Tube Holders and Microphonics?

Still shaking down my new (used) 5-50 and noticed some rattling whenever I play a Bb on the 6th string through the clean/green channel. The more bass, gain and reverb that's dialed in, the more irritating this is.

Swapping preamp tubes hasn't fixed the problem, but then again I don't have any brand-new tubes on hand now. One is on the way, but I'm just wondering what these spring-loaded cans are doing for the preamp tubes.

Are they supposed to:

A) Reduce microphonics?
B) Keep the tubes cooler?
C) Make the tubes hotter?

The correct answer is A.

One thing to try is to grab a power tube with an oven mitt or a towel while the offending note is played. If the noise stops or is reduced, you've found the bad tube. Microphonic pre-amp tubes are more likely to squeal than rattle, but, of course, YMMV.

:idea: Cheers!

So in this case YMMW = Your Microphonic-tube May Vibrate?

And if the pre-tubes AREN'T rattling?

The spring loaded cans keep the tubes from loosening in the sockets and shield them from electrical noise.

So it turns out that none of the preamp tubes were really microphonic, which was surprising because swapping tubes definitely had and effect on the amount of resonance/rattling in the back of the amp.

The culprit was one of the power tubes -- a brand new SED Winged C (- about 5 hours of use.) Transposing the tubes seemed to reduce the problem a bit. Is this kind of thing normal? Should I return the tube?

Quality control on tubes is poor. They are also quite complicated. So it's not at all unusual for them to go bad immediately. They are a total niche item. You can try to return it. Most places won't warrantee them.

I think of it this way: the tubes are pretty delicate mechanical items, just like a light bulb. I have had light bulbs fail after a few hours' use as well. Not very many, but it has happened.

elvis said:

Quality control on tubes is poor. They are also quite complicated. So it's not at all unusual for them to go bad immediately. They are a total niche item. You can try to return it. Most places won't warranty them.

I think of it this way: the tubes are pretty delicate mechanical items, just like a light bulb. I have had light bulbs fail after a few hours' use as well. Not very many, but it has happened.

Click to expand...

I guess so... Anyway, I put the Boogie STR-440s back in the amp. No more issues, and I think they sound better for crunch sounds. Thanks for your help.