Tube rolling - 12AU7 to 6922 adapter


I thought I’d transfer this thread over to this discussion category from tech talk. I recently changed preamps - from 12AU7 circuitry to 6922. Yet, over the years, I’ve accumulated a sizable stash of NOS 12AU7’s - some of which I really enjoy.

At @kdude66’s suggestion, I purchased these 12AU7 to 6922 adapters. My main concern was damaging my pricey new preamp. No problem. It’s sounding kind of great! These adapters are built very well using real ceramic sockets. They fit snugly in the 6922 sockets. For those using components with 6922 tubes, this opens up a whole new world of 12AU7 tube-rolling possibilities. The only drawback is that they add about 7/8" height. So, I need to build a riser to raise the preamp lid. It should be simple.
steakster
I did not know that could be done. A 12 type tube is 12 volts and a 6 type tube is 6 volts! Are you sure you won’t damage the preamp?
yogi: all that does is jump pins 4 & 5 and connects pin 9 to ground to put 6.3 volts in parallel to the 12AU7. The tube can run at either 6 or 12 volts.

op: There should not be an issue running a lower gain tube, however the circuit is optimized for the 6922 and the 12AU7 may be operating outside its sweet spot. Try listening to a 6922 to see if there is a difference.
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I just found this by searching for an adapter which would permit me to use 6922 types in a socket wired for 12AU/T/X7s.  In other words, the reverse of what the OP did.  Does anyone know of such an adapter?

Just a comment on this thread:  In all my experience, 12AU7s are not good sounding tubes when used as a gain stage.  They're OK when used as cathode follower or as phase splitter, but that's about it.  When confronted with a 12AU7, I change to a 12FQ7 or 6FQ7 (depending upon the filament voltage supply), or a 6CG7 (perhaps the best of all).  The change to 6CG7 does require some fiddling.  But all 3 of the latter tubes sound much better to me than does the 12AU7, in gain mode.