For me the best thing, although folks at Bottlehead do not recommend, was to lower the heater voltage. I do not remember well, there is thread on diyaudio, but I think I lowered the by like a half a volt. This stopped ringing without any music or movements I had. In my case on some tubes it was like a high frequency bell every 2sec for like a second. Very strange and very funny. I added some silicon rings as well this improved further but a small effect. What stayed is on my stepped shunt pot when I turn I have a short and very quiet zink....
This is a config I have now since summer no problem with tubes...
Pred
