I can replicate your situation with my MacBook Pro, core i9. I’m outputting HDMI from the MacBook Pro to an older NAD 765 home theatre. I can only get the NAD to play all 7.1 channels (with associated NEO 6 and EARS options on the NAD 765), if I set the MacBook Pro MIDI options to 2 channels. But in that situation, then I get a lot of drop outs.
If I set MIDI to 8.1 on the MacBook Pro, I get only the left and right speakers to play. No surround side or rear surround. Only options on the NAD are Direct and Stereo Downmix. No drop-outs at all.
But seems like I should be able to come up with a solution to get all 7.1 speakers to play with no drop outs.
Roon uses the macOS Core Audio API to interface with audio devices on the computer.
If you are able to play two-channel content to the “Built-in Output” zone in Settings > Audio with “Exclusive Mode” enabled to your Macbook’s speakers, it would appear that this dropout issue is occurring somewhere in-between the macOS Core Audio stack and the NAD 765.
In that case, there is little Roon could do to resolve this issue. You could try using the “Maximum Buffer” option or toggling integer mode in Device Setup, but I wouldn’t expect those preferences to change the behavior here.
Setting Roon DSP options to 7.1 does not result in 7.1 playback with my NAD 765. Only way I can get NAD to play 7.1 is to set MacBook Pro to MIDI 2.0 option, but not stable. Also having continual problems with MQA content. Appears my best optimal solution at this point is to set NAD 765 device as NAD 787 in Roon, with default options. I have played with Core Exclusive settings, and have determined that I can turn off all MQA support and MQA decoder to allow MQA content to play…still experimenting. I’m in the market for a new amp…may go with NAD M10 if it becomes Roon certified.
Thanks for the suggestion; tried it; does not work. The only way I can get 7.1 sound out of 2.0 input on my NAD is to set my MacBook Pro HDMI MIDI output to 2.0. Then NAD takes over with its own DSP, and I get all of the NAD DSP functions, like NEO-6 Music and EARS…but not stable. Hearing a lot of pops. I have chosen to go back to just 2.0 output to eliminate pops.
New solution to get 7.1 sound is to select not the Core Audio, but System Output on the Mac, then pick Apple TV as the System Output. Apple TV is connected to my NAD, and for whatever reason, plays back in 7.1 sound on the NAD, enabling me to pick NAD unique DSP options such as EARSs, NEO Music, etc. But playback is considered high quality and not bit perfect by Roon.