Captain Ned wrote:
Do you keep a cell phone or other wireless device close to the box?
This sounds like an EMI/RFI problem, and finding the source of these can drive many to strong drink.
I do have another Bose speaker. Unlike the Bose speakers I use on my XPS 410, this one is Bluetooth and it's used for my laptop (notebook). And while it's been close to my XPS 410 lately, this Bluetooth Bose speaker has been turned off the whole time. Other than that, the only other device near my XPS 410 is my Panasonic cordless house phone (but the home base for the Panasonic phone is downstairs).
PS I've heard the sound cards are not like video cards as far as going bad. And the sound comes out sounding great. It's just that intermittent thumping that was not there before I did my upgrades on the XPS 410. It's weird.