Class D Technology

The black background many listeners can hear with Class D indeed suggests the heavy filtering is in some way affecting the audible sound.

Myself I would not describe it as a "black background".
But rather a "harmonic black hole".

Cheers George

I will state just the opposite.  Violin sounds like violin without scratchy glazed harmonics of class AB amp.  Same goes for the cymbals that sound brassy and meaty instead of bright and splashy.  Cello sounds deep and resonant.  Transients are incredible while amps keep composure under heavy current demands (orchestra forte), most likely due to regulated power supply.  The other thing I noticed is low level performance.  When I listen soft at night - highs and lows are still there.  Imaging is even better, but it might be due to reduced reflections.

Somebody described sound of Hypex as a sound of very good class AB amp while  Icepower was described as more of a tube amp sound (half bridge vs full bridge output).  Icepower is very good in spite of some negative opinions here.  Now we have more choices, Pascal being one of them.  

Speed of Mosfets improves every single year, but now new switching devices are coming - like Enhanced Mode Gallium Nitride Fets (eGaN Fet) that switches many times faster without overshoot or ringing due to ultra low capacitance and inductance.  The best days of class D are ahead of us, but I enjoy it immensely already.  

So if its not obvious by now the question has been answered repeatedly in some cases.

Some like it already and some not so much.

I’m on the like it side with Kijanki.

So its pretty much on par with everything else audio these days. Some like it and some not so much.

its nice to have choices.

The difference is Class D will only continue to get even better.

Someday soon everyone may agree.

Or not.....

Cheers!

So its pretty much on par with everything else audio these days. Some like it and some not so much.

its nice to have choices.

The difference is Class D will only continue to get even better.

Someday soon everyone may agree.

Mapman - I would say Class D is similar to tubes as far as opinion goes. People either like the sound or they don't. I am not saying that tubes sound like Class D (far from it), just that they are both controversial. Very rarely will you hear someone say something bad about Class A solid state relating to sound quality/accuracy.  

This statement is false. 

It is not false at all! 

"It used to be a sign of superior good taste to diss class D. Today it's become a surefire tell of sad ignorance."

Anyone who degrades class D as a whole is clearly ignorant about the technology or has comercial interests against it. As with any other topology, making a generalization about sound performance is an error.

Just because you heard a class D amp sound better than a tube amp in a particular situation does not mean that all class D amps sound better than all tube amps, or even that the particular class D amp sounds better than all tube amps. It just means that in that situation you heard something better that you liked between the two involved. 

Who said that? That statement is completely erroneous, in fact is the complete oposite of what I clearly stated above:

I said: "I have experience with many amplifying topologies (meaning class A, A/B, D, H), and I have found good and bad examples in each".

Who makes the latest generation of Class-D? The best class-d I heard, Hypex has been on the market for a long time. I wonder how good the latest generation class-D is compared to Hypex.

Hypex latest generation is Ncore which has several years in the market. Anaview and Pascal also have very good designs, that when correctly implemented provide similar or in some cases even better performance than Ncore.

And as I said, not everything is the class D module in the design. The input buffer, for example, is a critical part that can completely alter the character of the amplifier. There's been greater progress in this matter, than in the output modules themselves.

Just because you heard a class D amp sound better than a tube amp in a particular situation does not mean that all class D amps sound better than all tube amps, or even that the particular class D amp sounds better than all tube amps. It just means that in that situation you heard something better that you liked between the two involved.

Who said that? That statement is completely erroneous

Who said? you know exactly who, since you copied.   This statement, made by Atmasphere,  is absolutely true stating that you can like any class of an amp more than another.  Nothing erroneous about that.

I'm very curious about Class "D" amps. No I've never heard one. How does Class "D" compare to SS? I'm a tube guy who has not heard the very best SS amps, but I did hear an ARC SS that I didn't like.

If a person prefers SS to tubes in general, his opinion is less valid to me, than someone who prefers Class "D" over tubes or claims that he can't tell the difference.

I've been told that for watts of power, class "D" is cheaper; that's nice, but I don't have a serious power problem, just curious.

My tubes have a black background; I know this is not supposed to be so, but current tube equipment has achieved that. Maybe not as Black as Class "D", and yes, there are levels of Blackness.

While the quickest way to find the answer to these questions is to buy one; that is not an option. I hope I've arranged my questions in an order that won't offend anyone, but will get an answer to the best of their ability in regard to Class "D"

The new Wyred  SX 1000R mono's sound great. They replaced the great Vitus RI 100, 13k retail. 6moons review pretty much on. Nothing beats big power if it is decent.

No I’ve never heard one. How does Class "D" compare to SS? I’m a tube guy who has not heard the very best SS amps

We, most are all in agreement that Class D is great in the bass. To me where they differ mainly is in the upper mids and highs, some saying there’s hardness up there, and others saying there’s missing information that causes larger then usual gaps between notes creating the "illusion" of a blacker background. I call it an opaqueness.

The different sound of Class-D especially in the upper mids/highs, comes down to how close to the audio band the mandatory output filter on all Class-D’s is bought down to get rid of the class d’s massive amount of VHF switching noise.

If bought down low to erase most of the switching noise, this intrudes into the upper frequencies of the audio band. Which makes it very smooth but robs most of the harmonic structure of the mids and highs, this "could" be compared to tube or class A s/s smoothness.

If it’s not bought down to low it lets quite a bit of VHF switching noise through, this maintains the harmonic structure of the mids and highs but also adds a certain hardness to the sound of class-D

To me the only way to cure this comes in future semiconductor component development, which will allow the switch frequency to be set 5 x higher, so the the output filter can be set much higher as well so then do it’s job properly to get rid of all the switching noise without effecting any of the audio band at all. Then they’ll also be able to drive full current even down to 1ohm from 20hz to 20khz, instead of today falling off a cliff below 4ohms.

Technics have a >$30k amp the they developed with their own components to get the switch noise up 2 x as high as anyone one else, a step in the right direction, but it needs to be higher again 5 x the norm today. They still do not include a 2ohm wattage figure in their specs, as it would still show limitations.
http://www.technics.com/us/products/r1/se-r1.html
When that day comes we’ll all be using them and our heavy, hungry, hot tubes and SS, will become boat anchors.


Cheers George

If bought down low to erase most of the switching noise, this intrudes into the upper frequencies of the audio band. Which makes it very smooth but robs most of the harmonic structure of the mids and highs, this "could" be compared to tube or class A s/s smoothness.

My class D amp has 60kHz -3dB bandwidth. Georgelofi - you must be a bat?

George you conveniently forgot to mention some think the sound including the high frequencies are quite good and not flawed.  

Lets not selectively filter feedback just to help make a case.   

Im listening to my Bel Canto C5i Class D integrated with Triangle Titus speakers currently.  Other than the clean articulate bass I could easily think the amp was a very resolving and clean and dead quiet tube amp.  The treble is as good or better than most anything I have heard.  The sound draws you right in. 

So so let's stop trying to convince people the technology is flawed or does not sound good.   It's as good as anything these days done well.   Done well is the key like with any technology old or new.  

Technical difference aside(which I am not an expert), purely based on the sound, tubes has significantly more naturalness and fatigue-less, yes I understand that every  own has  own preference, but end of the day we are thriving for the sound what we like, which give us endless pleasure and to me Class-D still lacks the connection to the mind which interprets as its as more of digital sound...
Yes, Class-D had the advantage of running cool, clean sound, lower utility bill....it matters with every own of us what we prefer the beautiful analogue  sound or the convenience of the Class-D technology??

There is absolutely no fatigue with the C5i driving any of my speakers including some that are documented to potentially lean that way with the wrong amp. 

Mapman +1.

Georgelofi - if you don’t like the sound of particular amp or even class of them just say it, but making up pseudo-scientific reasons is just plain silly.

Sean

You are so screwed if you buy into class D. 

As Donald Trump would say: trust me on this. 

Murgesh what clas d setups have you heard? Why assume that what you heard is indicative of all cases? That’s called jumping to conclusions. My experience is the exact opposite of yours.


The c5i is in fact a digital Class D integrated amp ( not just class d). and the sound is nothing like you describe.

I recall when I was in college I could hear well to 20khz. I know because I ran tests.

I also found it much harder to get sound that was not fatiguing. This is back in analog days even. 

These days I know I cannot hear to that extent which is normal for ears my age. I find listening not fatiguing at all and can listen enthralled for hours and not want to stop. With most any kind of music or recording. Well except the occasional really bad modern loud pop mp3. That’s what its all about. Maybe there is some advantage to getting older after all.

Mapman, with all due respect, how old are you? 

57

Mapman, I am using Spec RSA717ex, it has class of its own ,Spec is better sounding than the  Class AB Luxman-505ux I have used previously, praised in various reviews, luxman sounded cold  and suppressed to me.
And all my inputs given in my previous posts are after comparing Spec with Audio Note Oto phono SE, only 10watts....

My class D amp has 60kHz -3dB bandwidth. Georgelofi - you must be a bat?

What brand model? Maybe I can find some non affiliated bench tests

Even so with those figures do some homework at -3db at 60khz you will have phase shifts all the way down to 5khz,  because of the low order of the switching noise output filter.

Cheers George

Rowland model 102.  There are many class A or AB amps that have similar bandwidth but nobody talks about phase shifts.

The JR 102 uses the Ice 200asc modules as you are probably aware.

Look at the distortion figures for the highest their willing to put up in red which is just at 6.5khz. Look how fast the distortion rise is for the given wattage. And this is all at just 4ohms, I would love to see it at 2ohms.
If you can then visualize just what the 15khz one looks like, if they rise this rapidly from 100hz to 1khz to 6.5khz you have an idea of what’s going on the upper mids and highs.

Then you can imagine what happens if the’re driving an ESL speakers which can go to down 1ohm.
This is just one I found I'm sure there's more if I dig.
http://www.icepower.dk/images/200asc_700px.jpg

Cheers George

There are many class A or AB amps that have similar bandwidth but nobody talks about phase shifts.

That’s because good ones are usually much faster, and they don’t freak out at low impedances like ClassD does in distortion and loading.

I like to see bench tests v reviewers subjective listening. As Stereophile does.

But here is what a reviewer from another mag said subjectively, without any bench test to back his listening.

" Here is what the amp doesn’t do. It isn’t airy and it isn’t laid back."

Good highs are airy, they float with harmonic structure.
Cheers George

Georgelofi - you are talking about harmonic distortion below 0.1%, that are inaudible (unless you're a bat, of course).  I've noticed that you also tried to apply psuedo-science to sigma-delta converters.  I am afraid one day you'll find that SACD is the same.

George im guessing you should be looking at specs and data of the Rowland amp not the ice module it uses alone. I’m pretty sure Rowland like others do things like beefed up power supply to achieve performance. Again I think you are selectively choosing your facts and data to support your case. Are you a lawyer? Many of these amps get rave reviews and are happily owned by many. Your technical case for why these must sound bad does not add up. Plus I can assure you the newer good ones done right are right up there. It’s ok if not your cup of tea for whatever reason. But that’s about it. If I had listened to the skeptics a few years back rather than drawing my own conclusions to take he chance I’d have maybe missed out on years of enjoyable music by now.   

The output filter vs switching noises frequency is the bottleneck for Class-D HF distortion and low impedance drivability.

As I said when in the future when it is not a bottle neck, and the switching frequency is much higher, I too will dump the hot inefficient boat anchors and go Class-D.
But today it doesn't compete with good linear s/s or even tube (especially OTL tube) which has other limitations.

Cheers George 

D = duck.

I love duck!

The output filter vs switching noises frequency is the bottleneck for Class-D HF distortion and low impedance drivability.

It is ill minded and made up.  There are many amps that have similar bandwidth and great reviews.  My tiny amp is listed as 3 ohms minimum and it drives 3.6 ohm min. Hyperion HPS-938 speakers.  Larger modules, like one used in mapman's amp, can drive 2 ohm (this module can deliver 40 amperes for 0.5 sec and 36 amperes for 1s - not many amps can even do that).  One of our audiogon friends uses class D amp (H20) with Apogee Scintilla in 1 ohm mode with great results.  Please stop making pseudo-scientific reasons - it is not funny anymore.

Back to the OP's question (really two questions);

So my question is, if it weren't for efficiency & power, would there be any reason to own a Class D amp? Do they beat Class A in any other categories that count for sound quality?

The obvious reasons to buy a Class D amplifier are power per dollar, efficiency, and form factor (i.e., small).    They should also work well in powered speaker implementations.  From a sound quality viewpoint, some, like Guido who posts here, have had good luck with cutting edge designs from Rowland and Stereophile certainly gushed over the Theta Prometheus that uses NC1200 modules with a linear PS.  However, even the Mola Mola that 6moons praised has received some responses that it is not quite ready to compete with the best.

Based on my singular experience with a pair of Ncore NC1200 monos, the one sound quality based reason I can think of that somebody may like Class D over (high quality) Class A is low noise.  The Ncore NC1200 amplifiers were dead nuts quiet.  My Class A Clayton amplifiers are not as quiet as the Ncores but they are certainly no noisier than other Class A and AB amps I have owned, quieter than most, and quiet enough that noise is a non-issue.  Sonically, the NC1200 amps came close to the Claytons in several respects such as having a nice tonal quality and full, powerful bass, but even in those strength areas, the Class A Claytons offer a bit more realism and enjoyment.  In some other areas, such as high frequencies and soundstaging, I find the Claytons to be clearly better.  With respect to sound quality and listening enjoyment, of the amps I have owned, I would rank the NC1200 amps about fourth.

The best reason to buy is that the good ones sound great even with harder to drive speaker loads due to lots of power and current delivery possible out of a smaller package due to efficiency.  

It sounds like a Class D amp would be best for a sub-woofer, based on a comment above

If the new MOSFET designs will be out (as products) soon, I would not want to sink too many $$ into an amp right now...

One of our audiogon friends uses class D amp (H20) with Apogee Scintilla in 1 ohm mode with great results.

Then I feel sorry for this person as he has never heard his Scintilla’s at their best. It may work, but at their best?? FAR FROM IT!
As they are a great speaker and should be driven with the right amp and Class-D is definitely, absolutely, not one of them, not yet anyway, give it some time and in the future it will be.

Cheers George

It happens that this person (muralman1) knows everything there is to know about Scintillas and he adores them with class D amp. Nice try :(

randy-11
It sounds like a Class D amp would be best for a sub-woofer, based on a comment above
If the new MOSFET designs will be out (as products) soon, I would not want to sink too many $$ into an amp right now...

You are correct Randy, really good for bass
Technics have lead the way and developed a very expensive one
http://www.technics.com/us/products/r1/se-r1.html
with double the switching frequency as it is today @ 1.5mhz. This is a step in the right direction, but it really needs to get to around 5mhz before the right effective filtering can be done, and then able to get rid of todays Achilles heel that Class-D has.

So just go the cheaper not so glitzy ClassD’s if you want to dabble in it, or even do your own clone if you or a friend are able, and purchase the Icepower/Hypex?etc modules and the power supply modules they sell. They are very much a pluggable build to do, hardly maybe no soldering to do.


Cheers George

Before you offer your "expertise" get things right  - mhz is millihertz, proper unit is MHz (megahertz).  Keep posting - you might learn something one day.

"One of our audiogon friends uses class D amp (H20) with Apogee Scintilla in 1 ohm mode with great results."

georgelofi:

"Then I feel sorry for this person as he has never heard his Scintilla’s at their best. It may work, but at their best?? FAR FROM IT!"

Hi George,

My good friend Glen, a BIG tube fan, has the best sounding Apogee-based system I have heard (and that is more than a few). Had the Carver K-120 monos, then Kronzilla Mark II monos, and now living very happily with two H20 Class D stereo amps from Henry Ho running bi-amped into his Scintillas.

Proof is in the hearing and not found in blanket statements unfairly encompassing hundreds of products with one fell stroke. Glen’s Kronzillas are for sale if you are interested.

Best to you George,
Dave

So it's come down to mud slinging. 
Not from you sunshine, I think everyone knew I meant megahertz as there's 1,500,000,000 difference between the two.

Cheers George  

I believe you won’t find one tech guru here on Audiogon that would recommend a Class-D amp over "big current" linear amps for these kinds of loads, sure they may work, but are you getting the best from them? I think not. 2nd graph
http://www.lippaudio.org/old/MySystems/Scintilla/impedance.html

BTW: Carver 120 and Kronzilla Mark II are NOT big current amps, sure they consume big current, but they won’t push it into speakers load like these Appogee’s

Cheers George

It is far from mud slinging, buy it appears that you make strong technical statements on the subjects that you are completely unfamiliar with.  I pointed out units just to show that you don't have any electrical engineering education.  This thread is not too bad, but your crusade against Delta-Sigma converters is plain insane.  Cheers.

I understand your just protecting your JR120 investment, that "if" you had the knowledge you could have built for 1/8th of the price. http://www.usaudiomart.com/details/649188442-icepower-200asc-modules/

And I’ll bet you’ll be the first to sell it when the technology comes that get’s rid of the switching noises problems without effecting the amps sound.

Cheers George

It’s about sound George. Obviously from your many condescending posts, you consider yourself the foremost "guru". Try a little humility and you might learn something.

Best to you George,
Dave

Can’t "see the forest through the trees" even though they are presented to you.

The Apogee’s in 1ohm mode were never meant to be driven with tube amps, especially ones like you mentioned, they needed big s/s amps like Krells, Classe, Mark Levinson, yes and even the earlier big JR’s, ones that could pump current into most loads down to 1ohm. You should know this being an owner of a Krell FPB-600c and why didn’t you drive the Apogee’s in 1ohm mode with that, I’m sure you would have changed your mind about the classd-.

Only condescending to the posts that believe that Class-D can drive a speaker to "it’s full potential", when most of the load it represents is around 1ohm, and we’re not even mentioning -phase angles yet. Though I think they will be pretty benign being a planer speaker.

Cheers George

georgelofi:

"The Apogee’s in 1ohm mode were never meant to be driven with tube amps, especially ones like you mentioned, they needed big s/s amps like Krells, Classe, Mark Levinson, yes and even the earlier big JR’s, ones that could pump current into most loads down to 1ohm."

Oh, you mean like my Classe’ Audio DR-25, dual bridged-mono DR-9s, or my Krell FPB-600c (6000w/ch@1 ohm with 143 amps of current according to JA’s bench test in Stereophile)?

I had no idea that those would work well with Apogees. Oh, wait, I used the DR-25 and Krell with my Apogees for years before trading for the equally-difficult-to-drive Thiel CS-5i’s.

Best check people’s Virtual System page before spouting off. Where’s yours?

Best to you George
Dave

Please let me know if you want, I’ll post in Tech forums for guru’s to respond.

Tech advise needed, Apogee Scintilla in 1ohm mode which amp?

Krell FPB-600c or is there any Class-D you can recommend to equal the Krell?

And yes even any of the ones you just mentioned would be fine, why weren’t these mentioned instead of just the tube ones you tried before, as they had no chance, and you should have known that.
Cheers George

READ my first post George. It was talking about MY FRIEND’S H2O Class D amps with his Scintillas in challenge to your statements trashing all Class D amps as inferior as if there was no difference between them.

I normally do not need to qualify my posts with details of my system. I felt it to be unavoidable in this case.

Why would I need opinions of "gurus" when I have actual real-life listening experiences regarding this exact subject?

Best to you George,
Dave

I used the DR-25 and Krell with my Apogees for years before trading for the equally-difficult-to-drive Thiel CS-5i’s.

I assume that you had the same seeing you compared them to your friends.

Why would I need opinions of "gurus" when I have actual real-life listening experiences regarding this exact subject?

Because the ones I would ask, you’d have difficulty in dismissing them as well. Just ask and it will be done.
Cheers George

but nobody talks about phase shifts.

I do and all the time. The ear can't hear phase shift in single notes, but over a spectrum it can hear phase shift in a variety of ways- as a tonality or as a change in the soundstage. The engineering rule of thumb to prevent phase shift is to have bandwidth exceeding the highest frequency to be amplified by about 10 times.

Now that is generally interpreted to be a bandwidth of 200KHz (but might be higher- for example nearly all LPs have bandwidth well past 30KHz in record and in playback; usually this is limited by the source tape or file or the microphones themselves...). However you need the bandwidth in the playback electronics even if the source lacks the bandwidth if you expect to reproduce all the phases correctly! We get that out of our amplifiers but to do that with class D is still a bit of a trick. We are barely getting switching speeds much past 250KHz which means true 200KHz bandwidth isn't there yet.

Now the AES says that if you can get about 2 octaves above the limit of human hearing (80KHz IOW) that you are doing OK for a monitor amplifier. Audiophiles routinely operate gear that has performance in excess of that. And one of the things I don't like about many of the class D amps I've heard has been the lack of speed and spaciousness on the top end. Like mapman, there's no way my hearing is as good now as when I was in my 20s but I still notice this stuff nevertheless.

So if you're going to get that 200KHz response you need a switching speed of around 1 MHz and even then its going to be a bit spotty (2Mhz would be much better). There's no problem getting the converters to run that high. A prototype we're building here in the shop can do conversion at 3MHz easily no worries (the chips we're using have a bandwidth product of about 50MHz). The real problem is the switching speed of the output devices (and whatever junk occurs between the output of the converter and the inputs of the output devices...). If one were to spend the extra cash to get the really high speed stuff then one of the primary advantages of class D goes away real fast: low cost/high profit margin. Really fast, powerful switching transistors aren't cheap and you don't see them in 99% of all class D amps! So to compete against traditional solid state and tube amplifiers in a nutshell Class D has to improve bandwidth, and you don't have to be a bat to appreciate the difference.

This is one reason why class D is still a rising star. Its also why some class D amps are quite diss-worthy and others are not too bad. 

Atmasphere why does 200khz bandwidth matter if there are no sources practically (record or CD res digital) that can even come close to delivering it today?

Seems like a purely theoretical argument.

I agree and have stated on many occasions that higher bandwidth alone is better theoretically all other things aside and Class D can still get much better there.   It certainly cannot hurt  assuming it is done well/right like most things.

But practically I am less sure. I expected my Class D amps to not sound nearly as good as they do given the theory. I’m glad I did not let that stop me from trying because it seems to be a non issue already practically, at least for me.

Thanks.

Well said, atmasphere. One of things that stands out, at least to me, about the H2O Class D amp is that it uses an extremely robust power supply comparable to the great SS/Tube amps.

http://www.6moons.com/audioreviews/h2o2/1.html

http://iceh2oaudio.com/

What prominence does the heft of the power supply play in the sonic performance of Class D amps relative to SS or tube amps?

Best to you atmasphere,
Dave