Atma-Sphere Class D Mono blocks

JSA

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Dec 20, 2020
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Hi all. I had the opportunity to demo these amps in my system for a week comparing them to my Coincident Frankenstein 300B monoblocks. Note that my system is bi-amplified so the application we are talking about here is 300Hz - 20kHz so I can not give input on low frequency performance. I thoughts the Atma-Sphere-D was quite good. Very smooth in the midrange with extended non fatiguing highs. To me it sounds like a really good EL34 amp but dead center on the warm to cool spectrum. Reminded me a lot of the First-Watt-F7 bur with plenty of power. While the AS-D did not dethrone the 300B's in my system, I think many will find the AS-D to be a solution to tubes in normal full range systems.
Thanks a lot for this update. Let's see how it will compare to my Wavac MD805m monos.
 

Tuckers

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I've had them for about three months now. They took quite a while to fully burn in. Compared to the Purifi based stereo amp, Ralph's monos are a few steps up in transparency, neutrality, depth and width. They are real bass champs in my system, going deeper and with more control. The highs are very clear and extended. They reveal more instrument tonality and detail, more musical information, while still being neutral.

They have prompted me to work some more on my digital front end, as they revealed more issues with noise etc. I also got a Denafrips Athena preamp to use (I was going directly from my DAC before). This is has been a good decision as well.
 

JSA

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Dec 20, 2020
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Thanks to Ocean Aletheia from Belle Musique (Paris/France – European distributor of Atmasphere gear) I was privileged to be one of the first customers in Europe to test Ralph’s Atmasphere class D monoblocks in my own system/room. Thank You Ocean for arranging this!

Atmasphere Class D monos are a very intriguing piece of equipment. This is the first time that I have come across class D amps that truly remind me of all the top qualities of tube amps. In my system these were placed between Lampi Pacific and Usher Be-10 DMD speakers.
I am not a great reviewer when it comes to sharing my listening experience, however I would say that the most striking thing is how even the sound is across entire spectrum. Second thing is that most complex passages are effortlessly played with very good pace and rhythm (especially noticeably with classical orchestra and multiple instruments). Third thing (this you can find in some other class D amps as well) is that the background is very quiet/dark which means a lot of micro information is very well audible and clearly presented, soundstage is large and positioning of instruments/performers is very precise.

Regarding the build, I really like the front panels – they are silver in color but depending on the light they seem sometimes pale gold in color – which in my case (golden color Pacific) is just perfect.

Does it mean I will keep Atmasphere in my system? It was a tough choice, but I am still too addicted to my Wavac 805 SET monos. However, I think it says a lot about sound signature of Atmasphere amps that I had to take a serious consideration to make a final choice of keeping my current amps.

I wanted to say once again thanks a lot to you Ocean for making it possible to try Atmasphere class D in my own system.
Seems like audiophiles will part into two groups going forward :cool:: those who have already converted to class D and those that will become converts in not too distant future ;)

Great product Ralph!
 

Tuckers

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Certainly the Wavac's at 3X the price and using those glorious 805 tubes are some stiff competition! That the Class D's did so well in comparison paint them in a very favorable light!
 

morricab

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Apr 25, 2014
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Thanks to Ocean Aletheia from Belle Musique (Paris/France – European distributor of Atmasphere gear) I was privileged to be one of the first customers in Europe to test Ralph’s Atmasphere class D monoblocks in my own system/room. Thank You Ocean for arranging this!

Atmasphere Class D monos are a very intriguing piece of equipment. This is the first time that I have come across class D amps that truly remind me of all the top qualities of tube amps. In my system these were placed between Lampi Pacific and Usher Be-10 DMD speakers.
I am not a great reviewer when it comes to sharing my listening experience, however I would say that the most striking thing is how even the sound is across entire spectrum. Second thing is that most complex passages are effortlessly played with very good pace and rhythm (especially noticeably with classical orchestra and multiple instruments). Third thing (this you can find in some other class D amps as well) is that the background is very quiet/dark which means a lot of micro information is very well audible and clearly presented, soundstage is large and positioning of instruments/performers is very precise.

Regarding the build, I really like the front panels – they are silver in color but depending on the light they seem sometimes pale gold in color – which in my case (golden color Pacific) is just perfect.

Does it mean I will keep Atmasphere in my system? It was a tough choice, but I am still too addicted to my Wavac 805 SET monos. However, I think it says a lot about sound signature of Atmasphere amps that I had to take a serious consideration to make a final choice of keeping my current amps.

I wanted to say once again thanks a lot to you Ocean for making it possible to try Atmasphere class D in my own system.
Seems like audiophiles will part into two groups going forward :cool:: those who have already converted to class D and those that will become converts in not too distant future ;)

Great product Ralph!
What were the main differences that prompted you to keep your WAVAC amp?
 

Hear Here

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Feb 14, 2020
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Portsmouth, UK
Seems like audiophiles will part into two groups going forward :cool:: those who have already converted to class D and those that will become converts in not too distant future ;)
That certainly should be how things evolve, but there is a third group - the “ostriches”! These are the guys who will never consider Class D, despite their obvious advantages - they won't even do what you have bravely done – keep an open mind and arrange a home demo.

Some still decry "digital" in all its forms, but I suspect in short time they will have as much difficulty finding new non-Class D kit as they do finding film for their non-digital cameras! ;)
 
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the sound of Tao

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That certainly should be how things evolve, but there is a third group - the “ostriches”! These are the guys who will never consider Class D, despite their obvious advantages - they won't even do what you have bravely done – keep an open mind and arrange a home demo.

Some still decry "digital" in all its forms, but I suspect in short time they will have as much difficulty finding new non-Class D kit as they do finding film for their non-digital cameras! ;)
Your amp obviously has a sound you are very comfortable with… that’s great, we all have our own preferences… but calling people osteriches or inferring others are not being ‘brave’ enough :rolleyes: to fail to organise a home demo based on someone else’s preferences is well just a bit awkward.

There are people who love various kinds of SS or tube type amps… but the idea that others are osteriches for not necessarily agreeing with your choices might be more that they just don’t like someone else’s sound and would rather stick their heads in the sand.
 
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Atmasphere

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Thanks to Ocean Aletheia from Belle Musique (Paris/France – European distributor of Atmasphere gear) I was privileged to be one of the first customers in Europe to test Ralph’s Atmasphere class D monoblocks in my own system/room. Thank You Ocean for arranging this!

Atmasphere Class D monos are a very intriguing piece of equipment. This is the first time that I have come across class D amps that truly remind me of all the top qualities of tube amps. In my system these were placed between Lampi Pacific and Usher Be-10 DMD speakers.
I am not a great reviewer when it comes to sharing my listening experience, however I would say that the most striking thing is how even the sound is across entire spectrum. Second thing is that most complex passages are effortlessly played with very good pace and rhythm (especially noticeably with classical orchestra and multiple instruments). Third thing (this you can find in some other class D amps as well) is that the background is very quiet/dark which means a lot of micro information is very well audible and clearly presented, soundstage is large and positioning of instruments/performers is very precise.

Regarding the build, I really like the front panels – they are silver in color but depending on the light they seem sometimes pale gold in color – which in my case (golden color Pacific) is just perfect.

Does it mean I will keep Atmasphere in my system? It was a tough choice, but I am still too addicted to my Wavac 805 SET monos. However, I think it says a lot about sound signature of Atmasphere amps that I had to take a serious consideration to make a final choice of keeping my current amps.

I wanted to say once again thanks a lot to you Ocean for making it possible to try Atmasphere class D in my own system.
Seems like audiophiles will part into two groups going forward :cool:: those who have already converted to class D and those that will become converts in not too distant future ;)

Great product Ralph!
Thanks for your comments!

From all the feedback we have at this point, the class D clearly needs break-in time. We don't have a good handle on it but feedback suggests about 250 hours. It might sound a bit stilted prior to that! Also, we have several reports that they sound better if left on. Since they only draw about 5 Watts at idle, this is actually practical in some cases. I don't do it myself.

WRT to comparing directly to SETs, one of the problems you have is that loudspeakers meant to work well with SETs (which have a high output impedance) are built to sound right when used with an amp of high output impedance. We've been making amps like that for decades so I know how this can be an issue, particularly in the bass where the speaker may or may not have box resonance (such as my Classic Audio Loudspeakers, which employ bass reflex enclosures; 98dB but flat to 20Hz). For more information on this see Voltage vs Power paradigms

Many speakers meant for SETs and the like have level controls. If I were to make a comparison between an SET and the class D, I would use pink noise and a spectrum analysis of the room (easily done with apps for smartphones these days) to ahead of time figure out where the level controls need to be set to optimize the speaker for the amplifier (those controls are meant to allow the speaker to be adjusted to the voltage response of the amplifier, since that is an unknown with zero feedback amps). Then between comparisons readjust the controls so the speaker is working with the current amp under audition.

I'm sure you get what this is about, for example I somewhat doubt you would try to run your SET on Magnaplanars. The class D at any rate isn't going to be as romantic as a zero feedback tube amp, even if it has the same distortion profile, simply because it has so much less distortion overall!
 
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morricab

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That certainly should be how things evolve, but there is a third group - the “ostriches”! These are the guys who will never consider Class D, despite their obvious advantages - they won't even do what you have bravely done – keep an open mind and arrange a home demo.

Some still decry "digital" in all its forms, but I suspect in short time they will have as much difficulty finding new non-Class D kit as they do finding film for their non-digital cameras! ;)
Having owned 3 different classD amps and auditioned at least a dozen others, I can say thanks, but no thanks. I told Ralph I would happily audition a pair but the purchase first pre-requisite for something I would likely return was a no go for me being in Europe. However, knowing WAVAC the response above tells me my intuition was correct.
 

JSA

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Dec 20, 2020
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What were the main differences that prompted you to keep your WAVAC amp?
I would say that Wavac is a bit less neutral, but it might also be that I am just used to my Wavac sound.
So my evaluation is far more subjective than what I like to think of myself :cool:
 

morricab

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Apr 25, 2014
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Thanks for your comments!

From all the feedback we have at this point, the class D clearly needs break-in time. We don't have a good handle on it but feedback suggests about 250 hours. It might sound a bit stilted prior to that! Also, we have several reports that they sound better if left on. Since they only draw about 5 Watts at idle, this is actually practical in some cases. I don't do it myself.

WRT to comparing directly to SETs, one of the problems you have is that loudspeakers meant to work well with SETs (which have a high output impedance) are built to sound right when used with an amp of high output impedance. We've been making amps like that for decades so I know how this can be an issue, particularly in the bass where the speaker may or may not have box resonance (such as my Classic Audio Loudspeakers, which employ bass reflex enclosures; 98dB but flat to 20Hz). For more information on this see Voltage vs Power paradigms

Many speakers meant for SETs and the like have level controls. If I were to make a comparison between an SET and the class D, I would use pink noise and a spectrum analysis of the room (easily done with apps for smartphones these days) to ahead of time figure out where the level controls need to be set to optimize the speaker for the amplifier (those controls are meant to allow the speaker to be adjusted to the voltage response of the amplifier, since that is an unknown with zero feedback amps). Then between comparisons readjust the controls so the speaker is working with the current amp under audition.

I'm sure you get what this is about, for example I somewhat doubt you would try to run your SET on Magnaplanars. The class D at any rate isn't going to be as romantic as a zero feedback tube amp, even if it has the same distortion profile, simply because it has so much less distortion overall!
And it’s distortion profile is totally different ;)
 

morricab

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I would say that Wavac is a bit less neutral, but it might also be that I am just used to my Wavac sound.
So my evaluation is far more subjective than what I like to think of myself :cool:
Please a bit more detail…I doubt it is just you are more used to it.
 

Atmasphere

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And it’s distortion profile is totally different ;)
Not as much as you might think!

I have to assume that with any SET based system, there is a fair amount of optimization that has occurred. For example with any Altec, EV or JBL horn system you have to set the level controls for the midrange and tweeter. If comparing between an SET and the class D the correct setting will be different on those controls because the voltage response of the two amps is entirely different. Where you have less control over this issue is in the bass- so its likely that the SET will have a bit more bass on that account alone- and that will add to the sense of 'warmth'.

So you do have to be careful when doing comparisons like this- its not fair if the SET is placed on a speaker it simply can't drive as a gross example.
 

Hear Here

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Feb 14, 2020
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the idea that others are osteriches for not necessarily agreeing with your choices might be more that they just don’t like someone else’s sound and would rather stick their heads in the sand.
Tao - I think you may be deliberately missing the point!

If a Class A user (or tube amp user) looks impartially at the notion of moving to Class D and takes the trouble to include one or two Class D amps in their home demo sessions and still prefers the sound of A, AB or tube, then that's fair enough.

However there are undoubtedly many ostriches who simply won't consider Class D and won't even audition them. This may be an opinion based on listening to a Tripath or similar 20 year old design, or it may be the thought of leaving the "Class A Club" and letting down his Class A chums who have been harping on with anti-Class D jibes at those who HAVE bothered to give them a try - these are the ostriches.

I used tube SETs for about 17 years, but thought it was time to consider a move to SS. I home auditioned 12 amps of Class A, AB and D from numerous brands, some well-known (Mark Levinson, Accuphase, etc) and some less so (Valvet, Bakoon, etc) on the basis that I’d only switch if I could get as good or better sound from SS. I was expecting a Class A to be the best with my horn speakers, but the Class D Purifi technology pipped the Class A ones – and at a much better price too.

If, 10 years ago someone had suggested I could improve on my SETs with an SS amp and I'd dismissed this without even trying SS, I'd have been happy to have been described as an ostrich!
 

morricab

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Not as much as you might think!

I have to assume that with any SET based system, there is a fair amount of optimization that has occurred. For example with any Altec, EV or JBL horn system you have to set the level controls for the midrange and tweeter. If comparing between an SET and the class D the correct setting will be different on those controls because the voltage response of the two amps is entirely different. Where you have less control over this issue is in the bass- so its likely that the SET will have a bit more bass on that account alone- and that will add to the sense of 'warmth'.

So you do have to be careful when doing comparisons like this- its not fair if the SET is placed on a speaker it simply can't drive as a gross example.
My horns don’t have level controls
 

the sound of Tao

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Tao - I think you may be deliberately missing the point!

If a Class A user (or tube amp user) looks impartially at the notion of moving to Class D and takes the trouble to include one or two Class D amps in their home demo sessions and still prefers the sound of A, AB or tube, then that's fair enough.

However there are undoubtedly many ostriches who simply won't consider Class D and won't even audition them. This may be an opinion based on listening to a Tripath or similar 20 year old design, or it may be the thought of leaving the "Class A Club" and letting down his Class A chums who have been harping on with anti-Class D jibes at those who HAVE bothered to give them a try - these are the ostriches.

I used tube SETs for about 17 years, but thought it was time to consider a move to SS. I home auditioned 12 amps of Class A, AB and D from numerous brands, some well-known (Mark Levinson, Accuphase, etc) and some less so (Valvet, Bakoon, etc) on the basis that I’d only switch if I could get as good or better sound from SS. I was expecting a Class A to be the best with my horn speakers, but the Class D Purifi technology pipped the Class A ones – and at a much better price too.

If, 10 years ago someone had suggested I could improve on my SETs with an SS amp and I'd dismissed this without even trying SS, I'd have been happy to have been described as an ostrich!
Maybe it’s just that we are looking for different qualities and having different beliefs about where we are going, differing sensitivities, aims and benchmarks… preference is perhaps simply about that.

The idea that people should feel compelled to rush out and trial the pathway of others is not what realising what diversity in perception is all about. No-one should be viewed in an offhand or dismissive way because they have their own view of their own pathway.
 

morricab

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Maybe it’s just that we are looking for different qualities and having different beliefs about where we are going, differing sensitivities, aims and benchmarks… preference is perhaps simply about that.

The idea that people should feel compelled to rush out and trial the pathway of others is not what realising what diversity in perception is all about. No-one should be viewed in an offhand or dismissive way because they have their own view of their own pathway.
At least not for audio… ;)
 

Atmasphere

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My horns don’t have level controls
That's unfortunate! What that means is that if you use a different amp with a different output impedance (for example a 211-based amp as opposed to a type 45) the frequency response will be different, unless the impedance curve of the speaker is very flat. So you would get a tonal anomaly unless you use an amp very similar to what the designer was using.

That is why traditional horns like Altec, JBL, Electro Voice and others typically had level controls. Without them it would be difficult to do comparisons if the audition candidate was a very different amp.
 

morricab

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That's unfortunate! What that means is that if you use a different amp with a different output impedance (for example a 211-based amp as opposed to a type 45) the frequency response will be different, unless the impedance curve of the speaker is very flat. So you would get a tonal anomaly unless you use an amp very similar to what the designer was using.

That is why traditional horns like Altec, JBL, Electro Voice and others typically had level controls. Without them it would be difficult to do comparisons if the audition candidate was a very different amp.
It is quite high and flat (never below 6 ohms)
 

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