@parkergetdean - Totally agree. It’s interesting how our interests shift and evolve as we age. At this point in my life, I am fascinated with audio equipment, especially amps, and their ability to connect us to a world of musical experiences. In
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:
- Frequency balance — Is the tonal response even across bass, mids, and treble, or does it favor certain regions?
- High-frequency texture — Are the highs extended and smooth, or edgy, grainy, and fatiguing?
- Bass definition — Is the low end tight and articulate, or loose and bloated?
- Midrange character — Does the midrange feel present and natural, or recessed and thin?
- Transient speed — Does the amp respond quickly to dynamic attacks, or does it sound sluggish and rounded?
- Dynamic range — Does it scale convincingly from quiet passages to loud ones, or compress the difference?
- Soundstage width and depth — Does it create a convincing three-dimensional image, or sound flat and narrow?
- Image specificity — Are instruments and voices placed precisely, or do they blur and wander?
- Background noise floor — Is the silence between notes actually silent, or is there grain, haze, or hash?
- 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.
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Thanks for the insight. I jumped to Hypex Nilai 500 mono blocks some time ago. I found the resolution and sound staging excellent. What I really like about them is that class A power. It has limitless feeling. The power supply voltage rails show practically no modulation when you are playing music. These are switch mode power supplies rated at 800W peak 600W continuous at +/-70V. The slam they produce is very impressive. They have a very small footprint and are not heavy. Headroom is astonishing with very little distortion. I think top level class D can match and better some of the more esoteric amplifiers. But not all :) |
Listening trial summary: AGD Audion Mk. III vs. NAD M23 (v. 1) I wanted to share a summary of the latest round of ongoing Class D evaluations in my system. Methodology Three consecutive evening sessions, February 24–26, 2026. Amplifiers swapped within each session on the same material. Volume calibrated with a 250 Hz test tone, C-weighted, at the listening position. Sessions ranged from 82.5 dB baseline up to a deliberate high-volume stress test at 91.3 dB on the final night. System Holo Audio Spring DAC → solid-state preamp (Burson-based) → amplifier under test → JBL 15″ woofer / Beyma AMT tweeter on Townshend platforms. Treated room with diffusion, absorption, and bass trapping. Audience power conditioning. Test Material The playlist was varied and included well recorded material. Mix of Qobuz streaming and local files including an SACD rip at 24/176. Tracks included:
Findings Imaging. In general, the AGD’s imaging is more definite, with a faster, more dramatic presentation of dynamic events — particularly the way an orchestra executes complex passages, or the way a soloist stands out from the orchestra’s backing. N.B. There were many places where the NAD held its own, so these remarks are highlighting differences which showed up a significant number of times, and repeatedly on certain recordings. Bass was excellent on both: tight, fast, creating a real sense of musical involvement. The bass on both amps anchored performances and generated toe-tapping, rather than just filling in the bottom end. Tonality. Here, the AGD was clearly better, exemplified on tracks with well-recorded voice and piano. Gould’s piano sounded richer, more natural, more percussive – the piano was "there." On the NAD, the piano’s notes sound thinner – almost but not quite like a fortepiano rather than a giant Grand. In other words, the AGD's "midrange character" is a bit better; NAD in comparison is slightly thinner. The "shouty" or "cringey" factor. This is about tonality, but I’ll list it separately. The AGD never produced the "shouty" quality associated with a Class D amp. The M23 sometimes did, especially on louder tests. The diagnostic moments for this difference were Steely Dan’s "Green Book" (a closely miked snare hit), on Eno’s "Deep Blue Day" (the synthesizers’ swells became metallic and bright with the NAD), and on Muhlemann’s loudest soprano belt-outs on the Mozart piece. At these moments, the M23 felt like "oof, that’s loud, turn it down." Bright, metallic, and fatiguing. This did NOT happen with the AGD. Instrument separation. The AGD had better instrument separation in symphonic passages, and a more "coordinated" sound where instruments felt like part of the same performance. N.B. Here, though, the NAD often was comparable. Dynamic range for both is excellent. They scale convincingly. Background noise floor — both are dead quiet. Summing up: Key Differentiators
Outstanding questions and Practical takeaways
Prices and value: If I was sufficiently impressed by the M23’s v. 1 performance (versus the AGD), I would probably seek out a used NAD c298 because it has the same Eigentakt v. 1 module, same company, and while probably a less beefy design, my guess is that for the price, used (approx. $1650 to $1900), one could get mostly there and save a lot of money. I also expect the M23 v. 1 price to keep dropping with the v. 2 now being promoted. Onwards and upwards!
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@hilde45 Great comparisons! Can you share any thoughts on how the AGD amps compare to your Pass XA25 amp? Also, do you think you'll be able to demo a pair of Atma-Sphere Class D monoblocks to compare to the AGDs? |
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