So I have the original Buffalo and the IVY in a case with the two power supplies running of a single R-core xformer with 2 dual windings at 15V each and two dual windings at 9V each. I do not have the mains earth connected anywhere. I am starting to wonder whether this floating setup might explain the weird noise issues I am having when hooking up to a Roku (it has no connection to mains earth).

What is the recommended approach to any mains earth connection? Where should it go if it should go anywhere? (Yes, I understand the safety implications of not connecting to the safety earth; my question is strictly with regards to potential differences between different signal grounds potentially messing me up...)

Peter