The MBL preamp was used every time I heard them.. All cables are
Wireworld Platinum Series 7. The 101E’s are very detailed, open, great
imaging and tonality. They can sound too detailed, almost bright at
times.
I would not blame the speakers for brightness. I got to spend some time with the mbl line stage and that seemed to be bright; when we changed it out for a tube preamp (our MP-1) the mbl101s took on a much more natural sound and lost the brightness. They seem to be pretty neutral.
Every time I've heard then at shows though they've sounded bright; but that was with the mbl electronics as well. IMO the speaker is not a good match with their electronics as it gets too bright and sterile, although their amps IMO are better than their preamps in that regard.