Class A or Class D solid-state amplifiers (modern designs)

I would think it's very possible given some great designers out there. 

I personally prefer some Class D to some class A. And some A/B to A.  I currently use Class A/B in my Luxman 507ux and there is no way you could convince me to change to another amp based on the class alone.

Trying to label the value and quality of sound from an amplifier based on the class of the design is not useful.  Class A gets everyone's juices flowing due to the massive iron, heat and power consumption but it by no means makes it more desirable to an individual listener.

If you are able, perhaps make your way to Axpona in April where you will be able to audition a variety of many of the amps currently available and perhaps engage in meaningful social intercourse with the designers.

Even within Class D there are different technologies and designs which you have the opportunity to learn about in between now and zen.

I recognise perhaps two or three purveyors of Class D in that link. There maybe more that I don’t recognise.

You will pay a premium in TCO for a good power guzzling Class A amp. No need these days IMHO. So many practical and affordable and great sounding Class Ds in various kinds of integrated devices.  Class D is where it’s at these days and in the future.  Pick some and listen for yourself. Also consider features and practicality if that matters to you.

Lots of great Class D out there now.

Bel Canto.

Cyrus

AVM

NAD (okay)

Rogue

Just to name a few.

If I were in the market for a new amp, I'd definitely be looking at Atma-Sphere's new GaN class D monoblocks.  If there's anyone who will do class D justice, it's Ralph Karsten.  If they really give his tube amps a run for their money, then his class D might be very high level performers, and they aren't terribly expensive at $~5-6K.  For 2 channel, I've only owned one class D, the NAD C388.  It was very neutral, albeit a bit "dry" sounding in the treble, and perhaps a bit anemic in the midrange.  I don't think all class D is like that though.  It's all in the implementation, I have no doubt that some class D out there sound fantastic, I just have no interest in it at this point in the game.   

What is TCO?

TCO is total cost of ownership--I'm guessing he means power bill.

I haven’t heard these, and the size and price kinda makes me wonder, but AbSound gives them a product of the year award. The size is amazing. I am tempted to try a pair.

Orchard Audio Starkrimson Monoblock Power Amplifier

$1500/pr.

While virtually all Class D amplifiers use off-the-shelf output modules, the diminutive Starkrimson is built from a proprietary circuit topology of Orchard Audio’s own design. The Starkrimson features gallium nitride (GaN) transistors rather than silicon devices, which allow the switching stage to operate at a super-fast 800kHz, almost three times faster than conventional switching stages. This leads to fewer switching artifacts, lower THD, and higher SNR. With 150W into 8 ohms on tap, the Starkrimson yielded a remarkably transparent soundstage and a spacious presentation. The musical tapestry was vibrant with transients unleashed to their full dynamic potential. What also endeared it to reviewer Dick Olsher was its ability to scale dynamic peaks without changing its tonal character. This was coupled with stunning resolution of complex passages, which left DO thinking that this should not be happening with a $1500-per-stereo-pair amplifier. The Starkrimson sounds like a high-definition Class A amplifier, and surely offers a glimpse into the future of Class D amplification. An absolute must-audition, and our Budget Product of the Year.

Absolute Sound POY

Trying to label the value and quality of sound from an amplifier based on the class of the design is not useful. 

Totally this. Without knowing your system and budget, it's also difficult to make any suggestions. 

Let’s compare and contrast. Which one is technically better?

Here's what you're up against: distortion. Sure, class A does not have crossover distortion. Neither does class D.  The main thing you're dealing with is IMD and harmonic distortion.

Class A amps make both. They are class A to try to minimize that by being in the most linear portion of the operating curve of the output device (whether tube or transistor). But they will make distortion and unless the circuit is designed to be zero feedback there will have to be loop negative feedback to get the distortion into acceptable bounds.

That's where you get into trouble. Back in the 1970s and 80s, the semiconductors needed to actually be able to run the kind of feedback you need didn't exist. We had to wait until the 1990s for that.

If you're thinking that an entire generation of audiophiles grew up with amps that sound bright and harsh you are correct.

The issue is something called Gain Bandwidth Product. You need a lot lot of it! GBP supports the operation of feedback, and to have it support feedback at 10KHz you need more than was possible before sometime in the 1990s. What happens if there isn't enough GBP is the feedback value decreases at higher frequencies- resulting in higher distortion.

This is why the 1KHz harmonic distortion figure tells you little about the amp. What is more important is distortion vs frequency- it should not rise across the audio band, otherwise the amp will have higher distortion at higher frequencies, and this will translate directly into 'harsh and bright' since our ears convert distortion into tonality.

In addition to the semiconductors needed you also need the design. And the will to create it. That took until the 2000s...

As a result, us older audiophiles have been hearing 'harsh and bright' in solid state designs for decades on at this point. That is literally the reason why there are still tube amps around!

If you've been digging deep, you may have realized this isn't a class A vs class AB thing- both classes of operation have can have this issue.

Class D offers a way around this problem.

In a regular amp, if you try to put a lot of feedback in the design you run a risk of the amp being unstable and prone to oscillation unless the feedback loop is very carefully designed, and maybe even then. The reason is there are frequency poles in every amplifier design and they cause phase shift at high frequencies (often outside the audio band). At some frequency the phase shift is so severe that the feedback becomes positive rather than negative- and so the amp oscillates.

In technical/engineering terms this condition is described as 'the phase margin of the amplifier being exceeded'.

In a class D amp you can put a lot of feedback in the design, with the expectation that it will do exactly this. The oscillation is then used as the switching frequency, killing two birds with one stone.

At this point you can have enough GBP that the distortion remains constant at all frequencies, and the distortion normally caused by the application of feedback can also be cleaned up by the simple fact of so much feedback available. You really need to have 35dB or more of feedback to really allow feedback to work right- less than that and it contributes distortion of its own.

This is very difficult to do in a class A or AB amp, although there are a few examples.

That is why some class D designs can easily keep up with class A designs (and FWIW, I've been working with class A amplifier designs for nearly 50 years, if that means anything...).

My experience with SS, tube, and Class D amps over the years is consistent with what @atmasphere said about the nature of the various technologies over time and how that translates into good sound. I started with Class D amps over 10 years ago and it’s Class D all the way at this point for me. Tubes are fun but pretty much over that.

Jeff Rowland was asked a question similar to this a few years ago and basically replied that it's what a designer does with the technology that counts as opposed to one classification being necessarily better than another. 

I am reading this with great interest.  To date, we have not heard a class D amplifier that competes in sound quality.  We are open to hear something that comes close but not yet to our ears.

Happy Listening.

@bigkidz  when you say "we" have not heard a class D amplifier that competes in SQ who are "we"‽ 

@rsf507 - Vu Jade Audio come to our listening room in Northern New Jersey and bring whatever you want to compare.

Happy Listening

LSA Voyager GAN 350 wpc class D is a kick ass amplifier.  I have had multiple highly regarded class A amps and tube amps.  Not yet heard other GAN class D amps..

Let’s get more specific. Which specific class-D power amplifiers compete favorably with the best amplifiers by, say, Audio Research (tube) or McIntosh (tube and/or solid state) or Pass Labs (solid state)? 

I was more curious about the differences, good and bad between class A and D. Assuming that we are talking about amps that were designed for the best performance at their price range, it is a closer race to me about which I prefer. In fact, it matters as well about the amp matching the system to begin with, as I am finding out. In the best combinations that I have to offer in my system, each seems to hold its own. There may have been little competition years ago, but the gap is quickly narrowing. It makes me envy those who have the opportunity to own multiple systems.

FWIW, I just built a class D amp designed by Pete Millet, as well as another type of class D amp designed by Peter Nelson IIRC. Each of them sound different. And different sounding still is my class A amp designed and built by John Dee, formerly from Sudgen Audio. I just feel fortunate to have had the experience.

I'm very, very happy with my VTV Purifi monoblocks (the 1ET400A, not the Eigentakt). They easily bested my Parasound A21+, and cost 33% less.

@goheelz 

Specifically, we are referring to amps like the Merrill Audio Element 116

Merrill Audio - Element 116 Power Amplifier Monoblocks

the AGD Audio Gran Vivace

AGD Gran Vivace Monoblock · AGD Productions

the Nuprime Evolution One

The NuPrime Evo One Mono Amplifiers - Review & First Listening Session - SONIC UNITY

the Technics SE-R1

Technics SE-R1 Stereo Power Amplifier – AudioCubes.com

the Theta Digital Prometheus

Prometheus | Theta Digital

to name a few.

Take a listen when you get a chance an let us know what you think.

If I were looking for a new amp, I would be looking at Mola Mola monoblocks.

This is the only current amplifier that I have heard that left that feeling of that is special with me. Not sure what class it is but I know to me it was special! With the continuous increase in use of the internet there are very few brick and mortar stores left around here where top end equipment can be heard but this set of amplifier s I heard and really loved. 

Re comment above by atmasphere I can understand one of the reasons why my class A/B monoblocs sound so good - they use zero feedback and run very high into class A (400w each at idle). BAT VK655SE's.

You aren’t going to find better measured performance than a pair of Hypex NC400 Monoblocks.

Perhaps forget about 'technical performance' and configuration.  By 'quality' I presume OP means sound quality.

That's what all of us are looking for, but it cannot be an absolute - each of us has different tastes in sound reproduction.

So I suggest OP  just goes and listens to a range of amps of many configurations and takes the ones he likes best.

Check out the new Topping PA5 Class D amp. $349! Clips at 110wpc@8ohms with 1% distortion. Uses advanced circuitry and has an input level control. Ranks just below the Benchmark AHB2 in SINAD at 1/10 the price! 

TCO is total cost of ownership--I'm guessing he means power bill.

TCO for class A should include the cost of back surgery.

Has anybody had the chance to listen to LSA Voyager and Starkrimson and Hypex NC400?

Hi, about 10 years ago I owned a class D integrated from nuforce. on the long run I was not happy with it (too dry, a lack of soul) and I sayed to myself: never again class D! but that is foolish. things have changed very much. a few years now a class A preamp is working together with a class d power-amp from a little company in poland named acuhorn. it is a joyfull combo and I am pretty shure it is hard to beat in this price-category. I was very skeptical, but because of the money-back-guarantee I ordered one acuhorn rate-amplifier and he is still making music in my living room every single day.

+1 for the LSA Voyager GaN 350.

It is very chameleon like. Lovely oldies like Ella and Louie, Leonard Cohen sound full bodied rich and in the room. Lessor recordings sound, well, Lessor. Great value MSRP $3000, a veritable bargain compared to many class A or A/B amps whose MSRP are multiples

Sound improved considerably by replacing stock footers with Nobsound springs @ ~ $35/4. Now under all my kit, including speakers

Ck out the Jeff Rowland Design Model 125.

My previous amps were all class A mono blocks from Krell and BAT, then I switched to PS Audio M1200 and couldn’t be happier. They sounded great and are cheaper than my previous amps. 

another +1 for the LSA Voyager GaN 350

My friend asked for a recommendation to replace his Cambridge amplifier, traded it in for the LSA Voyager and thank goodness it was so much better.

I'll most likely go to GaN myself, just going to let designers play with it some more. I read with interest on the Atmosphere monos but my speakers are a little thirsty, and I'm running 2 x 400watt (not that I run them at 100%) at the mo.

Bel Canto e One REF501S is very nice class d and very affordable.

See if you can find an Audio Research DS225 or DS450.  Class D, but their own design - not just ICE modules in a different box.

To date, we have not heard a class D amplifier that competes in sound quality.  We are open to hear something that comes close but not yet to our ears.

I have. FWIW class D amps vary at least as much in sound as tube amps do.

In other words, could you have equal technical performance and quality in a Class D amp?

@jackhifiguy by what measure would we consider equal “technical performance” and “quality”?

Actually, the 70s were the Spec Wars.  Objectivism ruled and high negative feedback gave vanishingly low THD and IM numbers.  However, the resulting sound quality got worse, not better.  TIM distortion was discovered, feedback was dialed back, and the importance of listening was once again proved.

Anyone remember the Leach amp, designed by Marshall Leach?  Another young amp designer to emerge at this time was Nelson Pass.  His Threshold CAS amps were the result of a design exercise in minimizing the need for feedback by optimizing the circuit's inherent linearity.  While he was already producing STASIS amps, the CAS line brought his work into a more affordable range.  In many respects, they're the progenitors of First Watt.

@atmasphere  Are you showing these at Axpona?

@atmasphere besides your class D amps what others do you feel compete?

Thanks

I would suspect that a good salesman would not claim that others are close or better.

But I have also heard nothing but good about Ralph’s work.

There is Purifi and Benchmark that are generally well regarded amps in the Class-D space.

Or… personally… I would only be looking at those three for class-D HiFi amps.

FYI…Benchmark is not a class D amp. It’s a whole different animal. 

@bigkidz

My previous post answers your question. Why do you want Ralph to advertise for other people? Would you go to GM and ask them who else makes good trucks?

I have some really nice Class A amps. Though my fav amp is still the cheaper non-Class A Benchmark AHB2. I just wish it had more power, though in Mono configuration it is high powered for speakers above 2 Ohms. It has that clean Class A sound and is very smooth. I feel it is just the most crystal clean sound I have heard from any amp.

The stock LSA Voyager GAN 350, mentioned a few times above, is good but after the very low-cost mods by EVS it sounded a lot like the AHB2, my highest compliant for an amp. I sold the Voyager since I liked the AHB2 a little more. I kind of wish I kept it as a backup.

As posted above the AHB2 is not Class D.

Class D Orchard Audio Ultra Amplifier. No other will do for me. 

Thank You to all for the insight. Goes to show that my friend was right. This is easily the best audiophile forum on the web.

I have been listening to the Coda #16 with it’s first 100 watts of class A for almost a year now and recently brought in AGD Audion mono blocks. The Coda, to me is the pinnacle of class A goodness. I love the dynamic power. The AGD mono’s are right there with amazing speed and dynamic force of their own. I continue to switch between the two and right now I am leaning toward the AGD as my keepers. Not to mention the AGD is almost half the price of the Coda. So the Coda might be for sale soon.

I’m surprised no one mentions SPEC CORP, outstanding amplifiers. Another may well be LFD I suspect, who have recently turned their hand to class D.