You say you hear somethings not quite right in the upper-mids and highs, and phase shift going on in those areas. Could you, respectfully, enlighten me as to what you are hearing?Not just me, unless you’ve been hiding under a rock, it a common complaint.
What I hear from that technology, is dependent on where the "output filter is set" to filter out the switching noise.
1:Too high and it lets through too much switching noise but with reduced phase shift into the audio band, this to me sound hard and bright on music.
2:To low and it roll off the highs and causes too much phase shift into the audio band, but it filters out more of the switching frequency, this to me sound soft and opaque in the highs, and not involving in the mids, but at least it’s not hard.
Nuforce with their many different 9 models tried different versions V1 V2 V3 in them, of the above output filter that were retrofit-able for customer that had issues with the sound.
One of those version filters that was set way too high actually caused bluing of the Wilson Watt Puppy tweeter voice coil with HF switching noise (that only twoleftears dog can hear), didn’t stop them working just blue’d the voice coil with "undetectable to us" switching noise that was let through to them slowing cooking them over time. Naturally the diaphragms had to be replaced, he got rid of those amps.
I know from your past posts you are not a fan of class D.BTW, Incorrect I’m not a fan of it’s two Achilles Heels, dead time and switching frequency. And I have said many times I’ll be the first to get one when they don’t have these problems and are a module I can buy an throw in a box like they do now with the old technology, but say they "modify it" so they can charge $$$$$ for, if you look at a $10k Contiuum Class-D, it has a $100 class-D module in it (modified of course), the same module is used in the $500 Red Dragon S500 class-D, this is not uncommon.
Cheers George