I saw this on the Bose forum.

Sounds like this could be an answer to using only one amp for the Tyros and PSR3000 etc:

posted Thu February 12 2004 01:20 PM
Little Labs (http://www.littlelabs.com/ibp.html) makes a great phase alignment box called IBP (and a simpler junior version} allowing one of the stereo channels run through it to be continuously phase adjusted until it sounds right with respect to the other channel.
So there is an option instead of trying to force everything back to mono...
http://www.littlelabs.com/ibpjr.html

Best
Scott