12AX7 Questions:

A. If the tube has a spring loaded metal sheath covering
it what is the application: 1.) RF/EMI shielding?
2.) To mechanically hold the tube in place? 3.) Maintain the
tube in a higher temperature environment for some
technical reason? 4.) Something elser?

B. Would an Ensemble tube sock be a good replacement
for the existing metal shield. In other words, would
lowering the operating temperature while providing
some shielding and physical dampening to the tube body
result in a better performance setup?