Tube adapters??

[Paul Birkeland]

  Maybe time to contact the vendor on ebay.

I don't think I'd do that until you try a second 6SN7.

[dubiousmike]

Just wish I had one on hand.  Hate to double down and purchase another 6sn7 tube if the adapter is no good.  It took about a month for the first one to arrive.

[Paul Birkeland]

I'd hop onto eBay and look for 6SN7's available in your area (there are hundreds).

I see pairs around LA for ~$10, and most sellers are OK with local pickup.  Even with shipping, you'll get them in a day or two

-PB

[dubiousmike]

Thanks for the further thoughts all!  Per PB's suggestion, I went ahead and ordered a cheap TS 6sn7gt that should be arriving in a couple of days.  That should definitely help in ID'ing the cause of the issue one way or the other.

In the meanwhile, I've gone back to enjoying my crack with a 12au7 bugle boy (that's probably a better tube than any 6sn7 I'm likely to find at a reasonable price anyway). 

I wish I understood why the buzz (with my adapter and 6sn7) only becomes audible and then increases in volume as I turn up the pot.  Note that this is true irrespective of whether or not I have a song playing, so it is independent of having any signal passing through the tube.

[Paul Birkeland]

Are the voltages at terminals 1/5 within spec? (70-90V)

-PB

[dubiousmike]

All my voltages were right on spec last I checked (following my speedball install), but admittedly, that was more than a year ago.  Got held up working late last night, but hopefully I'll have a chance to grab my meter and reconfirm this evening.  Then again, given that my crack always has, and continues to, work perfectly with all 6 or so of my other input tubes - I have to believe the left channel "buzz" is simply the result of a defect in the adapter or in my lone 6sn7 tube. 

Either way, based on past frustrations, I am totally dreading attempting a return/exchange with the ebay seller of whichever component is faulty.  I love the deals you can score on ebay, but there would certainly be benefits to working with a mainstream seller like vacuumtubes.net

[adamct]

Not that it's worth anything, but my money is on the tube...

[dubiousmike]

You're probably right Adam - which is a shame given that it is otherwise a very nice sounding tube.  I should know once and for all Saturday when the new tube is scheduled to land.

Also - I just confirmed that terminals 1 and 5 are both measuring well within spec (right around 80V).

[dubiousmike]

Well - my new TS 6sn7 arrived last night, and it is giving off exactly the same left channel buzz (loudness proportionate to the level of the pot) as my Sylvania vt231.  Given that my voltages check out, and the amp continues to function beautifully with all my 12au7's and 12bh7's, I think the issue has to be the adapter...

Incidentally, the adapter has a hole down the center but there is a loop of insulated red wire poking out from the internals of the base into that cylindrical cavity.  Is the same true for others of you own this adapter, or might this signify a wiring issue?  It remains unclear to me whether or not there is actually any way to open the adapter up.

I have reached out to the seller, who responded with some initial questions about my amp, whether it is suitable for 6sn7's and whether the voltage is 6.3v or 12v.  I directed the rep to this thread and explained that many other bottlehead owners appear to be using these adapters without any issues.  Frankly, I hope she'll sign up and join in the discussion.  It would be much easier to work through the issue here than via ebay's primitive, character limited, plain text internal message system.

[Paul Joppa]

My working theory right now is that the wire to the grid pin is too close to a heater wire, so heater AC voltage is capacitively coupled to the grid. The volume control shunts that to ground, but the higher the volume control, the higher the resistance to ground and the less shunting is happening.

One of the heater wires is grounded, so if I'm right it's the other one that is close to the grid. To test this (if you want!) swap the heater wires, or ground the other end of the heater winding on the power transformer.

All theories are eventually proven false of course - it's just how long it takes, and how false they turn out to be ...

[Laudanum]

There is no wire, red or otherwise, that can be seen peeking down the center hole of the adapter that I have.  I wonder if they pinched a wire or trapped it and pulled it partially loose when closing the entire adapter up after assembly.   They dont cost an awful lot and cost much less than that to make so Im not sure why they wouldnt just replace the thing.  But then again, it is an HK seller and they can be a PITA to deal with, especially if the language barrier is an issue.  No offense intended to them as a people,  but the large volume asia based ebay sellers are quantity driven for the most part.  If they hoover in the 98-99% range on positive feedback with a big volume of sales, they probably arent likely to care whether they get another negative.   That said, the adapters work fine and look to be made pretty decent overall but unfortunately, it looks like you may have just gotten a bad one.  Maybe they will work it out with you when all is said and done.   

[dubiousmike]

Thanks for the further input PJ and Laudanum - it is much appreciated!  I haven't had a chance to do any more tweaking or testing in the last few days, but I'm guessing PJ hit it on the head.  I had referred the seller to this thread, and shortly after PJ posted, I received an email from ebay indicating the seller had sent me a full refund (without any suggestion or request that I ship back the part, which actually would have been consistent with their written return policy).  So Icelake deserves some credit for good customer service - even though it appears I got unlucky with a defective adapter. 

I think I'm going to give this another go - so here's the question.  Would you go with: 1) http://www.ebay.com/itm/1x-6SN7-to-12AU7-Vacuum-tube-adapter-socket-converter-/300914409464?pt=Vintage_Electronics_R2&hash=item460fe57ff8 or 2) http://www.ebay.com/itm/6SN7-6SL7-to-12AU7-12AX7-tube-adapter-adaptor-socket-converter-brand-new-1-piece-/151045740252?pt=Vintage_Electronics_R2&hash=item232b0716dc

[Laudanum]

The more expensive one looks like it may be easier to open up, depending on how they mounted the octal socket,  if there is a problem.  The Octal socket also looks to be better quality.  Looks like they just stuffed a decent octal socket into a sleeve.     The less expensive piece is being sold by Lowther Club of HK.  I believe that they are a pretty popular group in HK,  which may or may not translate to the quality of the adapter.   

I doubt that you would hear a difference between either adapter assuming you get a good one.   Personally, I'd probably buy the less expensive one because it's lower profile, the octal socket is flush mounted.  The other one has the white socket protruding out of the top of the adapter.  But if the looks of the bulkier adapter and extra 12 bucks doesnt bother you,  you would be getting an octal socket that may stand up to more tube rolling.  Of course, that doesnt take into account how well they wired the internals.

[grufti]

I have only good things to say about lowther_club. I have some of their adapters. They are very well made and plenty robust by the way. lowther_club is also pleasant to deal with.

The usual disclaimer.

[dubiousmike]

So take 2...  My adapter from lowther_club arrived yesterday, and it definitely works better than the last one! 

As compared to running 12au7's and 12bh7's, I still get a little bit of audible noise with this adapter, but it is equal in both channels, and not audible until the pot is turned up higher than I would want to listen in any event (with the exception of a few classical albums I have that seem to have been recorded at very low volume). 

I really like the aesthetics of the crack with a 6sn7 up front, and it is always fun to experiment with different tubes.  But from the standpoint of sonics, my initial impression is that I like the sound of most of my 12au7's and 12bh7's better than either of my 6sn7's.  Hoping to do some more real listening in the coming days to see if this holds true.