VT8233 on Linux – making S/PDIF work

I’m making this post hoping it might be useful in case someone googles for something related.

A long time ago when I bought the parts for my current desktop at home I chose Asus’ excellent A7V600-X motherboard. It comes with a fancy S/PDIF output RCA jack, and I thought to myself, ‘sometime I should get this thing working’. I never got around to it because I didn’t have access to a decoder which would be able to process the signal.

Recently Daniel brought the old home theater from his home, and so I get the opportunity. I bought the cables today and set out to the task.

The good thing is that the chipset which comes onboard is supported by Debian GNU/Linux out-of-the-box. I suppose that remains true for other distributions, since it’s really a matter of ALSA and kernel compatibility, which is reasonably homogeneous.

Anyway, after a lot of searching (and very few useful answers from almost everywhere, including Alsa’s own wiki), I found out that all you have to do is (assuming you run GNOME):

  1. In Volume Control, under Edit/Preferences, check ‘IEC958 Output’ and ‘IEC958 Playback AC97-SPSA’.
  2. In the Switches tab, check ‘IEC958 Output’
  3. Back in the Playback tab, set the slider for ‘IEC958 Playback AC97-SPSA’ to ZERO.
  4. That’s it, you’re done.

This is actually quite strange, since I don’t have any kind of control over S/PDIF’s volume output this way; anything different than zero simply kills any sound coming from the home theater set.

I hope this helps anyone who happens to stumble with this post.

Next step: to make my FX 5200‘s S-Video output talk to the television set.