Tube adapters??

I've used the adapter to run 6SN7's in crack.  The adapters work well.  I ultimately built an FPIII with 6SN7's and use a 12AU7 or variant in Crack.  If I was running the Crack standalone, Im not sure where I would have ended up.  Most likely the VT-231 (6SN7) primarily but I also have some favorite 12AU7's as well as some of the 12AU7 variants and 12BH7.  Tube rolling can be fun  ;)
 
mikek200 said:
Paul,
Thanks for your suggestion

I went on e-bay,& found a few tubes {12au7 }, that I might be interested in,.Amperexes Mullards,Brimar
These have odd labeling,but seem to be authentic..such as--Mullards ,made in India,and one or two others
Prices were low,& the readings were good-to like new...

Still waiting on my 6sn7 to 12au7 adapter..coming from China.
Click to expand...

Yea I believe mine took the same boat when I ordered, must have taken 3- 4 weeks to get them.  :-\
 
OK,really no luck with dealing with Chinese adapters..or,6 week delivery times.
Maybe you guys can still help?

Here is what I am looking for:

a 9pin base to 6sn7 {on top} adapter...that plugs into my 12au7 input
Does anyone know,of a seller in the USA,or,someone who can build me one  ,in the USA?

Is this idea doable,safe?

Thanks
Mike
 
OK found it..
Just in case anyone else may need one:

  http://www.ebay.com/itm/281031554093?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
 
Took less than 2 weeks for me to get those adapters from HK.  I think it was the same seller too.  They work fine.  Of course, YMMV on shipping time.
 
thanks for the link and feedback on the hongkong seller Mike and Laudanum - I was on the fence about ordering from a non-US seller but did just order one up.  here's hoping it gets here in some relatively reasonable time frame!
 
Well - finally received my 6sn7 adapter, and sadly I'm getting a bad buzz in the left channel (that increases in loudness as I turn up the pot).  With the pot at 0, no buzz is audible. 

I acknowledge that the problem could be my tube - but I only have 1 6sn7 on hand (a seemingly nice Sylvania vt-231 foil getter I picked up from tubemaze), so my money's on the adapter.  It has a hex bolt on the bottom.  Has anyone successfully taken one of these apart to check the connections? 

My amp continues to run beautifully with all of my other input tubes.
 
Never had the need to take one apart.  They had it apart to build it, shouldnt be too difficult, maybe just a loose wire/bad solder joint.
 
If the volume is at zero, and there is no buzz, then the problem is before the volume control.  The only things that are before the volume controls are the input RCA jacks and 3 pieces of wire (it may be four pieces of wire, but I remember the input wires being braided). 

Is the buzz in one channel?  It could be the interconnects.  Regardless, try reheating the solder joints on he inputs and the volume control.
 
Thanks for the input laudanum and grainger.  The buzz is only in the left channel, but to clarify, I dont have any issue when running the amp with any of my many 12au7's or 12bh7's.  So I don't think the problem is with the amp, interconnects, etc. 

Gotta be either my adapter or 6sn7.  I'll have to see if I can open up the adapter later today.  I pulled the hex nut from the bottom, but it doesn't fall open immediately.  Maybe time to contact the vendor on ebay.
 
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.
 
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
 
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.
 
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
 
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).
 
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.
 
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 ...
 
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