Can a 5687 work with the crack

[tdogzthmn]

I found a Tung Sol 5687 which seems to be similar to the 12AU7 but I think the pinout might be different.  Would this tube work in my crack which has the speedball upgrade or would the tube/amp need modification for it to work?

Thanks.

[Jim R.]

I think PB has already said this would work, but the pinout is different andd it would at least need a change of one of the resistors in the C4s, and maybe some other changes to another component or two -- don't recall exactly, but I think it's somwhere in the tube rolling thread.

-- Jim

[JC]

Beside the pinout being different, at a glance it looks to need about 3x the heater current.  You will need to have that available.

[Paul Joppa]

The heater current is available - just barely, but it is there. Trick is, you also need a lot more plate current. I think it's in the archived thread, too late tonight to check though ...  :^)

[tdogzthmn]

Ok, so can anyone see a good reason to make such changes, and what would be a comparable 12AU7 that I could try?

[grufti]

Try the E80CC mentioned in some of the tube rolling threads in the Crack forum.

[Paul Birkeland]

The heater current is indeed barely there to make this work.  The B+ current is also sufficient.  If you have the Speedball upgrade, let me know and I can revisit the resistor changes necessary. 

This would very likely be a nice alternate driver tube, and it has a little bit less gain than the AU7 IIRC.  You will, however, want to start with a fresh 9 pin socket to facilitate the modification (complete socket rewiring).

[Brillo]

Paul B.,

I would like to try a 5687 with my new Crack build (with Speedball).  I searching the forum, it's not clear exactly what wiring and component changes are necessary.   Can you (or someone) describe?

Chris

[Paul Birkeland]

Hello Chris,

Feel free to let me know if you need more info than was contained in my PM.

-PB