I've tried a lot of different amps over the years I've been with this audio hobby. Tried all types of Class A, AB, D solid state amps, and various tube amp configurations.
I have noticed a general improvement over time with Class D amps. Most of the earlier ones from the mid 2000's up to the early 2010's did not sound very good to me. The one exception was the Yamaha MX-D1. That unit was ahead of it's time.
The last Class D amp I owned was the Primare A34.2's in mono. Good sound, but not great.
The switching amplifier approach to me has a lot of potential going for it. I am a fan of a lightweight amp that can provide a lot of power. The large and heavy SS offerings from well known manufactures sound very good, but always sounded a bit hi-fi like more than live music.
Then, in 2017, came across a Devialet setup, and wow, what a huge leap forward in sound quality. Started digging into why they sound as good as they do, and found out that they are not a true Class D amp per se. Rather, the voltage is handled from a Class A section, while the current is supplied from a class D switching section.
The advantages of this approach are obvious. The Devialet is the only switching amp that does not have to have brick-wall filtering for ultrasonic noise. I suspect that is why the treble sounds as good as it does with these.
There are numerous other technical innovations with the Devialet approach, but the biggest one to me is the Analog Digital Hybrid (ADH) amp design. I would have thought that by now someone else would have come up with a different version that employs this approach. Granted, it is likely not easy, but it seems like that the Class D designs would migrate towards this approach.
So the question is: Are there any other designers working on a ADH approach of their own?
I have noticed a general improvement over time with Class D amps. Most of the earlier ones from the mid 2000's up to the early 2010's did not sound very good to me. The one exception was the Yamaha MX-D1. That unit was ahead of it's time.
The last Class D amp I owned was the Primare A34.2's in mono. Good sound, but not great.
The switching amplifier approach to me has a lot of potential going for it. I am a fan of a lightweight amp that can provide a lot of power. The large and heavy SS offerings from well known manufactures sound very good, but always sounded a bit hi-fi like more than live music.
Then, in 2017, came across a Devialet setup, and wow, what a huge leap forward in sound quality. Started digging into why they sound as good as they do, and found out that they are not a true Class D amp per se. Rather, the voltage is handled from a Class A section, while the current is supplied from a class D switching section.
The advantages of this approach are obvious. The Devialet is the only switching amp that does not have to have brick-wall filtering for ultrasonic noise. I suspect that is why the treble sounds as good as it does with these.
There are numerous other technical innovations with the Devialet approach, but the biggest one to me is the Analog Digital Hybrid (ADH) amp design. I would have thought that by now someone else would have come up with a different version that employs this approach. Granted, it is likely not easy, but it seems like that the Class D designs would migrate towards this approach.
So the question is: Are there any other designers working on a ADH approach of their own?
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I don't think there any other implementations of amplifier technology with the Class A voltage and Class D current is available besides the Devialet.
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A standard class d amp is class a input anyway from a pre amp.
As for output filtering, if they don't bother with it then are probably breaking EMC rules.
As for output filtering, if they don't bother with it then are probably breaking EMC rules.
The Devialet ADH is not strictly Class D amp.
Here is a link explaining how the ADH works:
http://www.dynamicaudio.jp/file/110125/201101DevialetWhitePaper.pdf
Here is an explanation regarding the filtering:
" Conventional class-D amplifiers suffer from high levels of ultrasonic switching noise riding on their outputs, which mandate use of a hefty low-pass filter between the output stage and the speaker terminals. In the D-Premier, there is no LC filter on the class-D amplifier's output; instead, the analog amplifier provides a very wide-bandwidth correction signal that cancels the ultrasonic switching noise that would otherwise be present.
Read more at Devialet D-Premier D/A integrated amplifier | Stereophile.com
Here is a link explaining how the ADH works:
http://www.dynamicaudio.jp/file/110125/201101DevialetWhitePaper.pdf
Here is an explanation regarding the filtering:
" Conventional class-D amplifiers suffer from high levels of ultrasonic switching noise riding on their outputs, which mandate use of a hefty low-pass filter between the output stage and the speaker terminals. In the D-Premier, there is no LC filter on the class-D amplifier's output; instead, the analog amplifier provides a very wide-bandwidth correction signal that cancels the ultrasonic switching noise that would otherwise be present.
Read more at Devialet D-Premier D/A integrated amplifier | Stereophile.com
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2009 Devialet US 7,545,212
2002 Korea US 6,396,933
1980 Vanderkooy and Lipshitz "Feedforward Error Correction in Power Amplifiers" (JAES, february) :
2002 Korea US 6,396,933
1980 Vanderkooy and Lipshitz "Feedforward Error Correction in Power Amplifiers" (JAES, february) :
Heard several Devialet amps. IMO cannot compare soundwise to similarly priced linear amps. Typical lifestyle product for the i-phone generation. Saves the planet too 🙂 They had rather ridiculous speakers too.
Have not heard their speakers, but IMO, Devialet Expert/Expert Pro amps sound a LOT better than the vast majority of linear amps. The Speaker Active Matching function works very well with Dynaudio speakers.
Almost all reviewers (even ones to only love tubes) have ranked Devialet as among the best sounding amps out there. They are WAY ahead of any class D amp I've heard, which is why I was wondering if other manufactures are looking into coming up with their own version of this approach.
Almost all reviewers (even ones to only love tubes) have ranked Devialet as among the best sounding amps out there. They are WAY ahead of any class D amp I've heard, which is why I was wondering if other manufactures are looking into coming up with their own version of this approach.
I understand about current dumping and feed forward. However, still haven't provided an example of any other manufacturer who is doing this.
Class D amplifiers do not use brick wall filtering. Typically they use 2nd order.
I guess the real question should be is it necessary? When you see the level of performance Hypex ncore achieves and now the improved purifi version?
The Devialet design is not a class D amp per se. It's actually an analog amp with a switching current souuce controlled by the class A analog section.
The reason that this should be pursued is overall sound quality. Not everyone tagrees that the Hypex amps are great sounding. The Devialet amps I've heard sound better than the Hypex amps I've heard. (YMMV).
Horses for courses.
The reason that this should be pursued is overall sound quality. Not everyone tagrees that the Hypex amps are great sounding. The Devialet amps I've heard sound better than the Hypex amps I've heard. (YMMV).
Horses for courses.
Well no one has heard the purifi amplifiers yet and class D amplifiers are analogue too anyway.
Yeah, I don't understand why there's so much talk about "digital" class D.
Must've been some marketing hype thing after a round of tequila shots during a brainstorm for marketing class D amps - "Digital is the fjutjah!" Crowd goes: "Yeeeeeeeaaaahhhhhhh! WOHOOOOOO!"
Must've been some marketing hype thing after a round of tequila shots during a brainstorm for marketing class D amps - "Digital is the fjutjah!" Crowd goes: "Yeeeeeeeaaaahhhhhhh! WOHOOOOOO!"
Hi
first page of the white paper
can you explain:
Current is following the voltage at he given load R. Why is the current rising at the top of the voltage? i remember that the maximal "event" is at the "zero crossing"
chris
Attachments
That refers to the offline convertor. It uses a stage of Power Factor Correction. Note reference to 50/60Hz.
Conceptually it is not really all that. Without referring to the patent documents you end up with something similar to that pictured in the attachment.
In respect of patents they seem to have been granted in the US but have fallen over in the EU. This is not unusual.
The rest is just a few sums and the implementation. Post the schematics, pcb, gerbers, BOM and pick and place when your done.
Thanks.
In respect of patents they seem to have been granted in the US but have fallen over in the EU. This is not unusual.
The rest is just a few sums and the implementation. Post the schematics, pcb, gerbers, BOM and pick and place when your done.
Thanks.
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