I don't know if this is specific to my hardware/circumstances or if others are in the same situation but I figured the theory might help someone else who is looking to do the same thing or something similar.

The info, at least for me was hard to come across, and when I finally found the solution it was very outdated. I would have liked to reference the thread here anyways but unfortunately I can't find it again...

So for me one of the major drawbacks regarding OS X on non-standard hardware was that while every other major OS, as long as drivers are available, has no problem whatsoever automatically sending audio to every output available at the same time, it seems OS X handles this very differently, it may be a much better framework than others when the expected components are there, but in this case it wasn't being very friendly.

After patching HDA built-in sound was recognized and everything I needed worked well, headphone, line out, S/PDIF, microphone. Nice. So now I just needed to have sound going to both line out and S/PDIF at the same time, no problem, everything I came across showed it should be very simple to create an aggregate device and it should "just work".

My actual result was that

a.) It didn't work at all, no matter what, sound would only go to one output, the first one listed in the aggregate device.

b.) Since I have no software volume control for digital out, that meant even if the aggregate device did work I would have no software volume control for the device.


So the answer in my case was to use a combination of Soundflower and AU Lab, which is a part of Xcode -> /Developer/Applications/Audio/AU Lab. Installing Soundflower adds a couple of psuedo? audio devices, a 2-channel and a 16-channel, but they don't really do anything until you tell them how and that's where AU Lab comes in.

After installing Soundflower and restarting, I opened Audio/MIDI Setup and added an aggregate device named Surround Sound consisting of my digital output, line out and the new soundflower 16 channel device. Then I opened AU Lab and put those new devices to use, in the first window that's shown when the app opens I added a couple outputs, so I had outputs for line out and for S/PDIF.



In the next section I only needed one input.



The following section is where it gets interesting, I clicked input channels and selected the soundflower 16 device



I then clicked on output channels and selected the Surround Sound device I created earlier then hit done



and ended up with this



The added bus 1 and 2 just act like an amplifier making the sound louder and clearer, the unused output is there because I found that without it I would get some horrible feedback at times.


This solution is less than elegant to say the least, it's also not really surround sound, it's stereo, but it works for me. I have sound coming from all 7 speakers and the sub, I also have software volume control. Setting the configuration to open at login means I just have to minimize or right click and hide it, so it's less of an inconvenience.

Well, hopefully someone else finds this info useful.