Have you tried completely removing power from the 1050 so it definitely can't be providing any type of signal or disconnecting the sub from the 1050? I never experienced an issue with my sub output in all the years I had my 1050 (original buyer that recently replaced it with a 975) but that doesn't mean it can't be the culprit. I'd go for completely removing power to the 1050 and see if the sub still crackles at you. If so, that narrows down the list pretty significantly.