Usually power tubes first then signal tubes in an amp. Also it’s the first signal tube in the series for a particular channel that has the most impact. For instance, if you have 3 -12 ax7s for each channel, the first one in the series has the most sound impact, the others less and less as you go to the last tube in the series.
Signal tube versus power tube, sound impact?
My mono block has eight KT 88 tubes(power tubes) and six smaller signal tubes. I'm using the stock tubes that came with each Mono. I think they are JJ tubes.
Rather than replace them all would it be best to change out the signal or the power tubes? Not sure how good the JJ tubes are but I hear they may not be the greatest.