So, I'm on my second class D amp. The first one, a Teac AI-301DA which claimed to use an ICE module, was unlistenable trash. I burned it in for a few weeks, it just couldn't perform, so I sent it back. Following that, I tried the new Emotiva A-300 (class A/B). It was significantly better, but lacking in too many ways for my tastes. So I changed gears, got an 845 SET from China -- and it was an immediate and massive improvement.
So, before I went further down the SET road, I wanted to try a better class D product using a modern class D module. I settled on the D-Sonic M3-800S with the Pascal module and custom input stage. I read from reviews that these things like to have big cables, so I picked up an eBay 8 gauge power cable (Maze Audio, el-cheapo Oyaide copy plugs, braided 4-wire cable) to go along with it.
Yes, resolution went up. Driver control went up, allowing me to play compressed rock/pop and orchestra with the speakers being able to render it all. But enjoyment in the sound is basically gone. Using my best power cable (LessLoss Original) improved performance, but didn't fundamentally change the amp's nature. I ran back to my headphones (Focal Utopias) to detox my ear canals.
So, how long does a class D need to burn-in? I want to give it a fair shake before writing the technology off forever.
Maybe we have to get use to the class D amp, as it has a very black background, which makes the instrument and voices sound very clear. Interestingly Primare i32 intergrated amp,that is a Class D design, and got very good reviews here in Europe since its release 5 or 6 years ago, will probably be replaced with a new model later this month. Primare have a long product cycle, so it will be interesting to see if they have advanced the Class D design, or gone back to a/b solid state.
"
Interestingly Primare i32 intergrated amp,that is a Class D design, and got very good reviews here in Europe since its release 5 or 6 years ago, will probably be replaced with a new model later this month."
No wonder why my humble bid was accepted. I wish the damn thing would arrive, already, so I could quit reading and get back to listening.
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.
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.
I'm very interested in checking out your take on the first Atmasphere class D amp. Too early to share any insider details like modules chosen. type of power supply adopted, any customized components, target price and expected release date?
As to the Audiophile Review article describing class D amps as 'digital' amps, I think the author, Skip Taylor,was a bit inconsistent in the entire article. I think you're right, he was all over the place on terminology and his knowledge base seemed outdated:
.1. He generically states "Class D Audio amplifiers" which is very close to the name of a class D company, Class D Audio.
2. He talks about "Class D amplifiers" having to use high levels of negative feedback to compensate for poor open loop performance and meet target levels of TIM, not seeming to realize that the inventor of many recent class D breakthroughs such as UcD and Hypex NCore power modules, Bruno Putzeys, believes there's no such thing as too much feedback in his amp designs and considers TIM to be an irrelevant and meaningless measurement as far as class D amps are concerned.
3. The author states:"
By definition, large amounts of feedback introduce transient intermodulation distortion (TIM), which introduces a 'harshness' that hides the rich subtleties and color of the music that were intended for the listening experience." His concept of feedback and TIM have more relevance for traditional linear amps than class D amps as far as 'harshness' is concerned and he doesn't appear to understand that high levels of feedback at all levels of the audible frequency spectrum are the key concept /tool that allow Hypex Ncore modules to sound so good over the entire spectrum, including a lack of 'harshness' and its high levels of detail that enables the rich subtleties and color of music to be reproduced so well.
4. I think the author's 'digital' experience is not primarily in home audio and it was reflected in his article. His discussion about keeping the signal in digital format as long as possible, without converting it back and forth between analog and digital, is a concept I remember from the earlier days of class D when the confusion between switching and 'digital' amps seemed to begin.
I think it's a good concept that kind of lost focus once it became clear that the adoption of the other system components that could make this concept a reality lagged considerably behind the adoption of class D switching amplifiers. Components such as completely digital sources and preamps, that would allow digital signals to be inputted into the audio chain, remain in the digital domain while being routed by a purely digital preamp and sent along to a class D switching amp still in the digital domain, where it would be converted from a digital signal to an analog signal before being amplified and sent along to the speakers.
Most of the early examples of class D amps were actually switching amps that were interchangeable with traditional linear amps but could easily accommodate the above with just the addition of digital inputs.
The author made absolutely no mention of any of this. However, I should point out that, while I think keeping an audio signal in the digital domain as long as possible would likely be a good thing sound wise and with the possibility of enhanced functionality, I believe it also creates a boatload of issues that could be fairly complex, challenge manufacturers' flexibility and budgets, would require industry wide agreement/guidelines and negatively affect the number of customers willing to adopt this new technology/paradigm. At this point, it may be more trouble than it's worth. Tim ,
I'm very interested in checking out your take on the first Atmasphere class D amp.
Too early to share any insider details like modules chosen. type of
power supply adopted, any customized components, target price and
expected release date?
We're doing our own circuit, so no modules, at this point we are using traditional power supplies.
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.
Anybody here running or have auditioned Auralic Merak monoblocks? Just purchased a couple and should be arriving today. Moving to these from a Parasound Halo A23
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."
I've heard Dusty's (Chanel Islands Audio) mono blocks a few times and was impressed by the sound. Very dynamic and musical. Most impressive was the power to weight and cost ration. Very affordable.
Not my cup of tea, as I much prefer the added realism provided by good tube gear.
A good source tells me that Dusty has a giant killer phono stage about to be unleashed for under $1000. I'd like to compare it with my ARC PH8 and write a review afterwards.
I use a Class D Classe Sigma AMP2 which works very well with my Audible Illusions L3A line stage preamp driving Martin Logan Ethos speakers. The Sigma seems to be very neutral to the music and inputs no signature sound. If more power is a requirement one can audition the Classe CA-D200. For me the sound is best when used with balanced ICs.
Over six hundred years ago, adventurous explorers were looking for financial backing to sail west on the Atlantic from Europe to see what was out there and ,hopefully, discover new lands. At the time, early explorers limited their explorations to sailing around the coast of Africa always keeping the land in sight and never venturing out to open uncharted waters. This is why these first explorers didn’t discover much beyond the trade routes from Europe to the East and back. The reason they were reluctant to venture out to uncharted waters and truly discover new things was because of the ’Flat Earth Theory’. The Catholic church was very influential around this time and it, along with other misguided opponents of scientific discovery, propagated the ancient unproven theory that the earth was flat and, if you sailed too far west, your ship and everything in it would eventually reach earth’s edge and fall off into God only knows what. I mentioned the above because your ’Low Class D Switching Frequency Theory’ reminds me of the ’Flat Earth Theory’ in many ways:
1.Just as the ’Flat Earth Theory’ (FET) postponed some early explorers from discovering new lands, your ’Low Class D Switching Frequency Theory’ (LCDSFT) could possibly postpone some of the more gullible audio explorers among us from discovering new audio fidelity in their systems.
2.Just as the FET promotion kept explorers close to the safety of the shore for awhile, your LCDSFT promotion could keep some of the more gullible audio explorers among us close to the safety of traditional linear amps for awhile.
3.Just as the FET proponents used repeated claims of the false affects of an unproven theory to mysteriously prevent the advancement of scientific discovery, you use repeated claims of the false affects of your unproven LCDSFT to mysteriously prevent the advancement of system discovery.
4.There’s obviously more allegorical meat on this bone but I’m stuffed.
You never responded to my earlier questions, possibly from this or another thread, about whether there’s any scientific basis for your theory that current class D switching frequencies are too low and negatively affect the sound of class D amps in the audible range. You also failed to respond about whether or not you have personally heard any sonic anomalies in the sound of class D amps you’ve listened to.and, if so, whether you could describe what these sonic anomalies sound like.
When I first read about your theory, I perhaps foolishly listened to several very familiar and very high resolution (96kHz/24 bit) music files I have trying, as best I know how, to be hyper-critical of the sound quality in an effort to hear if there was any subjective evidence I could actually detect to determine whether your theory had any merit. Well, after a few hours of failing to detect even a hint of a whiff of a scintilla of even a possible twinkle in the eye of even a single sonic anomaly, I decided it was safe to relax in the knowledge that my class D amps had no sonic anomalies in the audible range, at least that I could subjectively detect with my possibly tin ears. Subsequently, I searched the internet for any scientific or even any subjective or anecdotal evidence in support of your LCDSFT and discovered there is zero scientific evidence to support your theory and the only subjective or anecdotal evidence I discovered was numerous google references of your thread postings here and on various other audio forums. I find it hard to fathom why you have repeatedly made false claims of the false affects of an unproven theory on Audiogon and other audio forums.about class D amps. I tend to doubt you do it for some twisted personal version of fun and believe there must be some hidden motivation for someone to so diligently,consistently and repeatedly put forth the time and effort required, as you have, unless they personally judge achieving their mysterious goal as sufficiently motivating.
Don’t worry George Hi-fi, I doubt anyone expects you to actually reveal your hidden motivation or agenda. Fortunately for current and future class D amp owners, repeated suggestions of non-existent sonic anomalies produced by their amps are not audible to any human I’m aware of. Even in the infinitesimally small chance you’re theory actually has an iota of merit, the truth is if the thousands (millions?) of current class D amp users cannot hear these elusive, currently not to have been heard by human ears. very suspect and apparently extremely quiet sonic anomalies then they, by definition, do not exist.
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
I never set out to write long winded posts but I admit they tend to be overly verbose. I’m going to strive for more brevity starting now.
Your last post goes over information already discussed on this thread.and totally avoids answering both relevant questions concerning your theory asked of you in my admittedly long winded prior post:
1. Does any scientific evidence exist that in any way supports your theory that the current class D switching frequencies are too low and result in sonic anomalies that are audible?
2. Have you personally ever heard these sonic anomalies listening to good class D? If so, please explain what these theoretical sonic anomalies sound like. Apparently, you currently may be the lone known human believing in, and claiming the audibility of, these sonic gremlins.
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.
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.
I’d listen to modern Class D amps - like the ones listed above. I’d compare using A/B and extended sessions, all double-blinded.
I’d also listen to the Benchmark amp (not Class D), then buy the best one in my price range. if looked ugly, I’d stick it in a maple cabinet and glue some tubes on top of it.
But they will have to pry my tubed pre-amp out of my cold, dead fingers.
Just like the National Righteous Amplification club sez...
"1. Does any scientific evidence exist that in any way supports your theory that the current class D switching frequencies are too low and result in sonic anomalies that are audible?
2. Have you personally ever heard these sonic anomalies listening to good class D? If so, please explain what these theoretical sonic anomalies sound like. Apparently, you currently may be the lone known human believing in, and claiming the audibility of, these sonic gremlins."
Your response, is to post quotes from a very forgettable 10yr old roundtable discussion that actually is more concerned on the relative merits of class D amps than on the existence of audible affects caused by the switching frequencies utilized? And the panel consists of 9 traditional linear amp (both tube and solid state) designers and a single designer actually designing his amps around class D amp power modules that he did not design but purchased from another company?
Come On, Man! You didn't come anywhere near answering either one of my clearly straight-forward questions by quoting from the comments of a stacked deck panel of traditional linear amp designers, 90% of whom have absolutely no experience designing a single class D amp
Who's the genius who picked out this ridiculously unbalanced panel of participants? Is he the same one who selected the participants for that infamous 'A Remarkably Unbiased Roundtable Discussion on Christianity' that consisted of those 9 adamant atheists and that single choir boy? I would have found that Class D Roundtable a lot more informative, interesting and worthwhile had the genius invited an actual class D amp designer, such as Brruno Putzeys, the inventor of both the Ice and Hypex NCore class D amplifier technologies. Due to the complete absence of ANY evidence that even vaguely supports your theory, the complete lack of ANY description of what these theorized sonic anomalies actually sound like, you're reluctance to state whether or not you've ever actually heard them yourself and my personal experience of never hearing even a hint of sonic anomalies from my class D amps, I think you understand the reasons you need to come up with a new fake theory/boogieman to further your mysterious agenda. How about claiming they spontaneously combust?
^^ one of the artifacts of Class D is is that there can be intermodulations between the scan frequency and the the signal being amplified.
You can see this in the specs if the spectrum of distortions is graphed. So there isn't a lack of evidence!
In the digital world, they call this 'aliasing'. In the analog world (and since Class D is an analog process) we call it 'inharmonic distortion' to distinguish it from 'intermodulation distortion'; the latter being intermodulations between tones being amplified.
This is why the artifact of Class D is different from traditional solid state. The artifacts are similar to those of digital and you see many of the same complaints leveled against it- cold, sterile, that sort of thing.
Its a simple technology, and that seems in a way to belie the issues of how to correct the artifacts, which is rather tricky. Like digital though it is a rising star in high end audio (many think its already arrived but the fact that this thread exists is evidence that it has a ways to go, otherwise it would have completely supplanted tubes and traditional transistors; since it hasn't, we know without needing to know technical issues that its got a ways to go) and its potential can't be ignored (which is why we've been investigating and working on class D ourselves).
Hi atmasphere, Thank you for your explanation. I know your credentials and trust your comments have no hidden agenda. Unfortunately, I don't know georgehifi's credentials and whether he has a hidden agenda against class D. Okay, so you're stating that there can be intermodulations between the scan frequency and the signal being amplified in class D amps. Amp designers call this 'inharmonic distortion' and its affects may be a cold and sterile sound. I just have a couple questions about this:
1. Is there a consensus among amp designers that current switching frequencies (what I believe you're calling 'scan frequencies') being too low is the primary cause of 'inharmonic distortion'? If so, is there also a consensus that raising switching frequencies to the 3-5 MHz range would reduce 'inharmonic distortion'?
2. Can you explain why I, and apparently many other class D amp users, do not perceive our class D amps as being cold or sterile? Do you think the ability to perceive the affects of 'inharmonic distortion' differs among individuals or do you think it's more likely the degree of 'inharmonic distortion' varies by amp?
3. Are there any current methods of measuring 'inharmonic distortion'?
I suggest you ignore some of these criticisms before listening. There are like a billion claims, many old or outdated or downright false.
I can tell you I cannot, blindfolded, or sighted distinguish between my current amps based on Class D and my previous, Parasound Halo A23's. The latter are linear, hi bias AB. I've also heard megabuck class A amps and mine sound as good (within their volume / power envelope).
For this reason, I completely discredit anyone who claims Class D must have x or y artifact.
I am running two Class A/D Auralic Merak mono blocks and also switched from a Parasound A23. I'm happy, but have no reasonable way to do an A/B test between the Merak's or A23 so I don't know what differences I'm hearing! I'm getting old!
I am going to consider an amp replacement after a DAC/disc player upgrade and anything will have to prove itself vs. my current Sunfire (which I guess is closest to a Class G or H)
You know, there are a couple of interesting hybrid Class D which are reminiscent of the carver switching rails designs.
The Yamaha EEEngine and NuPrime. In these cases the voltage rails themselves are Class D which then drive a low wattage linear amplifier sandwiched between them.
randy-11, You stated: "of course, you can measure all sorts of distortion products - inharmonic means non-harmonic." Well golly gee, Randy, I would have never thought that 'inharmonic' means the same as 'non-harmonic'. Of course they mean the same thing, but that doesn't mean that either one is an accepted scientific specification and it definitely doesn't mean either one can be currently measured. Despite your claim of certainty, I am going to wait until atmosphere replies before I believe that there's a current specification for 'inharmonic distortion' and whether it's measurable. I know there's a specification for 'harmonic distortion' and 'intermodulation distortion' as well as standardized methods of measuring both. But this is the first I've heard of 'inharmonic distortion' and I doubt it's even currently a valid scientific term and, even if it is, whether there's a standardized method of measuring it. From atmasphere's earlier post, it seemed to me that the term 'inharmonic distortion' was an informal term used by some amp designers to distinguish it from intermodulation distortion and he made no mention of whether it could be measured.
Erik_ squires,
I'm in complete agreement with you and I hear absolutely no sonic artifacts/anomalies when listening to my class D amps, either. I know from personal experience that all of my class D amps outperform my former class A/B amps by a wide margin in every area that I care about, although my A/B amps may not have been as highly biased as yours. However, I try to keep an open mind about things and listen to the thoughts and opinions of others, especially from well respected sources such as atmasphere. Hopefully, he'll impart some more wisdom on this subject soon.
Ultimately, I realize I'm not concerned at all about whether the theory that current switching frequencies are too low and cause audible artifacts/anomalies is true or not, other than curiosity. If the theory is proven not true, it will just confirm what I have not been hearing since I began using class D amps in my system. In the unlikely case that the theory is proven true, I will be admittedly shocked for a few moments but then I'll just continue on enjoying my class D amps as if nothing had changed because nothing will have changed; I will continue to not perceive these sonic artifacts/anomalies that are proven to exist just as I did not perceive these sonic artifacts/anomalies before I even heard of the theory of their existence. Sure, I'll listen to a class D amps in my system that claim, either by employing better passive filtering or higher switching frequencies, to eliminate all theorized sonic artifacts/anomalies if they ever become affordable just to test if I perceive an improvement in performance. I'm just having a hard time conceiving of how the absence of something (sonic artifacts/anomalies), that I didn't perceive in the first place, is going to improve my system performance. I'm not planning on selling my excellent performing class D amps anytime soon, perhaps ever.
1. Is there a consensus among amp designers that current switching
frequencies (what I believe you're calling 'scan frequencies') being too
low is the primary cause of 'inharmonic distortion'? If so, is there
also a consensus that raising switching frequencies to the 3-5 MHz range
would reduce 'inharmonic distortion'?
No.
2. Can you explain why I,
and apparently many other class D amp users, do not perceive our class D
amps as being cold or sterile? Do you think the ability to perceive
the affects of 'inharmonic distortion' differs among individuals or do
you think it's more likely the degree of 'inharmonic distortion' varies
by amp?
A lot depends on what your reference is and different amps have differing amounts of distortion. Like anything else in this world, you have to try it. As a general rule of thumb though, if you can turn it up loud and it also **sounds** loud, then you know you have a problem. If your system is devoid of higher ordered harmonics and inharmonic artifacts, you won't know how loud the system is until you find that you have to yell at someone sitting right beside you to be heard.
3. Are there any current methods of measuring 'inharmonic distortion'?
Of course! The best use is with spectrum analysis.
Your confirmation that current class D amp switching frequencies are not causing 'inharmonic distortion', along with class D Ice and Hypex NCore power module inventor Bruno Putzeys' statement that current class D switching frequencies in the mid-500kHz range are "completely reasonable", refutes the theory that they need to be raised to the 3-5mHz range (to not affect frequencies in the audible range) as far as I'm concerned. These confirmations make sense since they mirror the more subjective perceptions many class D users have, including myself, of the total lack of sonic anomalies and very high quality performance levels of class D amps..
I'm looking forward to hearing the results of your first class D amp design effort. I suspect your class D amp will be transparent, detailed, with a very neutral overall quality while also having the extreme low noise and distortion levels that all seem to be common characteristics of good class D amp designs. I believe you'll also find that an amp with the above traits will be a great match with high quality tube preamps since the amp will operate as the audio ideal of 'a straight wire with gain' which will allow the sound qualities of your tube preamps to be amplified faithfully without any alterations.
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.
It's an interesting statement you posted George, and that’s from a large company that promotes/distributes Class-D amplification. Kind of gels with what I hear with Class-D. I must admit I’m still waiting for it to come of age, 'till then I’ll also stick with my linear amps. I'd say the writings on the wall though, 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) Great discussion nonetheless & hope to learn something from the various luminaries (and others) chiming in ....
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.
From my technically limited layman’ s perspective, the quote you posted from Optoma USA actually seemed logical and made some sense to me. If I didn’t know better from years of personal experience, I’d probably just accept what they stated as the truth, assuming they knew what they were talking about.
However, I find myself still resisting this theory that current class D switching frequencies cause sonic artifacts/anomalies in the audible range for several main reasons:
1.Two well credentialed and well respected amp designers whom I also respect and trust, atmasphere and Bruno Putzeys, have made statements that there’s no need to raise the switching frequencies for class D amps from the current mid-500kHz to the 3-5 mHz range.
2. If these proposed sonic artifacts/anomalies and supposed phase shifts actually do negatively affect the sound quality as theorized, I would think that a certain percentage of the currently thousands (millions?) of class D amp users, including myself, would be capable of detecting any peculiarities in the sound quality in their systems. I would also expect a certain portion of these users would be alarmed enough to post their observations on this or other audio forums seeking explanations and advice. Oddly, the only comments I’ve read questioning the sound fidelity of class D amps were made by you, George. To be fair, I have read comments by others claiming that they thought class D amps sounded cold and sterile but I’m not sure if these perceptions are related to sonic artifacts. I always made sense of these comments by questioning the quality of the class D amp they heard. After using 3 different class D amps from 3 different companies for soon to be the past 3 years, I’ve never perceived any of them to be cold and sterile and have never heard anything I would classify as a lack of fidelity. I’ve asked you numerous times whether you’ve ever personally heard these elusive,quiet and apparently very difficult to notice sonic artifacts from a class D amp and if you could describe what they actually sound like but you never responded. I wanted to keep an open mind and know what to listen for when I actually spent a couple hours listening to some very familiar music trying to be hyper-critical and detect anything that didn’t sound quite right. I didn’t hear anything amiss.
3. There seems to be a serious lack of any scientific studies or research concerning the affects that particular switching frequency ranges utilized in class D may have on the the actual audible musical signal frequencies being amplified. I’m referring to carefully controlled tests and experiments, with the results required to be consistently and reliably achieved when conducted by independent scientists before results can be verified, conclusions reached and a knowledge base on the subject can begin to be established.
The absence of a solid knowledge base allows individuals such as yourself, George, to put forth any theory that serves their purposes without being constrained by anything as silly as needing to support their theory with actual evidence such as facts or at least agreed upon truths.
But enough of this scientific mumbo jumbo, the simple truth is that I would have sent back my first class D amp for a ’no questions asked’ full refund, and bought a more expensive traditional linear amp, if any of these theorized sonic artifacts or phase shifts caused an audible lack of fidelity in any part of the audio spectrum. The only thing I heard was a small, lightweight, efficient/electricity sipping, cool running, $630 Class D Audio SDS-440-CS class D amp significantly outperforming my large, heavy, inefficient/electricity gulping, hot running, $2,400 former Aragon 4004 MKII class A/B amp in almost every amp criteria that I care about: much better bass response, a much lower noise floor, better dynamic range and a much more neutral and detailed presentation. Both amps had a roughly equal ability to present a solid, stable and realistic 3D sound stage illusion while both had similarly very good mid-ranges and trebles that were well extended but not fatiguing.
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.
You asked:"why do you think Technics have gone to the trouble to advance the class!"?
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.
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.
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.
Hi George, I think you're seriously under-estimating the performance of the many current good class D amps using switching frequencies around 5oo kHz. I say this based on my personal experiences with 3 different class D amps over the past 3 years. Since you've repeatedly refused. or are unable, to answer my pertinent questions of "how many current class D amps you've listened to?" and "What are the telltale audible signs that result from switching frequencies being too low and affecting the audible range?", I now have a new theory about why you continually make this claim without anything close to scientific or even subjective or anecdotal evidence:
I now believe you are the sort that enjoys reading and learning about audio technology and equipment but also one that has very little to no actual experience of listening to audio equipment employing newer technology. This is the only conclusion I'm able to reach given your apparent lack of knowledge about how good some current class D amps perform utilizing supposedly switching frequencies that are too low and your total lack of responses concerning what your theorized affects on the audible range actually sound like. 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.
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.
You stated: "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."
Protecting my investment? I've never considered my amplifiers an investment since I began buying them a few dozen amps ago. As I recall, the vast majority of "investments" I've made in my history of buying amps have been of the 'buy high and sell low' variety. Hardly a recipe for success.
Fortunately, every "investment" I've made in the many amp transactions in my lifetime were made with an expected ROI (return on investment) of improved sound quality in my system, not a financial one.
Since I consider improved system sound quality as my ROI when buying an amp, my 3 "investments" of about $3,500 in class D amps have already been extraordinarily successful, with Sonic Gains already greatly exceeding my expectations. The Sonic Gains continue to flow freely from these amazing, small, light, great sounding, neutral, low noise, powerful, highly dynamic, detailed and affordable "investments". Due to the very low levels of heat they produce, they'll likely continue to reliably provide their sonic dividends for many years to come. Regardless of whether higher switching frequencies and faster/better FETs are able to even further improve class D amp performance, my current class D mono-blocks are providing remarkable performance, with absolutely no detectable sonic artifacts/anomalies in the audible range, at switching frequencies in the mid 500kHz range. I, therefore, have no need to await affordable higher switching frequency class D amps to enjoy their promised benefit of not negatively affecting performance within the audible range since I've already been enjoying this for the last 3 years. While I already know and appreciate how spectacular class D sounds without the switching frequencies having affects within the audible range, out of curiosity I'll likely still audition a pair to hear how the faster/better FETs affect class D performance.
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.
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