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On the V22, tubes V1 and V2 deal with both the clean channel and the lead channel. When the amp is in the clean channel, the signal passes through one half of V1 and one half of V2. In the lead channel, the signal passes through both halves of V1 and V2. The signal then continues on to V3, which is the phase inverter before the EL84 power tubes.

The difference between the 12AX7A and the 12AX7B is the 12AX7A has a higher gain output than the 12AX7B.