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Atma-Sphere Class D GaNFET Amplifiers

fpitas

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Thanks and sorry for the OT.
there was talk if SiC for a while , but our company uses IGBT’s currently , but developers are tight lipped so if one major company in the business switch to SiC or GaN we hear about it soon enough.
A concern is standard packaging so that several brands of semiconductor can fit the product .
SiC is really still in its infancy. I expect in time, as people learn how to process it, package it etc. we'll be seeing lots more.
 

kipman725

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IGBTs are pretty bad for audio as you get a long 'tail current' (last bit of current flow takes ages to pinch off) so to have reasonable dead time you end up having cross conduction. Could do a limited bandwidth subwoofer amp with them but harder for full range.

SiC would be good for extreme high power amps. I made a 100kVA inverter switching 100KHz for a special application using SiC, this could have been a class-D amp with some changes (add modulator, output filter, feedback). Mostly people like it for its high blocking voltage. Cost is again an issue I think the modules we used where about £450 each.
 

fpitas

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IGBTs are pretty bad for audio as you get a long 'tail current' (last bit of current flow takes ages to pinch off) so to have reasonable dead time you end up having cross conduction. Could do a limited bandwidth subwoofer amp with them but harder for full range.

SiC would be good for extreme high power amps. I made a 100kVA inverter switching 100KHz for a special application using SiC, this could have been a class-D amp with some changes (add modulator, output filter, feedback). Mostly people like it for its high blocking voltage. Cost is again an issue I think the modules we used where about £450 each.
I wouldn't try IGBTs for audio, unless it was just a design exercise, or I needed 1200V swings. As for SiC, my First Watt J2 uses SemiSouth SiC JFETs in class A; surprisingly they have very little inherent distortion. At the voltages and currents for that 25W amp they're loafing along.
 

Zoso69

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After waiting 12 months for a Decware Zen 25th Anniversary amp, and at least another 6 months wait time left, and my 12 month old Willsenton R8 red-plating on me after only 10 months of use (with upgraded Psvane EL34's) I decided to put my order in for a pair of AtmaSphere Class D's today. I LOVE tubes, I love how they sound, how they look, and the history and science behind them is fascinating to me. I just don't like living with something that takes 30-60 minutes to warm up before it sounds it's best, how I have to manually bias them a couple times a month, how their sound is always slowly degrading over time and must be replaced every few years, how dangerous it is to accidentally leave them on, etc., etc. I may eat my words and go back to tubes when the Decware finally arrives, but for now I'm ready for a change. After breakin I'll share my listening impressions with you all.
 

goryu

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Curious why you chose the Atmasphere class d amps when there are better performing class d amps available at 1/5 the cost? Perhaps your love of tubes drove you to find a class d amp with a tube like distortion profile?
 

Zoso69

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Curious why you chose the Atmasphere class d amps when there are better performing class d amps available at 1/5 the cost? Perhaps your love of tubes drove you to find a class d amp with a tube like distortion profile?

Pardon me if I say I detect a hint of superiority and condemnation in your comments sir. I've taken the time to read this thread in its entirety and I'm not interesting in sharpening my sword with anyone here who seems intent on proving themselves right at the cost of civility.

All due respect, you don't know what I paid for them.

Have you actually heard these amps in your rig and can say they sound tube like?

In part I've based my purchase on feedback from those who've demoed the AS-D's, the Orchards, and the VTV's, and preferred the AS-D's. I also have a lot of respect for Mr. Karsten, who's been at this game for close to 50 years. His reputation for producing exceptional instruments, with many happy customers around the world also played apart in my choice. My expertise in reading graphs and interpreting measurements may be lacking (compared to most folks on this forum) however I am a musician, and I feel an affinity with audio manufacturers/designers who practice the art of music making, Mr. Karsten and Eric Alexander (Tekton) included.

Happy Listening.
 

BDWoody

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His reputation for producing exceptional instruments, with many happy customers around the world also played apart in my choice.

He makes instruments? I thought he made gear.

I am a musician, and I feel an affinity with audio manufacturers/designers who practice the art of music making

They make music too?

That's a pretty romantic take on electronics.
 

goryu

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First, being right and being civil are not mutually exclusive.

No, I don't know what you paid. I am basing my assumption on the MSRP of $5400 which I have seen quoted on line in several places.

I am basing my assumption of their tube like sound from comments made by the manufacturer.

Most on this forum prefer to let the instruments on the recording make the music, not their audio equipment. Regardless, I hope you like and enjoy your purchase. To each his own.
 

HarmonicTHD

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After waiting 12 months for a Decware Zen 25th Anniversary amp, and at least another 6 months wait time left, and my 12 month old Willsenton R8 red-plating on me after only 10 months of use (with upgraded Psvane EL34's) I decided to put my order in for a pair of AtmaSphere Class D's today. I LOVE tubes, I love how they sound, how they look, and the history and science behind them is fascinating to me. I just don't like living with something that takes 30-60 minutes to warm up before it sounds it's best, how I have to manually bias them a couple times a month, how their sound is always slowly degrading over time and must be replaced every few years, how dangerous it is to accidentally leave them on, etc., etc. I may eat my words and go back to tubes when the Decware finally arrives, but for now I'm ready for a change. After breakin I'll share my listening impressions with you all.
As you probably did some prior reading of this forum you might have noticed that individual listening experiences and their description here are not valued highly as they represent one’s individual preference and experience only and are therefore unfit for others to base any purchasing decision on.

I personally don’t make statements on listening tests at least not without a big disclaimer that they were done not level matched and sighted so people can put them in perspective.

And finally audio reproduction is a science not an art as music production is. It therefore adheres to the laws of physics and electricity and these are very very well understood among experts so it is not a mystery nor rocket science.

Happy you like your amp. Nothing wrong with that. The designer apparently made a design choice for which so far no hard evidence was presented that everyone or a majority find it pleasant. The story however nicely differentiates his products from others and that is an advantage for driving sales.
 
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Bob from Florida

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First, being right and being civil are not mutually exclusive.

No, I don't know what you paid. I am basing my assumption on the MSRP of $5400 which I have seen quoted on line in several places.

I am basing my assumption of their tube like sound from comments made by the manufacturer.

Most on this forum prefer to let the instruments on the recording make the music, not their audio equipment. Regardless, I hope you like and enjoy your purchase. To each his own.
You ruffled some feathers with your initial response. The first part of your reply was fine, the last sentence was the "dig". If the part bolded and underlined is omitted there would be no problem. Just an observation.

Goryu: post below
Curious why you chose the Atmasphere class d amps when there are better performing class d amps available at 1/5 the cost? Perhaps your love of tubes drove you to find a class d amp with a tube like distortion profile
 

goryu

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You ruffled some feathers with your initial response. The first part of your reply was fine, the last sentence was the "dig". If the part bolded and underlined is omitted there would be no problem. Just an observation.

Goryu: post below
Curious why you chose the Atmasphere class d amps when there are better performing class d amps available at 1/5 the cost? Perhaps your love of tubes drove you to find a class d amp with a tube like distortion profile

the manufacturer has made numerous comments regarding the distortion profile of this Atmas class d amp to be similar to tube amps. Since the poster made it clear he loves everything about tubes, I couldn't help but wonder if he felt this Atmas class d amp did indeed sound "tube like". Wasn't meant as a "dig", rather an attempt to verify the claims of the manufacturer.
 

atmasphere

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the manufacturer has made numerous comments regarding the distortion profile of this Atmas class d amp to be similar to tube amps. Since the poster made it clear he loves everything about tubes, I couldn't help but wonder if he felt this Atmas class d amp did indeed sound "tube like". Wasn't meant as a "dig", rather an attempt to verify the claims of the manufacturer.
Neither our OTLs or our class D amp were built to sound like tubes. They were built to sound like music and without euphonic colorations.

The problem with the OTLs (sonically) has always been that they are sensitive to the load due to a high output impedance. To really get them to work properly, the load has to be carefully vetted. To this end it does not have to have a flat impedance curve but does have to overall have an impedance that is high enough that FR issues are minimized. The careful vetting is why if you read about our OTLs you will find descriptions such as 'straight wire with gain' and the like.

The class D does not have that problem (the output impedance is measured in milliOhms) and so can demonstrate the same or greater neutrality that is possible with the OTLs and on conventional loads. Since it is also lower distortion overall compared to our OTLs it could be construed that its more neutral as well. Over the last 50 years I've had many people challenge me in person, on the phone or on the net that our OTLs make a prodigious 2nd harmonic (quadratic non-linearity) which is associated with the 'warmth' of tubes and so can't be neutral. But our OTLs under measurement don't produce the 2nd as their primary distortion product; like many solid state amps the 3rd is dominant (cubic non-linearity); amplifier circuits of this type tend to be overall inherently lower distortion. So over the last 5 decades that challenge has been easily met.

Regarding cost: while not as cheap as equipment made in the Asian rim, the class D is less expensive than much of its 'competition'. We're not a large manufacturer even though we've been influential (for example, introduced home audio to balanced line operation which since we did that has become so commonplace that you see it even on equipment made by such middle of the road manufacturers as Topping). Economy of scale and the fact that everything (including the surface mount) is done by hand here in Minnesota simply means its going to cost more. But its less expensive than Technics was with their power amplifier offerings and certainly less expensive than most tube amplifiers in the high end market and is one of our least expensive products. As I've mentioned to you before, if we were to use anyone else's module we would have a more expensive amplifier; for example with the Hypex module installed the price would easily be $1000 more (keeping in mind we support a dealer network which a lot of newer companies do not).

Personally I hate buying stuff that won't last (when I worked my way thru engineering school I worked as a consumer electronics repair technician and had to work on some truly terrible stuff) and to that end everything we make is built to last and built to be both repairable and update-able. All of our older products are update-able, and to that end when updated they also get a new warranty.

IOW we've always been in for the long haul.
 

fpitas

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Last I saw (I forget where) your tube amps are differential cascode balanced. Goodbye even-order harmonics.
 

goryu

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Regarding cost: while not as cheap as equipment made in the Asian rim, the class D is less expensive than much of its 'competition'.


Not sure what you consider your competition to be but the majority of class d amps available for home audio use are 1/2 to 1/5 the cost of the Atmasphere class d amp while measuring better.
 

atmasphere

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Not sure what you consider your competition to be but the majority of class d amps available for home audio use are 1/2 to 1/5 the cost of the Atmasphere class d amp while measuring better.
We figured if Technics could sell a 150Watt class D for $18,000 that we'd be OK. I saw that amp at AXPONA. Since we've been making tube amplifiers for nearly 50 years we also consider all tube amps to be competition as well. The more tubes we can retire, I think, the better.
Last I saw (I forget where) your tube amps are differential cascode balanced. Goodbye even-order harmonics.
Right. The other bit about that is that distortion is compounded less from stage to stage. So the higher ordered harmonics fall off at a faster rate as the order of the harmonic is increased.
 

goryu

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We figured if Technics could sell a 150Watt class D for $18,000 that we'd be OK. I saw that amp at AXPONA. Since we've been making tube amplifiers for nearly 50 years we also consider all tube amps to be competition as well. The more tubes we can retire, I think, the better.
That a rather novel pricing mechanism that I don't think I have ever heard before. Kind of like a new car manufacturer charging $400,000 for their new sports car because they saw a $600,000 Ferrari, lol. That's fine but would seem a hard sell when there are a few dozen other sports cars on the market that outperform the $400,000 model for $100,000. Most manufacturers use a more rationale pricing structure based on a variety of relevant factors including parts and materials, labor, r&d, etc.
 

DonH56

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I think jumping from Ralph's comment about the price of Technics to saying that is his justification for his pricing structure is too large a leap. IMO the competition is other high-end amplifiers, many of which start around $10k and go into the $100k+ range. I have not found Ralph to be irrational after many years of reading his online comments on various fora and a private conversation or two.
 

goryu

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I think jumping from Ralph's comment about the price of Technics to saying that is his justification for his pricing structure is too large a leap. IMO the competition is other high-end amplifiers, many of which start around $10k and go into the $100k+ range. I have not found Ralph to be irrational after many years of reading his online comments on various fora and a private conversation or two.


I should hope so yet from his answer it seemed a reasonable analogy.

I suppose one must define "high end amplifier". I would like to think performance enters into the definition and that there is some correlation between price and performance. When I see various class d amps with modules by Hypex, Purifi, or Orchard, among others, selling for as little as 1/5 the price of the Atmas amp, yet having superior performance, I wonder exactly what "high end" might mean.
 
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