Niagra 7000 HUMM

How much niagra 7000 humm is prevalent and does it bother anyone or interfere the quiet passages in music 

Ag insider logo xs@2xrizwanalimohd
Do you own one that humms? If not why would you expect that it humms?
i am about to purchase one used possibly
i have one and minimal hum after following AQ’s instructions.