Like the previous replyer, I'm also thinking that the issue has to do with assignment of inputs, and/or input "mode". You said you selected "digital" from the remote, but I'm not sure I understand what you meant. The input mode choices for my Yamaha RXV-750 are Auto, Analog, DTS. There isn't a choice of input mode called "digital". This is because the Auto setting uses a digital input as its first choice if there is a digital source connected to the selected input. if not, than it reverts to analog. The Analog setting is there to force use of the analog input when both analog and digital inputs are present. The DTS choice is there to notify the receiver that it is DTS signal, and not the default assumption of a Dolby Digital source. (Although, in Auto mode it is supposed to automatically detect Dolby Digital OR DTS, and automatically use the correct decoder. So I'm not sure why you would ever need to set the mode to DTS. Possibly this is because the automatic detection of a DTS signal doesn't work properly all of the time?)
If what you are doing is setting the input mode to "DTS", then it is not going to correctly decode a Dolby Digital source. You will get silence if it is anything other than a DTS source. I'm guessing this is possibly the problem. (You're manual discusses this someplace - in my manual it is in a section labeled "Input Modes Selection".)
Your issue may also be possibly related to assigning of inputs. Each of the analog or digital input jacks on the back of the receiver is pre-assigned to a particular input (e.g. CD, DVD, DTV/CBL, VCR, etc.). For sources that would normally exist in both digital and analog form, there are usually both types of input available. If you have done any renaming/reassigning of inputs, that might lead to some unexpected results.
I ran into this because my receiver has a single input assignment called DTV/CBL. I wanted to run a digital feed from my cable box, but also have an analog (2-ch.) feed from the monitor outputs of my TV. If I ran both sets to the inputs labeled DTV/CBL, then the Auto input mode would always select the digital feed from the cable box, even if the cable box was powered down and there was no actual signal present. In order to switch over to the analog feed from the TV, I could select the DTV/CBL input, and then change the mode of that input to "analog". OR, I could plug the analog feed from the TV into another input entirely (I used a VCR input). That way I just select a different input from the remote, and don't have to play with the input mode settings (all are just left on "Auto").
