That's a valid suggestion I suppose, but it doesn't explain why the same is happening when I put the old nVidia card back in, which I'm pretty sure doesn't have a soundchip on it (or does it? I can't find anything that says it has: Gainward GTX275
), and which didn't display this problem at all for years.
No, the problem has to be somewhere else, something that changed a few months ago.
It's either some kind of update that happened, or a defective part somewhere.
The last thing I added, hardware-wise, is the G930 headset, and that was still a few months before this problem developed. I've already tried removing that one from the system and the same still happens.