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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
tomcarr
1,817 posts
 

I’ve been listening to class D PS Audio M1200 monoblocks for the past year or so. They do have a tube also. 

I would say they throw a big soundstage, they float images beautifully, they are very dynamic, they sound neutral top-to-bottom, they are very powerful. They are rated at 600W/ch/8 ohms, 1200W/ch/4 ohms, stable at 2 ohms on transients. They are finished nicely and appear well made. I’m happy with them. Don’t feel like I’m missing anything.

hilde45's avatar
hilde45 OP
5,997 posts
 

I’ve been listening to class D PS Audio M1200 monoblocks for the past year or so. They do have a tube also. 

Thanks for weighing in. Interesting they have a tube in there. I wonder if they were unable to get the right sound without a tube. 

Also: I hear there is a new PS Audio PMG amplifier coming. Probably Class A/B. No tube. That's the gossip.

tomcarr
1,817 posts
 

OP- I'm guessing you're right about the reason for the tube.

decooney
2,564 posts
 

@sdl4 With regard to distortion profiles, Ralph makes a strong argument that his amps have a non-fatiguing profile 

A key discussion about "distortion profiles", and what amp designers decide to do.

I pay very close attention to amplifier designers who seek a careful balance between so-called "perfect" ultra-low distortion specs, vs. keeping the right amount of distortion around in order to not kill the "music" and for the most enjoyable engagement.

After trying a few pieces of gear with ultra low distortion specs, realizing the real musicality was taken away, boring, un-engaging, I started paying a little less attention to pure engineers and more towards proven amp designers with "great ears" who put the sound of music first. Could I listen to it "all day" is what I look for any more. Cold, sterile, dry sounding amplifiers with great specs are of no interest at all. None, nadda   This is why I keep older Class A SS and tube monoblocks around, for now. This whole thread is interesting to learn which Class-D designers, "get it" about the "music" vs so-called perfect specs. Is a razor sharp camera with the highest resolution in the world the best for producing beautiful photos?  

A reference below, to a well known solid state integrated amp many love the sound of, has this profile. Nowhere near close to a so called perfect low distortion profile.  I wonder if anyone here can guess which integrated amplifier it is, ?. Tip, this amplifier is not made in the USA. 

Key Distortion & Performance Characteristics:

  • Class A Operation: Operates in Class A, which eliminates the crossover distortion common in Class AB designs.
  • Harmonic Profile: The distortion is generally described as low-order, contributing to a "sweet" and "liquid" midrange without harshness.
  • THD Levels: Lab tests indicate distortion levels of 1% THD at 5W/8ohm and 10W/4ohm, rising to 2% at higher dynamic loads (15W/8ohm, 19W/4ohm).

   

avanti1960
1,744 posts
 

AGD Audion are the only Class D amplifiers I have heard that I could live with- and ENJOY! 

They are the only ones that do not sound dry and mechanical.  Some amps attempt to add a bit of liquid warmth but they seem to take on an opaque quality at the same time.  Not good. 

The GaN Fets are as billed- incredibly fast- but that is  where the good stuff ends.  

Final thoughts are that active speaker installations definitely short circuit much of the perceived Class D sonic biases- at the expense of the drawbacks of an integrated system.  

People that put an emphasis on measurements seem to be the most interested and capable of enjoying them.  

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