Just to throw my two cents in and since I started the thread: regarding input tubes , in my atmasphere ma 2 3.3 amps RCA 6sn7 input tubes sound the best to me. I also have a set of silvania 6sn7's. RCA's seem to add a great warmth and smooth vocals ( like wow vocals) , to me the silvania's sound thin in a bad way, sound stage is not as forward also. So there is no doubt that anyone would hear the differences in sound of different nos input tubes, so input tubes do make a real difference.
Even more inportant and able to modify the sound are the tubes in the mp1 preamp. Again I prefer RCA.
The one exception is in the 1st position in the amps I was lucky enough to find a pair of kenrad jan vt 231 black bottle, that are quiet and not microphonic, this one pair of tubes adds the necessary bass to round out my amps with either set of tubes.
