If you can find one for sale used, the Audio Prism Mantissa has worked excellently for several of us McCormack owners. The trick is actually finding someone who wants to sell it. Then again, you could also look for it's pricier incarnation with the Red Rose badge on it.
In any case, try a tubed preamp with the McCormack's. Just find one that's as transparent as possible (not always an easy trick).
Enjoy,
Bob
In any case, try a tubed preamp with the McCormack's. Just find one that's as transparent as possible (not always an easy trick).
Enjoy,
Bob