I had a thought. Some DACs do not like to reproduce any audio that is 0dBFS. They will create distortion even if the signal itself is not distorted. Please test using the profiles in this Dropbox Link.
To install these profiles copy them into Mac HD/Library/Application Support/Bongiovi Acoustics/External.
These profiles turn the output down about 0.1dB. If that does not work, please check your Audio/MIDI settings. Take a look at the drivers for your DAC to be sure there is no boost (any value greater than 1.000) for the volume controls there.
Let me know what you find. Thanks!