Sorry, I'm new to tubes and headphone hi-fi, perhaps I should've worded it a bit more clearly. One tube was emitting an incessant high pitched whine. I already have tube dampers, and last night while the tube was still being noisy, and moved the damper around and got it to stop, but it came a back a few times. Today, I had no issues. My question is, can a tube be noisy then stop?