Loosing dynamics with power plant

Hi ,
I'm experiencing that after I've decided on a multiwave to use with my PS Audio P500 power plant that after a couple of days my system appears to loose lots of dynamics. Could it be my cables getting used to or settling down after the ac frequency changes, the P500 itself or could it be the ac is just poor. I notice when I switch the multiwaves around and settle on whichever multiwave I decide that the music has regained it's dynamics. Then after a couple of days the music sounds flat again. Can any help with suggestions and has anyone else noticed this phenomenon?