Thought I’d leave a trail for anybody that may have same issue.
I was tuning audio using the setup below using tracks from the XLO Test & Burn in CD
Core/Player - Windows 10, connected via wasapi
Receiver - Emotiva XMC-1 (connected via HDMI), 5.1 channels configured
All seemed to be working fine, except for Track 4 ‘Clap Track’ which was barely audible and very muffled.
After futzing with settings, looking for unintended noise cancellation or dynamic range compression etc, I discovered that all was well when I enabled the roon option ‘Send stereo/mono content content as 5.1’ under the advanced settings for the wasapi device.
Hope this saves somebody some time !