Hello Sandman. Welcome to AA!
I owned the C2600 for a few months. Excellent preamp. It took about 80-100 hours or so for things to smooth over. First 20 hours IMO was a tad thin and bright. Really starting coming together around that 80 hour mark though.
I own 601's (previous model). They actually needed LESS break-in time compared to my MC452's. The 601's actually sounded pretty fabulous from the get go but after around 50 hours it was stunning.
Play some music and enjoy and don't get too caught up in nuances this early on. Listen of course and be amazed at what your ears hear.
Best of Luck!
