Do tube dampers improve sound?

I guess if I have to strain to attempt to hear a difference
I write it off as a bad investment. I put Herbies tube Dampers on my entire system (all tubed at that time) and failed to hear any improvement. The other thing I noticed is that the dampers used on my kt 90's got sloppy with use.
They are sagging on the tube and not really holding onto the tube. On the other hand herbies grungebuster is the best tweak I have ever tried. For 16.00 it made a large improvement in the sound of my cd's.

I used the Herbies dampers too on my tube integrated and have to say I could'nt hear a difference. Interestingly, HiFi News here in the UK, did a technical report on a number of tube dampers, including the pearl ones, though they are coolers too of course, in this months edition. They checked for microphony with and without the rings and found very little difference. Does'nt mean they are right of course, accurately measuring these things is'nt easy.

05-22-06: David12
I used the Herbies dampers too on my tube integrated and have to say I
could'nt hear a difference.

I agree. I use them on
my preamps tubes, and I don't hear any improvement or difference.

The effect of tube dampers might be noticeable on high efficiency/SET
systems...

I have high efficiency speakers and SET system and tried dampeners and found them to restrain(soundstage shrank) my system.I took them off and am happier for it.They also took the air and spaciousness away i felt.

I use very heavy brass dampers from Vintage Tube Services on the four 6SN7s in my Rouge 99 preamp. I have switched them in and out and used them with a variety of 6SN7 types.

I can report a tremendous sonic benefit. Bass is dramatic both in depth and definition. The soundstage is defined. With the dampers, highs are pleasant, not harsh.

I won't use tubes without them.

I do have the Herbie Halo dampers on the small signal tubes in the Zeus power amp. I do not notice much of a difference there, however.