Optical SPDIF audio from motherboard not working with receiver

Question

I hope someone can help; I can't get my SPDIF optical out working through my receiver and all the responses I can see on the web assume you have a sound card, while I settled for the (seemingly high end) sound on my motherboard (Asus P7P55D-E PRO), which appears to limit some of my options.

My set-up is a "new out of the box" one and is:
*Windows 7 PC (using PowerDVD10 for DVDs/Blurays and Windows media player for music)
*Asus P7P55D-E PRO motherboard - has 8-channel audio TRS jacks and SPDIF optical and coaxial out
*An old Yamaha receiver, whose only multi-channel input options are optical in and 6 channel RCA in. However, it still can handle DTS and DD
*Boston Acoustic Soundware XS 5.1 speakers

I've currently got the SPDIF optical out from the motherboard connected to the in on my receiver, have SPDIF enabled in the sound menu and the light is glowing red down the fibre. But I'm getting no sound at all.

What I want is to be able to play DVDs/BluRays in 5.1 but also to be able to play music in multi-channel mode (even though I know this will be "fake" multichannel; it's more about where I sit in the room and my requirement to use the sub because the Boston is a satellite/sub set-up)

My questions are:
*Will optical work at all for multi-channel? THe latest posts I can see suggest it does but some people seem to say optical only outputs stereo. Whom to believe?
*Even if it does work, I've read that I have to disable AC-3 decoding, or make various other changes, which don't seem to be possible without the menu options that a sound-card brings. Is the motherboard-only option just too inflexible?
*Although my SPDIF device is enabled in the sound menu, it insists under "Jack information" that it is a "rear panel RCA jack", when of course it is not (both TOSLINK and rCA jacks do exist). Has the PC just forgotten that it has an optical?
*I think I could relatively easily connect the 8-channel 3.5mm TRS jacks to my receiver 6-ch input jacks by way of TRS/RCA cables, but would that not stop me from being able to play music from media-player in multi-channel mode, as I'm not sure the motherboard can cope
*Or do I need to bite the bullet and buy a sound-card? And if so, how can I be sure the one I get doesn't have the same problem?

Any thoughts gratefully received,

Cheers,

simon

Solution

S/PDIF supports stereo, quadraphonic, and compressed audio. Generally, Windows drivers only support stereo output, and "passthrough" for, e.g., AC-3 or DTS audio from a DVD, thus your music will only be in stereo, while "true" multichannel from a DVD should work fine.

Your surround receiver may support handling the "fake surround" as you mentioned, through a process such as Dolby ProLogic, however this will be minimally higher quality than simply using analog stereo.

Buying a sound card should not be necessary, there is no reason for a dedicated sound card to have more "menu options" as it were. Dobly Digital decoding is, if anything, an "extra" feature. Disallowing disabling it would be... Not the most idiotic thing I've seen in the computer industry, but not something I would usually think of being done. If this specific card disallows disabling Dolby Digital decoding, it would be the first I know of.

If you are not hearing any sound, there may be more than one option to enable S/PDIF. I've used odd drivers in the past that had an "S/PDIF and analog" mode that had better success than "S/PDIF only", and vice versa. The audio codec in question, the VIA VT1828S, should be perfectly capable of sending DD or DTS encoded audio, as well as stereo audio out the S/PDIF port, and your drivers should be able to handle this seamlessly. Are you using drivers from the ASUS support site, or plug-and-play? A driver mixup could cause the mislabeling you mentioned, or could cause the codec to function improperly.

If the motherboard has 8-channel output, it's there because it can work that way. Connecting your surround receiver by way of TRS cables is a possible solution, and should serve your purpose, but should also be unnecessary if the optical output can be set up.

All in all, nothing should force you to purchase a sound card. Nothing about a non-integrated sound card should make it any more suitable for basic functionality, and the problem you're experiencing are either software issues, or flaws with this particular chip, not a lack of aboveboard sound card. However, if you do opt for the TRS jack approach, an aboveboard sound card might provide a higher-quality set of DACs, thus giving you better sound quality.

Comments

[Admin]

Thanks - a relief I'm not forced to buy more kit! I am using the plug and play drivers for the ASUS. When I go into the SPDIF properties it doesn't allow me to update, roll-back etc the drivers but I will go on to the ASUS support site and see what I can get. Any hints appreciated Cheers, simon