Tubes and vibration - Atma-sphere MA-1


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I wonder, have anyone experimented with tube damping with Atma amps, especially, the MA monoblocs?

I am concerned that small errors due to vibration (e g airborne vibration) in each of the output tubes, times 14 output tubes per channel, amount to distortion. I have a small OTL desktop amp with one driver and one output tube only, sounding amazingly clear (Audiotailor Jade). In my MA-1 amps, the driver tubes sit very tight, but the output tubes are loosely fastened and rattle easily.

To test, I made two wire rectangles from clothes hangers, and fastened them to the top of the output tubes with small balls of blutac, damping the structure a bit more with balls in between the tubes.

Results - only first impression so far, but yes, perhaps some benefits. More coherence? I will keep them for more testing. In my notes: drums and cymbals are better separated, better treble, bass also? Perhaps some darkening of sound and detrimental effects...

Special tube damping is part of some recent costly designs (like the Einstein The Tube mk2, said to sound better than mk1 because of it). But if cheap tweaks work, why not?

Perhaps other tube amp owners have tried similar things?
Note, I have tried ordinary tube dampers, like Herbie's on some of the output tubes, without much difference (have not tried on all 28 tubes though). If the socket sits loosely, damping a bit from above may be a better idea.
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Showing 4 responses by o_holter

The frame I am experimenting with is easy for anyone to make, use a metal clothes hanger. I like cheap tweaks, sometimes they work. Not yet sure, in this case. Version 1 had the frame resting direct on the top of the tubes with blutac. After two days, the blutac did not feel very good, to my finger tips, and the mod did not sound so good. Over-heating I think. Half-baked. I was lucky to find some small furniture polyester dots around the house, I am now trying a version two with these below the blutac. The frame gives a lighter touch to the tubes. Not sure yet, how it sounds, but my family tends to take up the listener position - usually a good sign.
The frames looked a bit strange and did not yield any clear benefit, so now, like many of my tweaks, they are gone again. Oh well...
Thanks! I think things are OK with my amp (factory upgraded to 3.2 last year), sockets work like supposed, etc, although Deoxit or similar may help perhaps. I also use some tube dampers on the drivers. However I think the frame wire rectangle idea deserves more testing. Therefore I made a version 2 today.

It turned out, with version 1, after 24 hours or so, the blutac had not really liked the heating from the top of the tubes. I could feel with my fingers, it had turned stale, sandy, no longer sticky. So even if "fresh" blutac is a fine damping material, this half-baked version - no.

The first direct blutac version of the frame gave body and coherence to the music, but I also lost treble and transients. A conclusion was "let tubes run free". My thoughts went in the same direction as Jtimothya - overdamping. And anyway I did not like the way the blutac behaved directly on the top of the tubes. I was lucky to find a set of small furniture damping pads around the house, light and round 10 x 2 mm, made of polyester, said to manage heat fairly well.

So the mk 2 version is a bit more complex: the same rectangular wire frame with blutac balls above each tube, now with the pads beneath the balls, adhesive side up. This frame with blutac/polyester "feet" sits on the tubes. My impression so far is, this is better, at least I no longer hear much of the negative effects of mk 1 (no darkening of the sound). I need to listen and adjust more, to judge. It is tricky to get each pad to rest on the top of the tube "just so". Version 2 is a light touch only, compared to the first.

As you can see I am on my way to a gold mine of sound, I should get a patent at once. Just joking! The idea with cheap tweaks like this, we can all do them, and test. They often fail but they also give added value to the community.
Thanks Atmasphere. This fits with my experience. The sockets are loose for a reason ("let the tube run free"). My testing shows that this works well. What remains to be seen is if a little bit of top damping makes it work even better.