[jhrlrd]

Just got an expensive pair of Ken-rad VT231 clear glass 6sn7 from Brent. They are hugely microphonic, even more than the Sophia 6sn7. I can hear the tray going in and out over the speakers, If I tap lightly on the oppo cover I can hear that too. Obviously I don't so those things while playing, but I'm concerned with chassis and airborne vibrations.  Herbies tube dampers don't fix the issue.
I have a pair of grey glass RCA that don't sound as smooth, but are way less microphonic.
Does anyone have experience with this? Does damping the board or chassis help with this? Are there any top quality tubes with less microphonics?
I don't want to keep throwing money at pricey tubes just to have them all like that.
thanks

[vinyl_guy]

I have the Sophia tubes and have never experienced a microphonic issue. They are the only ones I have tried other than the tubes that came with the mod.

sorry I can't help you

[Phil A]

Do you have tube dampers?

[Phil A]

Here's some info:  http://herbiesaudiolab.net/ultrafq.htm

[RPM123]

You may want to try placing the Oppo on some footers (Herbies or Daedalus) and something on top of the unit to dampen mechanical vibration. Also, Brent Jesse offers tube insurance for problem tubes. Can you actually hear any micrphonic issues while playing the Oppo?  If not, then the problem may not be as bad as you think.

[jhrlrd]

I'm using Herbies tube dampers already. The oppo sits on Herbies tenderfeet on a shot/sand filled stand.
I'm thinking if the tapping is that loud over the speakers, the tubes must be also amplifying vibrations from the transport/transformer and
chassis.

[Rusty Jefferson]

Try getting tubes from Vintage Tube Services.  Andy grades his tubes for microphonics.  My system is 102db efficient and I need quiet tubes.  Never been a problem getting them from Andy, including Sylvania 6sn7 for my preamp.

[rbbert]

I think this has been discussed in the other Modwright 105 thread.  Briefly, any NOS 6SN7's may be microphonic, they are old tubes even if they have never been used.  However, yours are the first microphonic Sophias I've heard of, and I would complain to Sophia.

Brent Jessee, like all the reputable NOS tube dealers, will take the tubes back within his exchange period.  He can suggest some tubes that are less likely to be microphonic, like the 5692 series and the Raytheons with the extra support rods.  He tests for microphonics, pretty much all the better dealers do, but some of these old tubes can go microphonic during the shipping process.

Tube dampers are another issue.  Many feel that using them on preamp tubes like the 6SN7 robs the sound of "life".  FWIW Brent sels some very simple teflon rings that damp a bit (way less than Herbie's) without seeming to otherwise affect the sound.

Last, the Oppo, with all its moving parts in close proximity to the tubes, is clearly a worst case scenario for microphonics.  I don't think airborne vibrations are within orders of magnitude of the mechanical vibrations of the drawer and disc drive.  Nevetheless, many users have been able to find good sounding NOS tubes that have little enough (or no) microphonics to be acceptable.  I would suggest continuing to try, and don't put too much emphasis on the specific dealer if they are reputable and have a good exchange policy.

[toddc2]

Brent stands behind his tubes. I sent my RCA VT-231's back to him. As posted on the LS100 tube rolling thread, one tube of the initial pair he sent me had a strange test tone sound that evolved into a microphonic condition. The noise tested replacement tube was noisy in my preamp. He mentioned that many VT's suffer from noise, microphonics, or both and that it can be frustrating to find a really good pair.

As I mentioned in that thread, I was fortunate to get some help finding quiet 6SN7's from a local dealer. I have two other pairs sitting on the bench that are known good in my preamp. I would be happy to "pay it forward" and let you try my backups.

[rbbert]

I also forgot to mention the importance of carefully cleaning the pins of these old tubes, since a loose fitting (mechanical) or poor electrical connection will substantially increase any microphonics.  I use a good silver cleaner followed by either Kontak or De-Oxit Gold (or both).

[jhrlrd]

Thanks for all the tips guys. Forgot to mention I tried walker silver contact enhancer on the pins. I sent an email to Brent to see if he would take them back for a better testing pair. I also am going to call Andy, I like how he has them categorized for microphonics. Maybe going to try sylvanias. I'm looking for something with extended highs/air.

[toddc2]

Andy cleans the pins like no one else in the industry! The extended highs you are looking for will likely be Sylvania, Andy really likes those tubes.

Good luck and keep us updated.

Todd

[rbbert]

The Sylvania 6SN7W, highly regarded for sonics, also have a reputation for being very microphonic.

Have you read the two links for extensive 6SN7 comparisons?

http://www.head-fi.org/t/117677/the-reference-6sn7-thread

http://www.dehavillandhifi.com/6sn7_vt.htm

[Rusty Jefferson]

The Sylvania 6SN7W, highly regarded for sonics, also have a reputation for being very microphonic.......

I wasn't necessarily promoting the Sylvanias, but VTS.  His grading of microphonics is accurate.  Puts a paint code on each tube so you can keep track of what you have.  He does also clean pins like no one else, as Todd mentioned.  Tubes are all he does.

[rbbert]

I wasn't necessarily promoting the Sylvanias, but VTS.  His grading of microphonics is accurate.  Puts a paint code on each tube so you can keep track of what you have.  He does also clean pins like no one else, as Todd mentioned.  Tubes are all he does.

I was referring to the desire to try Sylvania tubes; while the ones I mentioned are excellent sounding, this may not be their best application.

VTS is certainly a dealer with an excellent reputation, but there are many more.  And nearly all of them do only tubes.  Andy's listing for 6SN7's is still from last summer, and he didn't have much stock listed in the "MC" category (least microphonic), much less matched pairs.  And the unforunate fact is that one or more of these older tubes may go microphonic during shipment from him to the customer (I know, I've had this happen)

[Rusty Jefferson]

.....  Andy's listing for 6SN7's is still from last summer, and he didn't have much stock listed in the "MC" category (least microphonic), much less matched pairs.....

Andy doesn't maintain the web list.  You pick up the phone and call him, tell him what you need, and he'll tell you what he has.  I don't see any reason the OPs player should need a "moving coil" rated pair of tubes.

.....  And the unforunate fact is that one or more of these older tubes may go microphonic during shipment from him to the customer (I know, I've had this happen)

Although some tubes will become microphonic (to a degree) with use, I have never heard of a tube "going" microphonic in shipment. How on earth would you possibly know?  Did you hear it before it was shipped? 

We know tubes present microphonics because of their design and construction.  Some types (and brands within a type) are subject to the problem more than others. Many tube sellers don't grade their tubes for microphonics because it's time consuming, and potentially not necessary, i.e. someone who needs 12AU7s for the driver stage of a (relatively) low gain amp vs someone looking for them to put into an active preamp or phono stage. The OP asked how to get tubes that are less microphonic, and I mentioned a reputable dealer who grades tubes for microphonics in an active high gain circuit. I've not had any problems in my system with microphonics since switching to him.  That's all I'm saying.

[rbbert]

I received a microphonic RCA greyglass that was supposed to be non-microphonic; when I returned it the seller agreed it was now microphonic where it had not been before, and said he had had that happen before also.

I would indeed think the Modwright Oppo 105 needs a "MC" rated tube; I have a hard time imagining a possible use situation more prone to microphonics than the Oppo.  And I know that one needs to call VTS to find out just what is available, that's true with most of the NOS tube sellers, given the nature of their business.  My point was more that indications are that his stock of appropriate tubes for this application is likely to be limited, not that one shouldn't call him and/or any number of other reliable sellers (I have about 6-7 bookmarks in my browser, and that number is nowhere near all the good ones there are).

[jhrlrd]

I have a pair of Sylvania 6SN7s coming from Andy, MC rated. Will report back how they are...
BTW, Brent suggested to burn the microphonic ones in for around 75 hours to see if it clears up.
Can't really see it completely going away though.

[rbbert]

I have a pair of Sylvania 6SN7s coming from Andy, MC rated. Will report back how they are...
BTW, Brent suggested to burn the microphonic ones in for around 75 hours to see if it clears up.
Can't really see it completely going away though.

Cool!  Do you know more about which model/vintage Sylvania you are getting?

[jhrlrd]

They are 1950's era 6SN7-GTA tall base. I've tried other branded GTs but not GTAs. What I've been reading made me a little concerned with them being light in the bass region, But I explained to Andy that my system is warm already, and am looking for a bit more air/transparency/sparkle in the upper frequencies. He gave me a choice between the Tung-sols and Sylvanias. He also said I should have sent back the Sophia since they shouldn't be microphonic either.