Tube microphonics (article)

[tomchr]

Folks,

This may be old news to many of you, but I stumbled across a rather interesting write-up based on some Mullard measurements of the effects of acceleration on tubes. It's an interesting read. Given that microphonics frequently pop up as a subject on these pages, I figured I'd share.

Microphonics in Vacuum Tubes

~Tom

[Gordy]

I was just considering the subject when your post popped up, so thank you for the link!

[tyu]

Thank for your time an the link on the info

[kevinkr]

Thanks for posting a link to the article, it was an interesting read. The information may give some pointers as what to look for when prospecting for tubes at hamfests, flea-markets and elsewhere. The comments on the double getter mounting were quite interesting, I had never considered that, but it makes sense.

While I am not completely certain, I believe the 50mW speaker power cited is actually acoustical output and would therefore be quite LOUD.

In terms of microphonics anything you can do to isolate a tube from acoustical feedback and vibration is going to provide useful benefit. Light, flimsy aluminum and steel chassis with buzzing, vibrating transformers placed in close proximity to speakers or other noise sources isn't a recipe conducive to good results. Probably too obvious..

Placing the system electronics on the other side of the wall from a refrigerator wasn't too good either as one of my former clients discovered. (Or more correctly I discovered for him.)

[EC8010]

Originally Posted by kevinkr

Placing the system electronics on the other side of the wall from a refrigerator wasn't too good either as one of my former clients discovered. (Or more correctly I discovered for him.)

Odd you should say that. For a while mine was on the other side of the wall from the fridge/freezer. And wired directly to the same socket. Things are better now...

[kevinkr]

It was very odd. The turntable made some odd humming noises when the compressor motor was running. Removing the TT from the stand helped a little.. Picking up the 12AX7A based phono amp helped a lot. Turns out vibration from the compressor was being conducted through the floor joists to the rack where the electronics lived. The compressor starting and stopping caused popping on all sources, and the mains socket was not shared. EMI from the fridge caused this issue.. In the end moving the electronics solved all of the issues.