Could Class D really be that good?

I can't speak on the newer chip amps but I purchased a Hypex Nilai recently. To me it is a step above the Ucd & Ncore's I tried briefly in the past. I purchased the DIY model and feel it is a great amp for the money. Subjectively speaking of the class D modules i had tried in the past I found them to be a hair dry..touch analytical & 2 dimensional at times. For the low noise, transparency, power & size I still think the Ncore is a good amp.. especially when you consider the price. If I was still into Surround/Multi speaker movie systems I would be all about Hypex/Purifi modules. 

I tried an Elac Alchemy amplifier built around the older Ucd modules and felt that Class D amp was good for the money. Definitely better than just the basic older Ucd module but I still felt the top end wasn't as good as say a good class AB. Still a solid amp for the money in my opinion, I used a pair of them for almost a year. 

Anyway, the Nilai is definitely an improvement in my opinion. It's hard to describe an amplifier but I just find it smoother & groovier than D's I've tried in the past. I've only used it for a few weeks now but I can't find any faults in it. If Class D is able to improve upon this and keep it at these low costs I think that is a win for a lot of audiophiles. I definitely welcome more builders designing amplifiers around these new modules.. especially this Nilai.  

@atmasphere So if a class D has the same distortion signature as a good tube amp, it will sound like a good tube amp simply on that account.

Agreed. But I want to emphasize, with the low 2nd HD found in these Purifi / Hypex class D, you won’t be able to have distortion signature comparable to a tube amp and possibly produce the tube-like smooth sound. Let me give you an example of sound color signatures built in the Smsl Su-8. The 2nd, 3rd and other higher order spikes in the standard setting (upper left) are insignificant (-120dB, similar to Purifi / Hypex. Users could elect the "Tube 1-3" sound signatures to experience the emulated tube sound, where you could find the 2nd-order HD boosted to -90dB in Tube 1 (light) setting and -70dB in Tube 3 (strong) setting. That tells me the 2nd order HD needs to have high enough ’dominant’ spike (relative to 3rd & higher-order) to exhibit the tube-like smooth sound.

Here is the FFT plot for a real good tube amp, McIntosh 40, which confirms with the above. But, interestingly, Mc40 actually has slightly higher non-dominant 3rd hd.

Most agree that the 2nd harmonic is innocuous to the human ear; the real issue here is are the 2nd and 3rd able to mask higher ordered harmonics. I've heard the argument before that if they are 90dB down you aren't going to here them, which I think is false due to the fact that the ear uses higher ordered harmonics to sense sound pressure and it has over a 120dB range.

But if the 2nd or 3rd is masking them, then you have a 'tube amp' signature. The lower the distortion overall though, the more transparent the amp becomes.

@mattw73

I’m impressed with both the Nilai Mono and Apollon St in terms of their specifications. However, I lean slightly towards the Apollon for a couple of reasons: (1) it offers 25% more reserved maximum power in both 4 and 8 ohms (despite a slight sacrifice in dB noise in 4 ohms), and (2) it has the lowest measured power on/off noise, which is inaudible. Additionally, while the Nilai Mono has the advantage of being a stable 2-ohm load amplifier, the Apollon Stereo is half the cost of a pair of Nilai Monos. If you or anyone else has experience with these two amplifiers especially how they sound, I would greatly appreciate any advice or insights you could offer. Thank you!

Yes, the amount of distortion and its spectrum has some correlation to sound. However, it is not the major or only thing that makes and amp SOUND the way it does. You can give me 3 pairs of Atmasphere amps and I will change some of the parts in one to really bad sounding parts.....leave one of them stock and in the 3rd one I will change a bunch of parts and execution that I know will make the sound better. They will still all measure the same. Ralph or anyone would be able to pick them apart..........even on a double blind test.

All Hypex amps sound different from each orther. All Purifi amps sound different from each other. Please read the review on 10 Audio on the NAD Purifi based amp and then the review he did a little later on my modified VTV Purifi amp......way different and better sound. All parts and execution change the sound. I mod all these amps so I know that they all sound good stock.....but way, way better with mods. Yes, some do not believe it....they only believe in measurements. My mods do not change measurements.....they change the way an amp sounds.

I have been modding and manufacturing gear since the 1970s.....Everyone likes what I do......everyone (I mean, those that listen). If you change the coupling cap in a tubed piece of gear.....or brand of tube....or brand of resistor.....you change the sound.....but you do not change how it measures (obviously, the tubes must have the same gain). All op amps have a sound. Many amps out there right now (all the Fosi and Ayima amps,etc.) with sockets in them so you can "opamp roll". All the various op amps measure such low distortion that they do not change the measurement of the amp......but everyone can hear the difference in sound between the different op amps. This is why the best versions of Purifi and Hypex use discrete op amps and super low noise regulators (because they sound better). All the discrete opamps have a sound, as well. VTV sells various op amps for those that like different flavors of sound. I modify the Sparko labs Pro opamps to give better sound (one of my favorites, so far, along with the LKS discrete op amps). Warren at VTV sells various amps and he slightly prefers the Purifi (and especially the high powered Purifi) modules to the Nilai and NCX500 that he sells. He is a tube guy so he really likes the tube buffer in front of the Purifi module. Listening to a very modded VTV Purifi amp as I type.....Wow, what a great sound.

I am probably going to have a tour with a stereo dual mono high powered modded VTV Purifi amp soon. This way, this less than $3K (delivered including mods) amp can be compared to Atmasphere, Orchard, Hypex, Nilai and others. This dual mono stereo amp will do 222 watts into 8 ohms, 436 watts into 4 ohms and 750 watts into 2 ohms. I will warrantee the modded amp for 2 years. Fun stuff. Low distortion class D modules with serious tweaks equals serious goosebump factor.