newbie with sony str dg1000 question..

well little by little i'm piecing my a/v set up, i just got the sony (dg1000)replacing my very old kenwood h.t. system my question is now that i've hooked it up when i watch tv everytime the channel changes or program changes the volume changes with it from loud to low and vice versa am i missing something? any help, tips,tweaks or advice is greatly appreciated since this is my first real reciever.thanks,pat