Is there one brand of 12AX7 that tends to have more gain than others?
There's the RetroValve Red...
Probably not the answer you're looking for.
None of the tubes listed above are high gain. I've tested 100s-1000s of each.
Now, if you mean easily overdriven, which has nothing to do with gain, then some of those MIGHT be.
Gain is the amount of amplification you get from a device. It has nothing to do with overdrive/distortion.
Every brand of 12AX7 ever has had a +/- 10 % variation from the center point...20% span overall...so there are none that consistently rate higher for gain than others.
JJ ECC803S and ECC83 have some of the lowest gain readings I've ever seen.
The gain of the amplifier circuit completely overwhelms the gain of the tube most of the time. Variations in the gain of the tube will have little to no effect.
So, the question is, "what is your goal, what have you already tried, and what amp are you thinking about?".
It's a Phaez SIBLY that I'm looking to get more "distortion" out of, so I'm guessing that means more sensitivity? I'm assuming more gain would be good in the preamp too in order to overdrive the PI?
True!Be careful with 12BZ7s they are two 12ax7s in one bottle hence double the current draw. Make sure your PT can handle it.
It's sounding like there's no simple preamp tube swap that'll get me close to what a boost pedal does to get more gain out of my amp.