6SN7 microphonics, reality or myth?
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Covenant

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I keep hearing, in equal measure, about the microphonics problems consistent with the 6SN7 tubes, and reports from people who've owned dozens saying they've never had that problem.

DO 6SN7's exhibit more microphonics than other tubes? And if so, would there be any real practical use for something like this:

http://www.vintagetubeservices.com/Dampers.htm
 
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Glod

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I haven’t had any problems either, I think. Perhaps I should try dampers after all.


IME, it is only the 1940´s tubes that are really sensitive. Especially the war-time ones. Then I think it is very much due to the application of them, i.e. in what kind of amp they will serve. I could imagine there are amps with less vibration deaden chassis and those that are very inert.
 
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tom hankins

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I get one every once in awhile. This is out of a collection that has run between 80-100 tubes over the past three years. I dont see it as a problem. I have tried dampers but could not tell any difference. Perhaps in a speaker system where vibration is more of a problem they would have made more of an impact.
 
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Covenant

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Quote:

Originally Posted by tom hankins
I get one every once in awhile. This is out of a collection that has run between 80-100 tubes over the past three years. I dont see it as a problem. I have tried dampers but could not tell any difference. Perhaps in a speaker system where vibration is more of a problem they would have made more of an impact.


So they'd be kind of pointless eh? Almost a shame really, i'm growing (uncomfortably) accustomed to paying unearthly sums for cool-looking minor tweaks
 
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out of the 30 6sn7 tubes or so that have gone through my possession, only one has shown microphonics so bad i could not use it.

imo some of the 'magic' that comes with early 6sn7 tubes might just possibly be due to microphonics. anyone agree with me on this?
 
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Hirsch

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Out of a downright insane number of 6SN7's that have piled up here, I've run into three that have had microphonics so bad that the tube was not useable. However, I'd say that about 75% of the older 6SN7's are microphonic to some degree. I'd also say that most of the time this doesn't matter. For the most part, microphonics are not audible if used in a stage that does not add gain (for example, an output buffer). If used in a gain stage, the amp can become sensitive to contact. If you don't knock on the amp during play, you'd never know that you had a microphonic tube in place, though. These tubes are fine for headphone amp use (although they might have problems in a speaker rig, where room vibration would become an issue, and could be sensitive to footfall).

I try to insure that the gain tube in my amps is not microphonic. I haven't noticed any increase in tube "magic" when a microphonic tube slips by, and normally try and remove them when I find them in the gain stage (and save them for an output stage, where it just doesn't matter).

Tubes where microphonics are so bad that the tube can't be used are rare, but happen.
 
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Rob N

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Quote:

Originally Posted by Hirsch
Out of a downright insane number of 6SN7's that have piled up here,


What do you call an insane number?
 
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Hirsch

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Quote:

Originally Posted by Rob N
What do you call an insane number?


I'm not sure. I think I've got between 400-600 6SN7's of different varieties.
Many of these are not premium tubes (anyone want a dozen or two RCA or Syl 6SN7GTB's?
), but a lot of them are (I've got a lifetime supply of bottom-getter Sylvania's, Ken-Rad staggered plates, black base Syl 6SN7W's and TSRP's).
 
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6SN7s are not any more microphonic then other tube types in my experience. I have used about three dozen types of tubes (from 9 pin minitures to large 4 pin power triodes), and 6SN7s are not any more or less microphonic then other tubes.

The VTS tube dampeners really quiet down tubes. They are very heavy and thick brass rings with a inner high-temp rubber and metal coil ring which tightly holds the brass ring to the tube. Bottom line is they work, although you may not like what they do to the sound in some instances. The other choices to consider are finding Top Hat tube dampers (now out of production) or trying Herbie's tube dampers. Top Hats work very well too, but they don't deaden the sound as much as the VTS rings (I often prefer Top Hats to VTS). Herbie's has a more subtle effect which many people prefer.
 
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ALL tubes are microphonic, even the current-production "modern" tubes. It's just a matter of degrees. 6SN7's are not any more microphonic than any other types, but maybe there are so darn many 6SN7/VT231 tubes out there due to the huge production runs, especially in 1940's, that one can find more microphonic 6SN7/VT231 than some other types that may have had more production in 1960's-70's, some 20 years younger.
 
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Quote:

Originally Posted by Len
The VTS tube dampeners really quiet down tubes. They are very heavy and thick brass rings with a inner high-temp rubber and metal coil ring which tightly holds the brass ring to the tube. Bottom line is they work, although you may not like what they do to the sound in some instances. The other choices to consider are finding Top Hat tube dampers (now out of production) or trying Herbie's tube dampers. Top Hats work very well too, but they don't deaden the sound as much as the VTS rings (I often prefer Top Hats to VTS). Herbie's has a more subtle effect which many people prefer.


Just what effect DO dampers have on tubes' sound? Oh, and could you provide a link to Herbie's?
 
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I am experiecning some microphonics with my MPX3, however it does not affect the performance of the amp. I only hear it if I tap on the amp or the table surface right around the amp during listening. I can also hear it a little bit when the stepped attenuator clicks to the next level.
 
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Quote:

Originally Posted by Covenant
Just what effect DO dampers have on tubes' sound? Oh, and could you provide a link to Herbie's?



www.herbiesaudiolab.com
 
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Quote:

Originally Posted by Sleestack
I am experiecning some microphonics with my MPX3, however it does not affect the performance of the amp. I only hear it if I tap on the amp or the table surface right around the amp during listening. I can also hear it a little bit when the stepped attenuator clicks to the next level.


Unless something weird is going on, that is the driver tube (tube in front on the black chassis models). If you've got another tube of the same type, simply replace the tube and the microphonics should disappear (assuming the new tube is non-microphonic). Using the same tube in the center or rear socket should not produce the same microphonic effect.
 
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Quote:

Originally Posted by Hirsch
Unless something weird is going on, that is the driver tube (tube in front on the black chassis models). If you've got another tube of the same type, simply replace the tube and the microphonics should disappear (assuming the new tube is non-microphonic). Using the same tube in the center or rear socket should not produce the same microphonic effect.



Thanks. I'm going to try out the 12V option tonight, So I'll see if the microphoics exist with different tubes. In any case, it isn't a problem, except when I try to use it as a preamp in a speaker setup... which is rare.
 
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