I have connected both the 818 (SpeakerLink) and the 861v4 to the DSP7200s (818 and 861 are not linked). Now that I a writing this down I get the feeling that the solution of the no-sound problem is maybe related to the set-up.
I will check tonight I have configured the AUX source of the 861 in any way. The strange thing is that I have configured both the CD source of the 818 and the 861 and music is playing from both sources.
The 861v4 is connected to the 7200 via Coax. The 818v1 is connected to the 7200 via SpeakerLink.
So effectively you have two semi-independent systems sharing a pair of DSP7200s.
For this setup the 7200 that the 818 is connected to must be the MASTER DSP and its Aux (SLS) input must be configured to use the SpeakerLink input (not the coax).
Unless recent firmware has changed this behaviour. The SLAVE DSP always use just one input (either Coax or SpeakerLink dependent on config).
So this means that the SLAVE 7200 should just be connected to the MASTER DSP (not the 818) and I'd suggest doing that via SpeakerLink.
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Once this is working and note I suspect this will not work but it might now know with later firmware so it's worth a quick experiment to find out.
You could try to configure the SLAVE DSP7200 to use coax input (from MASTER DSP) for all inputs except AUX (SLS) which should be configured SpeakerLink and connected it back to the 818.
I will check everything tonight when I am home. From the top of my head I would say that both the 861 (I have not changed anything in the config file yet) and the 818 are set as controller.
Well... I did manage to play music from my Sooloos system. It is fantastic.
I received a new config file from Ratbert for my 818 and retyped the DSP7200s as suggested. And that combination certainly did the trick. I will still have to do some further clean up work (e.g. work on the controller) but now I have a good basis to work from.
Thank you all very much for your assistance and in general for all assistance given to fellow HHers. It is highly appreciated.