I agree with stereo5. Replacing the Mcintosh branded JJ tubes with Gold Lion 12AX7 (gold pins) is huge. Also I've tried Mullard 12AX7's reissues (not the 4004's) and liked them a lot, cheaper too.
From what I've the read My C2500 is suppose to have firmware issues but not mine (fingers crossed). Regarding other Mc pre's, They have made so many over the years it is hard to say.
From what I've the read My C2500 is suppose to have firmware issues but not mine (fingers crossed). Regarding other Mc pre's, They have made so many over the years it is hard to say.