Audigy 4 Pro - can only get 2 channel sound via SPDIF/optical connecti

Question

I have two PC's, one with an Audigy 4 Pro and one with an Audigy 2 Platinum (A2P), I have my 5. speakers hooked up to the A2P and the A4P connected via the SPDIF to the A2P, I would expect to get 5. - both are setup to use 5. speakers, (I know that as a standard Digital coax/optical connections should handle multi speaker configs my entire A/V sound system (7. Dolby) uses optical and coax and it works fine).
If I run the channel test on the Audigy 4 I can get nothing but sound through the left and right speakers, if I run the test on the Audigy 2 (speakers direct connected) the sound is fine, if I reconnect the speakers to my Audigy 4 I get sound on all speakers so it looks like its an issue with the SPDIF and optical inputs (I tried both).
I have emailed tech support, I'm waiting for them to come back and tell me that the Audigy 4 cannot transmit more than two channels down the SPDIF/optical outs, thats my suspicion anyway, if that is the case then I'm not going to be a happy man and the Audigy will be going back to the store. Could be a driver problem of course as I cant believe they would implement Dolby and THX and only transmit two channels on the optical outs, that would be a bit dumb considering the primary use for digital connections is sound system interconnects.
Anyone with any ideas about this let me know, perhaps theres a hidden setting somewhere or a registry setting that switches the digital outs to carry all signals.

Answer 1

Just before everyone kicks off, heres a response I got from a tech guy at Creative themselves.
If you connect speakers to your sound card using a digital cable
(RCA/SPDIF or optical) then the software speaker test will only output
from two speakers. The reason for this is that the speaker test signal is
not in AC3 nor DTS format.
The signal on a digital connection is either
Optical SPDIF - which is either Stereo PCM signal or AC-3/DTS Bitstream
RCA SPDIF - which is either Stereo PCM signal or AC-3/DTS Bitstream
If you play AC3 (Dolby Digital) or DTS encoded signals, the amplifier
decodes this and outputs it to all 6 speakers (5 satellites & subwoofer)
discretely.
When playing back stereo signals (such as Wav/CD Audio or MP3/WMA files)
the amplifier may generate 5. output based on the incoming stereo PCM
signal, provided Dolby Pro Logic decoding is available and activated.
Therefore the speaker test should not be relied on when using RCA or
Optical digital connections.
This applies to all speaker systems equipped with RCA or Optical digital
connections.
This makes sense to me and I'm pretty happy with it, basically as the reply says above the speaker test does not encode to AC3 hence if you hook two Audigys together and run the test you only get 2 channel output, if you play a DVD which is AC3/DTS encoded on one Audigy and listen to speakers hooked up to the other when both Audigys are connected via SPDIF or optical you should in theory get full playback on all speakers. Hopefully
Cheers
Simon