Vibration mounting a socket with a tube shield

[trobbins]

I was doing some noise floor measurements with a simple 12AX7 gain stage on the bench recently. Lots of ways that hum/noise can get in to the signal chain when trying to do measurements. I certainly had to fit a sprung steel tube with grounding wire to suppress local hum ingress showing up in the spectrum noise floor. But I'm describing a pretty low noise floor on a spectrum analyser plot, not a speaker being listened to for hum changes with/without a shield.