I'm just wondering, what is the point of the 12AX7s? They appear both on the TA and the 20:20?
Also, the 20:20 and the 2:50 are stereo, the 2:90 is simul class, what is stereo and what is simul class? Is simul class the A/B class that the rectifiers use? As for stereo, I've only heard it used...