I had similar experience with my unit, only that the volume was low on all audio. I too use a Mac desktop and connected it to the unit via the USB inputI just received the SMSL D400EX from SoundImport and this unit also has volume problem. Streaming from Tidal using USB from a Mac and on some tracks very low volume and on others normal. Could not see that it is related to MQA or PCM tracks. When I switch to a RME ADI 2 all tracks has the same volume.
Very strange. I will return this unit for a refound.