I've searched this site without a clear answer on this question. I recently purchased a Onkyo TX-SR602 to use with my DVD. I would like to find out which Audio outputs would produce a better result. I have the 5.1 multichannel analog versus optical digital or coaxial digital. Any thoughts??
as long as you have a decent DAC on your pre/pro or AV receiver (not familiar with your Onkyo, but it probably has decent DAC) you should go coax digital. the losses and interference of analog links between components reduce quality enough that you are better off using the DAC closest to the power amplifier.
5.1 analogue is aimed at high-resolution music, i.e. SACD and DVD-A. For other sources I'd recommend digital interconnect:
1) You are likely to find receiver much better at processing cinema sound.
2) 6 analogue cables perfoming better than digital S/PDIF is an expensive hookup.
On my equipment, I can sense some subtile differences between analogue and digital connection for low-resolution music (i.e. CD). But not really justifying cables that cost 3 times more. SACD/DVD-A is a different story, 5.1 interconnect is compulsary until HDMI interface becomes affordable.