Atma-Sphere Class D Mono blocks

[morricab]

Class D amps don't have jitter; they are not digital. When distortion is kept at a low enough point, the music itself will mask it. It needs to be -100dB or so for that to occur. If its not that low, then lower ordered harmonics (2nd and 3rd) will need to be present to mask the higher orders to prevent brightness and harshness otherwise being present.

'Slicing' isn't a good word here as it does not describe what's going on when feedback is used. 'Cancellation' and 'bifurcation' are better. Cancellation is the part where feedback is able to suppress distortion. Bifurcation is where feedback adds some distortion of its own in the process due to non-linearities at the feedback node. IOW feedback does not 'slice' up distortion to get rid of it.

Crowhurst is correct in stating that the harmonics generated by feedback become part of the noise floor. IME if this is going on, the noise floor cannot be penetrated by the human ear as is possible when the noise floor is actually just hiss (due to how the ear's masking princple operates). Keeping that in mind, the noise floor of most class D amps is a good 10-15dB better than that of a tube amplifier and some are closer to -20dB. Do you see where we're going with this?

"Keeping that in mind, the noise floor of most class D amps is a good 10-15dB better than that of a tube amplifier and some are closer to -20dB. Do you see where we're going with this?"

We just established that you can hear below the noise floor if it is truly noise...so what does it matter if the 'noise" floor of the Class D amp is lower...especially if it is not really noise? I also don't buy that argument because the quietest amps I have had on my horns were some very well made tube amps...I have 110db horn drivers that are very quiet with inexpensive 300B Taiwanese monos.

 

[Gregadd]

ThorL3's Activity - Instructables
350 watt Class D Self oscillating ampliifier

 

[Atmasphere]

Ralph, did your reading comprehension ability drop or you had too much wine? I wasn't saying Class D amps have jitter. I was giving examples of other, seemingly minute, processes that are audible.

A lot of people make the mistake that of class D, the 'D' means digital. So it naturally follows to expect jitter comments. Being out of context I felt that had to be cleared, since it appeared a red herring. Your explanation makes more sense.

I need to be clear about something else: I'm very much of the opinion that the distortion spectra I've been advocating applies to -6dB of full power as well as 1 watt. This is problematic for a lot of amps, including SETs (they tend to sound 'dynamic' if pushed beyond this level; that dynamic character being distortion interacting with the ear brain system and being falsely identified).

FWIW all but one of those amps you linked fail the requirement of not having increasing distortion vs frequency (surprisingly, only the Classe had a reasonably linear distortion vs frequency curve). This means that the 1KHz measurement isn't telling the whole story! I've mentioned quite a lot that if the distortion isn't low enough, its important to have the lower orders mask the higher orders, and this becomes more important above 1KHz.

I do not know exactly where it is that music can mask distortion. But I do know its less than -100dB. Over at ASR I get pushback on that- they seem to think -100dB is fine and I've no idea how they arrived at that. I also get pushback over the idea that distortion is audible in the first place. Personally I feel that when you can measure something you can also hear then its real. The old HH Scott thing from Daniel Recklinghausen.

 

[morricab]

A lot of people make the mistake that of class D, the 'D' means digital. So it naturally follows to expect jitter comments. Being out of context I felt that had to be cleared, since it appeared a red herring. Your explanation makes more sense.

I need to be clear about something else: I'm very much of the opinion that the distortion spectra I've been advocating applies to -6dB of full power as well as 1 watt. This is problematic for a lot of amps, including SETs (they tend to sound 'dynamic' if pushed beyond this level; that dynamic character being distortion interacting with the ear brain system and being falsely identified).

FWIW all but one of those amps you linked fail the requirement of not having increasing distortion vs frequency (surprisingly, only the Classe had a reasonably linear distortion vs frequency curve). This means that the 1KHz measurement isn't telling the whole story! I've mentioned quite a lot that if the distortion isn't low enough, its important to have the lower orders mask the higher orders, and this becomes more important above 1KHz.

I do not know exactly where it is that music can mask distortion. But I do know its less than -100dB. Over at ASR I get pushback on that- they seem to think -100dB is fine and I've no idea how they arrived at that. I also get pushback over the idea that distortion is audible in the first place. Personally I feel that when you can measure something you can also hear then its real. The old HH Scott thing from Daniel Recklinghausen.

Tell me what you would expect for the sound of this amp:

SoundStage! Measurements - Einstein Absolute Tune Integrated Amplifier (10/2007)

Totally flat distortion vs. frequency. Slight increase in distortion with increasing power. Only low order harmonics with some tiny (0.00003%) ones above 5th. It is a hybrid but the measurements are extremely clean. (no messiness from the power supply is evident either.)

 

[Atmasphere]

The damping factor vs frequency is telling you something- apparently at higher frequencies the output impedance rises. This suggests that feedback is falling off due to a lack of gain bandwidth product (put another way, the output impedance is rising; I'm doubting that is due to an output coupling capacitor). You can also see this suggested in some of the distortion vs frequency plots. In addition there appears to be a significant 5th harmonic. It would be interesting to see how the distortion measures out at 5KHz and 7KHz where the ear is most sensitive. I suspect this amp sounds a bit bright. How'd I do?

 

[Rob181]

Will the Class D amps run off universal power (i.e. can I use them in Sydney @230v)??

We're using a toroidal power transformer. It is dual primary and rated to 50Hz.

Ralph - for us less educated folk - can your amp be leave your production line ready & able to run in 230v countries such as Europe or Australia

 

[Atmasphere]

Will the Class D amps run off universal power (i.e. can I use them in Sydney @230v)??



Ralph - for us less educated folk - can your amp be leave your production line ready & able to run in 230v countries such as Europe or Australia

No- that requires a switching power supply and to do that properly for an audio power amplifier usually means the SMPS has to be made custom. Most off the shelf supplies have current limiting and other protection mechanisms that make them unsuitable for audio.

 

[Rob181]

No- that requires a switching power supply and to do that properly for an audio power amplifier usually means the SMPS has to be made custom. Most off the shelf supplies have current limiting and other protection mechanisms that make them unsuitable for audio.

I have two amps that use torids for power supply & they are both available in 100/110 & 220/230 volt varieties (one made in Europe & one made in Japan) - so no - a switching power supply is not the only answer - a wound & wired 220/230v torid for the amps is another & as we both know - these are "off the shelf" items - so no custom make is required. It would be a pity to see this amp restricted to US or Japan sales...

 

[ICUToo]

No- that requires a switching power supply and to do that properly for an audio power amplifier usually means the SMPS has to be made custom. Most off the shelf supplies have current limiting and other protection mechanisms that make them unsuitable for audio.

Phew! That's 5.5K you've saved me right there!!

 

[morricab]

The damping factor vs frequency is telling you something- apparently at higher frequencies the output impedance rises. This suggests that feedback is falling off due to a lack of gain bandwidth product (put another way, the output impedance is rising; I'm doubting that is due to an output coupling capacitor). You can also see this suggested in some of the distortion vs frequency plots. In addition there appears to be a significant 5th harmonic. It would be interesting to see how the distortion measures out at 5KHz and 7KHz where the ear is most sensitive. I suspect this amp sounds a bit bright. How'd I do?

I will start by saying the amp is not at all bright. I owned this amp for about a year (it didn't stay too long). I wanted to like it as it is a really beautiful machine and was at a time when my daughter was young and I was a bit concerned about high temperature tube exposure.

I bought the amp because I saw this review, the flat distortion vs. frequency, nothing much above 5th harmonic in the distortion profile (although the 5th is perhaps higher than desirable, it is still pretty low) and of course a tube input stage.

Long story short, it was smooth, it was clean but it was not engaging at all and tonality was not icy but it was not vibrant either... Everything was a bit drab and gray. Not horribly so and it did not commit a lot of the usual SS sins but it was far behind my previous amps (the one before was the KR Audio VA350i, which I had for about 6 years). In effect, the amp was quite understated and boring. It was one of the shortest stints that an amp has had in my system, even though it measures better than most SS amps.

I replaced it with the ambitious and somewhat unique NAT Symbiosis SE, which is a single ended hybrid. This amp had tube input, tube driver and ONE big MOSFET per channel for the output stage (on a huge heatsink). There were two more MOSFETs on huge heatsinks for output stage regulation. It sounded vastly better...once it fully warmed up...and it took a good 2 hours to do that (it weighed over 150lbs). Since I got rid of that amp it has only been SET (I did have a VAC 30/30 mkIII for a while to explore DHT triode Class A PP).

In short, given how radically most SS amps distortion increases with frequency, the Einstein looked promising (also the distortion pattern, while not really SET was more promising than most SS amps as well) but in reality it just sounded "meh" but definitely not bright.

 

[Atmasphere]

I have two amps that use torids for power supply & they are both available in 100/110 & 220/230 volt varieties (one made in Europe & one made in Japan) - so no - a switching power supply is not the only answer - a wound & wired 220/230v torid for the amps is another & as we both know - these are "off the shelf" items - so no custom make is required. It would be a pity to see this amp restricted to US or Japan sales...

That is how our toroidal transformer is set up. But it has to be wired for overseas operation, as opposed to an amp using a switching power supply, which does not have to be rewired for any particular country.

I will start by saying the amp is not at all bright. I owned this amp for about a year (it didn't stay too long). I wanted to like it as it is a really beautiful machine and was at a time when my daughter was young and I was a bit concerned about high temperature tube exposure.

I bought the amp because I saw this review, the flat distortion vs. frequency, nothing much above 5th harmonic in the distortion profile (although the 5th is perhaps higher than desirable, it is still pretty low) and of course a tube input stage.

Long story short, it was smooth, it was clean but it was not engaging at all and tonality was not icy but it was not vibrant either... Everything was a bit drab and gray. Not horribly so and it did not commit a lot of the usual SS sins but it was far behind my previous amps (the one before was the KR Audio VA350i, which I had for about 6 years). In effect, the amp was quite understated and boring. It was one of the shortest stints that an amp has had in my system, even though it measures better than most SS amps.

I replaced it with the ambitious and somewhat unique NAT Symbiosis SE, which is a single ended hybrid. This amp had tube input, tube driver and ONE big MOSFET per channel for the output stage (on a huge heatsink). There were two more MOSFETs on huge heatsinks for output stage regulation. It sounded vastly better...once it fully warmed up...and it took a good 2 hours to do that (it weighed over 150lbs). Since I got rid of that amp it has only been SET (I did have a VAC 30/30 mkIII for a while to explore DHT triode Class A PP).

In short, given how radically most SS amps distortion increases with frequency, the Einstein looked promising (also the distortion pattern, while not really SET was more promising than most SS amps as well) but in reality it just sounded "meh" but definitely not bright.

Thanks- another dot for the data!

 

[Vangelis]

I am using speakers of my own design, open baffle, no crossover, 15 inch full range drivers (25hz to 14khz), and Raven M1 supertweeters with a first order crossover at 16khz. All about 8 ohms and 98db efficient. I have made a custom speaker EQ (to boost the bass on the open baffle) that I implement in Roon and in my media server. Very transparent, fast, wide banded, dynamic, bass does go down to about 25hz in my room. So it really is a full range speaker. Very easy to hear differences between components, cables etc.

I've had the Boazu about three weeks. I love the Boazu's design philosophy. It does have a very pristine and transparent sound, definitely musical. But it also sounds a bit smaller, less dynamic, bass is clear, but doesn't have the power of my purifi. I will need at least another month working with it to get the best out of it before I make any real judgements though. My opinion may change!

I had the Orchard Audio Starkrimson GaN amp in for trial. It did lots of things very well, but I ultimately preferred the Purifi in my system. I felt that the qualities that fell short with it were really a matter of my taste rather than empirical. And I think that a real hi-end audio designer could probably get better performance from GaN, hence my excitement hearing about Ralf's new amp .

The best amps for them has been the Purifi, the First Watt J2 and the Shindo Sinhonia - 40 watt push pull F2a tube amp (I had a full Shindo rig from turntable to amps for a time - miss that!).

Which Purifi amplifier are you using?

 

[Tuckers]

Which Purifi amplifier are you using?

I am using the VTV Purifi amp. Its the standard Purifi board and Hypex power supply but a custom designed Sparkos Input buffer. It is shockingly good for the money. I have also added my small mods which help SMPS noise.

 

[Tuckers]

Well today I purchased the Atma-Sphere Class D Monoblocks. I'll be getting them in the next month. Now I've got to get some matching power cables ready, as I move to monoblocks!

 

[aLLeARS]

Well today I purchased the Atma-Sphere Class D Monoblocks. I'll be getting them in the next month. Now I've got to get some matching power cables ready, as I move to monoblocks!

Good move. I've been using them for about one year now. With 99dB efficient speakers they sound wonderful!
The first watt is sweet, the top end is open and extended and it has that incredible class D control of the woofer.
Give them around 400 hours for complete burn in.
I have found it to be a very transparent sounding amplifier. I also like the mono-block format as it lets you place the amps near the speakers and use very short speaker cables. Running longer balanced interconnects and shorter speaker cables has a sonic advantage.

 

[CKKeung]

Well today I purchased the Atma-Sphere Class D Monoblocks. I'll be getting them in the next month. Now I've got to get some matching power cables ready, as I move to monoblocks!

Hi Tuckers,
Have you got them?
What's your comments about their performance?
Thanks!

 

[Tuckers]

Hi Tuckers,
Have you got them?
What's your comments about their performance?
Thanks!

Unfortunately, they have been waiting on the transformers - supply chain issue. They still expect to get then soon though.

 

[jma6]

Unfortunately, they have been waiting on the transformers - supply chain issue. They still expect to get then soon though.

Did you get them ? How do they sound ?

 

[JSA]

Unfortunately, they have been waiting on the transformers - supply chain issue. They still expect to get then soon though.

Please share your experiences in case you have got already your pair.
I am still awaiting for first pairs to arrive in Europe.
German distributor promised to offer me a demo set for trying at my place, once they arrive (latest estimate is end of November).
I do have high hopes that with Atma-sphere Class D monos, finally we have a valid alternative to tube based equipment.
Let's see.

 

[Tinear1]

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.