If you have a 8 Channels MERGING+NADAC or NADAC Player, please set the Channel Layout to 7.1.
The Multichannel Mixing Strategy can be left to Downmix As Needed.
If you have a 2 Channels MERGING+NADAC or NADAC Player, please set the Channel Layout to 2.0.
The Multichannel Mixing Strategy can be left to Downmix As Needed, but may cause performances issues with High sampling rate multichannel files (especially DSD).
Please first disable any processing in Roon DSP Engine, which can also use some CPU.
If disabling DSP Engine does not help, you may need to set it to Channel Mapping only (but only Left and Right channels will be outputted) or get a lower sampling rate version of such file.
