You might have to swap the tonearm cable as well as the interconnect to preamp. If you swap channels on the tonearm cable, and the low output moves, it's in the cartridge. If you put the tonearm cable back, and swap the interconects from p5 to pre, it's the phono stage. I believe your p5 has a internal balance adjustment, call BAT to be sure.
Honestly, it's hard to say on tubes or not. You really should try the above. It's less work than taking off 24 torx screws and tube swapping...
Are you running stock sovtek tubes? If so, retube it if you want better sound quality. Better 6922's and 6sn7's will make a huge improvement. However, the 2 6922's on the 1st input stage are very critical for matching. Again, call bat, they will walk you through it.
I recently retubed my p10se. Wow....big diff.
Honestly, it's hard to say on tubes or not. You really should try the above. It's less work than taking off 24 torx screws and tube swapping...
Are you running stock sovtek tubes? If so, retube it if you want better sound quality. Better 6922's and 6sn7's will make a huge improvement. However, the 2 6922's on the 1st input stage are very critical for matching. Again, call bat, they will walk you through it.
I recently retubed my p10se. Wow....big diff.