I was able to hear differences in PC's on both M-60's and MA-1's in my system.
Looking forward to seeing what results you get in your system.
George
George,
I've heard differences, first pretty exciting, then got pretty "blah". I've talked to Ralph and the symptoms are consistent with 6SN7 aging, although my tubes are only a couple years old, so have maybe 2-3k hours on them and shouldn't be dying yet. I figure it's either aging 6SN7s or just a roller coaster with the PCs.
I'm exercising patience (or trying to) and after another couple hundred hours will give it another critical listening session. If I still don't hear magic, I'll roll in some Sylvania 6SN7s and see what I hear.
Thanks,
Evan