Expanding the Class D Conversation: How Would You Characterize Their Differences?

Expanding the Class D Conversation: How Would You Characterize Their Differences?

I'm currently trialing the NAD M23 (1st gen. Eigentakt-based), and I find it intriguing enough to want to understand it better — which means understanding the broader sonic landscape of class D. So I'm crowd-sourcing.

In a recent exchange, the estimable Ralph Karsten (Atma-Sphere Music Systems) made two comments that stopped me cold. For those who missed it, here's what he said:

"IME, class D amps vary in sound more than tube amps, which is to say, quite a lot."

"IMO there is a bigger difference between various class D amps than you hear between various tube amps. IOW just because you heard one class D amp says nothing about how the next one might sound."

Link: https://forum.audiogon.com/posts/2885828

As I think through this more carefully, these are genuinely important claims. My own experience with tube amps confirms that they produce audibly distinct characters across topologies and designs. If Ralph is right and class D exceeds that range, then generalizing from one class D experience to another is even more hazardous than I assumed.

One specific question for Audiogon members:

If you have a Class D amp or have compared class D amplifiers, how would you describe their character(s)?

Here are some criteria I use:

1. Frequency balance — Is the tonal response even across bass, mids, and treble, or does it favor certain regions?
2. High-frequency texture — Are the highs extended and smooth, or edgy, grainy, and fatiguing?
3. Bass definition — Is the low end tight and articulate, or loose and bloated?
4. Midrange character — Does the midrange feel present and natural, or recessed and thin?
5. Transient speed — Does the amp respond quickly to dynamic attacks, or does it sound sluggish and rounded?
6. Dynamic range — Does it scale convincingly from quiet passages to loud ones, or compress the difference?
7. Soundstage width and depth — Does it create a convincing three-dimensional image, or sound flat and narrow?
8. Image specificity — Are instruments and voices placed precisely, or do they blur and wander?
9. Background noise floor — Is the silence between notes actually silent, or is there grain, haze, or hash?
10. Long-term listenability — After an extended session, do you want to keep listening, or has something been quietly fatiguing you?

If you can include relevant system context — room, speakers, preamp — please do. Those variables will help me interpret what the amp itself is contributing.

I'm less interested in rankings than in understanding what Ralph mentioned, namely the [vast] range of sonic signatures class D is capable of. Eigentakt, Hypex, Pascal, Purifi, GaN-based, etc. — all fair game.

Price is no constraint here — I'm interested in the full range of what's out there.