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Class D Amplifiers


Ralf11
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I really like Class D. The noise level tends to be immeasurably low. They are the most energy-efficient, and cost-effective. I assembled mine from a kit (ClassDaudio.com). If I were to do so again, I would go for an NCore kit.

 

Some of the earlier designs attenuated some of the high-frequency output, and the significance of this tended to be speaker-impedence dependent. These kinds of problems are now a thing of the past.

 

Nuprime is unusual in that they don't like to use measurements for quality-control, so perhaps it appeals to some people who prefer euphonic distortion.

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I really like Class D. The noise level tends to be immeasurably low. They are the most energy-efficient, and cost-effective. I assembled mine from a kit (ClassDaudio.com). If I were to do so again, I would go for an NCore kit.

 

Some of the earlier designs attenuated some of the high-frequency output, and the significance of this tended to be speaker-impedence dependent. These kinds of problems are now a thing of the past.

 

Nuprime is unusual in that they don't like to use measurements for quality-control, so perhaps it appeals to some people who prefer euphonic distortion.

 

Bases on their THD measurement I don't think I would call it euphoric distortion

 

Ultra-Linear Class A Module (ULCAM) achieves audiophile-quality sound with Class-D’s dynamics, speed and efficiency. Extraordinary result of THD+N lower than 0.0015% and S/N ratio of -130dB for the preamp stage.

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I have auditioned a few Class D amps. I really wanted to find one that I liked. The low power usage and reasonably cool operation are attractive. To date, no luck.

 

I don't find that Class D sounds like tubes, or class a or a/b solid state. Unfortunately, it even sounds less like live music than the other types, as well. Maybe someday. I am certainly open to switching out of the Pass Class A monos, if the right amp came along.

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I have a couple of Pass class A clones I built and I love them, but they have their limitations. The ncores I assembled are seemingly without limitation and I have not gone back to the class A since they were put in my system.

 

Perhaps the word clone is the key word here to their performance ?

I have heard a pair Nelson Pass 150W Class A monoblocks through a >$100K system and I doubt that any Class D, or too many other amplifiers will come close to their performance, especially with the height of the image which very few other monoblocks can equal. A recording such as "The Storm" from a Chesky Hybrid SACD is great at helping to sort out the various amplifiers.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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any thoughts on the sound quality of this design (in general) vs. Class A or AB?

 

It's always specific implementation ultimately versus some global quality like circuit design class. I've heard both Pass and nCore amps sounding great, but you can get nCores for a twentieth the price.

 

Kimo, would be interested in which nCore amps you've had a chance to listen to.

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical to EtherREGEN -> microRendu -> ISO Regen -> Pro-Ject Pre Box S2 DAC -> Spectral DMC-12 & DMA-150 -> Vandersteen 3A Signature.

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I am assuming the class D amplifier is already load invariant. I used to like class D amplifiers until someone pointed out to me what to not like about them, including nCore. Whether it's real and audible is very individual dependent. I think I hear the problems but I may be biased incorrectly and that class D amplifiers actually sound as good as class A/B. One problem is that class D amplifiers can have varying degrees of noise floor modulation but that can be present in a lot of digital sources to begin with. Noise floor modulation adds a bit of edge/hardness/brightness to the music that's a bit unnatural to me. The other problem is that class D amplifiers switch usually at up to 500kHz. So for those who loves DSD or 2xDSD, you're losing transient resolution even though the sources were switching at 2.8MHz or 5.6MHz. Similarly for DACs that upsample say to 768kHz or DAC chips that eventually outputs at 5-bit 11MHz for example, you're then letting the class D amplifier switch at 500kHz. Whether the effect of "down-res" or loss of transient info is audible is another matter. I think so but I know people who'd disagree. I think as long as people are happy with their class D amps, that's all that matters.

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I have auditioned a few Class D amps. I really wanted to find one that I liked. The low power usage and reasonably cool operation are attractive. To date, no luck.

 

I don't find that Class D sounds like tubes, or class a or a/b solid state. Unfortunately, it even sounds less like live music than the other types, as well. Maybe someday. I am certainly open to switching out of the Pass Class A monos, if the right amp came along.

 

If you like (well designed) tube sound NOTHING is comparable. Forget measurements!

 

Even if Alex could chime :)

 

Roch

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Since the article was written a while back, I believe most of these problems are solved in the latest B&O/ICEpower amps or Hypex UcD/nCore amps through extensive feedback. So I don't think the article really applies to modern class D amplifiers. That's also why modern class D amplifiers sound really, really good to begin with.

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If you like (well designed) tube sound NOTHING is comparable.

 

Roch

I find it interesting that the hard line Objective crowd that use Class D amplifiers are those least likely to hear differences between USB cables etc. and don't feel the need for USB Isolators, USB Regens etc. and are also the least likely to hear any advantage between RB CD and 24/192 or DSD.

 

Alex

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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any thoughts on the sound quality of this design (in general) vs. Class A or AB?

 

I understand what you are asking, but there's no way to really classify sound quality. Class D amps can sound very different from each other, just like an A or AB. You just have to try them and see what works best for you. Also, Class D seems to be very polarizing. I haven't heard one I liked enough to buy. If I had to pick the Class D amp I liked the best, it would be the Audio Research 150.2. They called it Class T instead of Class D because they were upset that everyone called them digital amps. But they are Class D.

 

If you live in the US, try The Cable Company. They have class D amps to lend out. I wanted to try some, so they sent me a PS Audio, NuForce, and one other. I think it was a Rogue, but I could be mistaken. If you use them, you don't have to buy one just to hear what it sounds like.

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It's always specific implementation ultimately versus some global quality like circuit design class. I've heard both Pass and nCore amps sounding great, but you can get nCores for a twentieth the price.

 

Kimo, would be interested in which nCore amps you've had a chance to listen to.

 

Jud, I have only heard one pair of Ncore amps, Merrill Thor monos, and not in the house. Thought the Nuprime stuff sounded better. The Thors weren't that cheap either.

 

I believe that the top of the line Ncores from Merrill are about the same price as the Pass monoblocks, which I purchased. If they sound anything like the Thors, they don't really sound much like the Pass boxes.

 

Some amps can sound good at first, but wrong long term. Other amps can sound mediocre, but more right over time. Digital amps can excite, but don't sound "right" to me, at least so far.

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If you like (well designed) tube sound NOTHING is comparable. Forget measurements!

 

Even if Alex could chime :)

 

Roch

 

Owned SETs for a number of years. Also, I really like the Air Tight and Leben push pull amps. I owned a little Leben for some time. It was a nice piece running Mullard EL84s.

 

Now, I am stuck on Class A solid state, which is big hot and expensive, and not made by that many companies. If I ever venture back into tubes, I will probably search out the Air Tight, and likely electrocute myself one day biasing the tubes. Wouldn't have to worry about that with Class D.

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Jud, I have only heard one pair of Ncore amps, Merrill Thor monos, and not in the house. Thought the Nuprime stuff sounded better. The Thors weren't that cheap either.

 

I believe that the top of the line Ncores from Merrill are about the same price as the Pass monoblocks, which I purchased. If they sound anything like the Thors, they don't really sound much like the Pass boxes.

 

Merrill Thor is not nCore, it's UcD. Top of the line Merrill is Veritas which is nCore. The only nCore I've heard is Bel Canto Black. That obviously means I heard the entire digital chain which was not a fair assessment. I liked it a lot. I suspect it doesn't sound as bright/edgy as other class D amplifiers I've heard because it has less noise floor modulation. Not sure.

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Perhaps the word clone is the key word here to their performance ?

I have heard a pair Nelson Pass 150W Class A monoblocks through a >$100K system and I doubt that any Class D, or too many other amplifiers will come close to their performance, especially with the height of the image which very few other monoblocks can equal. A recording such as "The Storm" from a Chesky Hybrid SACD is great at helping to sort out the various amplifiers.[/quote

 

Well those are certainly out of my budget. I should have said Firstwatt clones. I don't think it's that these are clones, I have every reason to believe they perform close to the original Firstwatt products, I just feel they're a little low on power. I am in the process of putting together some higher power Class A amps and will be able to compare those to the ncores.

The Aleph J I have sounds warm and fantastic but just runs out of juice at higher volumes with my insensitive speakers, which is why I'm building some higher power class A amps.

 

I'll report back in a month or so, I'm picking up some parts for the build at Burning Amp next weekend.

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It sounds like none or few are willing to rule out Class D entirely.

 

The article's author makes statements that seem very odd, whether now or 11 years ago.

 

And... Bob Carver made an transistor amp that was comparable to tube sound. (For the record, I own a tube pre-amp and it is hooked to my Sunfire).

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The 2c worth is the new n-Core Class D amps perform excellently. I especially like their speed, tonal range and detail articulation. I don't notice any image size issues at all.

 

I was never really a solid state guy, having owned a range of tube amps, both pre and power over the years. But my new Class D-based system had drawn me in like no other.

 

Of course, the overall sound will be impacted by what you put in front of the amps and what you put behind them (synergy) then it depends on how your overall system deals with your room to give that final piece of magic...

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Crowns' Class D Drive Core's have a following for being very transparent. There is also their I-Tech series with interleaved Class D which is push/push like Class A but you can get 12,000 Watts :-)

 

They've been doing this style of amplification. The K2 series had a good following also.

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