Tube dampers?

Ditto the good things about HAL-O. Works for me.

Besides the tube damper rings, you want to add some weight to the top of each tube, some lead. There used to be a company that made hi hats I think that worked well but were expensive. You can make your own by going to a crafts store and buying some lead strips and make your own. These tweaks benefit the sound to make it more musical in every way if you system can provide enough details.

The Mapleshade Tube Anchors I used on the 12AX7s in my phono stage made it sound so good that I just installed four more (had to be custom-designed) on the 6GK5s in my Conrad Johnson Premier l4. I really like what they do and have had no overheating problems so far. The downside is that they are a bitch to install (a little too tight and you have cracked a tube - ask me how I know). And the thin copper foil grounding straps are no picnic to attach. But the pluses outweigh the minuses and the price is right, plus there is a 30-day moneyback to increase your comfort level.

For 12AX7/12AT7/6DJ8/7308/6922 type tubes, I have had excellent results with the ARC tube dampers.

The Hal-O are the choice!
Happy Listening!