I have had multiple Class D amps that sound cold and unnatural fresh out of the box and warm over time. I also have had some that have never improved and sound cold and unnatural forever. Of course, I can think of some Class AB and A amps that are just as bad.
@verdantaudio In all those cases you're hearing the distortion signature of the amp. Since you can never get rid of distortion, the distortion you do get should be innocuous as much as possible. Its nice when the designer gets that bit right, huh 😀?