Expanding questions about tubes in a preamp

Herbies tube rings are the only way to go the others over damp the tube and you loose life and dynamics.

if you buy into the tube damping thing, may as well go big
https://shop.mapleshadestore.com/Standard-Tube-Halo_p_1268.html

I use quiet  tubes, and I'm done with it. Careful, the more you learn, the more it increases unnecessary obsession. 

Getting rid of microphonic tubes is far more important than damping rings. They have a tiny effect by comparison. I would only use them if you already have decent tubes.

Heat in tubes causes failure. The more damping rings and the like, the shorter the life.

I've had tube preamps that were too noisy for my system's downstream gain structure (both rush noise and microphonic feedback), and no amount of super special tube selection or tube dampers or HRS damper plates or expensive isolation stands did jack about it. Certainly, once you get "Platinum" selected tubes from Upscale Audio, there's not much (if any) improvement to be had from better selection. 

You have to pick a preamp with reasonable gain for your system and good signal to noise ratio. This is one measurement you can glean from Stereophile reviews that actually matters - for example, see the ARC Reference 6's 100dB signal/noise, which is excellent for a tube pre, and tests in my difficult system bear this out.

BTW if your line stage uses 12AX7 and EF86s, those are NOT typical choices for a modern tube line stage. 6SN7, 6922, 6H30 seem to be preferred (also in my experience). Though with the old 6SN7GT types, it is HARD to find quiet examples today.

Gents, how the hell does adding damping rings change the sound of a tube. Nonsense! If your tubes are microphonic (ringing) adding dampers may quiet them down. If you have a noisy tube it won't help. But it also won't hurt. I have never heard anyone complain about, nor have I noticed, a change in sound due to the use of tube damping rings.

Using rubber bands as tube dampers? Sure, go ahead. As long as you don't mind smelling cooking rubber and the bands sticking to your expensive tubes, then cracking and falling off. Rubber bands are not designed to be heat treated.

Next silly suggestion: why not just coat your tubes with a healthy dollop of undercoating? It made my '67 Bug quieter.