Infection what I have done is used some of the plumbers teflon tape and wrapped the arm tube. It improved the sound so I left it. I would try that. If it sounds worse remove it or some of it.
And Raul is right. It is like a microphone and I wouldn't lose too much sleep, tapping on the arm tube while at rest is no indication of how the arm will sound. In fact generally I have found that the better cartridges are worse for this as they are more sensitive. I have a VDH Colibri that will pick up a fly walking on the arm tube at rest. It sounds fantastic. Higher compliance carts are worse than low for this but that is the same feature that makes them so detailed and sound so great.
And Raul is right. It is like a microphone and I wouldn't lose too much sleep, tapping on the arm tube while at rest is no indication of how the arm will sound. In fact generally I have found that the better cartridges are worse for this as they are more sensitive. I have a VDH Colibri that will pick up a fly walking on the arm tube at rest. It sounds fantastic. Higher compliance carts are worse than low for this but that is the same feature that makes them so detailed and sound so great.