The dealer/Norma indicated that it could be vibrations from the transformer being transmitted through the chassis and suggested placing it on a different surface, placing something else under the amp to support rather than using the feet, I tried all of this using oak cone feet and carbon isolators but still the hum remained. They then suggested removing the phono boards, however, that did not make a difference either.
The volume control isn't a showstopper, just me being picky and yes I agree the controls on a Luxman feel much better engineered.
My speakers are similar, the volume needs to be around the 9 o'clock position to get them to start dancing, once you get above this though it really starts getting its groove on and making me smile.
Just waiting for the dealer to arrange collection and it looks like the amp is going back to Norma.