From what I've understood so far, in a Sooloos system, the MQA-decoded stream has to end up at a Meridian DAC, because this is the only type of DAC that a Meridian MQA decoder can "profile" for.

This means that the digital path must either be MHR-encrypted all the way, or there needs to be a mechanism in the Sooloos streaming protocol which tells the 861 that it cannot output unencrypted digital (because this could then be used with a non-Meridian DAC for which the decoded MQA was not profiled...).

It's possible that the C15 might do a software decode and send the resulting 96/24 or 88/24 decoded MQA to an ID40 or ID41 (with the proviso that the 861 keeps it encrypted). In a legacy system, this is better than un-decoded MQA, but not optimal, because, with the ID40 and ID41 cards limited to 96/24, the (usually 192k-capable) Meridian DACs won't be driven optimally. However, that's exactly what I believe is happening in my situation: my 818v3 decodes the MQA and outputs 2x rate MHR to my 861v4, which can then process it and pass it on to my DSP loudspeakers as 2x rate MHR.

To the best of my knowledge, the C15 will not do MHR over SpeakerLink or coax, nor could the C15 stream to an MS200 or MS600, because neither (again, to the best of my knowledge) can do MHR on the digital output; the digital outputs of the C15 and MSx00 are unencrypted.

Still lots of unknowns; hopefully they will soon become clear.

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