I have done a lot more investigation of Tidal Masters & exchanged emails about this with Peter.
The big find was a utility freely available from MQA called MQA TagRestorer. It allows one to check if a music file is MQA and if it is restores the OrignalSampleRate Tag to the FLAC file which MQA deleted from all Tidal Master downloads a few years back. Its the OrignalSampleRate which enables us to get the right MQARATE for the .MTT files in XXHE.
There is a big BUT however. Many of the recent Tidal Masters reveal that the OriginalSampleRate is either 44100 or 48000 so there can't have been any music info to fold/unfold above 22 or 24KHz. So it looks like MQA does not fold these albums and I suppose it only De blurs. Measuring the Tidal App output I only see upsampling to 88200 or 96000 of these offending albums.
Back to XXHE and it always tries to unfold MQA and if you enter 44100 or 48000 as MQARATE it won't work.
So as suggested in an earlier post entering 88200 or 96000 is best way to make them playable. But this does not upsample them, XXHE will show 88200 or 96000 but the Unicode...wav file stays at 44100 or 48000. You can use XXHE's own ArcPredict upsampling but its actual output rate will always be half the value displayed. Custom Filters don't work because of this issue.
I don't want to get into a Sound Quality debate some of the low rate Masters sound ok. I don't understand why MQA have accepted 44100 or 48000 masters for encoding when higher rate files will be available in most cases.
You can get the MQA TagRestorer here:-
https://www.mqa.co.uk/tag435sdf43teHappy Pondering
Colin