There are two possibilities. First, you listen to SACD's and DVD-A's in 5.1 and the rear surrounds stay silent. Second (this comes out of the HD-DVD and Blu-ray format war and the odd tendency for those players to not offer 7.1 analog outputs), you split your left and right surround outputs from your player and send the each signal (left or right) to both side and rear surround channels of the 990's 7.1 input. Personally, I am doing the former - my rear surrounds simply don't do anything while listening to DVD-A and SACD.