I most recall from my brief time with them, which left me wanting more air and sparkle. But that’s my ears, my system, of course.
@wrm57, yea that is one of the differences I heard between the AtmaSphere and the XA30.8. I found the Pass to offer a little more detail/resolution, or at least present things in a more forward way compared to the AtmaSphere. In the high frequencies I did find my Pass offered more 'sparkle' and maybe more finesse in the small details overall. With a handful of other amps I've compared with either a X250.8 or XA30.8 it was always the other amps offering a little more detail over the Pass, so its strange for me to hear a solid state amp that presents a more laid back presentation than the Pass. AtmaSphere does specialize in tube amps after all :)
I switched between both amps a few times and its not like the general details are missing, its just they are more detailed and noticeable with the Pass, where the AtmaSphere seems to paint the overall sound with a wider brush and maybe has a little more color/fullness (think meat-on-the-bones) sound. My speakers are pretty detailed and not forgiving at all so I can live with the few rows back sound.
I found the AtmaSphere to offer a blacker background, way better bass, and excellent imaging, along with a very similar sound signature to the Pass.
Being the Pass is now $7100 I think the AtmaSphere Monos like most good amps I've compared to the XA30.8 (some more and some less expensive) are all in the same league, its just more personal taste/system matching. At this point to my ears at least, it is no longer the Class A design just beats the Class D design, its more of a what sound signature and attributes am I looking for... Compared to my first Class D amp I tried back in the early 2000s, that is a big step forward as the XA30.8 is great sounding amp!