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

@hilde

With my system I upgraded in a sort of orderly way.  I had been using a Rogue Sphinx v3 integrated (much earlier Class D power with tubes in the pre section) for a number of years.  Definitely like the tube aspect in the equipment chain.  Then decided to buy the KEF Reference 1 Metas after hearing them at audio shows two years ago and again last year.  The Sphinx was very nice yet I kept thinking I needed more power.  Neurotically reading and researching, it was clear that a modern Class D amp would give me not only so much more power "per dollar,"  but also substantial additional current for the KEFs.  The research and reviews and the improvement with modern Class D was very consistent.

I decided on a VTV Purifi 7040 based dual mono amp with upgraded op-amp and wiring.  My next step was to buy a preamp.  Again the research and, this time during travels, I went to a few hifi shops and auditioned some preamps; all with very nice different qualities.  Paid a restocking fee as well for the one I ordered directly and returned.  I really enjoyed the Rogue sound and wondered what if I should buy one of their preamps, yet there were many.  So the first thing I did was connect the Sphinx v3 to the VTV 7040 via the pre-outs.  Wow, could definitely hear a difference and louder volumes with the KEFs maintained really great coherence.  What would a better Rogue preamp do?  I decided the Rogue/VTV/Denafrips Pontus II (that I already had) were the electronics for me.

After much deliberation and again reading, reading, and more reading I decided on the recently new Rogue RP-7 v2 (spent more dollars than I anticipated).  Another wow moment. The detail I heard coming out of the KEFs relative to the soundstage positioning the Denafrips provided was just fantastic.  Never heard anything like this in my listening room previously.  I have been so thrilled in the less than a year I have had this current iteration of my setup, which has gone through so many upgrade changes over the decades. 

Then I went to Axpona 2026.  So much listened to.  As I posted previously to this OP question, I started to wonder if there was something about the sample of Class A/B amps that I heard at the show (despite the various effects of hifi show conditions) collectively as compared to the sample of Class D amps there.  Not a unit by unit comparison, but more generally comparing these two classes of amplifiers.  The difference I heard is still unnamed.  As I said in my previous posting, is it "presence," "musicality," or something else. 

Is it worth spending more money again to extract another 5 or 10% (maybe less); assuming what I thought I heard is real.  I do not know.   I will take my time as I am thrilled with what I have right now.  Very interesting hobby this is with regard to upgradeitus.  Been going on for decades with me.

@swaudiofan Thanks for the reflections. I have a couple of reactions.

First, I think the Rogue preamps are at another level than (at least) their Sphinx amps. I'm reading they still use older Purifi modules and are not really going to equal others by a longshot. I'll look up the VTV Purifi 7040 to learn more.

If, as Ralph said (paraphrasing), "Class D amps can all sound different depending on many factors) then what I take from your remarks is this question -- "Why not a Class A/B amp, if they all could sound different too?" 

Perhaps there is something about the "grip" of a Class D amp that connects them as a technology to embrace -- implemented as well as possible?

Then again there is that "presence"* factor that you mention. My tube amps have "presence" and so do my Class A amps. I am experiencing that right now with both a Pass XA-25 and a SIT-3 in my system. Either one, they have presence. In my opinion (already related in this thread), the AGD lacks presence, the NAD lacks presence, and the Hypex (Niali) DIY amp lacked presence. They all have "grip" but they all lack "presence." 

* "Presence" is a clunky word. By it I mean: Tactile, weighty, dense, warm, tonally layered.

@hilde

Nice response.  The words "grip" relative to "presence" might be a very credible way of differentiating the listening experience in this context.  The modern Class D certainly has grip; does it have the same presence as Class A/B.  I like that; thanks.

RECAP POST: This has been such a great --but long thread – that I decided to just add a summary of the main comparison. No need to comment if you have been following along. This is for people coming late, and for the final thought added below about Class A/B – raising the question as to whether a really good Class A/B might do what I want and that the Class D direction is, perhaps, misplaced.

LISTENING REPORT: Over multiple evenings, I ran a structured listening comparison of Class D amplifiers in my home system: a Holo Audio Spring DAC feeding a Burson-based preamp into custom speakers (15" JBL woofers, Beyma AMT tweeters) in a treated room. The contenders were the NAD M23 (running Purifi’s Eigentakt v1 module), the AGD Audion Mk. III monoblocks (GaN-based Class D), and my reference Pass XA-25. Volume was carefully calibrated at the listening position across a varied playlist — Ives, Gould’s Goldbergs, Steely Dan, Eno, Armstrong/Fitzgerald — drawn from Qobuz streaming and local hi-res files.

The AGD bested the NAD M23 v.1 in most meaningful categories. Imaging was more definite, macrodynamics faster and more dramatic, and instrument separation in dense orchestral passages (Ives, Ravel) noticeably cleaner. The biggest differentiator, though, was tonality at high SPL: the NAD could turn metallic and "shouty" on transients — a snare hit on Steely Dan, synthesizer swells on Eno, soprano peaks on Mozart — in a way the AGD simply never did. Bass was excellent on both. The NAD remained competitive on simpler material and quieter passages, but it hits a real-world ceiling where brightness and fatigue set in.

Against the Pass XA-25, the AGD’s strengths became liabilities in some respects. Where the AGD’s retrieval of detail could occasionally feel scattered — foregrounding background instruments at the expense of orchestral hierarchy — the Pass delivered everything with an effortless coherence and naturalness. Saxophone and vocals on the Pass were simply more human and sultry. The AGD was never quite strident, but on passages where it edged in that direction, the Pass wasn’t close. Both produced excellent soundstages and handled piano admirably.

So the search continues. And I’m opening it up to Class A/B. What I’m after in a Class D amplifier is what the best Class A designs do almost automatically: presence, organic tonality, and a coherent musical picture that doesn’t fray under pressure. The AGD is genuinely impressive and clearly a step forward from the NAD, but the Pass XA-25 still demonstrates what I’m reaching for. I’m increasingly uncertain whether Class D, at any price point I’m willing to consider, can fully close that gap — or whether Class A/B might still give me that combination in the qualities that matter most to me. 

And, yes, I realize this may be about the "right amplifier" and not the "right topology." That said, there has been something really nice – dynamics, snap, transients, etc. – in "Class D" as a group. So I’m not quite willing to abandon that label as a convenience.

P.S.Why else could I want what Class D offers that the Pass does not? The key point is that this would be an *additional* amplifier, not a replacement. The Pass isn’t going anywhere. But there’s something the better Class D amps do — a boldness, a speed, a dramatic snap to dynamic events — that the Pass, for all its magnificence, doesn’t quite deliver. The Pass puts music in the room with you, naturally and effortlessly; the best Class D amps launch that music at you. That combination of organic naturalness on one hand and kinetic, high-contrast excitement on the other is what I’m chasing. Whether any Class D can provide the former without sacrificing it to the latter remains, for now, an open question.