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Hello, My 12AT 7 groove tube is in the V4 position, like the original 12AT7 : my MK IV is a MKIVA. Do you think this tube is responsible of this situation ? The gain is weak, especially on lead channel. Volume is divided in two with my new tubes (simul class, pentode, mid gain). I need to play...

Hello, My old MK IV (1993) have been retubed last month with : four 12AX7 Boogie, one 12AT7 Groove Tube (the original tube was a 12 AT7 Boogie like in all MK IV before 1994 in the left socket preamp tube). Four 6L6 Boogie power tubes (grey code like the originals). Since this operation, I have...