Problem enabling sp/dif on Gigabyte K8VM800M / Realtek ALC655 on-board audio

[Mark Linford]

Hello, everyone:

I'm trying to enable sp/dif (digital) output with my new Fedora Core 4 (x64) 
install, and I'm having a heck of a time trying to get it to work. Here's my 
basic setup:

* Gigabyte K8VM800M motherboard
* Realtek ALC655 on-board audio
* Logitech Z-5500 surround speakers

I'm able to get sound via the analog outputs without problems, but nothing 
comes from the digital output. As this is the first setup with digital 
outputs I've ever tried, I'm at somewhat of a loss were I should even begin.

One interesting thing I did notice. My speakers have an lcd control panel 
which can show if it's detecting a digital signal or not. Normally, this 
shows "No Input Detected" when using the optical (digital) input on the 
speakers. However, after playing around in alsamixer, I noticed that if I 
changed the setting for IEC958 from "IEC958 In" to "Analog In", my speakers 
detect a signal, though there's no audio coming out. IEC958 Output is set to 
"00" (with no way to change it. IEC958 Playback AC97-SPSA is set to 
"100" (also, when I move this slider up and down, I hear an audible "pop" 
through the speakers). External Amplifier is set to "off," and I can't seem 
to change that setting either.

So, I'm stumped. Any advice on how to proceed would be appreciated.

Mark