A-B'd the CJ/3A/VAC preamps. CJ and 3A close, thought the CJ slightly more vibrant, a little less colored sound, an attractive pre. 3A's got nice slam, almost a little too chunky a sound and analog warmth at the expense of realism and detail.
VAC outdid both - more refined, more accurate, more dynamic; sounds are clearer and cut through in ways the other two can't. Same punch, same solidity of bass but stripped of the slightly artificial, exaggerated analog layer of the 3A. Noticeably more detail, depth, conciseness, and imaging vis-a-vis the other two.