New Class D amplifiers

How the measurements reflect the sound that we perceive?

I described that above.

Since the ear uses higher ordered harmonics to sense sound pressure, its keenly sensitive to them since the ear has a +120dB range. If these harmonics are not masked by the lower orders (2nd and 3rd) they will contribute to harshness and brightness, since the ear assigns tonality to all forms of distortion.

That is why you don't hear it outright as breakup in any amplifier that isn't being overloaded. You sense it as tonality instead. For example, the 'dry' quality some amplifier have is due to their distortion signature, which audiophiles call the 'sonic signature' of the amplifier.

I don’t understand why Roon requires having your amp on all day, but putting that aside, going from A all the way to D strikes me as somewhat extreme for one who is used to the Pass. Why not look into a good A/B first? 

going from A all the way to D strikes me as somewhat extreme for one who is used to the Pass. Why not look into a good A/B first? 

The main reason AB exists is to reduce heat and power consumption, with some of the benefit of class A operation.

Class D allows a good designer to sidestep some of the reasons for class A operation in the first place- a classic example being that of crossover distortion. Most class D amplifiers are literally incapable of this kind of distortion. In addition, the distortion of the output section isn't made in the same way that it is in a class A or AB design. The result can be that the distortion the class D amp generates can be far more benign to the ear. 

I've heard class D amps that compare more than just favorably to a Pass Labs amplifier. These days its not about class of operation, it simply about the sound.

Roon has an option to become a ’radio’ using the music you listened most recently. When the album/playlist is over, it will find other music that is similar (using your library, or if you are connected to Qobuz/Tidal?etc, a variety of similar songs from the entire available list via the web). I find myself listening for many hours as I go about my business, discovering new music/artists.

I just recently moved to New Orleans. Being much warmer than my previous address, I just ordered the Atma-sphere Class D. Going to put it up against my FirstWatt Sit -3 amp. Not a lot of extra heat from the FirstWatt, but it does add warmth in the summer.

Innuos Zen -> Exogal Comet -> Audio Hungary Quality APR 204 -> FirstWatt SIT-3 -> Rethym Saadhana

Should arrive early next month