I currently have the following HTPC setup for the home theater:
AMD X3 720 BE (unlocked to X4)
2x Sapphire AMD Radeon 4850s crossfired (I believe they are each 512 mb memory)
Corsair 650W PSU
One of the most annoying problems that I have is that I cannot leave the HTPC on. If the HTPC is already on when I turn on the projector I get "popping" noises (almost like fireworks). I am guessing that maybe it has something to do with the 4850 cards because that doesn't happen on any other A/V device that I have. And it happens with any A/V receiver. I used to have a Pioneer A/V receiver and I got the exact same popping sounds as soon as I would switch over to the HTPC. I always have to turn on the projector first and then the PC to avoid getting the popping noise.
Note that the problem occurs when the HTPC is simply "on". This is not an issue that is specific to an application running.
If the PC is turned on (or already on) before the projector is turned on, the result is popping sounds from the speakers. If I turn on the PC AFTER the projector is already on, no issue.
I think that there is some sort of ground loop problem occurring here.
I don't think we have the same problem. My problem is independent of a movie actually playing. It is related to whether the PC is "on" or "off" when the projector is turned on.
What do you mean by ground loop? Keep in mind that any other device that is always "on" does not have this problem. For example, my cable set top box is always "on". No problem. I have left my Bluray player and my WD Live devices "on" and there is no problem if I turn on my projector later. But for some reason, the PC results in this popping noise. So how would I correct this?
So I tried 2 different HDMI cables. Then I opened a brand new cable. Problem persists.
Interestingly, when I shut off the projector, the popping sound continues. I have to shut off the A/V receiver for the popping sound to stop. Once I turn the A/V receiver back on, popping continues. So the only way to stop the noise is to either (1) shut off the receiver, (2) switch to a different device on the A/V receiver, or (3) make sure that the projector is turned on before the PC is turned on. And once the popping starts, it can't be stopped without (1) shutting down the A/V receiver, (2) switching to a different device, or (3) shutting off the PC.
Note that I now have a brand new EVGA GTX 660 with HDMI connector for my HTPC.
Or if I leave the PC on (no apps running) and come back a day later to turn on the projector, the noises start and the only way to resolve is to reboot.
You mentioned a Pioneer AVR, what other AVR have you tried? Seems there's an issue with the AVR in my opinion. Have you this same issue on other HDMI inputs on the AVR? What other HDMI devices are you using and could changing to one of those have the same popping noise? Also, just to be clear, you've demonstrated this on a single ATI and a single nVidia video card, right? That's why I'm thinking the common link is the AVR.
1) Turn of the sound, of the beamer and cinema system, do you still hear it/
2) Turn off the beamer, does it still make the popping sound?
3) It keeps popping or for only a few minutes then stops? might be that the room temperature is to low, of course when the computer turns on it'll make sounds, like a radiator can do.
4) Last think I can think off is that it might be the harddisk, or Fans.