in my MC275 V with very good results. Musicality and instrument definition greatly improved with the Mullards over the stock 12AX7's. Also found that the amp benefitted from using Audio Research tube dampers on V1, V2 and V5. Tried the dampers on the 12AT7's and really didn't notice much of an improvement, at least not compared to the dampers used on the CV4004's.
Mixed driver tube for Mcintosh MC275
I just wonder if anybody know which sections of Mcintosh MC275's driver tube are most crucial? Is it all sections of equipment are the same in terms of the importance of the driver tubes. Another thing, is it using a tube that has a sonic trait that is different than another like combining a thinner more detailed tube like a Telefunken can actually work very well with a warmer tube like a Mullard?