I have a combo that develops power tube rattle on the single Power and rectifier tubes (not the preamps). It only happens at a couple frequencies (mostly "E"). I'm sure it's the glass on the tubes as I can stop it by lightly touching the glass with a pencil when it it happening. I can touch either one to stop it...almost like they are talking to each other. Does anyone have a good source for Power tube "dampeners". I don't want a metal shield.....Something that will slip over the tube. I have seen a plastic fishnet stlye on a Mesa Mk4? Any ideas? Thanks in advance.