[Herbie]

Commercial silicone o-rings are highly vulcanized, rubber-like formulations made from peroxide-cure silicone or what the industry calls "gum." They're highly vulcanized in order to achieve a lot of industrial strength for myriad commercial uses. Herbie's Audio Lab, however, formulates superior platinum-cure silicones that are loosely cross-linked (not highly vulcanized or cross-linked), which results in less strength but much more absorption of micro-vibration, specifically formulated and tweaked for home audio applications only.

Silicone o-rings are a cheap trick and used frequently to control vacuum tube microphonics, but they are only marginally effective. The silicone itself, being highly vulcanized and rubbery, has some resonance issues that affect sonic linearity, at worst causing bloopy bass and/or higher-frequency attenuation or false emphases. At best, they accomplish some microphonics control but the sonic results are usually mid-fi at best, achieving some benefit but at the cost of some detriment.

An enclosed o-ring of any material has no outlet to release excess vibrational energies other than to reverberate them right back to the vacuum tube glass. Herbie's damping instruments, on the other hand, are "C" shaped, with the open ends of the ring allowing vibrations to simply dissipate to the surrounding atmosphere and assimilate within the C-ring itself without forcing the vibrations back to the tube glass, to which all the internal tube parts are directly or indirectly coupled.

We have lots and lots of customers who have replaced silicone o-rings with Herbie's vacuum tube damping instruments for improved results. Never any mention that the o-rings did as well or better; Herbie's dampers are virtually always a "keeper" in this regard. Some tube gear manufacturers, Conrad-Johnson and Audio Research for instance, include cheap silicone o-rings on some of their component vacuum tubes. This is often better than nothing, but not sufficient to really bring out the best potential of the tube gear. According to feedback we've gotten from customers, representatives of both C-J and AR have recommended upgrading their own silicone o-rings with Herbie's Audio Lab damping instruments.

Our experimentation and auditions with both silicone o-rings and Teflon-coated silicone o-rings has indicated that these products might not really be worth the bother. You don't want trade-offs with your audio reproduction, only improvements, to whatever degree.

Steve Herbelin
Herbie's Audio Lab

[kernelbob]

I thought that damping rings seemed to help until I tried Herbies Tube Dampers.  After all, companies like ARC supply damping rings with their products.  When I tried the Tube Dampers, it was obvious by comparison that damping rings of various materials smeared the sound.  They seemed to store the mechanical energy and then release it back into the tube.

The Tube Dampers, by comparison, clean up the sound across the spectrum without adding that smearing quality.  They're effective on both preamp tubes and power amp tubes, even up to the big T1610 thermos bottle sized tubes.  I've ended up using five of the large damping devices per T1610 tube.  My two cents anyway.

[Herbie]

All of our T1610 (Kronzilla) customers that I know of are getting excellent results with either a single damping instrument or just two (most using one) per tube. With the exception of T1610 and perhaps big, tall 805 tubes that also sometimes benefit with a second damper, a single damping instrument per tube is virtually always all that's needed to bring out the best potential of the tubes and gear. Oftentimes, some experimentation with placement of the damper on the tube helps to bring out the ideal result. Every vibrational environment is unique, with all kinds of different synergies involved throughout the system, so it's surely conceivable that in some instances, "the more the merrier" might prevail.

Thanks for posting the comment, kernelbob,

Steve Herbelin
Herbie's Audio Lab

[jostber]

What about tube coolers for large tubes like 211s? Can they be combined with the dampers?

[jostber]

Well, I checked out the compare site now, so I guess I got the answer there.

http://herbiesaudiolab.net/compare.htm

[driguy]

There are of course different grades of O-Rings out there. Some are more heat resistant than others. I have been around them for many years in the maritime industry. Some of the lower grades are not that heat resistant and may leave a sticky residue on your tubes especially the ones that run hot. Now granted, I have seen them in some challenging conditions in relation to a tube damper but I have had to scrape what was left of some O-Rings out of their grooves.
As for Herbies' post regarding the physics of the dampers vs. O-Rings it certainly seems correct. The great thing is you can try them and if they do not work Herbie will take them back. I use them on my Emission Labs 20B and 300BXLS tubes as well as the rectifier tube.

Tony

[bdp24]

Steve---What were your findings, if any, of the Right Way Audio Top Hat tube dampers?

[Herbie]

Hi, bdp24. Quite a while back, I found Top Hats to be somewhat effective at reducing microphonics but terrible at the sonic results. The lead weights impart a particular and unavoidable upper-mid twang that's quite irksome once recognized.

If Top Hats (or any other commercially available tube damper at the time) had been a truly good solution to tube microphonics, I would have had no reason to experiment on my own and Herbie's Audio Lab would never have been established.

Steve Herbelin
Herbie's Audio Lab

[bdp24]

Thanks Steve. Since reading your comments on the GR Research forum in regards to decoupling/coupling of speaker spikes, I've been reading about all of your products on the Herbie site. Mighty interesting, and they pass my "smell test" (no BS)!