Srajan did a nice bit on this.I have seen many pre's with phase control but not polarity.Even Wayne Dockery did a VTL 2.5 and said they were same thing.
Chazz
http://www.6moons.com/industryfeatures/polarity/polarity.html
Chazz
http://www.6moons.com/industryfeatures/polarity/polarity.html