One thing that bugs some tubes is their susceptability to vibration causing microphonics. There have been all sorts of things devised that clamp onto a tube to try to stop external vibrations getting in the way of the wanted audio.

The best way to stop microphonics is to stop the vibrations getting into the tubes in the first place. A perfect example would be to use super fine wire feeding the pins and the tube suspended in mid air by a piece of cotton thread. Neoprene rings could also be put around the glass to dampen sonic vibrations having an effect on the tube envelope and making its way into the tube structure via the glass to pin seal.

The Tube preamps that I sell in kit form can have a very effective dampner made by using hair wire for the pin / lead connections and by mounting the tube in a cylinder of expanded foam polyethylene. I have found that this works the best of all the materials that I have tested.