I have read that typically you want NOS off, unless you are listening to certain very high res format.
Anyway, sorry to hear about your issue. Mine got channel imbalance issue and it caused slightly less highs impression as compared to my other dac.
Are you able to use REW to check your DAC channels?
Hi, do I need a special MIC for REW?
The channels look equal on the VU metres on my AMP but could it be more subtle than that?