Help! I'm trying to get 5.1 channel out of a PC digitally into the DAC in my AV receiver. I've tried 2 different USB to SPDIF devices, PC Link (http://www.cryo-parts.com/pclink.html) and Cables To Go 22327 USB 5.1 Audio Adapter. All I get is 2 channel. (2 channel works fine). Both use Generic USB Audio driver.

Machine is a PC running Vista with Realtek onboard audio. The chip supports 5.1 & SPDIF, but Acer did not put an SPDIF jack on the machine.

Source data: I've tried downloaded 5.1 files. I've played DVD's. Media Player Classic software says it's outputting 5.1. Control Panel Playback devices shows 2 channel output through "SPDIF Interface" (it's connecting to the AVR, but not in 5.1)

WinDVD dims out SPDIF Passthrough, allows analog only.

Interestingly, when I disable the Windows Audio Service, all the devices in control panel sound that would only offer 2 channel are now offering 6 or 8. WinDVD is offering SPDIF passthrough and surround sound. Only problem: no sound comes out.

Re-enable the Service, sound comes out but 2 channel only.

any thoughts?

What is the format of your multichannel files?

SPDIF is made for two channel audio, so only AC3 or DTS encoded multichannel audio can be sent through the interface.

Playing DVD's, .VOB(?), .wma.
Just tried a .ac3 file.

The hardware settings in windvd & control panel playback devices both only show 2 channel available. I'm listening now to a 5.1 channel ac3 playing back in stereo.

I come back to the observation that when disabling Windows Audio Service, 5.1 channel becomes available in these devices and programs, but no sound comes out.

I am not sure exactly how much help this is going to be to you, but..
I am using a headphone to rca wire. I think I got it at wal-mart.
I use VLC (a free and open source media player) to play my dvd.

I have not found a dvd yet that I couldn't play this way and maintain the same surround sound. Apparently, most computers can still output the surround sound signals through the normal headset stereo jack.

So, if the device you are trying to go into can take rca for the sound and svideo for the video you could still get what you are looking for.

As a note though, in VLC you have to change the audio device setting to 5.1 (the device will show all available devices, mono, stereo, dolby, dts).

Perhaps winDVD doesn't take advantage of the fact that 1/8 in jack even though stereo, can still handle the 5.1 signals.

Anyway, as I said, I'm not sure if this is even helpful (or perhaps something you already knew), but just thought I'd throw it out there just in case.
Sage