Humms only with power up and line stage tubes 12AU7s working.
Pulling the phono stage 12AX7s does not affect the hum.
Pulling the linestage 12AU7s stops the hum.
A friend who does guitar amps suggested pulling the 12AU7s
and putting the 12AX7s in their place to see if the hum is still there.
Is this doable? I know they're pretty much the same tube except for the mu.
Trying to keep all the smoke inside the components.