Hi Tony,
What equipment produces the hum you hear? (Module or KN7000)
Did you change something in the setup?

I own no KN but have strong doubts is has USB ports onboard, so I think it's not possible to use USB.
You write 'MIDI Jack'. As fas as I know 'jack' is mostly a 6.3mm TRS connector.

You could try to supply the mains power from non-grounded outlets. (To prevent ground-loops)

Roel