Tubes are microphonic. Depending on tube type and gain you may or may not ameliorate the problem by changing tubes until you find some less microphonic samples. Take a pencil with an eraser at one end, and gently tap each tube in your phono stage with the eraser end. That will tell you which ones of those tubes are responsible for the noise. You can then concentrate on finding quieter versions of that tube. Tube dampers are certainly in order and might be very effective to eliminate this problem. I don’t know what tube damper work best among the very many available on the market.
Artesania rack
Hi,
I use artesania krion platform on top of two shelves exoteryc rack. When tapping on the krion (with turntable removed) there is a metallic ringing sound that is heard from speakers. It comes from my tube phono preamp which stands on the lower position of the rack. Same exactly sound is produced when tapping directly on the phono preamp. But this should not happen. Krion turntable platform is considered to be isolated from the inner structure of artesania exoteric rack.