolerate. Here is the interesting thing. I have narrowed it down to this, when I have the video cable AND the audio cable plugged into the PC at the same time, I hear the hummmm. If I pull the video cable, it goes away, obviously if I pull teh audio cable it goes away. I have tried all the different inputs on the back of the onkyo. Now it gets more interesting. I have tested using an entirely different set of cables and get the same problem. Here is more interesting news, I two different sets of cables up to my laptop and hear the hummm. I even tried it from the laptop docking station and get the hummm... So, different cables, different PC's different jacks on the back of the onkyo, and even a different speaker cable going to the front center speaker, and by the way most of the humm is noticable from the center speaker. If I flip the Onkyo to DVD, or DVR, the humm is gone. Any suggestions? The weird thing is that I dont remember hearing the humm when I watched my first movie from my pc a few weeks again, and really nothing has changed.

I'm no expert, but it sounds to me like you've got a ground loop going on here. It's actually a fairly common problem, and you can probably hunt down exactly what is causing the problem. It appears that the issue exists between your computer and your receiver, are they by any chance plugged in to different circuits? If you look at the sticky thread (Hum FAQ) at the top of this forum, it's a great resource for hunting down and eradicating ground loops.

cool, that makes sense. The laptop was running off battery however at the time. Since this post, i realized it happens even when I kill the power to the PC. Also, I out it in DVR mode, and you cannot hear the hum, but if I pause the TV, and crank the volume, I hear it a little. I will check out the hum forum you suggested since it is dedicated to this.

thanks a million!

If the Laptop was running off batteries, I don't think it's a ground loop. Ground loop noise is also present whether you are on the offending input, or not. Many PC's and Laptops just have noisy souncards, which isn't really something you can fix in a laptop.

There are a lot of fans and other electrically "noisy" components in a PC. If the soundcard is not specifically designed to quiet this noise you will get significant cross talk and hum. If the laptop has a digital audio output try using that instead of the analog.