I know the simple answer to this question is "use your ears", but I thought I would ask for experiences... I have a new amp with three pre-amp tubes. I think it is a bassman config - input gain, cathode follower, phase inverter. The tube chart calls for 3 12AX7 tubes. I have a NOS Tesla 12AX7, a GE Jan 12AX7, a GE 5 star 5751, and a GE 12AX7. Where would be the best spot to use the 5751 if I want to change things up? I currently have it in V1, but I am reading that people seem to use these in the PI slot. Thoughts?