Does it make sense in using a Class D amplifier with 24/192

Dear All,

does it make sense to use class D amplifiers when playing example 24/192 files as the class D amps then to be limited in bandwidth.
I looked at the hypex units units which are -10dB at 100kHz.
Not that I can hear 100kHz, but my ribbon tweeters reach 40kHz.

Would it make more sense to use less bandwidth limited class A, A/B amps?
Or should I just stick to 24 bit and do not care much about 44kHz, 88 or even 192?



There is another reasons for higher source sample rates besides frequency response. Analog reconstruction without artifacts is allot tougher when the source is 44.1. Some would say impossible.


Hi Hjalmar,

The best guide is your own ears. Have a listen to different resolution material and see what you think.

No human can hear even 40 kHz, so you shouldn’t be at all worried about any equipment being down 10 dB at 100 Hz. It is actually an extremely good bandwidth measure.

You may be confusing bandwidth of the audio spectrum (usually 20Hz to 20kHz) with sampling rate (also measured in kHz). They are different things. The sampling rate is how often the digital sampler measures a value for the music. Higher rates mean finer resolution in time.

The two are related in that a higher sampling rate enables higher frequencies to be sampled. You need a sampling rate at least twice as fast as the highest frequency audio signal you want to sample.


In addition, one should acknowledge that the amplifier, in the vast majority of cases and regardless of whether it is Class A or D, it playing the analog signal, not a digital one. So, one should only be concerned with how well it does that and separate it from concerns about how one gets the best analog signal from a source.

Thanks, I was mixing up things.
Clear now

Depends on the amp. There is some really nice Class D amps available. I use Class D Wyred4Sound gear. I’ve been very happy with my equipment. It sounds great and runs cool.

Technical specs don’t always lend themselves to how something actually sounds. Work with your dealer and find what sounds best to YOUR ears.

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I predict that in 5-15 years, the best new amplifier designs will look an awful lot more like Class D than Class A.

Class A was pushing the boundaries with high-efficiency speakers in many applications, but with newer low-efficiency models, it is just a non-starter. Class D designs become the logical answer.

First: when I say “Class D”, I’m really referring to the whole family of “digital” or “switching” amplifiers. There are a few common design variants. This also includes things like “Class T” (Tripath) amplifiers, and hybrid designs that use Class D to produce most of the power, and another amplifier type mixed in to improve sound quality.

Class A amps really can’t get too much better than they are. You can keep working on power filtering and hunting for components with slightly tighter tolerances, but these improvements are really really tiny compared to the current state of the art.

Look at the difference between a Class-D amp 20 years ago–crappy car stereos and boom boxes–and the stuff that Hypex, NAD, Bluesound, and Devialet are putting out based around Class-D today. They’ve moved the state of the art by leaps and bounds, but Class A/AB have seen comparatively minor progress. Little tweaks, a % here and there. That is just a sign that those technologies are mature.

There is big funding available for developing Class-D amps–because we need them everywhere. Car stereos, Bluetooth/wireless speakers, Soundbars, mass-market integrated speaker products from Bluesound and Sonos. As the technology matures, it is “trickling up” to higher quality applications. And this is possible because of the huge R+D dollars available to work on this stuff.

Class A/AB research happens in small HiFi companies with limited budgets and team size. The AV Receiver companies dabble in it sometimes, but it is not their focus. Mature companies tweak designs that they’ve been shipping for decades to make them a little bit better every few years. There isn’t a whole lot of large-scale R+D funding going into the old methods.

There’s another force pushing towards Class D–Hoffman’s Iron Laws say that you can only have two of: “small enclosure”, “efficient speaker”, “good bass extension”.

Aside from the set of people willing to put big stacks of HiFi kit in their homes, everyone else wants lots of compact speakers with good bass extension. That tells us that these speakers must be lower-efficiency designs.

So what you used to do with 20W, Class A, and a high efficiency speaker, is now something you might do with 50-60W, Class D, and a low efficiency speaker. Class A was pushing the boundaries with high-efficiency speakers in many applications, but with newer low-efficiency transducers needed to meet consumer demand for small, bass-heavy speakers, it is just a non-starter.

Another trend with smaller powered speakers is to use a digital crossover–which means you need 2-4 amplifiers per speaker instead of one. This places even more pressure on the amplifiers to be small, relatively cool, and energy efficient–more reason for class D.

And that need for more power is a real problem for technologies like Class A and AB–which consume too much power and radiate too much heat to be embedded in a small low-efficiency speaker.

All of this is forcing Class D technology to improve at a rapid pace as the market for these products is huge.

Then there is the energy efficiency legislation. This is continually making it harder to produce Class A designs. Class A stuff likes to be kept “warm”–so it doesn’t get along with the EU low power standby rules. And it consumes more power all the time, which makes it likely to see collateral damage as further environmental legislation plays out.

So, we’ve got politics, R+D dollars, market preferences for small, bass-heavy speakers, and concerns about energy efficiency. And they are all motivating Class D technology to become really mature and achieve very high quality.

So, when you see a company using modern, intensively engineered Class D stuff–like what Bluesound, NAD, Hypex, Devialet are doing–it’s worth giving it a listen before discounting it because it’s class D–and if you don’t like it, give it another shot in a few years–because this technology is going to continue to improve quickly. These people are taking the state of the art in a fast-growing little corner of the world and applying that research with quality as a top priority. They are making sure that the global move towards Class D style amplifiers does not leave audiophiles behind by actually working on making it practical for us on an ongoing basis.

This is already a long post, but I wanted to point out three other areas where the same kinds of trends are happening.

One is sigma-delta architecture chipdacs. They started as a way to reduce cost in CD players, but have grown into the dominant DAC technology. Today, the best chipdacs have technical specs that meet or exceed the best discrete DACs, at a lower cost, in a smaller package that emits less heat. ESS DACs go into ultra-high-volume applications like mobile phones and are used in reference grade studio applications, too. They have so many more R+D dollars to work with, and plenty of incentive to work on cost, energy, and quality in parallel–and they are doing a fantastic job.

Resistor Ladders are a lot like class A–small improvements from year to year coming out of small, modestly funded boutique manufacturers. Lots of focus on high-tolerance components and careful assembly–since that’s where the remaining minor improvement potential lies.

Another example is switching-mode power supplies. Outside of specialty applications, linear power supplies are nearly extinct–whereas 30-50 years ago they were all over the place. EU efficiency regulations are making it harder to manufacture and sell them–because like Class-A amps they are very inefficient and radiate a lot of heat.

R+D dollars are pouring into making Switching Supplies smaller, more efficient, and (electrically) cleaner. There’s not much of a reason to focus on a clean power feed for a mobile phone charger, but switching power supplies are going to displace linear power supplies in all of the specialty applications–scientific, medical, test equipment, audio–over the coming years, too. And this will force higher quality options to be developed and for their prices to drop.

Yet another example is DSP. At first, it was bad equalizers, crappy “bass boost” features and stuff like that, and it was associated with quality bottlenecks. But over the past decades, we’ve seen digital crossovers completely change the shape of most inexpensive speakers, and many expensive ones too (Meridian, Dynaudio, KEF, Steinway-Lyngdorf, …). And of course technologies like RAAT are popping up to bring the audio stream to the hardware DSP stage digitally to avoid the analog->digital->analog conversion common in some older architectures.

We think of Dirac as room correction suitable for our highest quality rooms, but a big part of their business is automotive DSP–because making high quality sound in a car is very difficult, but there is a huge market for it. The research that they are putting into automotive applications is going to make it possible to do great things in weirder rooms with smaller speakers too. Dolby ATMOS is also working on the “making lots of small speakers placed carelessly sound great in a weird space” problem. So we will see more flexibility and convenience at a very high quality level as these things mature.

In Closing

This is basically all good news for any audiophile willing to be open-minded to the new approaches. We’re going to get better sound quality in more rooms with less heat, cost, and power consumption, because the powers that be are pushing everything that way.

For an audiophile’s main listening room, I expect there will still be a lot of people who prefer a big stack of discrete components that work like a small space heater. Nothing wrong with that–those systems sound spectacular. I think they will become less popular over time, though.

The main reason I took the time to write this up is because I want to encourage open-mindedness and respect towards some of these newer methods. It’s easy to hear about an awful Class-D amp and write off the whole category, or upgrade to a linear power supply and write off switching supplies forever–but given the pace of change here, those are not necessarily good conclusions to hold for a long time.

There are companies putting all of these technologies into very high quality applications, and really, those are the companies that are making sure that we will have great options in the future.


I think the advantage is it can be fed directly with a PCM signal without having a DAC in the front end.

The only downside is switching noise to the speakers; but careful design and better filtering can reduce the noise output.

Not commonly and not likely to become so. All the Class-D amps discussed have analog input.

Those are usually referred to as “Digital Amplifiers”. They are often found in speakers that cost a couple hundred dollars or less. Also an active area for R+D for all of the same reasons above.

But once you get beyond that inexpensive price point, there is almost always a discrete DAC and an analog->analog Class D amplifier.

Thanks for the walk-thru. I’ve been contemplating upping my game with a pair of Wyred4Sound monoblocks.

NAD’s Direct Digital ™ is certainly an implementation of this and an example of something which when done right can sound fantastic.

Yup, absolutely.

Although I don’t understand all of the technical information in this thread, I can say that I’m very pleased with my decision to purchase the NAD M12/M22 combo which has some of the technology described in this article. Streaming MQA files via Roon/Tidal/BluOS is amazing!


That is probably the best reason for choosing the highest (up)sampling frequency.

What is? I do not know what the antecedent is.

If you click on the pic of user, Dr. Tone, Max was replying to, it will bring you to Dr. Tone’s original post.


I’m sorry, I may have clicked the wrong ‘Reply’ button. I had just arrived home after an 800 Km. drive from the Munich High End show :wink:

Thank you Daniel Beyer :+1:

Off to bed now, it’s been five exhausting days…

Amplfiers are analogue voltage devices. Symbols (sequences of digits) are not amplified. D-class does not mean “digital”, quote marks or not. Before getting to switching frequency as a factor for sound quality, one hits many other more relevant limitations. The actual factors in perceived sound quality are in the sequence of importance: ear/brain mechanism, loudspeaker/room system, recording/mastering techniques not related to file types, quality of AD/DA conversion, amplifiers…
Listening in a nice room to “Kind of Blue” playing from a phone via Dragonfly over a 50$ D-class amplifier and 200$ ELAC speakers can be a thorougly satisfying experience. Add good company and a bottle of fine wine
to make it unforgettable.


…or featured in statement amplifiers like the TacT Millennium and 2150 series produced from about 1998 to 2005, famous for their involving sound quality; or as seen in later models from Wadia and NAD, also with a fine sonic reputation. There was/is also TacT’s estranged sibling Lyngdorf.

I believe they all involve computationally converting from source PCM to pulse width modulation at the switching frequency, perhaps with as little as one very high quality inductor between the switched power and the load.

I’m not sure about the other brands, but TacT also did a neat trick which involved reducing the power supply voltage for low volume output, so as to avoid the loss of resolution which would be associated with producing low output purely via digital scaling.