[pjnad]

I'm kind of a newbie to tube equipment having acquired my fist piece ( Modwright SWL 9.0 Signature pre ) lat year.
I've been enjoying it and doing some tube rolling. I just swapped in a pair of tung sol 5687s that I have...when I touch the volume knob or even the rack I can hear it through the speakers. This had been happening with another pair of tubes as well. I had picked up a pair of jtl tung sols recently and after installing them, no noise. When I swapped them out tonight the noise is back. The tubes sound great though and nothing is coming through the system while it's playing.
Originally I thought it was a ground or connection issue but I just remembered reading something about microphonic tubes.
Also, is there any issue other than the noise to be concerned about...
Any help is appreciated.

[JoshK]

talk into the tube with the volume up a bit, do you or your friends hear your voice?  Can you tap the tube and hear a ring or a buzz ring through the speakers...you have a microphonic tube.   Its a pretty annoying thing to hear when you hear it.

[SET Man]

Hey!

   Even the best measured tube will make a pinging noise is you tap directly on the tube. But a good one should stop ringing quickly 

   In your case hearing ringing from the rack is not a good thing. That mean it pick up vibration from the rack too. But if the tube sound good to you and no noise than maybe a good isolation feet or platform will help.

    A cheap way to do it to use a piece of dense wood or granite sheet with lightly inflated bicycle tire inner tube under it.... actually this is what I use with my system, with my amps, preamp , turntable and CD player.

Take care,
Buddy

[Levi]

+1

Noisy tubes surely are annoying.

[pjnad]

Okay. Thanks guys for the replies.
Interestingly enough now that the tubes have warmed up a bit I'm not getting any ringing from the pre or the rack...go figure 

I am using some isolation pieces: the amp is on a granite slab with herbies iso cups which are great -definite sonic improvement when I added them. The dac ( which is fairly small - bel canto ) is on herbies tenderfeet. The pre and the cd/transport both sit on vibrapod cones/feet.
I am thinking of getting more of the iso-cups to replace the vibrapods as budget allows...but that might have to wait a bit as I'm planning on having a dedicated line and an audiophile outlet installed this month- but that is probably a topic for another thread 

[SET Man]

Okay. Thanks guys for the replies.
Interestingly enough now that the tubes have warmed up a bit I'm not getting any ringing from the pre or the rack...go figure 

.....

Hey!

     Oh! It is normal for some tube to make noise and pinging sound when warming up. So, no worry there if they are quiet after warming up. Just enjoy them.

Take care,
Buddy

[JoshK]

yeah, warming up is not a fair judgement...it takes time for the plate, structure and cathode to get warmed up, expanded, etc.

[pjnad]

Again, thanks. I know that the tubes need to warm up to sound their best...but, previously I did have a pair in that rang warme or cold...so, when I put these in and they rang, I thought , oh here we go again.
Anyway, they do sound good and they are pretty quiet re:tube rush etc.
I'm learning thanks to folks like you and that's always a good thing.

[dB Cooper]

Another thing to consider is that microphonics can originate in other ways- some large "boutique" caps can exhibit much the same phenomena. Don't know if that pertains to your equipment or not.

[Ericus Rex]

If they don't ring and bother you when the music is playing then just enjoy them!  Changing a microphonic tube just cause it's microphonic isn't necessary if it isn't noticeable during playback.

[T]

Thanks guys.  I learned something today.  I never knew microphonic meant it could actually function like a microphone.  I have yet to try much tube rolling in my belles 21a preamp because I like my present sound.