Headphone amp is not working?
I have this Mac as my daily driver, and I regularly use the headphone jack. About a month ago there was crackling in the headphone jack only, and it has progressively gotten worse. It is not a grounding issue, since I've tried grounding the computer several different ways. The crackling is not present on powered devices like speakers, but for devices that rely on power from the port, like earbuds and headphones, the crackling is very noticeable. This has led me to the conclusion that the headphone amp is defective. Is this a board level repair?