zippyfrog: Over the past hour or so, I've tuned into the ESPN2 replay of the match, the crackling wasn't there early during the second set, now it's back in the third. It seems embedded into the recording; the crackling was never in the commercials. The TV I'm watching this on has pretty good built-in audio, and I have young ears, so maybe you just don't notice it through the ambient noise. The crackling isn't there when the arena is quiet; when it appears, there's a sort of buzz-like tone to the crackling, if that helps ESPN technicians any.
Here's the strange part: I was watching some footage of Djokovic's acceptance speech on Sportscenter, and there was no crackling. The crackling was there on the ESPN2 live broadcast. Are there two signal paths, and two recorders, within the Bristol facility?
On a side note, shortly after the match ended, I heard Chris Fowler wonder aloud, unprompted, where this match compares to the 2008 Fed-Nadal match at Wimbledon. I had been thinking the same thing.