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.