Could Class D really be that good?

I have heard Active Driven OB's with a configuration for Amplification with similarities to the method suggested by yourself.

The OB's although with 4 Drivers and a Amp for each Driver with Class D for the Lower Frequencies, has been the best Speaker Array heard in a unusual venue.

I would strongly suspect if heard in the home set up, they may be the best Speakers experienced over multiple years.

I made it known recently, that very recently, a friend who is a EE, has bought into a DHT Pre Amp Design, and in using this with a Neurochrome Amp, it has blown them away with what is on offer. I am yet to receive an Demo', but some of the Local HiFi Group have, and they are thoroughly impressed with the experience had.

I myself am still remaining thoroughly impressed with the Pass Korg B1 design for a DHT Pre Amp, especially after it has a few well known circuit mod's added.   

I could not agree more, @pindac. Such a ’bybrid’ amplification could be even better on a active crossover system. A good (mini)DSP could easily lead us there, which will be more convenient than the passive crossover system. A lot of class A / tube amp or these class D module amp do not even have ’pre-out’ or ’line-out’ any more for bi-amping.

@audiophil88 I have heard the Aavik D it is good on Borreson but if you look on the Aavik website their flagship amps are pure class A. Why do you think that is?

I added a THD (%) scale, which corresponds to the dB scale, into the graph for comparing more affordable NAD C268 ($1k) and the Bel Canto S300iu ($2.5k) with the Fosi V3. As shown, the NAD C268 is comparable to the Fosi V3, but the Bel Canto is far inferior. Again, measurements do not mean everything, but the THD measure does give an indication of the sound clarity. I just provided you with the data in one place for your convenience, and it is your discretion how you interpret the data.

@lanx0003 The THD really doesn't tell you how musical an amp might be. A better indication is distortion vs frequency. If it rises at too low a frequency, higher ordered harmonics might be unmasked and so contribute to brightness and harshness. Ideally (and a number of class D amps can do this) distortion vs frequency should be a ruler flat line across the audio band.

Zero feedback tube amps (like most SETs) have always been able to do this. But a good class D can do it better, with lower distortion (which obscures detail).

Once DvsF is sorted, the next hurdle is the actual distortion spectra. Ideally a 2nd harmonic should be the most powerful, followed by the 3rd with succeeding harmonics quite low in comparison. In this way the lower orders can mask the presence of the higher orders, allowing the amp to be as smooth as possible. Again, some class D circuits are very good at this, challenging SETs and other tube amps on their own turf.

@atmasphere Thank you for the very helpful information. I recalled someone asking / commenting about the musicality and I have examined all the ASR measurements but could not find one appropriate to be an indicator.  After a brief search I was only able to identify two gears (see below) that ASR give the THD vs frequency chart. I am not sure what the thought process was behind making this chart obsolete.

The THD vs frequency chart was soon replaced by the following load-dependent THD charts by frequencies.  As you may know, the load-dependent THD is usually tested using 1kHz tone in the industry but was later criticized because it ignores the adverse effect of higher frequencies over 1kHz on the overall THD measure.  So, including Erin, the reviewers start tests using multi-tones.  As shown in the following chart, the 15kHz frequency has big jumps in THD levels, while the better class D module like Purifi demonstrates a much more controlled increase in THD at these high audible frequencies.   

The phenomenon of even-order harmonic distortion (HD) contributing to a "pleasant" or "musical" sound in tube amps, while odd-order HD in transistor designs may sound "edgier," is a well-known concept among audiophiles. However, the idea that modern class D modules can also produce a "sweetened" or "musical" sound despite lowering total harmonic distortion (THD) might seem contradictory.  Can you provide some actual test done for those class D circuits demonstrating how they accomplish what you have described in the last paragraph?