I'm just now hooking up my Sony STR-DA4ES, and I can't get it to output 5.1 channels. I'm using it as a preamp, so no speakers are hooked up to it directly. When I play a 5.1 DD or DTS source, the display says: 5.1 -> 2.0 It won't let me select any sound fields, and then I hit the "2 Channel" button, it shows me the on-screen menu, with "2 Channel" displayed, but it won't let me switch to "Auto". I've made sure all speaker setup options are correct. Is there something I'm missing?