Swapping tubes in ART gear

[kinger]

To finish this saga, I picked up my set of N.O.S. G.E. 12AT7s and popped them in the MPA Gold and it made an audible difference, and for the better might I say. The upper mids always sounded a little "ringy" before, for lack of a better word, and now it's quite smooth and silky sounding. I tried popping one in the VLA and couldn't notice a lick of difference so I don't think I'll shell out for another pair for that. Just my impressions, but thanks to everyone who gave input!