Atma-Sphere Class D… Amazing

http://www.stereophile.com/content/benchmark-media-systems-ahb2-power-amplifier

Anybody remember this review? Look at JA's measurements and his concluding comment, "Benchmark Media Systems' AHB2 is an extraordinary amplifier. Not only does its performance lie at the limits of what is possible for me to reliably test, it packs high power into a very small package, especially when used in bridged-mono mode. It is truly a high-resolution amplifier"

And so I ask any of you, even in October of 2015 was this really an "extraordinary amplifier". In the literal sense of the word, not ordinary, maybe. In the intended sense of the word as something superlative in terms of measurements, maybe. A "high resolution amplifier"? BS. This is where JA gets caught up as an engineer in sound floors aka distortion masking. He falsely equates resolution with bits (in his flawed DAC reviews and measurement methodology) and distortion sound levels. But my recollection is that the unwilling innocent suckers who bought the amp back in 2015-2017 based in the superlative review were by and large not thrilled. KR never could formulate reliable subjective listening impressions imho. And KR's tin ear notwithstanding, humans can not assess amplifier performance the way they can assess transducer performance-it  takes long periods of time before the attributes of an amp are reliably evident. 

I have no axe to grind. When I find out that there is a switching amp that thrills listeners whom I trust, I will be glad to audition one. History has shown that switching amps can ace measurement testing and bore the death out of the listener. No meat to the bones. No there there. 

I’m curious why the Atmasphere Cl D amps are so low powered, compared to many others.   Most D’s seem to claim fairly high power. I guess the switching power supplies are not so constrained by size and weight limitations.  I had a D-Sonic, based on Pascal modules, that produced 800 watts into 8 ohms.  I went back to tubes, though.

@lloydc You just put your finger on the reason why, which is why bother if the amp won't sound like real music 😉 All that power doesn't do any good if the customer is going to go back to tubes (and lower power as a result...).

What are the cases in which measurements don’t matter?

I refer you to Daniel R. von Recklinghausen who was the chief engineer at HH Scott. He debunked, decades ago, the idea that measurements and the subjective experience are not intimately connected. 

@kuribo These two statements, one right after the other, seem contradictory:

I have provided an alternative view: subjective opinions carry no factual information. We must each listen for ourselves to find our own truth.

A lawyer might ask, in a court of law, 'which is it? Were you lying then or are you lying now?' 😁 I'm not suggesting that you're lying; I am suggesting that its impossible to be truly objective.

Subjective opinions can carry quite a bit of factual information. If all those opinions say the same thing and the people producing them are unaware of each other they carry quite a bit of weight. It seems to me that you've still not made the connection of how important measurements are to the subjective experience (and I see that all the time on the subjectivist side as well...). The rules of human hearing are the reason why; as I pointed out earlier all humans use the same perceptual rules. So if we can sort out what's important to the ear, then we can make the measurements to show if we've made progress. The former is the tricky bit!

You are aware no-one is going to beat Bruno's numbers any time soon. For that reason alone I really don't see what you are so concerned about what measurements we get. If that is the only concern just buy a Purifi and be done with it. The problem I see with that I already outlined.

Our goal was to make a class D amp that could allow anyone to enjoy the music and not worry about class D, tubes, class A or any of that stuff. In that regard we feel like we succeeded. A secondary concern is that tube production is waning due to a variety of events having nothing to do with the technology. IMO tube power amps are on borrowed time right now. The rest of it I've already explained.

@mapman The ones that come to mind are:

 

1) the published measurements are not sufficient or accurate enough to be useful

2) The user does not know how to properly apply the measurements

3) The user simply does not care and prefers to rely on other means to make their decisions.

I agree on point 1. Measurements ought to be much more accurate, They are currently so useless and sloppy. Ought to go to to a at least few more decimal places. We can agree on this. Or not.

Point 2 - that the user does not know. Yep. Many words could be used to describe that person. I won’t dare.

Point 3. Cool.. You have perhaps defined an audiophile - more dollars than sense. Some manufacturers rely on this aspect. And they are reading this with a mix of joy and dread in their minds.

I agree on point 1. Measurements ought to be much more accurate, They are currently so useless and sloppy. Ought to go to to a at least few more decimal places.  We can agree on this.  Or not.

Its a matter of whether the person making the measurements knows what he is doing and whether the equipment needed is available. If you want to know how an amplifier will sound look at these things:

Distortion vs frequency; for best results it will not rise

Distortion spectra at 1 Watt

Distortion spectra at -6dB of full power. This particular measurement is where SETs fall on their collective faces as this is where the higher ordered harmonics show up, causing the amp to sound 'dynamic'.

In the case of the distortion spectra the lower orders must always be of enough amplitude to mask the higher orders regardless of the overall amount of distortion. THD as a measurement usually tells you almost nothing and is a good example of Daniel Von Recklinghausen's famous comment.