I had one Cardas Cross PC for a year or so. I tried it in different positions, and although it added nothing remotely resembling brightness, the system seemed to have a disparity between the highs and lows. There was a nice midrange, but the highs and lows were totally different, with the midbass on down being thicker and less defined. I blamed it on the Cross PC and sold it. I have since had the same effect, even worse, at different times depending on the combination of ICs, PCs, and power conditioners. Even had the same effect with Golden Reference PCs at times, but with them working great at other times. Perhaps other things contribute to the characteristic (speakers, room, amp), and certain combinations of cables or conditioners exacerbates it. At any rate, it may not have been the Cross PC (otherwise it was pretty good).
