6sn7, 6j5, 76's?

[ALL212]

When I built the BAC I wired and socketed it for 6SN7 in the 12au7 spot.  With the upcoming Crack sale I'm considering wiring this one for a pair of 6J5's for fun.  The old 76's look kinda ok...

Are a pair of 6J5's ok in the 12AU7 position (rewired and resocketed)?

Are a pair of 76's there ok - can the rest of the circuit handle this?  Much more research into availability to yet be done.  A friend was giving me "idea's".  I understand I'll need to source some 5 pin sockets.

 

[Paul Birkeland]

The 6J5 should be about dead nuts on.

The 76 may need to have a little more plate current run through it.  Try an R1 around 213 ohms on the small board (215 should be fine/available).

 

[Paul Birkeland]

So, you could start with this adapter:
https://www.ebay.com/itm/GARAGE1217-6SN7-TO-12AU7-TUBE-SOCKET-ADAPTER-OUTSTANDING-BUILD-QUALITY/254027687944?hash=item3b253ae808:gYAAOSwOyJX-neh:rk:1f:0

Then plug in this adapter:
https://www.ebay.com/itm/1-6J5-6J5-To-6SN7-6SL7-Vacuum-Tube-Amplifier-Convert-Socket-Adapter/283135241967?hash=item41ec2ceeef:g:M0wAAOSwJbpbfMxH:rk:1f:0

Then plug in a pair of these:
https://www.ebay.com/itm/1pc-Gold-plated-RCA-76-TO-6J5-VT94-6C5-6C2-tube-converter-adapter/191594222892?hash=item2c9be7d52c:g:78UAAOSwqfNXkNee:rk:1f:0

If you actually do this, I promise I will try not to poke fun at your stack of adapters.  ;D

 

[ALL212]

I've got the first two adapters!

I turned a Schiit Saga into a two holer with the 6SN7 to 6J5 adapter and had folks at Odyssey Audio sweating (or was it I that was sweating) when I used 6SN7's in the 12au7 sockets on a Candela - no smoke from either.

Might be time to source some 76's...  8)

 

[ALL212]

Let the giggling commence!

 

[Paul Joppa]

FWIW, 6P5GT is a 76 with octal pinout - one less layer of adapters!

 

[Paul Birkeland]

Now I'm going to be thinking of what adapter you could plug into the 5 pin socket.

You can also go from a 6J5 to a 6C4.

 

[Tom-s]

Here's 6J5 in my Crack. I like the sound. https://ep1.pinkbike.org/p5pb16745694/p5pb16745694.jpg
Another option might be to run 7193 tubes for driver with GEC A2293 for output tubes.
Because more tubes are better  ;D

 

[Tom-s]

I'm always willing to try new tubes, just for fun! Read the mention by PB in other topics about the 76 and 37 later developing into 6sn7/12au7. So I've order a box of 76 and 37 tubes to try in my Crack.
Anyone tried these yet? I'm a bit worried about the operating points not being optimal with Crack.

I use ECC82 -> 6J5 and bought a 6J5-> 76/37 adapter.

 

[Natural Sound]

This was a fun thread to read. Like the OP I installed a second octal socket and use a 6SN7. I've rolled quite a few of the alternatives with adapters and such into my first generation Crack amp. I always return to the 6SN7 for synergy. Specifically a Sylvania T-Plate "chrome dome" voltage amplifier with a Sylvania JAN triple mica 6080 power tube. As they say your mileage may vary but this seems to be my destination. At least until I can scrape up enough dough for a mainline.

 

[ALL212]

Let's say that I'd like to go a bit crazy on this one.

76's, maybe 37's in the pre circuit.  6J5's for sure if stock on those looks low from suppliers.

How about those 7193's in the pre (not power) side?  I think it would look pretty cool with those Dr. Who dalek's running around.

I'm having a new plate cut anyway and it will be landscape oriented instead of portrait.  I've still got to check room for all of this but I think it might work.  Plate size will be about 10 1/4 x 8 1/2.

The odd plate size comes from a miscommunication between myself and the woodcutter for a prior base and then an additional issue with basic math.

Base.pdf would be "normal" just oriented differently
Base1.pdf could be a new dual tube layout.  Still much thinking needed on that one!

 

[Tom-s]

Really nice! Looking forward to your new Crack!
The only tube i know of that might work as dual output is the GEC A2293.
Can't think of another that might work in the output of the Crack.

 

[Paul Birkeland]

Why four socket holes in the base?

 

[ALL212]

The four holes would be a misguided dream that I could split the 6080 somehow...

Unless there's a miracle it's going to be a three holer at best.

Base3.pdf is probably fairly realistic

 

[Paul Joppa]

The 7233 is roughly half of a 6080.

 

[ALL212]

After careful consideration of making a two tube unit into 4...I'm a gonna stick to no more than 3.  I'll leave the 6080 alone.

Maybe the next build!

 

[Tom-s]

The 76 has a very nice sound to it! Holo-graphic, filled, easy listening. Pleasant bass, spacious mids, soft highs. Like it a lot! I've tried the Sylvania and RCA (VT-76 JAN version) variety in my Crack. I'm not good at this kind of descriptions, they have a "bigband" kind of sound to them.

Not the most Hi-Fi type tube ever heard in Crack, but a very pleasant surprise!

Beware, very susceptibel to trafo hum, environmental sounds, some are a little microphonic (but all very listenable).
Must be because of the adapter stack  :-[.

Edit: I have to note that i also tried the 37 tube (RCA). And this one aint bad either (little more "dull"). The 76 has something extra and is real nice!
It could be the operating points differ. Will check later on.

 

[attmci]

:The crack is still a crack no matter how many tubes you installed.  ;D ;D

 

[ALL212]

Would someone check my homework?

If I go to dual 6J5's from the 12AU7:

12AU7 Pinout            6J5 Pinout

Plate A      1              3  Plate Tube 1
Grid A      2              5  Grid Tube 1
Cathode A 3              8  Cathode Tube 1

Heater    4,5,9        2,7 heaters, tube 1 and 2  (Split the wiring at 6080 socket)

Plate B      6              3  Plate Tube 2
Grid B      7              5  Grid Tube 2
Cathode B 8              8  Cathode Tube 2

 

[Tom-s]

You are correct.

https://www.radiomuseum.org/images/tubeenvdiag_klein/6j5.png

Maybe PB has some insight on connecting pin 1 of the 6J5's to ground.
Might help in getting all as silent as possible.