I'm not 100% with this suggestion as It is something I am considering myself but....

You could consider a BeoPort box,

I'm not sure how a DAC Magic works but I think it works as an Independent Sound Card which means the mac should show to individual outputs which could be used simultaneously.  You could have the digital out from the DAC into the TV with an HDMI cable and then use the Analog out from either the Mac's normal line out into a BeoPort's analog in.  Obviously the Mac's sound card is not going to produce as high quality output as the DAC and not knowing the DAC Magic it might produce Analog and Digital output simultaneously without the need for clicking any buttons.  If this is the case then you can get Digital output from the DAC into the TV and an analog stream into the BeoPort.

The BeoPort could be used to distribute N.MUSIC around the home and the DAC the Digital In for dolby surround. 

Maybe this sound a bit substrus (?), but when I had a mac mini connected to my BV7-40 I used a Philips Suround headphone amp HD1500. This device converts digital audio - DD, DTS, PCM - to analogue stereo including passthrough of digital sound. So Mac mini digital out -> HD1500 digital in -> HD1500 analogue out (headphone out) .> Scart audio in BV7 AND HD1500 passthrough digital out -> digital in BV7-40. Now you have digital sound, no matter whether DD, DTS, stereo, AND analogue stereo for the linkrooms. Simultaneously and everything in lipsync. No need for changing or switching connections, no need for the Cambridge converter.

BTW: you can`t distribute video via masterlink.

Hope this helps

Stefan

The Cambridge DAC Magic is doing a great job to convert Digital to Analog so it's excellent when listening to music. 

A solution for me would be if I have two connections for example DTV (with SPDIF) and V.MEM (analog) and chose the same HDMI input. The problem is when I select HDMI input on V.MEM (A for example) then the BV8-40 will remove that HDMI input from DTV. The last option is to use a HDMI splitter and use both of my HDMI inputs.

I may have found a solution:

If I use the HDMI B and select to use a HDMI EXPANDER (GEFEN). I can then select the correct input sound on DTV(SPDIF)/V.MEM(ANALOG via RCA) and the HDMI selection will be HDMI B.1/B.2 but it will just send an IR-code to PUC1 that doesn't exists?

I have test this and it works like a charm! I get the same picture from one hdmi but have two types of sound connections (SPDIF/RCA). The only think is that I can't use the same PUC selection for both DTV and V.MEM but this isn't a issue when the excellent program LinkPlayer will handle my IR-reception for the Mac Mini.