“No, there is no night and day difference between the Accuphase and the Parasound it replaced.”
@milpai
Congratulations on A-48S. You’re an astute listener, most of your early impressions are spot on even with only one hour of warm up. I would recommend allowing this amp to settle in for atleast 250 hours and you will realize the difference between the A21 and A-48S is far from subtle.
What you’re describing is exactly what I experienced when I heard Accuphase in my system. Better placement of “artifacts” within the soundstage usually points to improved linearity and lower noise modulation, which tends to stabilize images and give vocals more density and focus. What you hearing is shift in headline resolution and a change in how the amplifier handles low-level information and spatial cues.
The bass description is interesting as well…“bouncy” yet better defined often suggests tighter control over the speaker load rather than simply more output (quality of watts over quantity). And the treble shift from sharp to shimmery is something I’ve consistently associated with amps that manage high-frequency distortion products more gracefully. Accuphase’s Class A designs really do seem to have that aspect mastered; smooth, resolved, and fatigue-free without sacrificing detail.
Agreed—classical is often where these differences become most apparent. I recently picked up a few classical UHCDs from Elusive Disc, and they’ve been very revealing and enjoyable in this regard. When an amplifier can resolve hall ambience and decay without pushing the image forward, orchestral recordings become far more engaging and believable.
The A-48S doesn’t seem to distinguish itself through dramatic tonal shifts, but rather through coherence and spatial integrity. The presentation feels more continuous and organized, allowing the recording venue and scale to emerge naturally rather than being spotlighted.
Enjoy your listening sessions, you’re in for aural treat my friend.
I musta missed a post.... 
I may get more.