Wiring for 6SN7 instead of 12AU7?

[Bubbatwoa]

The 6SN7 seems to be universally preferred over the 12AU7 in the Crack, so I'm considering building my Crackatwoa with modified wiring to the input tube socket for 6SN7 so that I won't have to use an adapter.  I hate the look of adapters.  Can this be done?  Any downside to doing it?  Can I use the 12AU7 that came with the kit and just wire it differently, or will I need to purchase a different socket?  If I have to buy a different one, will it fit the hole in the top plate without modification?  And lastly, is there a guide somewhere I can refer to that will show me how to wire it correctly?

[Natural Sound]

I'm not sure if I'd agree that the 6SN7 is, "universally preferred over the 12AU7." It is my preferred tube in "most applications" but that is my OPINION. And as with all opinions not everyone will agree. I bought one of the early Crack amps (v1.0) and wired it for 6SN7 from the beginning. Be advised that this is NOT the recommended way to build a Bottlehead amp. I relied on my 40 some odd years of experience with electronics and took an unsupported gamble.

An octal socket that is required for the 6SN7 will not directly fit in the Crack or Crackatwoa kits. The hole needs to be enlarged for the larger tube format. That modification may be difficult with the laser cut airflow design in the Crackatwoa top plate. You will be on your own for the most part if you pursue this path.

My recommendation is to build the Crackatwoa completely stock. Then use one of the adapters that you find aesthetically unappealing to try out the 6SN7 and the 12AU7. After you spent some time comparing (AKA Tube rolling) you can make a decision if you'd like to pursue a permanent modification.

[Paul Joppa]

There is always the 6CG7 / 6FQ7. Same 9-pin socket as 12AU7, but different pinout.

[Bubbatwoa]

Thanks guys.  I would only undertake this mod if it were as simple as I had hoped.  It sounds like I'd be better off just biting the bullet and getting an adapter.  I paid $944 for the kit + Twoquiet upgrade, and I don't want it to end up as a hack job.

[Paul Birkeland]

PJ's suggestion is the winner, just use the 6CG7.  It is electrically identical to the 6SN7 but still uses the same 9 pin socket. 

[ALL212]

Easier peasier ...

Get the 12au7 to 6sn7 adapter - then you can go both ways at will.

[Bubbatwoa]

PJ's suggestion is the winner, just use the 6CG7.  It is electrically identical to the 6SN7 but still uses the same 9 pin socket.

I'll certainly look into the 6CG7, thanks to both Pauls. 

[Gerry E.]

Hi - If you decide to give 6SN7 adapters a try, I highly recommend Garage1217.  I use a pair for my BH Paramount amps.  Highest quality adapters I have come across (scroll down): 

http://garage1217.com/garage1217_diy_tube_headphone_amplifiers_012.htm

Gerry

[ALL212]

Can I use the 6SN7 to 6922 adapter in the Crack with Speedball installed assuming I've socketed it for 6SN7?  I noticed there is one of those on that site.

[Paul Birkeland]

The 6922 and the 12AU7 do not have the same pinout.

Garage 1217 sells adapters on eBay and advertises one for using a 6SN7 in a Crack.  I would use that one.

[ALL212]

Yessir!  I realize that and I did a poor job of communication.

I built a Crack some time ago with the 6SN7 socket instead of the 12AU7.

Would it be “safe” (smart doesn’t count here ) to use the 6SN7 to 6DJ8 adapter in this Crack?  I do have the speedball installed.  I’ve a collection of 6DJ8’s I could try here.

Thanks!
Aaron

[Paul Birkeland]

The 6DJ8 is a poor choice to use in this circuit for a variety of reasons.

-PB