Do tube dampers improve sound?

I find it makes a difference where you put them. Dampers seem to work best near the top of the tube, not in the middle. Hey, maybe that's where the "top hat" idea came from.

But thinking of the glass as a transmission line (or guitar string), this makes sense. You minimize reflections, and hence resonances by damping the ends, where refections occur. In fact, some of the spots in middle (or harmonic fraction thereof) could be null points and have no effect. Depends on the resonance mode, if fundamental or higher. Only way to damp them all is to do it at the top or bottom.

I am not saying that the dampers work or don't work. I, too, THINK I hear an improvement when using Herbie's Halos on 6dj8-type tubes. It really makes little sense, and is kinda sickening actually, that the sound of, say, a $5K phono stage which is said to be the "end all" by its maker and ardent users, could be so dramatically improved by a $10 plastic tube ring. There is just something odd and wrong with that equation. (I realize that such oddities aren't restricted to tube dampers).

Virtually all vacuum tubes are prone, to some degree, to distortions caused by microphonic vibrations, and some tubes internally generate their own microphonics. This is true whether a component costs $200 or $20,000. Microphonic distortions will vary from one kind of tube to another and according to other factors such as microphonics-induced distortions in capacitors and other electronics, which might "mask" a cleaning-up of tube microphonics. Audio improvements are quite subjective, and what might be a minor improvement to one could be quite major to someone else. Even so, the affects of tube dampers varies hugely; sometimes the improvement is miniscule or barely perceptible, and sometimes very upfront and dramatic.

There is no "end all" product or accessory; everything in an audio system must synergize together to achieve the desired end result. If tube dampers are not the "cat's meow" with your system or not really worth the investment, send them back. It seems likely, however, that if you "think" you hear an improvement, you do. You might consider keeping them as part of an overall vibration-control solution.

Thanks,

Steve Herbelin
Herbie's Audio Lab

I even noticed that the placement of tube rings on the tube matters. If they are placed right in the middle of the tubes, they become too much of a good thing. But at the very top of the tubes, they provide a nice improvement. Although I didn't hear any drastic tonal changes, but separation, definition of instruments and overall soundstage clarity definitely improved. Dressing all the tubes in the preamp with Hal-O damping instruments doesn't cost much and I think it's a worthy improvement.
At least in my system it was.

Once again I have to make my plug for trying the inexpensive solution first. I got 50 industrial grade silicone o-rings from here:

http://www.marcorubber.com/material_selection.htm

for $10 plus shipping. I have a preamp with all octal tubes, so the S1000-216 o-rings were the perfect size. I use 2 per tube, and they make a noticeable difference in microphonics and smoothing out the bass, which is a little woolly without them. Would Herbie's or one of the other far more expensive dampers be better? Maybe, but I'm not sure my rig has enough resolution to prove it. I'm happy with my cheap o-rings.

Plus, you can get them in about 10 different colors to match your decor. :-)

David