Class D - A Fork in the Road

@kennyc +1 

@kennyc +1 

theoretically, class D amp can be precise one on frequency and time domain. in reality, it’s extremely hard to design device, with flawless transfer of continuous analog signal, into width modulated pulses, and then back, by integrating pulse energy using LPF (LPF very challenging part of design, typically not linear due to magnetic cores used for inductors, capacitor ESR, etc.). limitations are: nor precise / fast degrading components, resistive connections, hard-to-shield magnetic fields, fast aging switching SS devices, capacitors, and more.. analog amplifier is much simpler than D class, thus more reliable and predictable over time. 

class D amp has one significant advantage, - power efficiency, and excellent power per weight ratio. class D amp is the amp of choice for live performance PA system, car sound system, and other applications where high power efficiency, low weight are crucial. 

I cannot help with the comparison. I did, however, spend a fair amount of time listening to the AGD Gans and Fischer&Fischer speakers at CAF. I don't remember the model, but the AGDs were, for a good deal of the time, one of the less expensive models. The setup was very impressive. Plenty of well controlled bass, very natural midrange and no glare on top. I thought the sound was exceptional, even under less than ideal "show" circumstances, and destroyed much of the stereotype concerning Class D.

I have compared a few. Unfortunately I’m not up on the architecture so I can’t comment on the different core designs and of course implementation matters. 

Began with Fosi V3 monos which were quite good for the money but was getting random clicks and pops even when no signal was being sent (pre-amp off).

Then I tried SMSL PA200 bridged so 2 running a channel each. The build quality was much better and didn’t run as hot. The sound wasn’t as thick in the low end and a bit drier overall. However detail was moderately better and the stage more accurate so more depth of stage and less wall of sound.
 

Finally tried a Buckeye Hypex NCx500 2 channel. Separation of instruments, clarity, transients, attack, etc is all the best I’ve heard by a significant margin. They say there is no inherent sound to these, no specific color to the tone or effect on the stage. That they produce exactly what’s on the recording. I agree. If the recording has width to the stage, you’ll hear it. If there are details you’ll hear that too. What’s great about them is you can crank it and it doesn’t become mush. And not every recording will sound the same which some find tiresome. Tonality is maybe just ever so slightly warm. 

The OP poses an interesting question and it appears most of us haven’t been able to do a direct comparison. I’ll add my my experience, but I’m not sure it’s worth more than $.02. Please bear with me for a bit of 10 year historical context before I share my experience.

In the past, I’ve owned in one system or another:

Parasound A23 - (class A/B) - connected to the P3 preamp

PS Audio Stellar S300 - (ICE module) - connected to their Stellar DAC/preamp)

NAD M22 - (Hypex module) - connected to the M12 preamp/DAC

NAD M33 (Eigentakt module) 

T+A R2000 integrated

T+A PA 3100 HV integrated

currently own Atma-Sphere Class D monos in one of my systems, and Simaudio North 761 in the other.

Of course, there were other variables involved - preamp sections, DACs. But I did have a feel for each. Each purchase was an improvement over what it replaced. The Parasound was flabby/tubby in the bass compared to the others. The PS Audio was pleasant but lacked a bit of what the reviewers call “tone color”. The M22 was a bit denser in that regard, but still not there. 

The M33 (eigentakt and relevant to this conversation) - was clearly better than the hypex module but was that the preamp? The DAC? I’m unsure. And yet, i still didn’t like it - finding it lacked emotional impact. The speakers I had at the time (Sonus Faber Olympica Nova III) sounded nice, but lacked the drive and resolution I knew they were capable of. Too polite.

I reference the T+A gear because it fully satisfied in a different system but my needs there changed (different DAC, etc.). They were class A/B and offered warmth with resolution and impact. World class? No. Very good? Yes.

@westcoastaudiophile - your comment about the significant advantage of class D being low weight and high horsepower is only partially true, but also misleading. Yes,  those can be advantages, but class D, implemented well, has no sonic disadvantages against other topologies whatsoever. Indeed, it can be superior.

The Atma-Sphere Class D monos are as good as anything I’ve auditioned as a standalone amp. I now have them fronted by a very good preamp and DAC and that combo drives the SF speakers spectacularly. Yes - I changed a lot of gear in there, but the amps showed no limitations in that setup. 

I’m in the process of setting my 2nd system up in a new room (hopefully done w/in the year - we’ll see). I decided to upgrade the speakers when my SF dealer offered me a trade up I couldn’t refuse so I’ll be using the Class D’s to drive SF Il Cremoneses. Some would say a mismatch. I’m guessing not - but we’ll see. 

I’ve directly compared the Class Ds to the Sim North 761. They’re different sounding, but closer than you might expect - and I find the Sim North to be (to my ears) significantly better than previous Simaudio gear and vastly better than many of the $20k amps I considered.

My conclusions: implementation matters greatly - more than topology. Based on my limited sample set, GAN has more upside than Eigentakt, ICE and Hypex and probably has the potential to be as good as anything out there. 

Maybe that was all worth $.03.

Thanks for sharing your experiences. I would say that was $2.00 worth.