Does changing preamp tubes affect bias?
No. The preamp tubes (V1, V2) and the phase inverter (V3) do not affect how the amp biases. Having to change out the phase inverter every time you change power tubes is an “old wives’ tale.” Also, putting in a 12AT7, 12AY7, etc instead of a 12AX7 will NOT affect bias. Fact: the power tube’s bias supply is completely isolated from, and independent of, the phase inverter!
