I've been tube rolling lately with some different 6080's and 12AU7's, and came across a weird issue I haven't seen before. My Tung-Sol 6080, after warming up for a couple of minutes, will start to make clinking sounds that come from the physical tube itself. The best way to describe it is -- it's like the metallic clinking you hear if you warm a pan up on the stove.
I'm not sure if this is actually a problem or not, or if it means that the expanding metal may cause the tube to spontaneoulsy break on me. I just found it be quite bizarre. If I wear the headphones while it makes this clink sound, I can hear it resonate into the headphones as well. Should I get this thing replaced?