Class D: Turns Out it Does Suck!

[GUTB]

Taken second-handed from someone who posted the following from an Absolute Sound Roundtable of master amp designers on class D:

 

Bob Carver
"I built many of them right here in my own laboratory with the thought they could and would fulfill that final promise.... I was never able to build a Class D amplifier that sounded as good as a linear one."

 

John Curl (Parasound, CTC, Vendetta Research, Constellation)
"Some version of hybrid Class A/D looks like the future in optimum audio design."

 

Cyrill Hammer (Soulution Audio)
"If you want to have your product performing at the cutting edge it is not possible with today's known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz."

 

Lew Johnson (Conrad Johnson)
"I tend to think that Class D circuit design is an approach best relegated to producing low-cost, physically manageable multichannel amplifiers where one might accept some compromise in sound quality for the sake of squeezing five, six, or seven 100 watt channels into one moderate-sized package for a budget home-theater installation."

 

Vladimir Shushurin (Lamm Industries)
"No, it is not. And I would like to respond to the second part of this question with an allegory. Any field of human activity defines a number of requirements which, when properly implemented, guarantee a positive outcome. For example, the basic requirement in the army and sports is an able-bodied individual. So, it would be quite natural to concentrate on searching for such an individual (especially as we know where to find him). However, out of the blue we decide to choose a feeble-bodied person who, on top of that, is encumbered by various diseases. Having made this decision (which is a priori improper) we start justifying it to ourselves and others by citing the great state of our medicine, which is capable of curing many ailments."

 

(Savage! -- GUTB)

 

Fumio Ohashi (BAlabo)
"No. Class D can't really be considered for super-high-end performance in its present stage of development, although it can be fine for mid-market products."

 

Nelson Pass (Pass Labs)
"Does a $10 bottle of wine compete with a $100 bottle? Of course it does, and it often wins based on price. Right at the moment Class D designers seem to be still focusing on the objectively measured performance of their amplifiers. I expect that at some point the economics of the marketplace will encourage them to pay more attention to the subjective qualities, and then they will probably play a greater role in the high end."

 

(Most diplomatic -- GUTB)

 

Jürgen Reis (MBL)
"I have worked a lot lately with Class D. Ninety-nine percent of Class D circuits are not competitive with linear circuits. Most Class D sounds sterile. It's tricky to figure out what to do to compensate for that."

 

Thorsten Loesch (iFi - AMR)

"I have yet to hear a pure class D Amp I’d rate above "below average for solid state" (which is not very high performance). In a little update of my classic 'Valve Analogue Stages for DACs' I wrote: "Perhaps more crucially, so called Class D Amplifiers, which have in recent times sprouted up like mushrooms after a warm rain, continue to use the straight two or three level modulation scheme described above. And thus they still require the use of heavy handed noise shaping to attain anything like acceptable 16 Bit Audio performance.The clock frequencies for these amplifiers are usually at 300 KHz to 1MHz in the best cases. That is 3,000 to 10,000 times lower than what is required to attain 16 Bit / 44.1 KHz performance without noise shaping and other forms of signal manipulation! And again, one is baffled and perplexed by the rave reviews many Class D amplifiers receive, as baffled as one was about the late 90s reviews of timeslicing DACs. The best of breed I have auditioned were certainly not bad; however in direct comparison to the best available valve and solid state amplifiers they do not produce a very good sound. Well, at least they offer novelty and the reviewers something to write about other than another (however good sounding) 8 Watt valve amp. Incidentally, the best sounding Class D amps tend to be really low power single chip devices (putting out little more than the 8 watt valve amps), presumably because they are faster AND because they always work near what one might call a full scale, if they would be DACs. On second thought, they of COURSE are DA Converters and where a Class D amplifier accepts analogue input directly it is an A2D converter followed by a power D2A converter! What an insight!?"

 

Mark Levinson

"Interleaving of multiple Class D Amplifiers is potentially a step in the right direction, but does not go far enough.Personally I think that the best option would be something that combines a Class D Amplifier for the heavy lifting with something Class A for fine detail. Probably implemented in the style I did for AMR’s AM-77 "Jikoda" Style. In this case both of the circuits involved can operate fully open loop. In many ways the problems in Class D Amplifiers are analogous (but not identical to) those in Class B Amplifiers (but without an option to implement Class AB or Class A) so similar solutions apply. All Class D amplifiers are essentially delta-sigma DAC’s. If the input is not digital PWM signals (aka "DSD") but analogue audio then it is also a Delta Sigma Analogue to digital converter...Now DSD (aka SACD) which to my ears fails to come close, never mind equal true PCM CD Replay in most aspects of sound quality, operates at 2.8MHz switching, or around 10 times as fast as common Class D Amplifiers...Why anyone would want to listen through an A2D followed by an D2A Converter that are around 10 times worse than single speed DSD is beyond me. But with enough hype and snazzy naming it cannot help but sell high and wide." 

 

And, don't worry, we haven't forgotten:

 

Jeff Rowland
"I consider Class D to be highly competitive in the present, and to offer an evolutionary pathway of audio design that may produce even more astonishing results in the future."

[firedog]

First, another silly attempt of yours to troll, isn't it?

I will partially take the bait:

 

1. This is mostly comments of guys who don't do Class D. Not exactly an objective group. In addition, designing Class D properly takes specialized knowledge and experience if you want good results. Probably lots of these guys, even thought they may be great designers, haven't given the time or thought to Class D to make it work, and don't truly understand it on the most sophisticated level.

 

2.  This is only a few years old, but already dated. Several newer generations of various Class D technology have come out in the past few years. General consensus is that they ARE competitive with non-Class D solutions, and often thought to outperform them, dollar for dollar, except at the most expensive, over $10k levels. 

[esldude]

I have owned product from five of those guys, and have lots of time listening to a sixth.  I respect them all as they represent quite a large body of knowledge. 

 

Yet I have this feeling you have just quoted the pronouncements of dinosaurs who ruled the last paradigm of audio. Only Jeff Rowland has caught wind that the times are a changing.

 

Had I been there I would have asked, for $3000 can you build an amp better than class D for the same money with comparable power?

[kilroy]

deleted

[wgscott]

[GUTB]

4 hours ago, wgscott said:

 

Devastated!!

[GUTB]

6 hours ago, firedog said:

First, another silly attempt of yours to troll, isn't it?

I will partially take the bait:

 

1. This is mostly comments of guys who don't do Class D. Not exactly an objective group. In addition, designing Class D properly takes specialized knowledge and experience if you want good results. Probably lots of these guys, even thought they may be great designers, haven't given the time or thought to Class D to make it work, and don't truly understand it on the most sophisticated level.

 

2.  This is only a few years old, but already dated. Several newer generations of various Class D technology have come out in the past few years. General consensus is that they ARE competitive with non-Class D solutions, and often thought to outperform them, dollar for dollar, except at the most expensive, over $10k levels. 

 

I'm sorry if quoting legends in amp design is "trolling", but I don't believe there have been any fundamental improvements in class D since then....has there? Which specific modules are you talking about?

[firedog]

46 minutes ago, GUTB said:

 

I'm sorry if quoting legends in amp design is "trolling", but I don't believe there have been any fundamental improvements in class D since then....has there? Which specific modules are you talking about?

Trolling is when you give your " innocent"quotes a title like "turns out class D does suck" - that's about as blatant a troll as you can get.

 

Specific modules? Less important than how they are implemented. But to name just a few, some of the newest implementations of ICE, Ncore, and Nuprime. All out since that article and all reviewed - by both hobbyists and professionals -  as being as good or better than anything in conventional amps at their price and often far above their price.

When someone says a $2000-$5000 ClassD amp compares favorably to a well known "audiophile" amp costing that much or even twice that, I think they are saying it is a damn good amp, I.e., it doesn't suck.

 

Your list of experts is no more authoritative than the many amateurs and professionals who don't think class D sucks.

[blownsi]

While I realize that all of those guys have far more experience and expertise than I will ever have, none of them have my ears.  To my ears Class AB "sucks" and I have no idea why they bother with it at all.  Build a proper Class A like Mr Pass or imitate one with a quality Class D design is what sounds the best to me.  

[GUTB]

1 hour ago, blownsi said:

While I realize that all of those guys have far more experience and expertise than I will ever have, none of them have my ears.  To my ears Class AB "sucks" and I have no idea why they bother with it at all.  Build a proper Class A like Mr Pass or imitate one with a quality Class D design is what sounds the best to me.  

 

I've heard a couple of class A and A/B amps which suck. But the problem with class D is that it sucks by nature. That's not a troll, but a hard fact. Vladimir Shushurin from Lamm was the most brutal about the issue, calling class D feeble with a bunch of diseases on top of it, while we deal with all of its shortcomings with modern medicine.

 

Guess which one of these 10 KHz square waves is from a class D and and which one is from a class A amp:

 

 

 

[Panelhead]

  I would guess the top waveform is from a Class D amp. Also the modulator runs at 400Khz in that amplifier. 

  Hope I am wrong.

[andifor]

55 minutes ago, GUTB said:

 

I've heard a couple of class A and A/B amps which suck. But the problem with class D is that it sucks by nature. That's not a troll, but a hard fact. Vladimir Shushurin from Lamm was the most brutal about the issue, calling class D feeble with a bunch of diseases on top of it, while we deal with all of its shortcomings with modern medicine.

 

Guess which one of these 10 KHz square waves is from a class D and and which one is from a class A amp:

 

 

 

 

Is this FLAC or MQA? ;o)

[firedog]

1 hour ago, GUTB said:

 

I've heard a couple of class A and A/B amps which suck. But the problem with class D is that it sucks by nature. That's not a troll, but a hard fact. Vladimir Shushurin from Lamm was the most brutal about the issue, calling class D feeble with a bunch of diseases on top of it, while we deal with all of its shortcomings with modern medicine.

 

Guess which one of these 10 KHz square waves is from a class D and and which one is from a class A amp:

 

 

 

And it proves absolutely nothing about Class D amps as a class. Your so called "fact" is an opinion, not a fact. 

 

We get it, you don't like ClassD. 

 

What you don't get is that nothing you think is provable. Every argument you are going to make can be countered - believe me, we've already heard them all. The arguments aren't new. 

Like the rest of us, you are free to think what you want and come to whatever conclusions you want. 

What I don't get is your compulsion to try and prove it and argue about it.

I think that defines "troll"....

I'm out of this one, I can tell it will be a useless so-called "discussion".

[GUTB]

21 minutes ago, firedog said:

And it proves absolutely nothing about Class D amps as a class. Your so called "fact" is an opinion, not a fact. 

 

We get it, you don't like ClassD. 

 

What you don't get is that nothing you think is provable. Every argument you are going to make can be countered - believe me, we've already heard them all. The arguments aren't new. 

Like the rest of us, you are free to think what you want and come to whatever conclusions you want. 

What I don't get is your compulsion to try and prove it and argue about it.

I think that defines "troll"....

I'm out of this one, I can tell it will be a useless so-called "discussion".

 

Would you care to explain why these legends of amp design are wrong?

[kilroy]

Ignore the troll.

[GUTB]

2 minutes ago, kilroy said:

Ignore the troll.

 

Hey, here is what several top amp designers think.

Check out these screwed up measurements.

 

"Ignore the troll". Lol.

 

Look. I've listened to various class D products including the latest Pascal module. It's true modern class D has come a long in my experience from "unlistenable" to "excellent with a few deadly flaws". But, in the end of the day, it doesn't matter how resolving and controlled it is if its filters destroys soundstage depth and it struggles with musicality. I wish I could just buy a sub-$2000 amp that I can pick up with one hand and be happy with it. I'm sorry I have certain expectations from speaker listening.

[Ralf11]

What is the least expensive Class D amp that will sound a lot better than my 1990s Sunfire amp?

 

(must have good current delivery at 4 ohms)

[esldude]

15 minutes ago, GUTB said:

 

Hey, here is what several top amp designers think.

Check out these screwed up measurements.

 

"Ignore the troll". Lol.

 

Look. I've listened to various class D products including the latest Pascal module. It's true modern class D has come a long in my experience from "unlistenable" to "excellent with a few deadly flaws". But, in the end of the day, it doesn't matter how resolving and controlled it is if its filters destroys soundstage depth and it struggles with musicality. I wish I could just buy a sub-$2000 amp that I can pick up with one hand and be happy with it. I'm sorry I have certain expectations from speaker listening.

Of course you are listening thru colored glasses, you keep comparing them to a highly linear SET.  Now talk about your oxymorons. 

[GUTB]

Well, as a matter of fact, I'm still resisting upgrading to an end-game SET. I have a few options on the table, the one I'm leaning towards now is an enormous pair of Line Magnetic 845 monoblocks that weigh in at 140 lbs and cost $6,000 from China. I'm also going to the Dallas audio fest this weekend where I will be checking out KR Audio among others. But I still don't WANT to have big iron in my listening room.

 

I heard the Linnenberg monos at AXPONA and was quite impressed with the sound. I'm arranging an in-home demo (ie, purchase with return option lol) with their US dealer as we speak. These are super high-bandwidth (350 KHz after low pass filter), very high-speed, low-noise amplifiers at "only" $5,500. I'll try these out.

 

Even though the weight of evidence does seem to suggest class D sucks, I'm still listening to counter opinions.

[mrvco]

We would need an objective head to head comparison between equally priced amps with comparable output capabilities to determine whether a modern Class D amp "sucked" in comparison to other amp designs in a particular room and system.  Now we really just need a Class D zealot to blindly declare that Class D amps will "kill" all other designs to send this thread into a proper circular Internet orbit 

[tmtomh]

Honestly, I don't feel that @GUTB is trolling - or to put it another way, I have no idea what GUTB's true motivation was in starting this thread, but I found the content of the OP to be interesting and not trolling.

 

I'm not replacing my admittedly not high-end, but still great-sounding Nelson Pass-designed Adcom MOSFET power amp with a Class D amp in my main system anytime soon. And I do believe that as of now, a well-designed Class A or AB power amp is going to beat out most if not all Class D amps in critical listening.

 

But I am open-minded about the future of Class D and would love to see much faster-switching technology or other improvements come online to enable more accurate amplification with the low cost, small form factor, and low-heat benefits of Class D.

 

I think the "Class D for the mid/woofers and Class A for the tweeters" approach of the KEF LS50 actives probably has a lot of legs, given the raves those speakers have gotten and the intuitive way it makes sense. In this respect I found Levinson's comment on-target when he talked about A/D hybridization. (Although as usual I found his comment arrogant and of little value otherwise.)

 

And I found Nelson Pass' comment not so much "diplomatic," but rather emblematic of his down-to-earth, open-minded, unpretentious attitude: He's basically saying that he doesn't necessarily agree that Class D is definitionally bad. Rather, he seems to think it might be susceptible to major improvement as the market matures and Class D designers' attitudes and incentives mature with it. I always find his modesty refreshing.

[esldude]

If anyone doubts the OP is trolling look at the tags he applied to his thread.

 

SAVAGE

FACTS

BRUTAL

CLASS D

 

Yep he's trolling. 

[ShawnC]

A local dealer has Bel Canto's Black series The system (class D mono amps) (expensive) hooked up to Wilson's Alexia's speakers.  It's the best sounding system I've heard them assemble.  A while back they had the now discontinued Audio research DS450 (class D amp) and Magnepan 3.7 together. That also sound amazing.  The dealer said that the DS450 was there best selling amp.

 

 

[GUTB]

53 minutes ago, ShawnC said:

A local dealer has Bel Canto's Black series The system (class D mono amps) (expensive) hooked up to Wilson's Alexia's speakers.  It's the best sounding system I've heard them assemble.  A while back they had the now discontinued Audio research DS450 (class D amp) and Magnepan 3.7 together. That also sound amazing.  The dealer said that the DS450 was there best selling amp.

 

 

 

I listened to a Vandersteen Channel D combo, it was basically unlistenable but I don't necessarily blame that one the amp.

[Ralf11]

I wonder why Audio Research dropped class D ??