06-23-2011 Post does not mapped to Knowledge Tree Romy the Cat Boston, MA Posts 10,131 Joined on 05-27-2004 Post #: 1 Post ID: 16529 Reply to: 16529 Shaky tubes, echo testing fiogf49gjkf0d A few years ago somebody, I think it was “drdna” from California, told that he has a habit to listen the mechanical noise of the tube hold the tube at his ear by hitting the balloon of the tube. I did not exactly acknowledge it at that time as it was not my experience. I do not use the tube that have some after-shake or any long vibration in the tube guts. When I get a new tube I shake and ping it and it I hear anything that is bit off the bitten path then I just put the tube in the box with faulty tubes and do not use it. However, I have discovered recently the there is more to it.  Even the tube that I pass as acceptable still have a minor Shaky differences and to my surprise I learned how to hear that difference from the loudspeakers. So, if you use tube amps or multi-amping then make sure that the tubes from right and left on the identical channels of your multi-amps do have the same shaky residue. It means the MF from R and L or the Fundamental channels from right and left must have the same echo in the glass and to have the same decay in response to mechanical vibrations. Rgs, Romy the Cat "I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche