Tube Preamp for Mcintosh MC501 Monoblock

If you want the best, try the VTL 7.5. sounds devine with the MC 501's.

WOuld there be impedance mismatch with BAT & CAlypso into a 10K input impedance amp?

Aesthetix recommends a 10k or greater load which the MC501 can manage (10k unbalanced, 20k balanced). The BAT has a very low ouput impedance (200 ohms). There should be no issues running either of these preamps with the Mac as it's input impedance is high enough to not load down either preamps output stage.

I use a Cary tube SL98P with my Mac 501s (driving an old pair of Apogee Duetta II's) and I am extremely satisfied. Very smooth, detailed; much better than the Audio Research LS2B I was using previously.

BTW, I A-B tested the MC2200 vs. the Cary and liked the Cary much better. Listen to a good recording of a horn section or viola and hopefully you'll know what I mean...