Is your problem that you cannot connect SPDIF3/4, or that you can connect it and it does not work ?
Well, if by "cannot connect" you mean having the choice, yes, I can choose S/PDIF 3-4 to any Main input, but I won´t get a signal, only on Main Input 1-2. I´ll try this once again and list you the sheet again, I´ll also look at the meters when the signal stops. As far as I know it was at the DSP´s Inputs, so very early….
You should be able to get an output with no dry (direct) signal. This will depend on which routing and preset you are using, and also how your external equipment is connected.
First try loading a suitable Factory Routing ("Analog A-B") and Preset 11 "Mute". You should be able to adjust Wet/Dry to give no signal at 100% Wet and full signal at 0% Wet. If this is not so, the problem is in your external equipment. Otherwise, then try loading a simple pitchshift effect such as 313 "4 Pitchshifters". You should then be able to select between 100% Wet and 100% Dry. Let me know.
oh, ok. I use the H8000 as an insert in ProTools in this case. So the Mic is connected to the 003 from Digidesign, as is the H8000 (via S/PDIF) I then use it as an inert effect.