Thanks, Gonk. As it turns out, I'm not getting any digital input--the "faint sound" was actually from the TV, I now realize.

And thanks for checking the manual--I do have the Sony set to digital output "On," "Dolby Digital" and DTS "On."

I also have the DVD input configured on the Model 990 for Optical 1 audio input.

So you'd think a bad cable--except that putting the OPPO back in the system worked fine.

I'll recheck everything, though.