Ringing Sound In Tube Gear

I recently have begun noticing a feint "ringing" sound while playing my Onix H34 integrated. It comes and goes and I'm sure it's not my ears. Could this be a problem with the output tubes? Any advice would be helpful. Thanks
Does it increase in volume when you turn it up?

In my limited experience with tubes, it is always a good start to replace the tubes and see if the problem goes away. A lot of ringing/buzzing/soft intermittent pops/crackles are tube related as the tubes get older (or in the case of minor pops...sometimes when you first put them in).
No, the ringing does not increase with the volume. These EL34 tubes aren't very old (I replaced them just this past spring). Thanks for your input.
hmmm...take them out, tap them gently on top and replace them back in the socket? i do get occassional ringing (faint), and Brent Jessee has recommended this easy first step. It has worked for me in the past.
Are you using tube dampeners?
The others have hinted at this, but tubes can be microphonic. The glass shell can vibrate with the sound in the room and this can get amplified again. Some brands or types of tubes are worse than others in this regard. Normally one would expect any problem to increase with playback volume.

An easy test is to tap very lightly on a tube with a pencil and see if you hear anything through the speakers. If so, tube dampers can help with this issue.
Is the ringing coming from one channel or both? If one channel try swithcing the tubes to the opposing channel and see if the ringing moves.

Do you hear it in both channels? If so for it to be a tube it would most likely be one that services both channels. I'm not familar with your amp but a single tube serving two channels is not uncommon, they have two sections.

Ringing is most often associated with the small tubes, try them first.

In my experience ringing in power tubes is not common except for a headphone amp I use :-), so it is possible, but again it would usually appear in only one channel.
According to the specs I found, that unit has:

Tube Compliment:

4 X EL34
2 X 6SN7
2 X 6922
2 X 12AT7
2 X 12AX7

It's probably not the EL34's or the 6SN7's. It's more than likely one of the 6922/12AT7/12AX7. I'm not sure how Onix uses these tubes in the circuit, so it's kind of hard to pin-point the culprit. I agree with tapping each tube with a pencil eraser lightly to see if you can find the noisy tube. Wow, that unit sure uses alot of tubes...
Tubes with long plates tend to be more microphonic. With the system on and at idle you can tap on each tube with a pencil or you can tap on each tube with your fingernail to locate the microphonic tube or tubes. I have heard of microphonic output tubes, so be sure to check all tubes.
Be very careful and diligent with precious tubes...isolate them from harsh vibration and nurture them like sweet little gentle babies. Be nice to them. Except for the tubes in the 147 guitar and bass amps I've dragged all over the world since 1967.
Thank you for all the input (no pun intended). I will follow up with pencil test and dampers and let you all know the results. BTW: This is what I love about Audiogone we are a community which can rely on the knowledge, experience and good will of each other. Thanks!
"we are a community which can rely on the knowledge, experience and good will of each other."

Are you sure you are in the right place?
Hah! Good luck Tarraga...hopefully the knowledge experience and good will...will prevail and your ring will be sorted out. Good luck...and remember - sometimes when you tap on output tubes...be careful. If the tube is causing a problem even the gentlest tap will be quite loud thru your speakers. On the other hand, if not, a gentle tap should not result in any noise coming thru. If you use a pencil, use the eraser part...you dont need to tap with the wooden/lead part at all.
Hmmm the tapping (gentle w/eraser)produced no major noise during tests, but the ringing seems to have abated for now. I may try tube dampers anyway as the amp I have in another system came with them already installed on the tubes (it sounds great, btw) and it seems like a good idea.
Well, I could start singing, "WE Are Family...," but that's not really my style. :)
;) hey if it stopped...great! If you like your tube dampers...you may wish to try EAT tube dampers at some point. 19 bucks each and they are stunningly good. I got one on the recommendation of the distributor. I now have them on my other tubes as well.