This may be of interest to aficionados of Class D.
http://www.psaudio.com/stellar-m700-mono-amplifier/
http://www.psaudio.com/stellar-m700-mono-amplifier/
Class D Technology
So I get the obvious strengths of Class D. Efficiency, power output & running cool which allows for small form factors. I also understand the weaknesses somewhat. 1. Non-linear & lots of distortion that needs to be cleaned up with an output filter.
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?
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?
527 responses Add your response
Agree with Kijanki, I have a class D amplifier that retired my favorite class A/B amplifier of over 20 years (recently modified about 2 years ago). I find my class D amplifier to be superior in terms of detail, spatial placement, sound stage and especially dynamics. Clearly from my listening position I could always hear my class A/B when music was not playing...doesn't happen with my class D. |
George - it appears that TI bought this tech. Quote Originally Posted by amirm View Post I thought Tact Licensed that technology and the actual company that designed Equibit was Toccata. My sense is that it is a different design. But to be sure, I have email into Harman people and will report back what I hear. The Equibit design was developed by Tocatta, originally implemented by Tact T. But TI purchased Tocatta and the Equibit design. Not many companies are using the technology that I know of. Lyngdorf (formerly Tact T) still does, and I know Panasonic built some AV receivers using the Equibit amps; I own one of those. Tim Todd_Packer said: 07-16-2012 02:18 PM Quote Originally Posted by amirm View Post I thought Tact Licensed that technology and the actual company that designed Equibit was Toccata. The Harman Drive Core amplifier chip is a completely in-house design done through Crown engineering. The only thing we used TI for was their expertise in IC Chip manufacturing. There are several patents on the chip design, although the basic topology is a Class D output stage. The Drive Core technology is used in several places, including the Lexicon DD-8, and several Crown amplifiers. There are 2 chips, one is a complete amp on a chip that includes an output stage that is capable of delivering 75 - 150 watts into 8ohms (depending on power supply and application requirements) and is table to 2 ohms, and the only thing that is really needed is a power supply and an input stage. The first use of the technology was in the Lexus LFA supercar. The requirements were high output, small size, high efficiency (greater then 90%), and great sound. Moving the input and output stages onto a single IC allowed much tiger tolerances of the clock and triangle wave form generator that is the heart of all digital amp designs, and often the cause of the "Class D" sound some people don't like. There is also a version that is everything without the high output stage (the input, waveform generator, feedback circuit, etc...) that can me used to drive higher output stages either Class D or our patented Class I, where more then 150 watts is needed. thanks for the interest, Todd Packer Harman Luxury Audio Group Field Application Engineer |
http://www.futurlec.com/News/TI/AudioSolution.shtmlTry to find any of these module numbers on the TI website, especially the last one that drives the analogue speaker, I couldn't. Someone once told me never ever get anything from these guys. Cheers George |
I think Grannyring is right. Even the fairly modest Bel Canto c5i digital integrated amp is evidence of the excellence that can be achieved with newer digital technologies integrated and done well and that it need not cost a fortune. It is a true revelation of the magnitude say of HDTV compared to what was prior. Totally disruptive of what came before and not just another minor tweak or minor improvement on older technologies. |
Fact is the times have changed in audio. Digital is blossoming with tech that combines dac, amp, preamp, room correction etc.. all into one or two boxes keeping the signal all digital up until the point the signal is sent to the speaker.Grannyring - there really hasn't been much discussion on this thread about digital Class D...mostly analog Class D using modules from Hypex and Ice...a few from Pascal & Abletec. Your Lyngdorf appears to use the TI Equibit technology, which combines amp & DSP. Very interesting stuff. http://www.futurlec.com/News/TI/AudioSolution.shtml |
Fact is the times have changed in audio. Digital is blossoming with tech that combines dac, amp, preamp, room correction etc.. all into one or two boxes keeping the signal all digital up until the point the signal is sent to the speaker. Read all the recent reviews of my Lyngdorf 2170 or the Exogal Comet and Ion amp. The future is here right now. This gear is better than all those Class A /AB amps and separate boxes of tube preamp, dac with extra ICs and power cords. We are really experiencing a very exciting time in audio history. It is happening right now as we type these posts. I sold my cutting edge and arduously fine tuned tube and SS gear nicely packaged in numerous separates and assorted hook-up wire for today’s exciting digital tech. The sound is better. I would have never believed it, but I experienced it and love the fact that is comes in one cooling running 15 pound package. Some very special and unrivaled sounding digital gear is currently being introduced and it is nothing short of a sonic revolution. It will sweep our landscape and render our old sonic technology as mere collectors items of days gone by. This is not some sort of small evolutionary change from classic tube gear to modern day tube gear. Rather, this is disruptive change and innovation that will forever change our hobby. This is not somewhere off in the future folks, it is here right now. What a wonderful time to be an audiophile! Especially and essentially if you are an open minded Aphile not blindly holding onto past paradigms and experiences. The cheese has indeed moved. It may take longer for some to fully accept it😊 I still like soldering and building/modding point to point wired tube gear and enjoy the way they sound. However, I know my Lyngdorf is better in every way. While it is fun for me to drop in my latest tube amp project I fully realize it is a hobby and not SOTA. |
Can someone tell me what can be observed when measuring a class a/b amp that indicates its inferiority to pure class A?In a class A amp as mentioned the output devices never turn off. Unless its a single-ended amp that makes little power, one advantage is that even ordered harmonics are canceled in the speaker load due to the opposing operation of the output devices. In a class A amp this happens at all power levels but not so with class AB. Execution is a major portion of the differences between various amplifiers. For this reason it is possible to find inferior and superior amps in nearly all categories. I personally think D is going to win out over AB and A simply because of the cost. If done right, the output section is pretty benign and most of the sonic artifact seems to come from the input section and the converters. Now this has nothing to do with tubes and both traditional solid state and class D still have inroads to make there. I think part of the advantage of D is that its likely that due to its simplicity and the input section being the lion's share of the artifact, that it will be able to eventually challenge tubes in a way that traditional solid state has failed to do (for those that doubt this last statement, if traditional solid state had really been able to challenge tubes, tubes would be a thing of the past. Gone. Nada. They aren't and that's really all anyone needs to know, and there are good sound technical reasons why this is so). Because there is less to color a D amplifier, it should be easier to create the neutrality and smoothness that tubes have had all along. Not seen it yet, but they get closer every year. |
Guido, Thank you for the detailed answer to my question yesterday. One attribute you stated, Aliveness of "black" background... Also called the sound of the silence between the notes... Or the reproduction of ultra-low level information....reminds me a bit of what I found missing from the NC1200 Atsahs, at least compared to my other amps. I am curious about what JRDG has done to bring out the best of the Ncore amplifier module but there are so many features incorporated in those amplifiers, over and beyond the stock Ncore modules, it would be impossible to isolate the specific contribution/benefit resulting from any one of the features. I hope to hear a pair some day. |
Here is another argument for Class D. It can be argued that once you get the bass right the rest is not so hard to sort out. I have found a lot of truth to that in recent years. Efficient Class D amps are both on paper and in practice hands down best at handling bass. That seems to be common knowledge based on application and sure enough I have found it to be true in practice. In a nutshell that’s mainly because of Class D high efficiency and the fact that doing extended bass well is exponentially more work for an amp than doing higher frequencies and efficient amps do it best. Just like efficient speakers make it easier for an amp to do bass well. The end result when done right (ie sufficient efficiency or efficiencies in play to facilitate doing the needed work) tends to sound similarly good in the end I find. |
Erik I’m just trying to frame up the comparison between the various amp technologies in purely technical terms as an extension of georgelofis argument against Class D based purely on switching frequency. I am of the mindset that understanding the technology helps to make decisions where needed but alone does not dictate what sounds best in the end. Technology alone cannot predict what sounds best in specific cases. A system together makes the sound not just one component. Its a team sport as they say. Plus individual preferences vary for many reasons though some technical people have a greater tendency to associate these with specific aspects of technology that matter to them whereas others (I’d like to think myself included) are not so fast to jump to conclusions. So I think we are on the same page in practice. Guess what? My Class D amps were preceded by two different Class A amps that were fine on their own terms but far from perfect in my application. The Class A amps were preceeded by many a Class A/B amp and even a 70’s vintage Class G that was nice overall in its day especially if space is limited but sound quality could not hold a bone compared to any good quality newer amp I compared it to. I heard the Benchmark amp at Capital Audiofest last summer (along with every other kind of amp imaginable) and thought it to be a top performer easily in the same league with the best I heard there. I would own it in a heartbeat. I am strongly considering giving Benchmark preamp/DAC units I heard there a try which if if successful (as I expect it would be) would finally happily eliminate the last tubed gear in my house. I'm all about the sound. The technology used is just a means to the end. |
@mapman I will not agree to any such prejudices. While I can say that class A lacks notch distortion, it is by no means the only type of distortion or non-linearity! We can't on the one hand talk tech. theory on a subject like notch distortion while rejecting THD figures, which is (oddly) what a lot of audiophiles like to do. The distortion and noise measurements between high end class A, A/B and D heavily overlap. I'm also not sure that what audiophiles like to hear is always "better" if "better" = "more accurate." I think audiophiles like sweetening (which is fine!) in which case trying to match an argument with notch distortion and sound quality blows up. The "sound quality" isn't found in the technology per se. If I had all the time, money and space in the world I would not mind having a pair of Conrad Johnson Premier 8 for instance, knowing full well they lie lie lie. :) Best, Erik |
Erik it seems reasonable to me to say Class A/B is technically inherently inferior to Class A for the reasons you cited. IS not good Class A always preferred over Class A/B for sound for the technical reasons you cited? Class A/B is used to keep cost power demands and size and weight down for the masses mainly (sound familiar?), not for better sound or performance. Whereas Class D is totally different and can actually challenge Class A especially as the technology continues to improve even further. Of course I prefer my Class D amps over any Class A/B amp I’ve tried already and even a lesser Class A I once owned. The most unique value of Class D is when much power and current is needed (mainly for bass) as in case of many smaller more extended less efficient speakers that many prefer. As speakers get bigger, loads easier, and efficiency higher, then most any good quality amp can perform well without being too large, heavy and expensive for most, although each will still probably sound different and individual considerations including personal preferences come into play. So practically, it really pays to decide what one wants or needs the physical profile of their gear to be to meet their needs then choose speakers and amps together accordingly to meet those needs. This practically is the most important thing to consider together I would say way more than any particular technical achiilles heel of any specific amp technology one might obsess on. No amp including most Class A amps I would say are perfect so choose your poison. In general., I find Class D amps are the best of all at taking total complete control of speaker which I find tends to yield the best results possible. The result is greater articulation and detail in the bass and a cleaner more dimensional sound overall. Cleaning up/controlling teh bass prevents masking detail at higher frequencies often buried by poor quality or muddy bass when amp is not up to the task of totally controlling the speakers, especially at the low end which is the most demanding and requires an amp to work hardest. Class D amps are MOST efficient and that helps enable achieve this more often than not compared to the competition I would say. Bass reproduction requires the most work by far and is the biggest challenge for most amps. Class D does this best. For higher frequencies, other amps perform well as do the better Class D amps around these days so not as much to differentiate the technology there although skeptics will attack class D high end as its relative weakness which is a fair statement at least historically. But that "weakness" is one that seems to not matter at all practically as best I can tell these days. Even my modest newer BelCanto C5i integrated that I picked up for a mere $1000 used seems to have gotten everything just about as right as possible and that is a complete integrated amp with phono and DAC 60 watt amp and headphone amp. Its easily as good sounding as anything I have heard within its modest 60w/ch power limitation which will come into play in some cases. OF course no single sound will appease everyone so YM will always vary. |
Inferiority... well, I don’t believe this is true either... but! :) In Class A the transistors (or tube) never switches "off". It’s at least minimally on through the entire voltage swing. This is what causes all the heat. At 0 output volts, the + and - transistors are maximally conducting!! To swing in the positive direction the negative transistor has to start reducing current, and vice-versa. The result of all this is that a class A biased device never has "notch" distortion. This is caused by the transistors shutting off during part of the swing. To turn them back on the voltage has to exceed the diode voltage, when it suddenly "snaps" on. It’s not perfectly linear from 0 to 1 volts After the transistor is conducting it gets linear quickly. Whether this is audible.... well, that’s a whole other discussion. :) There's also a lot of debate and misinformation about feedback. This notch distortion is measurable, but reducible by increasing feedback, to the point where the distortion figures can become incredibly tiny, regardless of bias type. There are also a number of interesting single-ended Class A designs of very low power, which use a single device. Look up some of the Pass Labs First Watt designs for lots of info on this. Best, Erik |
Can someone tell me what can be observed when measuring a class a/b amp that indicates its inferiority to pure class A? I am off the opinion that Class A is the bomb when possible. However class A amps to power less efficient speakers are large heavy expensive and power hungry. So enter Class D as a practical option to inherently inferior (to class a amps) class ab amps. |
Ok, let me clarify then: I cannot hear 500kHz, not only because of my hearing apparatus (at my age I have difficulty hearing 15kHz), but also because tweeter’s output drops like a rock with combined effect of membrane inertia and increasing tweeter’s impedance (easy enough to check tweeter’s frequency response chart). There might be intermodulation products, but only if tweeter’s membrane can move at 500kHz - no chance . In addition output filter, set to about 1/10 of the switching frequency, is at least two pole resulting in >40dB/decade suppression. 500kHz frequency that I cannot hear and tweeter cannot response to is already suppressed by >40dB from the peak loudness. I challenge anybody to detect, form the seating position, when my amplifier is on. |
I do not have "ice modules" . i have stated repeatedly I have BelCanto Ref1000m amps. These use ice modules but also custom input and power circuitry and the price and sound reflects that accordingly. Again generalizing and glazing over facts and details to help an argument helps nobody and is a disservice. I would likely not have been satisfied using that older revision of vanilla Ice modules to drive my speakers which is why I opted for a better design. The original Bel Canto ref1000 was vanilla icepower (and much cheaper) and the differences between the two are well documented. I don’t know what KEF uses or why. Its their choice so better to ask them. Probably just easier or cheaper or better for them to biamp in general which opens up options to use different amps for different purposes rather than try to get either one to do it all best at their price point. I’ve heard those those KEFs in my home and they are small power and current hungry speakers. I'd definitely use Class D for teh bass with them but if biamped then many decent options for the less demanding (power and current-wise) high end. |
Bel-Canto Ref 600 mono’s as the newest and most complete.+1 They have sounded the best Class-D to me so far, but they have modded the filters of the newest Hypex modules to do it. As you said "are they the last word not yet", and I agree, as for me to have liked them, they had to be driving a very benign 6ohm load of a very expensive Raven Ribbon to get me to say this. Even then with long term listening they were still a bit too "cold/analytical" sounding in the upper range. Cheers George |
Mapman, I'm glad that you enjoy your Ice Modules. The KEF LS50 was just released in an active version. The woofer is powered by Class D and the tweeter is powered by Class AB. Does this mean that there is a problem with Class D higher frequencies to some ears...or is it just an issue with procurement budget and not being able to purchase the better Class D modules? I don't have those answers but it is food for thought. Kef know what's better for the upper range with using an A/B amp for it, otherwise they would have used another smaller Class-D for it as well, instead of just for the bass, and it would have cost less to manufacture, and been "greener", then they could have called it Kef LS50"G" active. Cheers George |
To me the fact that that a number of forums are now being devoted to class D amps indicates the importance and growth of this tech. I have 3 different class D amps all at different levels of sound quality. with the new Bel-Canto Ref 600 mono's as the newest and most complete. They really respond to tuning with power cords! They are green, run cool, but perhaps as important they are much easer to move around. Are they the last word in amps? not yet.. but getting much better day by day. |
Hi Mitch2, my PFO article on Veritas details all the technical information that I have gathered on Veritas, based on conversation with Merrill, and by reading the publicly available technical literature on the amp. See: http://positive-feedback.com/Issue68/merrill_audio.htm Unfortunately, I have not heard the ATSAH, so I really cannot comment on internal differences, nor sonic differences. In itself, Merrill Veritas is exceptional value for its $12K list price. In a more traditional SS design, At the time of my review a couple years ago, I would have expected such sound to be more in the capabilities of an excellent amp in the lower $20K range. Although there are obvious commonalities between the behavior of M925 and Veritas, there are quantitative and qualitative audible differences, which are however less than the price difference would suggest.... Famous laws of diminishing returns that audiophiles are acquiented to *grins!* Thus, were I to ignore any budget considerations, my preference would comfortably go to M925 for the following parameters: * Power reserve * authority. * Macro and micro dynamics. * Harmonic exposure. * Linearity. * Frequency extension. Transparency. * Sweetness and complexity of treble. * stage size and concreteness. * Imaging concreteness. * Aliveness of "black" background... Also called the sound of the silence between the notes... Or the reproduction of ultra-low level information. * Immunity to electronic background noise. * Immunity to intermodulation artifacts in the treble region. Yet again.... let us Keep things into perspective.... the rowland M925 was engineered with a sophistication commensurate with its pricepoint just shy of $60K, several times the price of Veritas.
Saluti, Guido
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Don’t listen to the negative propaganda especially from just one or two who repeat the same thing over and over. Just try them for yourselves if interested and see.Mapman, I'm glad that you enjoy your Ice Modules. The KEF LS50 was just released in an active version. The woofer is powered by Class D and the tweeter is powered by Class AB. Does this mean that there is a problem with Class D higher frequencies to some ears...or is it just an issue with procurement budget and not being able to purchase the better Class D modules? I don't have those answers but it is food for thought. |
(reduced price,electricity consumption,heat, size and weight) Take the "green" thing out of it has nothing to do with sound quality. Audiopiles have never been "green" let face it those that keep on about the "green thing" are a bit hypocritical. It's a wonder we aren't dead just listening to our "non green" audio. I bet the greenies that spruik the "class d green thing" ignore the rest of the toxic waste dump inside their other audio equipment. the energy tube and s/s use before vinyl it was bakalite then vinyl Boron cantilevers Nickle inside tubes Toxic fluid in capacitors Beryllium dome drivers CD's ect ect ect Cheers George |
Guido, in your posts you have indicated the Merrill Veritas are among the Class D amplifiers you enjoyed listening to and that do not display, "any displeasing high frequency artifacts or limitations." I owned the Acoustic Imagery Atsahs, which should be a close sonic twin to the Veritas. Unfortunately, I cannot confirm the differences between the two since Merrill does not condone opening their amplifier casework and looking inside and I can find no posted pictures of the insides of a Veritas amplifier. Based on my review of online information, the differences between the Veritas and Atsah amplifiers include, hook-up wire and binding posts, individually milled spaces inside the Veritas chassis - although both use solid milled aluminum casework, soldered wire connections (Veritas), and the use of the Hypex input board (Atsah). I would not expect these differences to substantially, or possibly even noticeably, affect sonics as perhaps would items such as a linear power supply, input buffer or input transformers. One listener over at Whatsbestforum who tried both amps (and ended up buying Mola Molas) posted this; "They are sonic siblings. It would be silly to argue otherwise. The basic designs are the same. They both use the same unmodified NCORE SMPS and NCORE 1200 module from Hypex. Sonically, I would give the nod to the Veritas. They are a little more resolving, but not by much and I don't have them side-by-side. So, if an Atsah owner calls me out on this, I won't fight back." So, proceeding on the assumption that by owning the Atsahs for over a year, I have a mostly reliable understanding of how the unmodified SMPS1200 and NC1200 modules sound, whether in the Veritas or Atsahs, then my question to you is, would you describe what you hear differently between the Veritas and the Rowland M925 amps that have earned the M925s a permanent place in your system? - Thanks |
David, My main points of contention are with your earlier post in which you implied that class D amps have inherent compromises in sound quality and your last post in which you said class D sacrifices sound quality for efficiency. You don't specify what these supposed compromises are and I consider it irresponsible to mention sonic compromises in class D as if they were well known and givens. As a result, I feel the need to respond by stating that I noticed no sonic compromises when I replaced my class A/B amps with class D amps. In fairness,mitch2 did state in a subsequent post to yours that, when he compared some class A amps to the very good class D Acoustic Imagery amps (based on the NCore 1200 module), he thought these class D amps had some very good qualities (bass, tone, power, body and lack of noise) but they lacked the 'musicality' that he perceived with his class A options. Fair enough, in his system he preferred the class A ( not class A/B) amps because they sounded more 'musical' than the class D amps. This 'musical' quality, by which I think he means that his system portrays a realistic sense that he is in the original venue listening to the actual performance, is obviously a very important quality to him as it is to me. While I didn't directly compare class D amps to class A amps in my system I did compare them to my former class A/B amps. I do not perceive a lack of 'musicality' in my class D amps (D-Sonic M3-600-M mono-blocks) in my system and room. I have no interest in arguing the point or about why we had such different results. I just think we're both fortunate to have found such good amp solutions and we both should enjoy our systems no matter what type of amps we use. The main point I want to convey is that current good quality class D amps perform very well. Based on my experience they outperform my former good quality class A/B amps- Adcom, McCormak and Aragon-in all categories that count for sound quality. Getting back to the OP's original question: "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?" My answer is I do not think class D amps beat Class A in any categories that count for sound quality yet, based on others opinions who have compared them directly in their systems and my auditions of class A amps in dealer systems. However, class D amps have so many other advantages over class A (reduced price,electricity consumption,heat, size and weight) that some may opt for class D anyway. Then there are class G and H amps which I'm keeping an open mind about until I learn more and hopefully hear them. Other than the above, David, I have no issues with you. However, I am a bit curious whether or not you utilize or offer class D amps in your HT business. I certainly have no issues with you voicing your opinions just as I think you have no issues with others voicing their opinions. After all, I think that's the whole purpose of this very good forum. Thanks, Tim |
mapman Those who discount or ignore the advantages inherent in newer more efficient and overall higher performance Class D technology are doing others a disservice.Don't be silly. Those who exercise their personal preferences here do a disservice to no one - except, perhaps, themselves. No one here owes anyone else anything. |
savdllc (can’t "at" you for some reason) you wrote: What I did state is that Class D designs tend to sacrifice fidelity in favor of efficiency, which is true in most cases. This is the bias I was trying to answer, my apologies I did not connect my statements more clearly to your writing. I am unable to support this statement based on any evidence at all. I do believe that Class D is in a much wider quality range of products than Class A. By this I mean from cheap portable music players to high end. Class D is, numerically, overwhelmingly dominant and across every market segment, while the ONLY place in audio I know of with Class A being produced today is high end, often mono-blocks. (There’s probably some Bugatti with Class A amps, but lets get real) This may lead us to make unfair apples to oranges comparisons which don’t actually tell us much about the overall potential of Class D. At the high end, I see no sacrifices being made for Class D except to my carbon footprint. I DO hear differences in amplifiers. However to hear those differences and say "OH, well Class D is inferior, so the A/B amp must be better sounding" is an snobby prejudice. There are even some strong benefits, as some have very high damping factors (output impedance) and therefore more consistent performance across speakers. I think that the subjectivity of the "high-end" can be quite trendy, or go pretty far from neutrality. If that keeps a Class D from reaching top-tier status, then it's just a matter of time before a vendor creates the right input buffer for you. Again, to everyone, please please buy what you like to hear, but let’s not use cost as our golden calf of determining what’s best. Best, Erik |
Don’t listen to the negative propaganda especially from just one or two who repeat the same thing over and over. Just try them for yourselves if interested and see. Myself, I’ve had way less trouble finding top notch sounding Class D amps than others. Will probably never go back to anything else. If I had unlimited budget and/or went only with very easy load speakers, perhaps it might be easier to find other amps to match overall performance and sound quality I have experienced with Class D. But even so I have no reason to ever go back to anything else. My Class D amps do it all as well or better than anything else I have heard in recent years. If I were to seek a particular unique flavor of sound only available with a tube amp, maybe. A good Class D amp is like a high performance car engine. it makes the entire experience a lot more effortless and enjoyable. Those who discount or ignore the advantages inherent in newer more efficient and overall higher performance Class D technology are doing others a disservice. I know I’m glad I went with my gut which told me to actually see what this popular and innovative newer technology is actually capable of before resorting to older more familiar solutions that never seemed able to fit the bill for me 100%. |
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 " Let me try to respond to the question posed by the OP in the crispiest way I can: 1. I am deeply dissatisfied with at least 90% of amps on the market that I had the fortune, or the misfortune, to audition, regardless of class of operation. 2. I have selected my class D amps because I fell in love with their total audible performance, for every parameter.
4. I found less than a handful of amps that enthrolled me as much, or almost as much... The leading contender was made by Solution... Enchanting class A/B amp, which I would put more or less at par with the classs D Rowland M925 As for which class is inherently audibly superior .... It is an absurd question, which has no meaningful answer. On the other hand, I grant you that when class D misses the musicality mark, either because the amp is not properly broken in, or because of inherent design flaws/limitations more common on older designs, it has the ability of outschreetching and outtubbing most everything on the market... The most unendurable listening experience for me was in fact that of a lower cost class D amp... Closely followed by that of an uber-stratospheric SS class A/B system... Conversely, even the worse uber-expensive tubed amp I heard, was only marginally worse than totally uninspiring.
G. . |
"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?"That is the debate, my answer is no, not yet, (except in the bass & upper bass). And it’s not because of the power, but more the damping factor (low impedance output) which some say is aided by of gobs of feedback. Cheers George |
@erik_squires and @noble100 , I'm glad you both have found systems that you are happy with, and you are certainly correct in that there are some great Class D options available on the market - I do not believe I stated anywhere in my post that Class D in universally inferior to A/B. What I did state is that Class D designs tend to sacrifice fidelity in favor of efficiency, which is true in most cases. Are there exceptions? Sure, though that's not really what the OP was asking; his question was not if the best Class D designs can compete with Class A/B, it was: "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?" And while audio quality is somewhat subjective, I think you're going to be hard pressed to argue that even the best Class D amps will rival the best Class A amps on the market. I brought up Class G and Class H as being potentially better options in the ongoing search for increasing efficiency while preserving fidelity, which from a sheer technological and design point of view, is hard to argue with when it comes to reproducing full-range audio. The only downside is cost, as it's a much more expensive technology than Class D, and that may well be what prevents it from ever becoming a mainstream option. Anyway, I've no wish to start an argument with you or anyone else - I was simply trying to share my thoughts on the subject based on my experience as both a long-time enthusiast and owner of a home theater company. Cheers, -David |
Kijanki, I don't think that anybody is doubting that your amplifier sounds brilliant to you. At the same time, I think it's okay for others to be less satisfied about what they hear. Don't get me wrong. Class D is the future and there are a lot of audiophiles sitting on the sidelines, waiting for the technology to mature.+1, and the only way is to speak up and get it done. So far Technics is leading the way. Cheers George |
I am not sure where obsession with the switching frequency comes from. It is inaudible while the only other thing that it might cause is filtering network phase shift - that can be beneficial since speaker has much larger positive phase shift at high frequencies. Placing nonsense about signal being "destroyed" (while SACD works exactly the same way) is trolling.If you read my post I used a question mark and asked for clarification and correction...which Atmosphere was kind enough to reply to and correct my confusion. Kijanki, I don't think that anybody is doubting that your amplifier sounds brilliant to you. At the same time, I think it's okay for others to be less satisfied about what they hear. Don't get me wrong. I want a tiny powerhouse amplifier that sounds brilliant to my ears as much as the next guy. Class D is the future and there are a lot of audiophiles sitting on the sidelines, waiting for the technology to mature. We need early adopters to buy into the technology so I'm thankful that the modules are good enough or even perfect right now for many people. |
I am not sure where obsession with the switching frequency comes from. It is inaudible while the only other thing that it might cause is filtering network phase shift - that can be beneficial since speaker has much larger positive phase shift at high frequencies. Placing nonsense about signal being "destroyed" (while SACD works exactly the same way) is trolling. In fact raising switching frequency might be harmful because of the dead time, forced by the controller to avoid shoot thru, that Atmasphere mentioned. Since this time is fixed, error it makes will be larger at the higher frequency. One might not like the sound of particular class of amplification but making pseudo-scientific explanation i plain silly. |
"Maybe it's some that are so pro Class-D as it stands, and can't/refuse to see that it's maybe it's not become of age yet. If they can concede that Technics with their SE-R1 are showing the way in the area of switching noise frequency development, maybe then there'll be an even faster development in that area by other class-d manufacturers demanding to have those components to make it happen. " Is this Technics you keep referring to class D ? Or is it a digital amp ? Totally different technologies ? |
In learning about Class D, it appears that after the linear signal is destroyed and turned into a saw tooth wave form, the output filter? tries to put the signal back together...doing an incredible job considering the complexity of this task...but ultimately is unable to restore micro details to recreate the original signal...which people such as myself notice very quickly, while others either don’t notice or enjoy the new coloration. The opening statement here is false. Here's how class D works: There are essentially 3 building blocks: 1) the triangle wave generator (sets the 'scan' frequency) 2) A comparitor, the compares the incoming audio signal to the triangle wave 3) the output section. This is the power transistors that switch on and off, and any circuitry needed to drive them The sawtooth or triangle wave generator is running all the time. The comparitor is too- taking the audio signal and turning either on or off depending on the state of the triangle wave and the audio signal at any given time- the output is a series of pulses of varying width, which are used to switch the output transistors either on or off. This technique is called 'Sigma Delta' and is a means creating the output pulses of varying width so is also known as 'pulse width modulation' The scan frequency is a function of the triangle wave generator. Some ICs can't make a good triangle wave at higher frequencies so quite often this can be the reason the scan frequency is limited. The other reason might be the output transistor's ability to switch (these days its pretty easy to find inexpensive parts that can switch at well over 1 or 2 MHz...). There is usually a filter at the output of the amp to filter out the scan frequency. Once that is filtered out, all that is left is a much higher current version of the input signal. The scan must be kept constant to maintain fidelity. The output devices can sometimes stay on longer than they are supposed to (typically they take longer to turn off than to turn on) so they can both be conducting at the same time. If this happens, you get a phenomenal called 'shoot-through current' which can heat up the outputs really fast, so sometimes additional circuitry is used to make one transistor wait until the other is off before it turns on. This wait time is called 'dead time'. The longer the dead time the higher the distortion. Dead time is usually needed at higher switching frequencies, so you can see that the need to go to higher frequencies to reduce distortion (and increase resolution) is hampered by the fact that more dead time might be required, which increases distortion. So you can see that the designer has to weigh options! This is it in a nutshell. Some things are glossed over and others omitted entirely, but if you know what is written here then you have a pretty good idea of how they work. |
Hi George, I am amongst those who cannot hear any displeasing high freequency artifacts or limitations in some -- and by no means not all -- class D amps in current production. I would include at least: Rowland M925 and 825 (both based on NC1200), Continuum S2 (Pascal M2-Pro). Bel Canto Black (NC1200 derivative). Merrill Veritas (NC1200). Conversely, a number of older amps, like the old Rowland M501 and 201, and the NuForce did display modrate to severe audible limitations. It is also worth mentioning that even the best class D amps can sound limited, oscillating between screetchy and tubby until break-in is complete, which unfortunately can range between 600 and 2000 hours, depending on power conversion module and amplifier design... THus, breaking in a class D amp can be an exercise in extreme patience and anxiety control *Rolls eyes!*
Yet, As you are mentioning the switching frequency as a probable cause of limitations that you perceive, would is your estimate of the switching frequency one would require to push any such artifacts into the inaudible stratosphere for good? Saluti, Guido |
mitch2, Thank you for your reply, I agree with all you stated and now have a better understanding of your thoughts, situation and position. I'm glad we were able to clarify and think it's a good sign that we were both able to find amplification that we're pleased with utilizing different amp types. Later, Tim |
That is trollingOnly in your mind, because you refuse to accept that the higher switching frequency has yet to be realized, and you can't hear anything wrong with it where it is at the present. Even though companies like Technics are showing the way and striving for higher frequencies, with their very expensive SE-R1. And as far as not giving any positive post go, I said they have a bass control that can't be equaled, and I'll be the first to get the newer generation of higher switching frequency ones, when they evolve which will fix the problems that many hear in the upper mid and highs, and you obviousely can't. Cheers George |
All is good Noble100, I can certainly understand how folks like the Ncore amps so much since, in my system, they did a lot of things right
(bass, tone, power, body and lack of noise). However,
even with very good and highly regarded amplifiers, seemingly minor sonic characteristics can affect one's level of satisfaction with how their system sounds. Everybody has their own personal "right" sound. I really wanted those to be my "final" amplifiers because they had the desirable combination of high power, high input impedance, balanced operation (my system is fully balanced), small size, low energy usage, low noise, and the ability to remain powered up all the time. Unfortunately, my preference was for a pair of large, heavy, and hot Class A amplifiers. |
mitch2, My comments in my previous post were solely in response to savdllc's/David's post on 12/31.and were not directed at you at all. After reading your post and the review you linked to on the Mola-Mola class D preamp and amps, you are clearly not included in the group of posters that have never heard a good class D amp in their system. I concede your point that some have compared class A and A/B amps to 'current good class D amps', not just the early class D amps,and still preferred the class A or A/B amp. In regards to what I consider ' current good quality class D amps', I would include any amps utilizing the NCore-1200 modules (Acoustic Imagery Atsah, Merrill Veritas, Theta Prometheus, etc.) as well as those utilizing Abletec and Pascal power modules (Marten, D-Sonic and Rowland). There are also other current good quality class D amps such as H2O, W4S, Red Dragon and Bel Canto. Sorry, I probably missed a few other current good quality class D amps,too. Your attached review of the Mola-Mola preamp and amps were one of the few reviews I've seen on the Kaluga monos that was not extremely positive. The review was not totally negative but it seemed to me like the reviewer had such high expectations going in that only near perfection would result in a positive review. Both you and the reviewer mentioned 'a lack of musicality' which is a quality that is very subjective and uniquely perceived by each listener. Regardless of how each person defines it and perceives it, however, I think 'musicality' is probably the most important quality a home music system needs to possess. I understand it's a quality you require in your amp and I feel the same. I believe we both perceive the bass,power, tone, body and lack of noise in good class D amps (NCore-1200 based amps in your case and Abletec based amps in my case). but you also perceive a lack of 'musicality' whereas I do not. As a result, I'm much more enthusiastic about good class D then you are. You're very pleased with your class A or A/B amps and I'm pleased with my class D amps. I'd call that a win-win scenario, congrats. I believe no amp technology has a monopoly on good sound quality and think we both agree that class D is not right for everyone. No big deal, right? Tim |
You originated this thread pretending you want to learn about class D, while knowing you hate it.Maybe it's some that are so pro Class-D as it stands, and can't/refuse to see that it's maybe it's not become of age yet. If they can concede that Technics with their SE-R1 are showing the way in the area of switching noise frequency development, maybe then there'll be an even faster development in that area by other class-d manufacturers demanding to have those components to make it happen. Cheers George |
