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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
sdl4
251 posts
 

Like @doni above, I have not been able to compare my Atma-Sphere GanFET Class D monoblocks to any of the AGD amps. I have also not had the pleasure of listening to any of the Orchard amps. Fortunately, I am very happy with my Atma-Sphere amps, so I'm not actively searching for any demo days.

When I first started reading about the latest versions of Class D amps, several European makers of Class D modules were saying that faster-switching FETs (like GanFETs) were not needed to achieve optimal Class D performance. However, several U.S. amp designers (like Ralph Karsten, Alberto Guerra, and Leo Ayzenshtat) saw clear advantages in going the GanFET route. The reviews of modern Class D amps (whether using GanFET designs or not) seemed to emphasize that these amps were clear, neutral, honest, and great at saving you money. While all those nice things could be true, this description sounded more like what you might look for in a banker rather than in an amp that helps you establish an emotional connection to music. 

So I began looking for a GanFET amp that was not only clear and transparent, but which also had richness, fullness of tone, and natural warmth coming directly from the music. I wanted the music to be engaging and "real," too, like there were real musicians playing/singing in the room. Of course, I couldn't judge these characteristics without listening to several amps in my home system. But I didn't want to go to the expense and hassle of buying three or four amps to demo at home, so I made an educated guess and chose the Atma-Sphere monoblocks based on online reviews and respect for the career of Ralph Karsten as an amp designer.

Two design issues helped sway my decision on the Atma-Sphere amps: (1) use of a linear power supply with a toroid; (2) having a distortion profile that minimizes harshness or hardness. Both AGD and Orchard offer toroidal power supplies, but only on their most expensive models. AGD offers a LPS on the Solo at $24K (per pair) and Orchard offers the Starkrimson Mono Ultra Premium LPS at $7K (per pair). I can't confirm that the solid foundation of the Atma-Sphere amps is related to its LPS, but it's a distinct possibility.

With regard to distortion profiles, Ralph makes a strong argument that his amps have a non-fatiguing profile that minimizes harshness in the sound. AGD and Orchard do not discuss this issue. When Ralph speaks, I tend to listen.

These are just a few of the issues I considered before I decided to invest in the Atma-Sphere Class D monoblocks. I've been very happy with my choice.  

 

greenngoldcheesehead
100 posts
 

I think Class D can be implemented to sound very good.  I have yet to hear a Class D version that can make you feel the music like an A or A/B can.  Also, I've yet to hear a Class D that doesn't fatigue me fairly quickly.

yyzsantabarbara
5,547 posts
 

I have been listening to the Class D GanFet 6.5 stereo amp for about 24 hours now and I might as well make a comment on this since my system changes tomorrow.

GaN FET Amp: Premium 6.5 Class D Audio Review

With the great imersiv D-1 DAC the 6.5 amp sounds a little lifeless. This is surprising because with the CODA #11 and CODA #16, mostly Class A amps, the imersiv D-1 is super lively with the ultimate in resolution. With the 6.5 amp that magic is not there. I would have said this amp is no good if that is all I heard.

The other DAC that I am listening to is the Meitner MA3i on demo from my friend. What a change in sound from the imersiv D-1. The MA3i has great synergy with the 6.5 amp. It is lively with a juicy Class A like sound. The difference in sound and engagement is really surprising.

I think the CODA #16 on this system, my office Magnepan Mini system, is a bit better. It hits harder and has a bit more of a thicker Class A sound. The CODA #16 and the Meiter MA3i and imersiv D-1 are spectacular. The thing is the 6.5 and the Metner are not far behind. The 6.5 costs $1k and the CODA #16 costs $16k. My speakers in the office cost $2k. 

I have to return the Meitner MA3i tomorrow, but I am going to buy it soon. I already sold $5.5k of gear (unused Audience FrontRow speaker cable | Schiit Byggy DAC | extra Sonore OpticalRendu streamer) to make the Mietner purchase happen. I think I am going to keep the CODA #11 over the #16 since the #11 has a bit of a warmer sound and is spectacular with the imersiv D-1 on my Livingroom speaker, the Yamaha NS5000.  The #16 is great too but it is a cleaner sounding amp, and I like the warmer #11 with my super resolving imersiv D-1 DAC.

I do not think the 6.5 will be as good on the Yamaha as the #11. However, I cannot give it a good test because I am returning the Meitner MA3i. No point pairing it with the imersiv D-1 on the Yamaha.

The 6.5 definitely does not have glare. If it did, I would get ear fatigue immediately. The bass is amongst the very best I have had, such as the CODA #16, #11, #8, Krell DUO 175XD, Schiit Wotan. Not saying the 6.5 is better in the bass than any of them, but it is close enough. The #16, #11, and the Wotan are tops here

The soundstage is large and goes outside the speakers, but the Maggies make that easy to do. The depth of the stage seems a bit less than the CODA #16 (do not care for my office setup). The sound is very clean and seems like a slightly less warm Class A amp. Likely why I like it so much with the warmer Meitner and not so much with the highly resolving imersiv D-1.

Anyways, this amp is going to be my new office amp, and the CODA #16 looks like it will go to make way for the great Meitner MA3i DAC. If I had the cash, I keep the #16 and buy the Meitner. However, I made a goal of not spending new money on audio. Got to sell my existing gear if I want new gear. The 6.5 really helps me in this regard and I am loving the sound. If the CODA #16 is a 10/10 on my office setup the 6.5 is 8.5/10. That is a reflection more on the CODA and not a negative on the 6.5.

My Maggies are small speakers and need to only fill a small space. Not sure how the 6.5 would do in a bigger space. I know the CODA #16 can play small and large with the very best amps.

I am getting the #11 back from CODA after a refresh in a week or 2. I will do a head-2-head with the #16 to see which to keep.

I wish I had the Schiit Wotan amp in the house to compare with the 6.5. I thought that was a fine amp. I do know that it was not as good as the CODA #11 and #16. If I remember correctly the bass was stronger on the Wotan than the 6.5 but the 6.5 sounds a bit more Class A and cleaner.

Next week I will listen to the 6.5 in my office with the Schiit Valhalla 3 OTL/OCL preamp ($500) tuners, and RME DAC. I briefly listened to the similar Allnic HPA 15000 OTL/OCL as a preamp ($15k) on the Maggies and the 6.5. That was really good though I am also returning the Allnic tomorrow after my demo.

I should add that the 6.5 worked nicely when either an RCA source, the Valhalla 3, or the Miethner DAC (XLR) played. No toggle needed between RCA and XLR.

 

 

 

 

 

 

parkergetdean
1,032 posts
 

I had two SMSL PA200s in dual mono mode a month ago. They were very harsh,  with limited soundstage, I returned them.

ashoka
107 posts
 

Class D was preferred because of Efficiency and cost. If Class D costs as much as other class amp dump the class D in first place. Debate is not needed.  

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