Hi again Iain,
Interesting results:
1. Contrary to what I thought, OBS only supports ASIO IN - and that worked fine
2. Google turned out (again) to be my friend and I found an
ASIO tester that picked up the U86XT ASIO driver instantly and sent a 1kHz tone output to it, audible in my headphones attached to the U86XT.
My conclusion is that there is nothing wrong with the U86XT/ASIO drivers and that the problem is somewhere in HW - in the set up no doubt. At least I now know where to focus my attention...
John