Tube dampers screw up the thermal heat transfer of the tube and should not be used!
Tubes, to damp or not to damp?
I’ve not had much luck with dampening devices when it comes to tubes. For myself, it seems to strangle the life out of the music. Tubes just seem to have more life without them. Maybe I’m using the wrong ones? I purchased a few from Audio Research the black rubber type. Any thoughts on this subject would be interesting to hear.
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I think it is situational to the gear and the tubes. And some manufacturers seem to design their gear around the tubes with dampers, so it is part of the "voice", as it were (ARC for one). But these damping devices aren't expensive, and it isn't hard to try them out and hear what you hear. Herbie's will let you try and return if you aren't grooving on it, which have taken them up on more than once. My experience with their dampers has never been positive with the squishy clear silicone cylinders strung on the teflon parted-ring. But I have used the FKM O-Rings strung on the metal parted-ring style with success. Different horses for different courses could well come into play, but that is my experience. I would estimate that dampers have worked in ~40% of cases when I tried them over the years, but it all gets down to the particular gear, the particular set of tubes, my system's voice at the time and my preferences - - and, of course, the particular dampers. Tweeks take work to tune right. Hard to categorically state that dampers are all good or all bad, IME/IMO. |
Not a fan of any of these devices. Very simple solution if your tubes are microphonic then replace the tubes. If all your tubes are microphonic then replace the component. In all but a few poorly designed components microphonics is rarely an intrinsic problem. If you like the sound of dampened tubes then more power to you. |
I'm a rubber formulation chemist and mechanical engineer, working in the field for 40 years. Silicone can well withstand the heat generated by the vacuum tubes used in our typical audio equipment (can't speak to the massive exotic 160W SET amps!), as can fluoroelastomer/FKM/Viton materials. I wouldn't use any other "rubbers" on tubes, as they can't take the heat, literally. Teflon, a plastic, can take the heat, too, but it has almost zero rebound when stretched, so not a great ring choice. Silicone can have fillers added to it to enhance its thermal conductivity. I added ~40% aluminum powder to some custom rings I fabricated to damp the 6DJ8's in my Counterpoint 5.1 way back in the latter 80's (boy did those tubes and that preamp need that!!!). I did it because I could - - not sure it really mattered. Adding fillers dilutes the polymer which increases the elastomer's damping quality. Silicone in general is "livelier" than FKM, which is pretty "dead" and dampens well. Which one is best in an application probably depends on what your ears tell you. As JEA48 mentions, placement is an important variable to play with. You definitely can influence the resulting damping and the sound resulting by shifting the rings up or down. Experiment and see what sounds better. It's like working with any vibration control device for your system, offering a degree of tuning, as it were. I am really surprised to hear that people experience glass deformation with the application of an O-Ring - - that must be some hoop stress fit! I would hate to have to put those on. My AR Ref 40 uses two FKM rings per tube, and even after the tubes have played out their 4,000 hour life the glass looks undeformed to me (just slapped a straightedge on a recently expired set). And AR chooses about the tightest hoop stress fit I have seen - - I hate changing them out! I am sure that AR is simply buying the standard size O-Ring that best works in their judgement, and that it is a garden variety "A" type FKM (still expensive stuff, by rubber standards). Number used and placement were likely their more important decisions. |
O-rings are too tight and apply pressure on the glass.Only if your a total (whatever) and purchase them too small. here there are sizes that vary in just 1mm ID diameters, from 4mm to 61mm ID (inside diameter) with 2mm thickness to suit every tube you have, on this site. Others have them up to 85mm ID Just measure your tube diameter and go 1mm less for a neat fit without being tight!!!! https://www.ebay.com/itm/2mm-Cross-Section-OD-8-65mm-FOOD-GRADE-Red-Silicone-O-rings-Washers-50-100pcs/193009581470?var=493208405430&hash=item2cf0447d9e:g:sOcAAOSwKTddNtGK Cheers George |
There are different silicone compositions. Some of the compositions are ferrous, some are not (alloys). Others just a single added element, like lead, copper, or silver. The highest temp silicones are conductive, (graphite, carbon). The high temp o-rings in hydraulics are very dark, nytrill, teflon, silicone all kinds of o rings for REAL high temp... I’ve seen entire pieces of heavy equipment burned to the ground. Aluminum pumps burn the O-Ring was still there... The high temp SILICONE HOSES, engine block, rims and frame, was all, that was left. Aluminum/Magnesium, burn just fine, add a little diesel yahoo, ride um cowboy. 50 years I’ve always removed the o-rings. Valves acting a little shady. Microphonics for me, means one thing, change the valve... I don’t use valves to play instruments. I use them to reproduce, what someone else has already messed with.. Not mess with the sound while it’s being reproduced... Easier to stay out of trouble, than get out of trouble. O-Rings are just that... They will distort the glass, too. Never been a fan... Regards |
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@ hiendmmoe Another vote for the Herbie’s tube dampers. I purchased several pairs of the Herbie’s HAL O dampers back in 2005. I use them on 6922 signal tubes. The Herbie’s still look like new to this day. (Tubes are various manufacturers pairs of early to middle 1960s 6922/E88CC and 7308/E188CC tubes.) As for placement of the Herbie’s on the tube. I first installed them where the general consensus, back then, was to install tube dampers at the top mica support or slightly above. I like you found it sucked some of the air/life from the music. I then experimented adjusting the placement of the Herbie’s on the glass envelope of the tube. The best place I found, for me, my system, was at the of the tube just before the fold of the tube. Jim |
silicon or rubber is a no for two reasons, the crack over time due to heat and loose their grip and overdamp but are cheap.Sorry you’ve got that wrong the red silicon are very high temperature industrial silicon rubber, made for extreme temps and don’t stretch or crack over time. The black ones are not high temp and may sag. Cheers George |
Hi, silicon or rubber is a no for two reasons, the crack over time due to heat and loose their grip and overdamp but are cheap. I found herbies to be a much better solution, they come in different configurations they are nice with the less signature but all of them make tubes sound more or less linear if you like that. If you want to go extreme, damping at certain points the pcb will bring the best results. |
Don't spend a fortune on audiophile o ring dampers, get these a couple of dollars. https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=Red+silicon+o+rings&_sacat=0 But not too tight as over time they will dent the glass with the heat. Cheers George |
Tried Herbies. Strangles the life sounds about right to me. A much better approach would be to try fO.q tape. Not directly on the tube, they probably get too hot. But on the cover near the tube. Or on the caps inside. Have not tried it in those locations but where it has been tried- tone arm, crossovers, speakers- it works wonders. Unlike most vibration control that relies on mass or mechanical damping, fO.q tape uses the piezoelectric effect to convert vibration energy into heat. Very high quality tape with an extremely high quality adhesive it sticks easily and yet can be removed just as easily and without leaving any residue. Impressive stuff. Not cheap, but worth the money for what it does. |
I’ve used Herbies UltraSonic SS dampers without any over damping effects. They prevent acoustic vibration from speakers or resonance from audio racks, especially on components with exposed tubes. Also good for tightening up the bass on some tubes. The ring type dampers can suppress overtones and harmonics. I generally don’t use them on tubes enclosed in a component unless a tube has some microphonic issues. |
