I have played a little with the 218, 861 and Amethyst and want to share my experiences here.
The 861v6, 218 and Amethyst are plugged in with their ethernet connection on one network switch/distributor.
So I can stream from all three devices under Roon, each item is one zone.
The 218 SL-Master out go the 861v6 SL input.
The front three speaker outputs run through the Amethyst and get processed or the amethyst is bypassed/disconnected.
All test are done with the Amethyst bypassed to exclude the influence from that.
I discovered that only with MQA studio sources streamed into the 218 MQA and then get out to the 861 (see above).
Stream the same music with the 861/ID40 doesn't sound so good as going trough the 218.
So as speculated here on the forum, the 218 makes the first unfold or simply the ID40 card isn't as good as the 218.
To find out that listening test without MQA should be done.
To get the blue light on, Roon's "DSP engine" has to be completely turned off, no "upsampling, no "headroom management", even no "show clipping indicator" also with "headroom adjustment 0".
Of course all other possibilities in Roon had be disabled to get the blue light.
So the 218 watches perfect if he receive an "untouched" MQA stream, but at the same time that means, all Roon "DSP engine" features cant used to see and hopefully hear the advantages of the blue light.***
Now I am playing with the Meridian DSP presets like "Music" or "Trifield" and have so an intermediate "MCh" solution
Who have done similar tests or even compared non MQA music with 218 through the 861 and "pure" 861?
And I made a quick test compared the 218 direct in my 8.2k and through the 861 with MQA.
For the first try I did not hear a difference, but it's to early to make a fair statement.
It would be interesting to discuss/share all the experiences here.
Just for information, RC without destroying the MQA stream can only be done AFTER the MQA stream is fully unfolded, otherwise the "hidden/packed" info from MQA are lost.
So the solution to use a third party processor and the 571 means also, that MQA only can get place correct, when either no RC at all, or after full unfold of MQA in the third party processor is done.
Of course, non MQA music get the full advantages of the new codecs from the "cinema world" and to have a state of art RC and Meridian great DSP's.