Jolida Hybrid humming noise through speakers?

I have 1501RC and when the amp is on, there is quite a noticable humming sound that comes through the speakers. You don't hear it from the amp itself, but throught the speakers. You can hear it from several feet away. I have this plugged into a power strip/surge protector, but my other power amp had no problem. Is this a common thing with tube amps? Is there something that can be done before I send it out for repair? Thanks