You access the preamp input settings from the NDX2 window using the remote. The button with the wrench on it brings up the right menu, then scroll down to system automation, then scroll to preamp.
Under preamp, there’s selections for what source uses which input.
And you have to push exit when yer done to save the changes.
I’m doing this from memory, at 2 am; so try it and let me know if it’s not clear and I’ll check it phycically in the morning. But I think you’ll see what’s going on when you get there.
Best of luck.
Dave