How to change DVD-A groups on Linn Unidisk

A good friend has the Linn Unidisk 1.1. He had some problems with it, which have now largely been resolved by Linn. However, he has some DVD-A's which require the selection of "group two" in order to play back the high resolution (24/96) in two channel. He has a two channel system. How do you do this with the Unidisk, and does it require a video monitor? He and I would appreciate any advice from Unidisk owners.