Found some old used tube shield available in the market. Are they useful to improve sound quality?  Any comment?  There are expensive audiophile tube damper, anybody have experience with this kind of tweak? Appreciate sharing to help improve sound.

http://www.surplussales.com/tubes-sock-acc/TubeShields-1.html

https://www.fairradio.com/catalog.php?mode=view&categoryid=1418

I am still wondering about the efficiency of those devices. Not those depicted in the links, but the ceramic rings and such. I once tried a diy device made of kevlar rope on input tubes, and the image and soundstage did improve dramatically (not just merely, I really mean dramatically, hence very noticeably). All I did was wrap kevlar multi thread rope tightly around the middle portion of the 12ax7 tubes and keep it in place with a drop of crazy glue. If the tube does not run hot in your setup it is a very cheap alternative to those fancy rings. the visual aspect is to be taken into consideration, they do look like broken limbs wrapped in bandage, but what if the sound THE SOUND is more enjoyable??????
As far as I can tell the aforementioned contraption does exactly the same thing a ring will do, maybe even better, as it spreads pressure evenly across the circumference of the tube, for the price of a meter of rope that you can find in a sports shop, the kind that sell climbing equipment and such. La Cordee, in Canada. Kevlar rope is always yellow I think, once you remove the outer, polyester shield.
Have fun
ps: you have to extract one strand of kevlar, since they are interwoven.

Achtung achtung all of you,
I have received in the mail my 2 pairs of Duende Criatura tube rings. Yes, in my setup, and I do not see why it would be particularly prone to vibrations of any kind, they make a huge difference. And one desirable difference that is. I had time to relisten to a murky sounding cd I tried to listen to yesterday. With the rings in place on the 12at7 and the 6v6 I realized that there was nothing wrong with the recording (Sephardic Romances on Naxos). Timbre, soundstage, they turned out to be absolutely alright, whereas yesterday the voices sounded nasial, the strings had a weird ring to them and it was impossible to tell where everything was placed. Another visible difference, I can now turn up the volume and the sound remains palpably clean.
Not inexpensive at 100$ for 2 pairs, but very interesting per se, apparently sturdy and indestructible, backed up by 15 years of existence.
In my experience they live up to their official claims of cleaning up the soundstage and tightening the bottom end. I haven't yet tried to listen with only 1 pair in place, some say that there is a danger of overdamping the tubes and thus making the amp sound less musical. The mechanics of that elude me and I do not like to believe in things that I don't understand, but I will keep you posted if my experience confirms any of that.

I got mine from the tubestore.com, based in Ontario. What was in that box full of tubes?? I am curious. I want a box full of tubes too.

Jon from the tubestore pointed out that my jj 6v6 tubes are larger than the usual 6v6 type and need rings that won't fit other brands. I like my JJs so I went for a non standard ring. SOmeone was saying that he obtained the best result by applying the rings only to the input tubes. I haven't had time to play around with that yet.
Cheers