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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.

hilde45
hilde45's avatar
hilde45 OP
6,005 posts
 

Let me try to reply.

foggyus91:   Thanks for sharing—it's telling that your Class A-B tube amp is collecting dust now; that's a strong practical endorsement of the pairing you mention.

mapman:   Good point about specificity; I'll use those tools. The idea that newer Class D tends to resemble the best tube or SS amps but in smaller, more efficient packages captures what people seem to be discovering.

yyzsantabarbara:   Thanks for the clarification—version 6.5 without glare is useful to know, and your side-by-side comparison of the GanFet with the CODA #11 next week should be revealing

bluethinker:   Your framing—whether modern Class D delivers the emotional experience we started this journey for—is exactly right, and your AGD experience validates that. 

kirkwallace:   Thanks for the detailed scoring —exactly the kind of systematic feedback that helps. I'm very curious about your Gato DIA 400S report.

earthbound:   Let us know about your Orchard Audio monoblocks; a good additional data point on the broader Class D landscape. A local audio reviewer I know has them with Spatial open baffle speakers and they're pretty magical.

dwest1023:   That's helpful—the Nuprime bringing you closer to the music; the preamp pairing matters enormously.

doni:   Your experience mirrors bluethinker's—the "just keep listening" quality and lack of harshness with Atma-Sphere suggests a really good design. Have you heard the AGD or are you just comparing it to Atmasphere?

twoleftears's avatar
twoleftears
5,360 posts
 

I would endorse everything said so far about AGD.  I had an AGD Tempo for several years and only that well-known itch led me to get a pair of AGD Duets.  The Tempo didn't leave but went into the second system.  With the Duets I don't feel I'm lacking for anything.

riaa_award_collectors_on_facebook's avatar
riaa_award_collectors_on_facebook
1,020 posts
 

From what Ive read in the past from owners of both AGD MK3 and Ralph's Atmosphere's the AGD is more Tubey and Ralphs design has more grunt like SS.  Earlier in this post Ralph stated that his amps are more "tube-like" although he didnt compare his amps to AGD MK3.  So I guess one must decide for themselves.

bluethinker's avatar
bluethinker
324 posts
 

@hilde45 - For additional context, my primary system includes: 

QLN prestige 3 speakers: Known for a somewhat laid back and musical sound  signature.  
AGD Audion mkiii monoblocks 
Linear Tube Audio level 2 preamp: Has proven to be an ideal pairing with the AGD amps. Spacious and imparts a tube tone but with solid state speed and dynamics. 
SoulNote D2 Dac: Lively, lots of leading edge energy, brings density to the sound. 
Innuos Pulsar Streamer

Cardas Clear speaker cables and interconnects

Mad Scientist Prime USB cable
Mix of LessLoss, Cardas and Kubala Sosna Emotion power cables 

Puritan 156 with the Puritan Ultimate cable 

hilde45's avatar
hilde45 OP
6,005 posts
 

@bluethinker Great system. Thanks for the context.

I wonder if anyone has an opinion about SMSL. Here's a review of a newer model:

https://www.youtube.com/watch?v=SS6Xp_m6KwE

These reviews on YouTube get dismissed. I understand the skepticism. But there are claims made here worth considering – and then if there's reason, they can be dismissed.

Jay claims that this is a real competitor to  AGD and Orchard Audio. Those brands justify their higher cost through (he says) superior build quality, componentry, and (he says) marginally greater refinement—particularly in high-frequency neutrality and overall sonic polish.  For example, he says that AGD Audion is the "most neutral" and "most refined," while Orchard offers similar high-frequency refinement.  

However, he does say he prefers SMSL's sonic character to Orchard's, finding it more transparent with better high-frequency refinement and less edge. He also prefers its overall build quality. 

I'm trying to either take this video seriously or eliminate its claims by reasoning. Because given the modest performance gap described, it makes some of us hesitate. After all, we're talking about a gap between a $419 SMSL and amplifiers costing $2,500-$8,000+.

It's a puzzle how viewers can weight the descriptors used—"refinement," "neutrality," "build quality"—to determine whether amplifiers 10x or more expensive are actually worth the investment? What threshold of difference in these qualities justifies that price multiplier?

The obvious answer is always, "You have to try things for yourself." So I just might. 

But you can see the bind reports or reviews like this can put people in. While those who need a budget GaN amp can just try this one out, others who might be willing to spend a lot more are left wondering – am I about to be a sucker if I pay 10x more?

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