Hey @John_Capra,
Thanks for writing in and for sharing your report! We were able to review a fresh Roon Server diagnostic report, and saw that the Magnetar UDP900 MKII only Advertises 2-Channel PCM formats to Roon.
Take a look:
"supported_formats":"96000/16/1|2, 44100/16/1|2, 192000/16/1|2,
48000/24/1|2, 96000/24/1|2, 88200/24/1|2, 48000/16/1|2,
44100/24/1|2, 88200/16/1|2, 192000/24/1|2, 176400/24/1|2, 176400/16/1|2"
Notice the channel counts, every single format ends in 1|2, meaning mono or stereo only. The Magnetar is not advertising any multichannel formats (like …/1|2|3|4|5|6) to Roon via RAAT, and there is no DSD listed at all.
Compare this to the Nucleus One HDMI output in the same log, which advertises 1|2|3|4|5|6|7|8 (up to 8 channels) for every format. Roon has no choice but to downmix to 2ch and convert DSD to PCM because that’s all the Magnetar is telling it to accept.
So it appears the device is not properly advertising its multichannel and DSD capabilities to Roon’s transport layer, even though the hardware is fully capable.
Here are some next steps for you to try:
- See if there are any available firmware updates for the Magnetar.
- Test: use the Nucleus One HDMI output as a workaround. The logs show the Nucleus One HDMI does correctly advertise up to 8-channel formats. You could send multichannel audio from Roon to the Nucleus One's HDMI out → AVM90, bypassing the Magnetar's Roon Ready implementation entirely for multichannel content.
- Contact Magnetar support directly and report that your UDP900 MKII is only advertising stereo PCM formats via RAAT (no multichannel, no DSD) even though it's capable. Share the
supported_formats string above as evidence.
When you browse files directly on the Magnetar without Roon, the Magnetar uses its own internal media player, which has full native access to its hardware capabilities. Roon only knows what the device tells it via the RAAT protocol, and the Magnetar’s RAAT implementation is currently telling Roon it only supports stereo PCM, which is the misconfiguration causing your problem.
We’ll be monitoring for your reply, thank you! 
