Why do I get a poping sound??

When I switch digital channels on cable or mute or switch from CD to Video1,2,3 on my Rotel 1068 I get a POP sound, light on the panels of my Innersound Eros speakers and ofcourse more pronounced on the bass cone, it is Bi-amped and this is my second unit, Rotel said the heard nothing on my last unit and sent this one brand new.
I know the speakers are 98db efficient but I really dont think this is normal, but after 2 units I wonder if it is something I am just going to have to accept?