Atma-Sphere Class D… Amazing

@fsonicsmith - I guess time will tell if Ralph's assessment pans out, but I'm essentially with you none of my tube amps are going anywhere unless I purchase some other tube amp, or the powers to be come breaking down the door to mandating its cart-off.

 

 

How much hubris can a man possibly have to make such a pronouncement! This man has solved the problems leading to 20 years of "terrible missteps" of all that came before him?

People have been jumping all over @kuribo, which as @noske described earlier in a puerile fashion, with Troll and Fan Boi descriptions. But this seems like more like what they are describing.

When someone has 40 year in the industry, and brought balanced XRL to home audio, it is different than PS Audio YouTube videos.
 

One can only be so humble and demur, and honesty is not exactly overdoing it in a self promotion way.

I am not sure how Ralph can respond and communicate any better than he has? He certainly does much better than I can do in the sense, but I am also not an expert in the field.

. Who is Ralph to declare that his subjective opinion of the sound of his own product is absolute? Ralph will no doubt diplomatically respond that he is not just referencing his own Class D amp. If so, than tell us Ralph which other Class D amps are you declaring to be subjectively better than the best tube amps other than your own?

He also said that if people like the absolute best numbers and even lower distortion, that Bruno has those in the Purifi Class-D that they sell.

Perhaps you could be so kind as to look me up three, five, or ten years down the road and tell me when my ARC Ref 150SE and ARC Ref 80 power amps have been rendered value-less. on the market so I can inquire of my accountant if I can declare a depreciation deduction.

We can also roll in ARC with Purifi and Atmasphere, but that does not change the fact that they are running a business and have decided that a move to Class-D is a direction that they want to be poised for.

if one asks hard questions, or makes statements that are not appreciated they are referred to as Trolls and Fan Bois, and if they respond civilly then they are referred to as an ambassador.

But that is fine. I will not say another word in this thread and I truly wish you the best.

^great^

@atmasphere  Thanks for the helpful comments in response to my questions about  the choices of switching frequency and power supply for your Class D amps.

@atmasphere

Thank you for your patience and great explanations. With regard to the high-lighted statement below:

That is why we never ran feedback with our OTLs, since keeping distortion vs frequency linear across the audio band is pretty important if you want the amp to not sound harsh. That’s easy in a tube amp if you don’t run feedback! Our OTLs have as few frequency poles as you can get in a tube amp and even with them we ran into issues with their phase margin. IOW, very difficult to prevent oscillation even with a carefully designed feedback loop if running large amounts of feedback. Conventional amounts were no problem but had all the downsides that have given feedback a bad rap in high end audio.

Would you please expound upon your statement: "keeping distortion vs frequency linear across the audio band"? I am afraid I don't quite follow.

Also, since you mentioned that your Class-D amp uses a fairly large amount of loop feed-back, which helps keep THD down, would you please inform what your amp produces by way of Transient Intermodulation Distortion (TIM)? In that light, since there are many different methods of measuring TIM, and also since it's very difficult to measure, would you please inform which method(s) were used?

You have side-stepped your bold declaration that tube amps, the entire category bar none, are on their way out.

@fsonicsmith That was not my intent. To my understanding I've not side-stepped this issue at all:

IMO power tubes are on life support- even in the guitar industry class D has been making significant inroads in the last couple of years. Its clear that any manufacturer of amplifiers now has to contend with class D technology in a way that they did not a decade ago; in particular manufacturers of tube amplifiers will find their market shrinking dramatically over the next ten years. The reasons for owning tube amps (the 'sound') is being heavily eroded by advances in class D technology; any manufacturer that ignores this does so at their own peril.

Would you please expound upon your statement: "keeping distortion vs frequency linear across the audio band"? I am afraid I don't quite follow.

@atulmajithia In order for an amplifier to exhibit the same smooth character as the music itself, in order to not sound bright, distortion must not rise with frequency. This is one of several characteristics needed to allow the amp to be musical and not bright. If a tube amplifier is zero feedback and has sufficient bandwidth (not including the output transformer if one is present) then this really isn't a problem. Of course the designer needs to pay attention to other issues but distortion vs frequency is pretty important.

The ear is very sensitive to higher ordered harmonics since it uses them to sense sound pressure. It also assigns a tonality to all forms of distortion and higher ordered harmonics get the value of 'harsh and bright'. In addition distortion products occurring in the Fletcher Munson region (3-7KHz) causes distortion in that range to be more easily heard.

TIM is a product of an amplifier having high feedback but also has part of the amplifier outside of the feedback circuit so unable to compensate for certain types of distortion. An example might be the base of a transistor in a differential pair, wherein the input signal is applied to that transistor while the feedback is applied to the base of the transistor's mate. This is a common circuit in many solid state amps over the years. Class D amps  of the self-oscillating variety (like ours) don't have that kind of input circuit and so avoid this problem.