[malldian]

I have a RCA front tube for my DV 336i and it has began to make a god awful noise when i touch my desk or anything moves around it. How do I fix this?

 

[Enthusia]

Tubes are very sensitive and even the slightest vibration can affect the sound quality. I would invest in a vacuum tube damper which basically wraps around the tube to prevent unwanted vibrations. Other than that I think the tube could be loose or dying.

 

[sacd lover]

Sounds like you have a badly microphonic tube. You cant fix this. The best you can do is attempt to damp the tube and make the tube useable. Be aware, no typical tube damper is going to work if the tube is badly microphonic.

If the tube is an expensive one I would try to salvage the tube using three high temperture O rings you can buy from an Auto parts store; like Autozone. These only run $.50 and IMO damping a microphonic tube at multiple points works better than something like a single Herbies Halo damper ..... as well as being much less expensive. Damp the tube at the top mica support, just below the first O ring and then put the third damper at the tubes midpoint.

Here is an example of the O ring damping. As you can see I only used two as my tube was only slightly microphonic.

 

[braillediver]

“Tubes are very sensitive and even the slightest vibration can affect the sound quality.”

No Not true. Some tubes are microphonic and there’s not much you can do about those particular tubes but in general tubes are very rugged and don’t exhibit microphonics.

At the most I’ve found maybe 1 in 100 tubes to be microphonic. But even 1% seems high. Remember they used vacuum tubes in airplanes, on board ships, in automobiles and portable radios just to name a few applications.

So some individual tubes will be bad.


Dampening a tube can help if the tube is only slightly microphonic but it can also make the tube sound dry and less vibrant so some caution is advised.

A microphonic tube has personal issues and it would be better to replace the tube than to continue using it since you don’t really know the cause of the microphonics.

You can also wrap the tube in Teflon tape like used on pipe threads.


Mitch

 

[Skylab]

Unless your tube is one of the uber-expensive 6SN7 types (and the only RCA that even comes close is the grey-glass VT-231), then I strongly suggest you just get a new tube. A tube that is THAT microphonic isn't worth saving, just as Mitch said. Just look at it as a good opportunity to tube-roll. You can still get some decent vintage 6SN7 tubes for very little money if you poke around a little.