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Class D must read papers and publications

Soren

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You hand waive and generalize a lot, but these explanations are not legitimate to prove your claims.

No one can prove subjective impressions right or wrong.
Even if 100% chooses the same as preferred in an ABX test, this will still not prove them right, that´s just marketing.
To be able to hear the difference is another thing.
What I´m saying is, that you can experience differences in sound, in spite of premium measurements in both cases.
Try it out yourself.
Get an ICEPower 1200AS2 and compare it with i.e. nCore500OEM, and listen if they sound the same or almost.
I did not expect them to sound different, or if I somehow did anyways, then I expected the nCore to be the one of choice.
Btw it is a well known thing, that bridged amplifiers change their sonic character compared to half bridge equivalents.
 

boXem | audio

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No one can prove subjective impressions right or wrong.
Even if 100% chooses the same as preferred in an ABX test, this will still not prove them right, that´s just marketing.
To be able to hear the difference is another thing.
What I´m saying is, that you can experience differences in sound, in spite of premium measurements in both cases.
Try it out yourself.
Get an ICEPower 1200AS2 and compare it with i.e. nCore500OEM, and listen if they sound the same or almost.
I did not expect them to sound different, or if I somehow did anyways, then I expected the nCore to be the one of choice.
Btw it is a well known thing, that bridged amplifiers change their sonic character compared to half bridge equivalents.
Do you have any valuable comment or question about the documents linked by @pma in his first post?
 

VintageFlanker

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Get an ICEPower 1200AS2 and compare it with i.e. nCore500OEM, and listen if they sound the same or almost.
AFAIC, I did not "listened" any difference between 1200AS2 and Ncores.
 

Killingbeans

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But it really should not surprise anyone, that subjective differences occurs in different designs.

Of course not. What I'm mostly interested in is getting a clear picture of whether the subjective impressions comes from the sound of the amps or from other factors.

To be able to hear the difference is another thing.

That's where controlled testing comes in.

Again, I actually really like the idea of differences in how amps sound, but an idea is not a good starting point for defining problems.
 
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Jim Shaw

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Class D? Three observations:

1. The best of them sound really good and measure well. They transfer energy and power to/from most speakers well. They are more efficient, therefore can run cooler and be smaller.

2. Switching amplifiers have been around for about 40 or so years now, first in labs. Class D is not some new upstart technology. But the state of the Class D art is still incrementing forward. Switching speeds keep increasing, rise times keep getting smaller, and feedback and coupling schemes keep evolving. Today's Class D will be a little different than tomorrow's Class D.

3. If you don't understand the technology inside and out, refrain from mouthing an uninformed opinion via some bad design you heard once upon a time, long, long ago. And if you don't want to listen for a long, long time, don't ask a clockmaker what time it is, or an engineer about Class D.

And one more for good measure:
4. Understanding analog technology is fairly trivial compared to understanding switching, much less digital tech. Don't let that make you hate progress.

-Just one engineer's view
 

Abe_W

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No one can prove subjective impressions right or wrong.
Even if 100% chooses the same as preferred in an ABX test, this will still not prove them right, that´s just marketing.
To be able to hear the difference is another thing.
What I´m saying is, that you can experience differences in sound, in spite of premium measurements in both cases.
Try it out yourself.
Get an ICEPower 1200AS2 and compare it with i.e. nCore500OEM, and listen if they sound the same or almost.
I did not expect them to sound different, or if I somehow did anyways, then I expected the nCore to be the one of choice.
Btw it is a well known thing, that bridged amplifiers change their sonic character compared to half bridge equivalents.
You are fighting a pointless fight at the Walmart headquarters in Deafenville. All amps, dacs and maybe speakers too sound the same to these deaf audio scientologists as soon as they start the el primo ABX tests. They will gleefully get their mass produced cheap Chinese smps boards primarily aimed at boosting manufacturer profit margins. These class D connoisseurs are the quintessential Walmart shopper: cheap, utilitarian and sterile.

So, save your breath and let them have their well deserved future.
 
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I found insightful videos on Youtube comparing the PS Audio (Class D) to the Parasound Class A/B amps. This audio store in Canada sells both of them as well as Macintosh. They said the PS Audio was livelier while the Parasound had more meat on the bone. I think this is one of the key differences with Class D amps. They have great bass, don't weigh much and have a very clean neutral sound. However they lack the character that make music more exciting.

I also talked to someone who reviews audio gear on line. He reviewed both the PS Audio M700 and Parasound A21+. He said he prefers the sound and character of the Parasound. , In speaking with a salesman at an audio store, he said one of the reasons Macintosh sells so well besides its look is this reason; 80% of music recorded, regardless of how it was recorded will sound good on a Mac. A good portion of the 80% will sound great on a Mac. This is because of the slightly relaxed sound and smooth mid's. The character helps reduce splashy cymbals, vocals that have too strong ssss, and grating guitar sounds.
 
D

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I would like to open the thread dealing with important publications on class D amplifiers principles, topologies, characteristics and limitations. One of the great sources is the Hypex publications library at

The most explaining and resourceful publication is IMHO the "AES Class D master class" presentation
which explains in detail class D principles and also the main different basic topologies, the hysteresis modulator and the phase shift controlled oscillator. Benefits and limitations of both approaches are explained and it would explain to the reader what he could expect from both approaches.

UcD principle and comparison to hysteresis modulator is also explained in

and NCore improvement over UcD in

and also in

I believe that these publications might help the ASR visitors for better understanding of results of class D reviews here at ASR.

I would be very grateful if @amirm , @BDWoody or @AdamG247 could make this thread sticky, as it links to basic and necessary literature to understanding of class D function and parameters.
----------------------------------------
https://www.cornestech.co.jp/images/uploads/file/products/pdf/oa_product7-4_201503.pdf
Audio Precision white paper "Measuring Switch-mode Power Amplifiers". All the basic measuring methods like THD, THD+N/level, THD+N/frequency, IMD, DIM, noise, damping factor, crosstalk are explained quite in detail. A lot of permanently repeated questions is answered.
Thank you for your hard work with this! Very interesting indeed, and as a class D amplifier owner it’s just great to read about the different implementations. Well done.
 

joeren

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I would like to open the thread dealing with important publications on class D amplifiers principles, topologies, characteristics and limitations. One of the great sources is the Hypex publications library at

The most explaining and resourceful publication is IMHO the "AES Class D master class" presentation
which explains in detail class D principles and also the main different basic topologies, the hysteresis modulator and the phase shift controlled oscillator. Benefits and limitations of both approaches are explained and it would explain to the reader what he could expect from both approaches.

UcD principle and comparison to hysteresis modulator is also explained in

and NCore improvement over UcD in

and also in

I believe that these publications might help the ASR visitors for better understanding of results of class D reviews here at ASR.

I would be very grateful if @amirm , @BDWoody or @AdamG247 could make this thread sticky, as it links to basic and necessary literature to understanding of class D function and parameters.
----------------------------------------
https://www.cornestech.co.jp/images/uploads/file/products/pdf/oa_product7-4_201503.pdf
Audio Precision white paper "Measuring Switch-mode Power Amplifiers". All the basic measuring methods like THD, THD+N/level, THD+N/frequency, IMD, DIM, noise, damping factor, crosstalk are explained quite in detail. A lot of permanently repeated questions is answered.
Here’s an additional source for class D information. An ex-colleague of mine, Dr Michael de Rooij, is in the video at the bottom of the page.
 
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atmasphere

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So the overall distortion of the required external gainstage and the module combined still has superior performance, which eventually couldt be even further enhanced, if someone could create an additional feedback loop around both the external gainstage and the class D amplifier together.
A self oscillating class D (UcD, Hypex, NCore etc.) has a multiple order feedback loop which has to satisfy the oscillation criteria such that the amplifier cannot find other oscillation solutions (different switching frequency) under any conditions. To do this the feedback can't include the input buffer. So this really isn't a thing AFAIK.
 

Kijanki

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Well we have used several different models as reference amplifiers alongside with my old school and very bulky class A amplifier.
I.e we used nCORE 500OEM, ICEPower 1200AS2 to compare the audio experience to our own design.
Compared to ICEPower The nCore has the best measured performance, but the ICEPower is a full bridge design, where the nCore is halfbridge.
This leads to different behavior in the real world. Full bridge will not suffer from power supply pumping, but it will be more noisy, as the noise stems from 2 amplifiers in bridged mode.
They also sound different, all though data should be sufficient for transparency (se datasheets)


Our own design would be a bit more like the nCore, since it is also a halfbridge design, but with much more gain (28dB), and can thus be driven by i.e. a unity gain buffer, or a strong pre-amp directly if wanted.

I do believe in good measured performance, I´ve never heard HI-FI gear with problematic measured performance giving af superior audio experience, but it is also my experience, that you cannot always cook everything down to measurements alone.
Different design principles can also contribute to the final experience, despite they might have almost equal performance in the lab.
The example above with half bridge vs full bridge is just one of theese, they sound different maybe because they are different, but they do not differ that much in the testlab.
Some other class D designs performs very well because of i.e. very low dead-time, this is a very important aspect in class D design.
Excessive dead-time leads directly to distortion, thus dead-time is important, and should be lowered, but this is not easy to do.
First of all insufficient dead-time leads to shoot through in the switching devices and is fatal in milliseconds, very low dead-time rases the risc of excactly that. It also develops excessive heat, if the dead-time is to low, so dead-time has to be sufficient, allowing higher distortion, if you consider reliabillity important.
The solution to this problem is feedback technology, advanced feedback loops of higher order can reduce the distortion stemming from dead-time to very low values, and at the same time reducing stress placed on the switces and adjacent components significantly, thus improving reliabillity.
Also these two ways of reducing distortion sounds different, despite that measured performance indicates that this should not be the case.
In this example one could say, that you have "Clever engineering" vs "Precision engineering".

Low levels of distortion, Zout, noise and any unwanted signals are always preferable, but this will not always result in excactly what you expected.
This is not spooky, but probably just something that doesn´t show significantly in a normal set of measurements, or what do I know, and that is yet to be discored I think.
Noise should not be a factor, since up to final averaging not the voltage but the duty cycle is a quantity of interest. Driving 4 N-Channel Mosfets vs 2 is only matter of inverting logic. At this point time is what matters. Half bridge design have problem of placing half of the supply voltage as Common mode voltage on the speaker terminals. It means that when signal/output is zero speaker terminals show half of the supply voltage vs earth GND. For example, 40V on speaker terminals might still be considered safe (<48V) but I wouldn't like young toddlers next to it.
 

Hipster Doofus

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So it’s Friday and a good one at that….in much of my journey into music listening equipment there is one truth I have learned, and it usually comes around this time of the week. It’s time to forget the battles of data driven this or that. It’s time to forget bits and bytes, linear transparency transmissions that would not only supply inverse reactive current for use in unilateral phase detractors, but would also be capable of automatically synchronizing cardinal grammeters. Such an instrument is the TURBO-STEREOHOPIC IPA by Lagunitas of Petaluma, CA. This product brings reduced normal lotus-o-delta type placed in panendermic semi-boloid slots of the stator, every seventh conductor being connected by a non-reversible tremie pipe to the differential girdle spring on the “up” end of the grammeters.

so chill one up and greatly improve your listening pleasure.


DD34A13F-8B27-46C6-92FF-547BF6A21E70.jpeg
 

Killingbeans

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There's a whole thread just for that here ;):
 
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