Atma-Sphere Class D GaNFET Amplifiers

[kevinh]

So AT&T did studies in the 1960 when transistor amps were being developed as to what sorts of distortion the ear/brain system reacts to. IIRC they found that 2nd harmonic was mostly ignored by the brain, 3rd harmonic was identified as providing a fuller sound and higher harmonics especially odd higher order harmonics were annoying to the brain. @nd and 3rd

If a recording is produced with transparent electronics then playback with equipment works very well so the 122 sinad is great. However many recordings (mostly older) were produced using equipment with poor Slew Rates and copious amounts of high (with 741 op amps for example) order odd harmonics. These recordings when played back through new hardware with distortion with inaudible distortion can sound very harsh. So if some equipment in the playback chain has some 2nd and 3rd harmonic distortion to mask the nasties then they experience for the end user can be more pleasurable.

This is why Tube amps can be so popular. Many artist I and other enjoyed produced performances we love on horrible equipment. Some companies cater to these customers. The Atma-Sphere products has a reputation of lasting forever rather like MacIntosh products.

 

[goryu]

This is why Tube amps can be so popular. Many artist I and other enjoyed produced performances we love on horrible equipment. Some companies cater to these customers. The Atma-Sphere products has a reputation of lasting forever rather like MacIntosh products.

No doubt some like certain distortion profiles- I would rather my equipment adds as little as possible.

I can understand and appreciate long lasting products but in a market segment where the technology is still evolving, I doubt anyone really believes they will be using their present class d amp for the next 30 years. With digital music storage, streaming, etc. now becoming the thing, it seems reasonable to expect class d amp tech to take a few more twists and turns.

 

[kevinh]

No doubt some like certain distortion profiles- I would rather my equipment adds as little as possible.

I can understand and appreciate long lasting products but in a market segment where the technology is still evolving, I doubt anyone really believes they will be using their present class d amp for the next 30 years. With digital music storage, streaming, etc. now becoming the thing, it seems reasonable to expect class d amp tech to take a few more twists and turns.

In the case of this company people have used their products for 30 yrs +. YMMV. Choice of equipment can also be dictated by the music you listen to. I listen to a lot of music that was recorded in the age of 741 op amps so a amp like this one with some 2nd and 3rd harmonic has a lot of appeal to me compared to something like the new HYPEX which is a great amp I like to build whenever I can. but might not be the best fit for the music I listen to much of which was recorded in the mid 60's through the mid 800's.

 

[antcollinet]

In the case of this company people have used their products for 30 yrs +. YMMV. Choice of equipment can also be dictated by the music you listen to. I listen to a lot of music that was recorded in the age of 741 op amps so a amp like this one with some 2nd and 3rd harmonic has a lot of appeal to me compared to something like the new HYPEX which is a great amp I like to build whenever I can. but might not be the best fit for the music I listen to much of which was recorded in the mid 60's through the mid 800's.

On the other hand - if I believe I need 2nd/3rd harmonics added to enjoy old muic** I can simply add an effects box, or some DSP to my system to do that for me, rather than buy an amp with it baked in. Then I don't have to put up with it for music that doesn't need it.


**I don't.

 

[atmasphere]

No doubt some like certain distortion profiles- I would rather my equipment adds as little as possible.

Something we agree on.
FWIW, as pointed out earlier, the 2nd harmonic is so innocuous to the ear/brain system that you don't know its there. Put another way, when listening, no-one ever objects to it. Knowing it is there however puts you in danger of confirmation bias.

So AT&T did studies in the 1960 when transistor amps were being developed as to what sorts of distortion the ear/brain system reacts to. IIRC they found that 2nd harmonic was mostly ignored by the brain, 3rd harmonic was identified as providing a fuller sound and higher harmonics especially odd higher order harmonics were annoying to the brain. @nd and 3rd

If you know of a link to this study I'm very interested. I remember reading about this when I was in engineering school, but IIRC it was GE, not At&T. I'm glad someone besides myself remembers something about this.

 

[sarumbear]

At least the engineering is excellent.

How did you surmise that? Or do you mean mechanical engineering as seen from the photographs?

 

[sarumbear]

@atmasphere what do you say people, like me, who say make the amplifier as clean as possible and add a circuit to dial in the distortion you want along with a by-pass switch?

Do you disagree with the term High Fidelity?

 

[sarumbear]

EPC's GaN isn't that great, Bruno should check out GaN Systems: https://gansystems.com/wp-content/uploads/2022/03/GS-065-060-3-B-DS-Rev-221004.pdf
Perfect for high power applications (apart from cost...).

Which he did and rejected because of cost. Read his words earlier in this thread.

 

[kevinh]

Something we agree on.
FWIW, as pointed out earlier, the 2nd harmonic is so innocuous to the ear/brain system that you don't know its there. Put another way, when listening, no-one ever objects to it. Knowing it is there however puts you in danger of confirmation bias.


If you know of a link to this study I'm very interested. I remember reading about this when I was in engineering school, but IIRC it was GE, not At&T. I'm glad someone besides myself remembers something about this.

I used the term AT&T but it was actually Bell Albs, Murry Hill NJ the link is long since gone, I saw it in the early 1980's IIRC. I am sure GE and RCA did similar studies.

 

[kevinh]

On the other hand - if I believe I need 2nd/3rd harmonics added to enjoy old muic** I can simply add an effects box, or some DSP to my system to do that for me, rather than buy an amp with it baked in. Then I don't have to put up with it for music that doesn't need it.


**I don't.

That is fine for you I was responding to a person who attacked a company for design choices. Although I don't feel the distortion in the spec is audible. Back to arguing about the number of angles that can fit on the head of a pin again.

 

[SIY]

How did you surmise that? Or do you mean mechanical engineering as seen from the photographs?

I’m very familiar with the circuit he uses.

 

[Ken Tajalli]

Something we agree on.
FWIW, as pointed out earlier, the 2nd harmonic is so innocuous to the ear/brain system that you don't know its there. Put another way, when listening, no-one ever objects to it. Knowing it is there however puts you in danger of confirmation bias. ...I'm glad someone besides myself remembers something about this.

I also remember, that my professor (professor Sutcliffe at Salford university) back in 1981, mentioned the same to me.
He was a keen designer and a Hifi buff, if memory serves.
If he is still with us, I owe him a hell of lot, that I didn't know at the time.

 

[sarumbear]

I’m very familiar with the circuit he uses.

Understood.

 

[atmasphere]

@atmasphere what do you say people, like me, who say make the amplifier as clean as possible and add a circuit to dial in the distortion you want along with a by-pass switch?

Do you disagree with the term High Fidelity?

I say to such people that we have always made our circuits as low distortion as we could get. Adding more does not make sense to me.

I'm not sure how I would disagree with a term, unless it was some sort of oxymoron like 'honest government' or 'Microsoft Works'.

 

[sarumbear]

I say to such people that we have always made our circuits as low distortion as we could get. Adding more does not make sense to me.

I misinterpreted your wax lyrical about some distortion doesn’t matter as we don’t hear it, as your amplifier to have noticeably larger distortion than similar amplifiers on the market and no, I’m not expecting it to compare with Purifi only.

I will leave you in peace and wait to see the rest results.

 

[kipman725]

Which he did and rejected because of cost. Read his words earlier in this thread.

rude....

Bruno: True. On the other hand, silicon is doing the same. More recent devices are getting frightfully close to GaN. Sadly they only come in SMD packages that require fairly expensive methods to get the heat out. Like most GaN devices. It looks terribly ancient, but the good old TO220 package is still a neat compromise in terms of performance for the price.

I disagree on these points. I don't disagree that it's cheaper to make a Si amp.

 

[Gorgonzola]

So AT&T did studies in the 1960 when transistor amps were being developed as to what sorts of distortion the ear/brain system reacts to. IIRC they found that 2nd harmonic was mostly ignored by the brain, 3rd harmonic was identified as providing a fuller sound and higher harmonics especially odd higher order harmonics were annoying to the brain. @nd and 3rd

If a recording is produced with transparent electronics then playback with equipment works very well so the 122 sinad is great. However many recordings (mostly older) were produced using equipment with poor Slew Rates and copious amounts of high (with 741 op amps for example) order odd harmonics. These recordings when played back through new hardware with distortion with inaudible distortion can sound very harsh. So if some equipment in the playback chain has some 2nd and 3rd harmonic distortion to mask the nasties then they experience for the end user can be more pleasurable.

This is why Tube amps can be so popular. Many artist I and other enjoyed produced performances we love on horrible equipment. Some companies cater to these customers. The Atma-Sphere products has a reputation of lasting forever rather like MacIntosh products.

I'm glad you mentioned the deficiencies of some, mostly older, recordings. I have noticed that many audiophiles discuss the merits of playback equipment endlessly but rarely mention that some records just don't sound very good while other sound great. That was something that I noticed going 'way back to the pre-digital era: record quality, IMO, is single most significant factor in listening enjoyment, 'way ahead of minor differences in equipment performance.

I thoroughly agree you and @atmasphere about is that 2nd & 3rd order harmonics are not only benign but also serve to mask more unpleasant distortions. What is clear to me, and what you re-enforce is the masking works not only to mitigate the nasties in equipment but also in recordings. Yes, so for example tube preamps were popular ahead of solid state power amps because their 2nd/3rd order harmonics masked the higher order harmonics of the s/s amps.

To dwell a bit on recording quality, many (older) audiophiles rhapsodize on the recording quality of 'Mercury Living Presence' recordings. This praise is warrant but applies mainly to one aspect of the recordings: the capture of the ambience of the recording venues. Many contemporary recordings, (not all), are better than MLP recordings in all respects but certainly in terms of the "cleanest" of their sound.

BTW, something Deutsche Grammophon, (e.g.), employing its many microphones systematically failed to do was capture any sense of the performance space, (and which its eventual, "Original Image Bit Processing" mitigated to only some extent).

 

[fpitas]

So AT&T did studies in the 1960 when transistor amps were being developed as to what sorts of distortion the ear/brain system reacts to. IIRC they found that 2nd harmonic was mostly ignored by the brain, 3rd harmonic was identified as providing a fuller sound and higher harmonics especially odd higher order harmonics were annoying to the brain. @nd and 3rd

If a recording is produced with transparent electronics then playback with equipment works very well so the 122 sinad is great. However many recordings (mostly older) were produced using equipment with poor Slew Rates and copious amounts of high (with 741 op amps for example) order odd harmonics. These recordings when played back through new hardware with distortion with inaudible distortion can sound very harsh. So if some equipment in the playback chain has some 2nd and 3rd harmonic distortion to mask the nasties then they experience for the end user can be more pleasurable.

This is why Tube amps can be so popular. Many artist I and other enjoyed produced performances we love on horrible equipment. Some companies cater to these customers. The Atma-Sphere products has a reputation of lasting forever rather like MacIntosh products.

I have no trouble believing that, at least provisionally. But I doubt anyone can hear the distortion this amp makes. Once you get down to below the 0.1% level, the vast majority of people can't hear the distortion. Now on the other hand if you crank up a SET with 2% distortion at normal listening levels...

 

[kevinh]

I have no trouble believing that, at least provisionally. But I doubt anyone can hear the distortion this amp makes. Once you get down to below the 0.1% level, the vast majority of people can't hear the distortion. Now on the other hand if you crank up a SET with 2% distortion at normal listening levels...

I agree past a certain point there is NO difference that I certainly with my 70 yr old ears will hear.

I'm glad you mentioned the deficiencies of some, mostly older, recordings. I have noticed that many audiophiles discuss the merits of playback equipment endlessly but rarely mention that some records just don't sound very good while other sound great. That was something that I noticed going 'way back to the pre-digital era: record quality, IMO, is single most significant factor in listening enjoyment, 'way ahead of minor differences in equipment performance.

I thoroughly agree you and @atmasphere about is that 2nd & 3rd order harmonics are not only benign but also serve to mask more unpleasant distortions. What is clear to me, and what you re-enforce is the masking works not only to mitigate the nasties in equipment but also in recordings. Yes, so for example tube preamps were popular ahead of solid state power amps because their 2nd/3rd order harmonics masked the higher order harmonics of the s/s amps.

To dwell a bit on recording quality, many (older) audiophiles rhapsodize on the recording quality of 'Mercury Living Presence' recordings. This praise is warrant but applies mainly to one aspect of the recordings: the capture of the ambience of the recording venues. Many contemporary recordings, (not all), are better than MLP recordings in all respects but certainly in terms of the "cleanest" of their sound.

BTW, something Deutsche Grammophon, (e.g.), employing its many microphones systematically failed to do was capture any sense of the performance space, (and which its eventual, "Original Image Bit Processing" mitigated to only some extent).

That has been an issue for me for years. I always want performance over 'audiophile' recordings. I currently enjoy live you tube recordings of performances (Grateful Dead, Jef PAt Metheny, John McLaughlin ect. those are most pristime recordings but the music is for me.

 

[kevinh]

On the other hand - if I believe I need 2nd/3rd harmonics added to enjoy old muic** I can simply add an effects box, or some DSP to my system to do that for me, rather than buy an amp with it baked in. Then I don't have to put up with it for music that doesn't need it.


**I don't.

A link for a box to add 2nd/3rd harmonic to a recordings I would be interested.