We have a sound system with 6.1 channels (7.1 if we use two active speakers in addition to the sub-woofer.) We're going to use the optical SPDIF connection. Are some sound cards better than others if they use optical SPDIF, because they don't do any DAC? In other words, are there any benefits of paying more for a sound card when we use the digital output?
Digital is digital, so if you are using an optical cable between your sound card and sound system, you should be fine.
But don't trust me, grab a S/PDIF cable and hook it up. How does it sounds?
There are two main reasons for using external sound cards, neither of which apply to your situation.
- External sound cards allow you to isolate the analog signal path from the high-frequency digital noise generated by your computer. You aren't using the analog output, so this isn't an issue for you.
- External sound cards give you more space for I/O ports. My MOTU 828 has 12 ins, 10 outs, S/PDIF in/out and ADAT in/out, plus some other random stuff like MIDI and various clocking options. You don't need any of this stuff.
Another consideration is that 5.1 and up surround sound audio is going to be compressed when it is transmitted over the optical S/PDIF cable. I'm not familiar enough with the DVD and Blu-Ray specs to know whether the on-disc audio is compressed using the same codec, but I'd guess that it is. If it is, then switching to a sound card with individual analog outs for each channel won't improve your sound quality because you are already dealing with a compressed data stream.