i just came across this on DIYSB and someone was able to get it into a 1590a. would be real awesome to have a mini tube amp, especially since the tiny giant amp was finally verified. so i'm bumping this.
The "challenge" is that the 12ax7 requires more than 9v, and also AC power, right?
Not that we are incapable of using a different power supply, it is just that it's a different ball of wax.
You can find 12 V. AC wall warts like the ones for the cheap A.R.T. tube preamps. I have one from a dead preamp bought long ago, maybe the wall wart is worth saving at least.
I have seen people use different tubes, but IMO you aren't going to get that magic sound for guitar unless you use a 12ax7.