Class D = Trash?

I would like to see one and compare bit by bit to verify that they are the same,

I would like to know, what a 1 off price is from EveryChina  site
can’t be too much knowing these types of outlets.
http://discosoundequipment.sell.everychina.com/p-99120690-professional-audio-disco-sound-equipment-class-d-modules-for-active-speakers.html

Or even the maybe tweaked version from Denmark
http://www.pascal-audio.com/amplifier-modules.html

Cheers George

Also at this time about 5 yrs ago, my high powered class A/B Aragon 4004 MKII amp's power supply capacitors leaked and it went dead.  I had to make a decision on whether to have the amp repaired for a quoted $1,800 or buy a new amp.

  I decided not to spend $1,800 to repair my nearly 15 year old amp and instead viewed it as an ideal time to audition a class D amp  
 
It outperformed my former Aragon amp in every area I cared about; power, dynamic range, quietness, imaging, distortion, accuracy and musicality.
I'm going to try and keep an open mind,
     Tim  

Of course it did Tim, in case you don't know, your Aragon didn't die over night, leaky caps start to deteriorate the sound over many months even up to a year, so in actual fact you were comparing the sound of a very sick amp, to one that was healthy. The real comparison would have been to fix the Aragon amp then do the comparison.

Cheers George 

kdude66George,

That is the one.
You probably would need 2 of them to pwr your big panels.

Though so! it uses the same Class-D modules as the Jeff Rowland Research Continuum 2, for much cheaper without the glitzy chassis.
500w into 4ohms would only need one for the ML’s bass units only.


http://www.theaudiobeat.com/equipment/pics/jeff_rowland_continuum_2_large_inside.jpg

https://www.reddragonaudio.com/products/s500?variant=969867425

http://discosoundequipment.sell.everychina.com/p-99120690-professional-audio-disco-sound-equipment-class-d-modules-for-active-speakers.html

Anyone know the price of these Class-D modules? as I would like to power my bass with them which Class-D’s to me is good at. Couldn’t see them costing too much coming from China. $100-$200 maybe.

Cheers George

kdude66

This S-500 Kenny your talking about, is this the Red Dragon?

https://www.reddragonaudio.com/products/s500?variant=969867425

Cheers George

Continuum S2 it’s not a B&O Ice Power Class-D module but this.

http://www.stereo.net.au/forums/topic/123187-high-end-integrated-amps/?do=findComment&comment=1847641

Cheers George

Jeff Rowland 102s power amp only version

Rowland:
"Model 102 stereo amplifier employ the ICEpower 200 AS power conversion module" 


Cheers George.

http://www.stereo.net.au/forums/topic/123549-jeff-rowland-102s/

Jeff Rowland Class-D poweramp version going here for 1/2 price if anyone wants it, owners going back to linear tube or solid state.
  
Being SMP power supply it will run off all mains voltages.
https://www.gzhifi.com/fy/images/201701/1484868519699273857.JPG

Cheers George

sfseay
The 1000 hours is urban legend with no basis in science or audible difference to a golden ear.

msalha
  Also I am not sure what warm up period of 1000 hours mean.. It does not make any sense to me as I read these posts. The speakers need warm up period because they are mechanically moving parts that need to settle or get flexible.  If electronics change behavior that much with time.. that's scary to me from a Computer engineer perspective.

+1 sfseay and msalha, this is just a lot of Class-D paranoia rubbish, it’s said just to calm owners down that don’t like it from the get go, to eventually take it on the chin and live with it.

Cheers George

Again can't see the forest through the trees.

Not one mention of the output filter that has to address the switching noise of the switching frequency, which is the Achilles Heel with present day switching frequencies.

Cheers George

There's also the matter of you seriously over-estimating the improvements that will result from using higher switching frequencies in the 3-5 mHz range.  I think the new faster switching FETs are more likely to improve class D performance than higher switching frequencies.

Still can't see the forest through the trees, once more and I can't make it any simpler.
It's the output filter that you never mention that has to get rid of the switching frequency noise that is the problem, 
And that output filter stops becoming a problem "if" the switching frequency is "much higher", as it will be too.  
And then it will not have effects that today reach down to 5khz sometime 3khz as they do now, with today's switching frequency. 


Cheers George 

So it is quite possible both the Technics use ICEedge at their core.

If your saying that they used a "similar" topology as Ice, that maybe possible.
But I doubt very much that Technics is using Ice modules or anything from Ice, even licensing permission, as they have always used their own development technology, and never relied on anyone else.

Cheers George  

Most likely to sell them at $30k each to gullible buyers. that believe higher switching frequencies amps actually sound better than the $630-$3,000 competition , and have more dollars than sense.

Head in sand ,forest through trees.

Like I said protective owners like yourself will be one of the first to change, to higher switching frequencies when it becomes main stream. Even though at the moment they are blindly bagging it.
All your doing at the moment is trying to protecting your investment so it won’t take a monitory nose dive when this new technology becomes mainstream and finally puts Class-D into the hi-end Audio bracket, with today’s great linear amps
Keep that finger on the sell button and press it before they become obsolete.

Cheers George

No need to war and piece it with no substance, so long as it sounds good to you that's all that counts, to others and myself it doesn't, yet! why do you think Technics have gone to the trouble to advance the class!

But I guarantee you'll be one of the first to dump your current Class-D oscillator before it becomes unsalable, as soon as there's a whiff of a far higher switching frequency around the corner about to come onto the market mainstream for Class-D

The absence of a solid knowledge base allows individuals such as yourself, George

Pardon?? your the one who can't see the forest through the trees.

Cheers George.     

tradeontheweb
  with the advancement of Class-D’s higher switching frequency, one that  Technics have used with their SE-R1 (which I have not heard yet)

Doubt you will S, I contacted Technics and it is still special order only ex Japan, and none yet have been allocated for Australia, even if you have the deep $40kaud pockets.

Cheers George 

This is a statement from Optoma USA customer help, a world wide company who I believe handled NuForce, maybe still do.

Digital Switching Amplifiers (commonly known as Class-D) have been around for years. Nevertheless, it is nearly impossible to engineer a conventional Class-D amplifier that handles the full requirement, 20-20,000Hz, for full-bandwidth music reproduction. A Class-D amplifier works by utilising a high-frequency saw-tooth waveform to modulate the music signal (to learn more about how Class-D amplifier works, click here).

The constant presence of the saw-tooth waveform, which is very high in frequency spectrum and its inevitable frequency jittering, can mask or corrupt low-level music signal. The output filter designed to filter out noise and overtones caused by the saw-tooth waveform adds a 180 degree phase shift to Class-D output stage, causing possible instability and adding distortion due to its own inherent non-linearities.

Additionally, the output filter presents frequency-variant output impedance that can interact with a speaker’s complex impedance. Variants of Class-D amplifiers with the addition of Digital Signal Processor claim to improve music reproductions.

However, because of their lack of close-loop design, especially from the speaker’s terminals, spurious interaction between the speaker’s complex impedance and back-EMF with the amplifier’s resonant output filter can result in harsh sound reproduction.

The fundamental flaws of conventional Class-D amplifiers remain unresolved.

Cheers George

Yes, and they are the industries top designers, nothing will change until that dreaded switching frequency is taken up much higher. So then the output filter can do it’s job properly without any effects down into the audio band.

Technics is leading the way with the SE-R1 with twice as high switching frequency, but it’s not mainstream yet, and really should be even higher, one can only hope.

Cheers George

Make of it what you will, something more for the OP to read, on the title of his thread.

"Switching Frequency" it’s mentioned a few times here.

This was an Absolute Sounds Round Table discussion with the industry top dogs on Class-D, the only one in favor is the one that manufactures them Jeff Rowland but had little to say amongst his peers.

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 (Souloution)
"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)
"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."

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 (Threshold, Passlabs)
"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."

Jürgen Reiss (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."

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."

Thorsten Loesch

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 DAC’s #" 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 90’s reviews of timeslicing dac’s. 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 “full scaleâ€, if they would be dac’s. 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 Levinsons 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.


Cheers George

I've always admitted Class-D is the future for hi-end, just not yet.
Very long winded post, but still can’t see the forest through the trees.
Read again and try to let it sink in.
https://forum.audiogon.com/posts/1417196

Cheers George

May not be trash for long madavid0.


Class-D that can finally equal or better hi-end linear amplifiers, tube or S/S.

 It's closer than you think.

Why We'll Soon Be Living In A Class D World 

"In fact, that transistor technology is available today and is increasingly being used by manufacturers to create near perfect sound quality for Class D audio systems. The greater switching speed of Efficient Power Conversion's (EPC's) eGaN® FETs allow amplifier designers to increase PWM switching frequencies, reduce dead-time, and drastically reduce feedback; in turn, producing a sound quality previously limited to large, complex, heavy Class A amplifier systems. Further, this innovative high-speed switching technology has already disrupted myriad other industries, including telecommunications, medical, and automotive to name a few.  
A high-definition eGaN FET-based system with higher PWM switching frequency, reduced feedback, and higher bandwidth produces the sound that has the warmth and sonic quality that audiophiles demand; while actually improving upon the power efficiency of traditional Class D. Class A audio's historic lesser child Class D is coming of age with eGaN technology. And in the next decade, these systems will replace Class A technology, as well as the silicon MOSFET Class D systems in active use today. 

Significantly, audio manufacturers are taking notice and incorporating GaN-based Class D FETs in their systems. This is why, in another two or three years you will start seeing a slew of new Class D amps - ones based on GaN - rolling out to the market; and, for such varied uses as home theatre, car, boat, portable wireless speakers, along with high-fidelity home systems."  

Cheers George

seanheis1
  I started a thread about it and it appears that the switching frequencies aren't currently high enough to avoid degrading the signal. If it was a simple break in issue, they would be broken in at the factory.

Don't give up on Class D though. When the switching frequencies improve, they will become the solid state amps of choice. Some folks don't hear what we hear and they are fortunate to enjoy these small and efficient power houses. More power to them.

Well said the day will come with much higher switching frequencies, as I also posted to Randy's question

randy-11I always thought the gentle filter slope was b/c steep "brick wall" filtering caused caused audible distortions...

It’s because a simple low order output filter can take the amps full power, but it’s effects reach down into the audio band and still leave some switching noise left overs, hence the need to take it up much higher as Technics did with far higher switching frequencies, so they can be effectively removed, without effecting the audio band.

These days when Stereophile tests a Class-d amp, they put on an external output filter, the Audio Precision’s AP0025 filter, which has a -50db rolloff after the audio band so the 1khz square waves look half decent without the switching noise embedded right across it, (good for sales) 10khz square wave still looks a mangled mess though, trouble is this AP filter can only take very low power, would be real nice to leave it in to listen to, but it would blow up in a micro second.

http://www.stereophile.com/content/class%C3%A9-sigma-2200i-integrated-amplifier-measurements#31YFAPfYVDGeowzZ.97  
And yes steeper filters as you said do have their own set of problems re sound, as ML found out with their No.53 monoblocks.

Cheers George 

No but I believe from what others have said, the output filter in some Class-D’s is included into it’s global loop aiding it’s effectiveness? that's why I bought it up, just to cover all bases.

Cheers George

A high-definition eGaN FET-based system with higher PWM switching frequency, reduced feedback, and higher bandwidth produces the sound that has the warmth and sonic quality that audiophiles demand;

For a quality Class D audio solution, it is possible to avoid these transitions all the way through the system to the final Output Filter

The key to great Class-d, is to get it’s LOW ORDER output filter to do it’s job of getting rid of ALL switching noise from the audio band before it get sent to the speakers, and without creating any phase shift.
The only way to do this successfully is to raise the switching frequency noise much higher so this low order output filter (without masses of feedback) can do it’s job properly without any residue effects or switching noise remnants being left within the audio band.

This is why Technics have led the way with the new SE-R1, have striven to DOUBLED the switching frequency with these new eGan Fet transistors, to get closer to the ideal above results.

Credit to Mark Levinson a couple of years ago tried to solve this problem with todays switching frequency, by using much lager (to take the amps power) higher order output filters and less feedback, but it was a bit of a flop, with their very expensive. (see the size of the 4 x chokes for the higher order output filter for each monoblock).

http://www.stereophile.com/content/mark-levinson-no53-reference-monoblock-power-
amplifier#rJEmkELOsfXsME4b.97
It’s 10khz!! (not 1khz) square wave without!!! the AP filter, is the best ever seen for a class-d amp (almost as good as a linear amp) because of it’s massive higher order output filter and less feeback, but this high order filter obviously created other problems, and was not received well, that’s why low order with low feedback is the way to go, but it must do it’s job properly, and the only way to do that is to raise the switching frequency noise much much higher.

Cheers George

So, you’re saying it may be a year or two before you buy your first class D amp?
If you’re going to wait until class D is absolutely perfect, the good news is that it’ll probably be the last amp you’ll ever need to buy.
Good strategy.

Yes, I’m waiting till it gets to what I believe will be time for me to turn to the dark side, with a 3-5mHz switching frequency, then it will address the problems I think it has "trying to filter out ALL of it" without effecting the audio bandwidth, and then my linear amps WILL become boat anchors.

One of the tell tale test will be to see in mags an almost square 10khz square wave without any buzz saw ringing across the top "without the use of test AP0025 (Audio Precision) inline filters" that are now being used by mags to hide it when measurements are being done, as I queried here on Stereophile.
http://www.stereophile.com/comment/565267#comment-565267
This then will show good audio bandwidth with total filtering out of the switching frequency.

This is what an unfiltered (by test equipment) square wave looks like on Class-D. If this was a linear s/s or tube amp a tech would say not to use it it has a major problem.
https://www.google.com.au/search?q=Class-D+square+wave&espv=2&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj_g9zOsaDTAhWMnZQKHax5C8kQ_AUIBigB&biw=1255&bih=782#imgrc=OFuO9FVLq5xJeM:

Cheers George

noble100658 posts04-13-2017 2:15amgeorgehifi,

Here’s a link to what I was referring to in my last post about reading of faster switching mosfets:

Yes I posted about these before, same guy invented the Mosfet.

https://forum.audiogon.com/posts/1414493

And yes it’s on the way, but this is just a small company able to supply Technics, not the world "yet"
Companies like Motorola will copy it and then the ball will be rolling, but with this transistor the Switching Noise Frequency has been doubled to 1.5mHz but I would like to see it to get to 3-5mHz.
This way the low order filter that has to be used on the output of all class-d amps can do it’s job well away from the audio band, without it’s effects (phase shift) or left over switching noise getting down into the audio band.

Cheers George

 input buffer boards that allow a choice of op amps
  Maybe this will be the future of class D, with op amp rolling

Can they get any cheaper, in manufacturing with opamps instead of discrete transistors.

Any hi-end linear poweramp that used opamps as the input stage for their amps wouldn't be recognized for very long and die a slow painful death.

Cheers George  

approximately 1500 hours break-in for Class-D.

Wishful thinking, more like breaking the owner down, more like it making him submit.

At 2hrs listening every day of the week, that's close to 2 years before break-in, that's just ludicrous, and you would have rocks in your head to leave any poweramp on while nobody's at home.

Cheers George

    

Here is what a well known quality speaker manufacture believes with what they put into their own active monitors.

 JM Labs Focal Speakers.
" The amplifiers are conventional Class A/B designs rather than the increasingly common Class D option, because Focal thinks the traditional technology gives a better sound."

Cheers George

seanheis196 posts04-01-2017 9:36am Very interesting point about switching frequencies… What is the acceptable switching friequency range is targeted by the pundits?
Below is a quote from George from the Class D technology thread.

The day will come when Class D will compete and very well be better than any linear amps tube,s/s, class A, AB or whatever, BUT!!

Class D needs much higher switching frequency (needs to be at least 5 x higher) technology isn’t there yet but in the future it will come, only then will ClassD become a contender. Till then good for budget hifi and subwoofer/bass amps.

Technics has progress the Class D race and developed 2 x the present switching frequency with their own made components, in this amp but it’s very expensive $20-30k
https://forum.audiogon.com/posts/1334662?highlight=Technics

When the switching frequency is 3mhz or better, then it can be called hi-end, and will own it myself, then my linear heavy boat anchors will be sold or become door stops.



Cheers George

Yes it actually, the filter that’s needed to rid that switching frequency and all it’s artifacts that does the damage also to the audio band at the moment.
( switching frequency artifacts left over are the buzz-saw ringing that one sees on test 1khz square waves)
http://www.stereophile.com/images/archivesart/805CIAfig2.jpg
(And the filter also causes phase shifts in the 5khz to 20khz of the audio band)

If the switching frequency were higher, then the filter can do it’s job without effecting the audio band, and get rid of all ringing that’s left over on those square wave tests.

So I wait in hope for technology to advance so the switching frequency can be up around 5mhz.
Technics in the above link have got it up, with special transistors to 3hmz they are showing the way, but that amp costs $20-30K and is special order only.

Cheers George

I'm with you  madavid0 .

The only one I've heard that did something for me was the Bel Canto 600 monoblocks, but that was only with an expensive two way with a Raven tweeter that had a very flat, benign impedance curve of 4ohms.

I didn't like it on a different speaker that had an impedance curve that had up and down impedance's like most speakers have. I could see it being good with Maggie's as they are also a benign 4ohm load.

Cheers George