Since getting back from Canada, my Budda's been a bit temperamental. I've been getting occasional crackle/pop sounds (which may have been solved by changing cables) but it will randomly go from a darker smoother sound to a brighter crunchier sound in a sort of smooth fade that will last only about a second or so. Definitely weird.
Is this a tube failure symptom, or something that should get checked out by a tech?
Try swapping the tubes around. That should tell ya.