Tubes and vibration - Atma-sphere MA-1

I used Herbie's dampers selectively on the 6SN7s in my MA-1s but never damped the power tubes. NOS Ken-Rads, Sylvanias and RCAs occasionally can be microphonic - the MA-1s are so transparent you will hear the tube's state - so I pretty much went on a tube by tube basis because it's easy to over damp as well.

If those tubes aren't snug in their sockets, you should expect problems. All pins should be more than just touching or you can get shorts and all sorts of other issues that a dampener or weight will help a little but not cure.
I have had some cheap brands/runs of tubes that the pins were simply poorly manufactured. Do you have other tubes that don't rattle in the sockets?
Personally, I wouldn't want to use loosely fitting tubes for the chance of blowing something bigger...

Might try coating the pins with Deoxit to provide a tighter connection.

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.

The sockets on the MA-1 and all our amps are supposed to let the tubes wiggle a bit. Any good tube socket should do this to avoid shortening the life of the tube.

The contacts are tin-plated. Tin, like gold, does not corrode easily or quickly, and it is a lot harder so the socket can last for decades as a result.

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.

if you search the archives here, you'll see that several people have tried damping the tubes. Note that, from these discussions, it is important where along the length of the tube you damp - damping at the top or middle or bottom seems to have different effects. Got to play with it some w.r.t. your specific situation. FWIW.

For Sylvania 6SN7GTs, bad boys, I find that two Herbies dampers are better than one, one on the glass about 1/3 of the way up the glass, the other on the base. Yabba dabba doo!

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...