Djm700 hum noise

Hi guys, am new to the forums so I apologise if posting in the wrong place . Basically my djm700 when powered on makes a very faint hum noise and just wondered if this is normal or could be a problem.Ive had the mixer not long and its never left the bedroom etc, but a mate has the cdj/djm nexus platinum set up and his mixer is completely silent.Any help or feedback would be appreciated cheers guys.