Thanks for the input.
I have seen that some amps don’t even use 12ax7 for the driver/phase inverter but use a 12at7, which, I think, is a lower gain version of the 12ax7 and basically interchangeable electronically. I am very happy with the amp as is, to be honest. It is very quiet 95% of the time and I have no complaints with the tone. I have a full set of the SPAX7 tubes and another set of 12AX7 (all MESA branded tubes) and was just wondering how I should use them. The SPAX7 are only a couple of dollars more, so I don’t think it is necessary to go to great lengths to “save” them but at the same time, no point in using them where the differences are negligible or nonexistent.
Something else I was wondering about...
When I swap some of them out I was thinking of also swapping the inner and outer power tubes. I pretty much always have the amp in 45W mode (all channels) which only uses the inner pair. I figure it has been about a year or so on those power tubes so the outer should be “fresh” and swapping them with the inner pair would even out the wear on them? Thoughts?