Logic Pro X 5.1 surround HDMI output

Question

It seems that Logic Pro X (all Logic versions for that matter) cannot use HDMI output for 5.1 surround mixing. Yet all the preference settings in Logic, in Apple Sound and in Midi/Audio Interface utility seem to indicate that it should be possible.
Has anyone ever had any success ??
If not, what is the best alternative ?
I have an Impact Twin that can have 8 optical outputs going to a DAC then to a 6-8 channel amplifier or 6-8 amplified speakers. Expensive proposition when an HDMI would be so much simpler and cheaper.
Thanks in advance to PanCenter for his comments.
Phil

Answer 1

Hello octopi - wanted to answer earlier when I get all hooked up, tested and running, but got caught up in some other business.
In any case, you'll find pretty well all the info you need from this thread. https://discussions.apple.com/thread/3639822
In short, you can get 5.1 out of a Mac by 3 avenues :
1. mini HDMI (Mac) to HDMI (AV amp) - for Mac products since late 2009 - or
2. headphone converted to SPDIF (Mac) to SPDIF (AV amp) - for Mac products a bit before that (2006???).
3. an external sound card, either USB (as early as USB 1.1) or FireWire.
For recent Macs, there is also the Thunderbolt option which doubles as a HDMI.
There are also FireWire to HDMI adapters, but I'm not sure how that would work.
For the soundcard options, you need the right amount of audio outputs - 6, for 5.1 - many are 8, which gets you up to 7.1 And of course, you need amps for all those outputs, or powered speakers. Not a cheap avenue.
For the HDMI or SPDIF avenues, you need an AV amp to do the Digital to Analog Conversion, plus an appropriate wattage distribution, the sub needing much more power than the satellites, etc. So there is lot of processing to do on the fly, and that's why there are no special computer speakers with HDMI or SPDIF inputs - would almost be as expensive as an AV amp.
The HDMI and SPDIF are not equivalents. For one, the SPDIF goes only up to 5.1 whereas HDMI can go to 7.1 (or more?). But more importantly, transfers through SPDIF are downmixed to stereo then upmixed to original format - a point that caused some confusion on the posts. In any case, that will work fine for most DVDs played on the Mac or Movies played through iTunes & Quick time.
But if you want to work with 6 (or more) distinct PCM audio files, like you would if working with Logic Pro or Final Cut, then you need to go the HDMI route.
Btw, all AV amps, even the cheaper ones, are supposed to be able to read PCM - it's mandatory. Check here : http://www.the-home-cinema-guide.com/dolby-ac-3.html#axzz37kwyN8FK
But get an AV amp that can read Blu-Ray which can process up to eight PCM channels in 48kHz/24bit depth.
Hopes that helps. Phil