Class D Technology

@mapman 

I will not agree to any such prejudices. While I can say that class A lacks notch distortion, it is by no means the only type of distortion or non-linearity!

We can't on the one hand talk tech. theory on a subject like notch distortion while rejecting THD figures, which is (oddly) what a lot of audiophiles like to do.

The distortion and noise measurements between high end class A, A/B and D heavily overlap.

I'm also not sure that what audiophiles like to hear is always "better" if "better" = "more accurate."

I think audiophiles like sweetening (which is fine!) in which case trying to match an argument with notch distortion and sound quality blows up. The "sound quality" isn't found in the technology per se. If I had all the time, money and space in the world I would not mind having a pair of Conrad Johnson Premier 8 for instance, knowing full well they lie lie lie. :)

Best,

Erik

Erik I’m just trying to frame up the comparison between the various amp technologies in purely technical terms as an extension of georgelofis argument against Class D based purely on switching frequency.

I am of the mindset that understanding the technology helps to make decisions where needed but alone does not dictate what sounds best in the end. Technology alone cannot predict what sounds best in specific cases. A system together makes the sound not just one component. Its a team sport as they say. Plus individual preferences vary for many reasons though some technical people have a greater tendency to associate these with specific aspects of technology that matter to them whereas others (I’d like to think myself included) are not so fast to jump to conclusions.

So I think we are on the same page in practice.

Guess what? My Class D amps were preceded by two different Class A amps that were fine on their own terms but far from perfect in my application. The Class A amps were preceeded by many a Class A/B amp and even a 70’s vintage Class G that was nice overall in its day especially if space is limited but sound quality could not hold a bone compared to any good quality newer amp I compared it to.

I heard the Benchmark amp at Capital Audiofest last summer (along with every other kind of amp imaginable) and thought it to be a top performer easily in the same league with the best I heard there.  I would own it in a heartbeat.   I am strongly considering giving Benchmark preamp/DAC units I heard there a try which if if successful (as I expect it would be)  would finally happily eliminate the last tubed  gear in my house.  I'm all about the sound.   The technology used is just a means to the end.

Guido,
Thank you for the detailed answer to my question yesterday. One attribute you stated,

Aliveness of "black" background... Also called the sound of the silence between the notes... Or the reproduction of ultra-low level information.

...reminds me a bit of what I found missing from the NC1200 Atsahs, at least compared to my other amps.  I am curious about what JRDG has done to bring out the best of the Ncore amplifier module but there are so many features incorporated in those amplifiers, over and beyond the stock Ncore modules, it would be impossible to isolate the specific contribution/benefit resulting from any one of the features.  I hope to hear a pair some day.

Can someone tell me what can be observed when measuring a class a/b amp that indicates its inferiority to pure class A?

In a class A amp as mentioned the output devices never turn off. Unless its a single-ended amp that makes little power, one advantage is that even ordered harmonics are canceled in the speaker load due to the opposing operation of the output devices. In a class A amp this happens at all power levels but not so with class AB.

Execution is a major portion of the differences between various amplifiers. For this reason it is possible to find inferior and superior amps in nearly all categories. I personally think D is going to win out over AB and A simply because of the cost. If done right, the output section is pretty benign and most of the sonic artifact seems to come from the input section and the converters.

Now this has nothing to do with tubes and both traditional solid state and class D still have inroads to make there. I think part of the advantage of D is that its likely that due to its simplicity and the input section being the lion's share of the artifact, that it will be able to eventually challenge tubes in a way that traditional solid state has failed to do (for those that doubt this last statement, if traditional solid state had really been able to challenge tubes, tubes would be a thing of the past. Gone. Nada. They aren't and that's really all anyone needs to know, and there are good sound technical reasons why this is so).

Because there is less to color a D amplifier, it should be easier to create the neutrality and smoothness that tubes have had all along. Not seen it yet, but they get closer every year.