I’m a little puzzled by all this "switching" talk. My class D amp has 60kHz bandwidth while tweeters are almost completely quiet with my ear next to them (200W amp). I’ve read the same in many reviews of different class D amps. It was much worse with class AB amp in the same setup. Highs in my amp are very clean while midrange is simply wonderful. As for SMPS being noisy, nothing can be further from the truth. New zero current/zero voltage switching SMPS are extremely quiet and that’s why Jeff Rowland uses them not only in class AB amps but also in preamps purely for their low noise (efficiency is unimportant in preamps). Just to show an example: Benchmark reduced noise floor in their latest DAC by 10dB using SMPS instead of Linear PS used in previous model of the same DAC. It is because Linear PS is not linear at all. It is simply unregulated noisy switcher that switches at 120Hz at max voltage producing not only hard to filter 120Hz but whole bunch of high frequency harmonics - since current is taken from the mains in huge narrow spikes. Power supply is line and load unregulated and requires huge amount of capacitors to keep voltage steady. These high inductance capacitors are in series with the output (circuit closes thru them). Adding parallel non inductive caps might help but it will also create (with inductance of electrolytic caps) a parallel resonance circuit that will ring. That’s why class D amps with SMPS are praised in many reviews for keeping composure under heavy peaks (orchestra’s forte). Lets forget about "switching" - speakers are unable to play 400kHz while we are unable to hear it at all. It is imagined problem by "experts" that have absolutely no clue trying to find something wrong. Class D are linear amps where duty cycle, instead of voltage, is used as adjusted quantity.
Who tried Class D only to return to S/S or Tube
And what were the reason you did a backflip back to S/S or tube.
As there are a few pro Class D threads being hammered at the moment, I thought I'd put this up, to get some perspective.
Cheers George
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Thank you George, yes I have heard the screaches you describe, as well as the dark uninvolving sound several times at RMAF.... Quite consistently from some class D brands, and unfortunately equally consistently from some brands that produce otherwise well regarded class A, A/B, and a variety of OTLs and other tubed amps Luckily none of the amps of any class that I have owned since I sold an Aragon 4004 Mk.2 in the late '90s have had an even remote propensity of creating such audible horrors. Somehow, my home is blessed by marvellous music... Yes, I hear music that is congruent with the sound of live acoustic instruments that I have experienced since I was six years old. Can it be enhanced further? ... Of course! |
Can it be enhanced further? Yes it can and soon I think, and I'll be there when it does, as soon as I see the technology about to become available from the big multinational component manufacturers, to supply the Class D manufacturers with. I'll get the jump and flick my expensive power hungry potential boat anchors before it's too late, and wait for the 2nd generation Class D to appear, even if it means I'm without music for a while. Cheers George |
2nd generation is already here. Ableteck, Pascal and Hypex are all making 2nd generation class d amps that are competitive with nearly anything ss or tube based at less than ridiculous prices. There is no issue with the switching frequency nor the filtering in these modules. None of these produce any audible distortion products at the tweeter. I have heard all three. They are all excellent and have been well reviewed. |
Have you heard an Ncore, Pascal, or Abletech based amp? I have. They have all been reviewed very positively with no complaints about switching frequency artifacts. Perhaps future products will operate at high switching frequencies, but that is no panacea as high rates introduce other issues. Read Putzey’s papers on class d design. He addresses switching frequency. With the audio quality attained with these modules, your switching frequency concerns are a solution in search of a problem.... |
George, the answer is... Yes, the current switching frequencies of approximately 500KHz in the power conversion modules are sufficient for some OEMs to implement some marvellous-sounding amps.... Kuribo and several others have already mentioned some example brands and models. Having said this, and knowing how things proceed in technology, the word "enough" hardly ever applies, no matter where one stands in the evolutionary curve. Whether a switching frequency increase of 5X or 10X yields an audible enhancement or not, such featture will eventually be introduced at some time in the near/medium/long term future by module and SMPS manufacturers. And with such next gen component parts, some OEMs will create even superior amps... While other ones will persist to develop "Creatures From The Black Lagoon", and all in between. 'Tis all in the handle, George! G. |
Kijanki, in your zeal for Class D I'm afraid you mischaracterize linear power supplies. Not all are cap input. Choke input linear supplies do NOT draw power in "huge narrow spikes". In fact they draw power continuously throughout the conduction cycle, resulting in smooth, fast and clean power delivery. No "huge amount of capacitors" are needed since choke input supplies have very good inherent regulation. I use choke input in everything I build, including amps, preamps, DACs, even for DC IDHT tube heaters. Best feature though is no RF nasties flying around the room, which are inevitable with high frequency switchers. |
Ait, Choke at the input as well as choke and big capacitor in my Furman Power Factor correcting conditioner serve as filter. Charging Linear PS capacitors is still done in narrow spikes of high amplitude - no escape from that. Current is switched on and off when voltage is the highest (worst possible moment). Choke filters out spikes from the power cord but problems inside still exist. Switching noise propagates thru the circuit affecting sound. The only linear part in "linear supply" is that it is unregulated. Output voltage still depends on the load while line regulation is zero. I wrote about "linear" supplies, to show that switching can be done smarter in SMPS that has very tight line and load regulation - usually not possible in power amps linear supplies because of power dissipation in voltage regulators. There are great sounding amplifiers with linear supplies, even without any input choke. I’m only stating that it can be done better with quiet SMPS. Switching supplies designed by Jeff Rowland are extremely quiet. FAQ on his website explains why he abandoned traditional "linear" supplies. http://jeffrowlandgroup.com/kb/questions.php?questionid=145 |
Kijanki, I believe you misunderstand what a critical inductance choke input supply is. The input choke serves to smooth the current draw - I have attached two simulations of the power supply I use in my amps showing the current draw in the first power supply capacitor. The left half of the picture is the supply as-is (with choke input); the right half is the same supply set up as cap input. http://i1243.photobucket.com/albums/gg559/Quagmire22/Choke%20vs%20Cap%20Input%20Supply_zpsnywzj0ww.p... Notice that with choke input the draw is a smooth sinusoid. With cap input the draw is as you describe - sudden sharp pulses. The energy storage of the input choke smooths the current draw and also contributes to the very good regulation of the choke input supply. |
Ait, Perhaps I'm missing something. Imagine rectifier charging capacitors to 50V with 5mV ripple present. http://i.stack.imgur.com/BLGnf.gif Capacitors are charged ONLY during voltage increase on capacitor. This period for 5mV ripple (1% of 50V) is: Arccos(0.999) x 16.6666ms / 360deg=0.12ms Charging current has to be huge (hundreds of amperes) during such short time to meet average current draw. In addition to this huge current spikes rectifiers are not fast enough to turn off at the peak of the voltage conducting current for a moment in opposite direction to snap back to zero. That creates extremely short spikes that large inductive caps won't filter and that will couple to any LC circuit. Using "softer" diodes (faster switching - slower snap back) helps to reduce this noise (makes pulse longer). There is a lot of switching noise from Linear PS polluting from 120Hz to tens of kHz In addition to noise created by linear power supply huge spikes of current have also huge rms/average ratio causing big losses in transformer windings while high frequency component causes losses in the core (eddy currents, hysteresis). You might filter these spikes with chokes but capacitor itself can be only charged during very short time (fraction of ms). |
I showed the current waveforms through the first PS Capacitor in each case. It's clear that in one case there are sharp spikes through the cap, in the other there are not. The rectifier is not directly charging the cap, it's charging the inductor, which stores the energy in its magnetic field, then the inductor output charges the cap. Filter topology is LCLC. |
Ait, I think it is possible to place very large coil in front of capacitors in order to obtain constant charging current in form of sinewave. The problem I can see with this scheme is size of the coil (huge inductance with low resistance) and the fact that voltage on the capacitor will depend on the load. Voltage with load should be roughly 2/3 of peak voltage, but without any load it could climb up to 100% (peak value). I guess it should be possible in class AB amps to provide minimum load with additional resistor (if necessary). Interesting concept, but I suspect seldom used because of the cost and size. On the other hand high end audio is never practical. Thanks for the info - I will find some articles to read on this subject. |
[quote]Atmasphere made no big logical mistake - his assumption is valid, though
the result of the technological evolution is by no means guaranteed. In
other words, class D amps might get a little better and then exhaust
their potential, or they might keep improving more and more with no end
in sight.[/quote] Exactly. One can assume that since there is a 3rd gen out there, that there will be a 4th gen sometime too. This thread and others like it exist as proof that class D is still not a mature technology as the improvements that have appeared in just the last few years are made out on those threads and this one to be pretty profound. If the technology were mature, the improvements would be incremental, possibly taking a decade or more before the improvements accrued really meant something important. |
Mature or not, it has arrived, and is already making major inroads in the amp market. Many, as mentioned, have replaced their big name tube and ss amps with class d. It’s here, it’s thriving, and it can only get better, which is scary to think about...especially for those invested in tube and ss tech... |
Kijanki, The choke needs to be of "critical inductance" at minimum, for this type of supply to work properly. Lcrit = V(dc) / I(mA) So higher voltage and/or lower current require a bigger choke. This type of supply was often used decades ago when capacitance was expensive compared to chokes; once capacitance became cheaper it fell out of favor in the mass market, but it retains its unique advantages to this day. Happy reading! |
Not sure what others have said...but I've really like the Peachtree 220 and Rotel 15 series class D amps. Those 2 are very musical...and no reason to go back to A/B amps unless the configuration of a specific piece is something that you like. Personally...I found older Bel Canto and Channel Islands to be a bit cooler sounding...some folks might call them a little "clinical" I'd guess. |
kuribo, it appears that we need some common language here. Saying "technology is mature" is a polite way of saying "It hit dead end" - therefore don't expect major improvements and place your order today. There are many technologies still improving in exponential rate HDTV, Phones, Computers, DSP processing etc. that most likely will keep improving, but it doesn't mean they are inferior to such mature technologies like B&W analog TVs. The fact that effect is achieved by switching instead of steady value doesn't mean it is worse. Plasma HDTV operates on class D principle and to many people it looks more natural (colors, motion etc) than LCD/LED HDTV. Modulator used in class D amps resembles Delta-Sigma A/D converters that already went thru many years of improvements (PWM is a byproduct of Delta-Sigma processing) and in my opinion will keep improving for a long time. It is not even a question what class amps are the best, but rather how good is the amp I can afford. Many class D amps offer a lot for the money. |
tfats, I've never heard Channel Islands but I know they were based on Hypex modules and had great reviews. Bel Canto used Icepower modules (that my are in my Rowland 102 as well). Hypex had dual supply (+/-) but only two output Mosfets switching (thru Zobel filter network) one end of the speaker (the other end at GND). Icepowers used single voltage but four Mosfet output bridge switching speaker direction between + and GND. Somebody mentioned sound difference between two families, Icepower being closer to tube amp while Hypex closer to very good SS amp. I'm not sure if output configuration has something to do with it or it is just different signal processing (modulator). Hypex configuration is more practical (output can be further bridged), but I'm happy with Icepower. It sounded different with different speaker cables - a little thin and colder with older AQ cable and fuller/warmer with Acoustic Zen Satori. Lower midrange got stronger, cello sound fuller, male voices have depth (chestiness). |
I've briefly listened to class D amp's, not my preference, did the same with class a/be amp's, btw, as it turns out, my preference is class A solid state and tube equipment, the heat has never bothered me that my amp has, to each their own, I've always been a class A fan, and likely will continue to enjoy for years to come. |
I think the main
reason some folks dislike the "good" Class D of today who
have actually tried it in their own systems is because they haven't
let themselves adjust to hearing how a musical presentation sounds
without audible distortion interfering. Yes, like it or not all that
"creamy warmth" people talk about IS distortion that is not
likely found on the original source material.
|
Hi ENIAC, your post could not be timelier. On Friday 11th, Marc Mickelson of The Audiobeat, posted his review of the Rowland M825 stereo amp, which sports those very class D NCore NC1200 modules that you have experienced in your system. Marc's findings are based on prolonged use of the amp in his system,, which protracted for a number of months... Yes, I estimate the device to have been fully broken in. He appears to concur with your opinion that appreciation of musical neutrality in high achieving class D amps may require a paradigmatic shift for some audio lovers, away from some much beloved traditional warm sound. Amongst other things, he expresses the following thoughts in his conclusions... "Such a peripheral line of reasoning underscores what is very best about the Model 825 -- and potentially any great piece of audio equipment: it makes you forget that you're listening to a complicated and expensive audio system. This is more than the ability to suspend disbelief; it's a disarming of critical faculties, even when you're trying to be critical and unravel what you're hearing. In my experience tubes do this more readily than solid state, and class D almost never does it. The Model 825 does it as a matter of course -- it can't not do it -- and it happens not because of one or two or three of the sonic traits I discuss above, but all of them, in their exact proportions. If the Model 825 were somehow more natural, bordering on romantic, or more round and rosy, especially through the mids, it would be a different amp and perhaps a very good one, but not a great one. And the Model 825 is a great amp -- in numerous ways, greater than any amp I've heard. It speaks not just in its own voice but in a voice I always wanted to hear, such is the pull, at least for me, of the utterly clear yet composed way it reveals all that's on each recording." http://www.theaudiobeat.com/equipment/jeff_rowland_model_825.htmSaluti, As for Marc's caveat that "class D almost never does it", I respectfully disagree with him... And suggest that listening to a broad range of current high performing class D amps tends to reveal that class D in general has the same chance of sounding great or horrid as any other topology. Guido |
Class D is a cheaper implementation of amplification! , the manufacturer's make way more money and less over head, also, a high quality class A amplifier is extremely more complicated to implement! , an example of what I'm saying is, pass Labs class A amp's cost a lot more then their other model's, ask your self, why is that? , my system is so clear, you can hear the feet shuffle in the back ground, and page's turning with high quality classical recordings, I have class A, however, I also paired this with quality cable's to retrieve such information, also, their is tube equipment, we all know tube amplification is class A that is incredible sounding, class D will never have the clarity and sound stage, naturalness, detail that class A has, I understand this is my opinion, however, it's based on experience as well, been building systems for 36 year's. |
Hi Audiolabyrinth, I am absolutely vdelighted to hear that you love your class A amp. I feel exactly the same about my class D Rowland M925, which like your own device, appears to have a propensity for conveying feet shuffling, page turning, and.... Plenty of subvocalizations on old Glenn Gould and Andras Schiff recordings... Did I mention that it is so musical it makes me forget where I am? Unfortunately, I have no idea how to evaluate amps according to parts count or soldering joints... I just listen to the music from components that I have had the fortune of owning, or at least listening to, with as little prejudice as I can muster in the process. BTW, In SS class A/B, I truly adore Solution. in high power tubed amplification, ARC and VTL realy strike my fancy. In SS class A.... I am sure I will eventually find an amp that takes my heart away... I am sure it exists out there already *grins!* Y Regards, G. |
Rsf507, I did not say class D amp's are over priced! , I said, they were cheaper for a manufacturer to build-make,, my cable's were not the topic of this thread! , you attempted to change what the thread is about here, but I will say this, my cable's are the best investment I've done, no regrets, worth every penny I paid!, that said, please, let's move on and stay on the amplifier subject at hand here, thankyou. |
Guidocorona, you know, I have no issue with any one who enjoys class D amp's, but I will mention that you and I have a mutual friend that has a great system that uses the burmester 911 amplifiers, they are class A amp's, I understand most people cannot afford such amp's, the mutual friend is audiogon user name mattnshilp, cheers. |
Hi Keith, doing well, and... Wow, I knew I was forgetting something important.... Fact is that Burmester is my other prefered uber-high SS brand, together with Solution and Rowland. How could I forget, given that I was the one who pointed Matt onto Burmester?! Only thing is... Seems I had a misconception. I thought Burmester ran in high bias class A/B, hence my original assertion that I had not found a class A amp that took my breath away. Well, seems that I had already found one after all... Burmester 911 and likely 909 at RMAF.
Burmies are an interesting case for me. In olden days, think about 15 years ago, they were not my cup of tea at all... I thought them to be both a little dark and a little hard sounding. Yet in the last several years they evolved into what for me are creators of true magic. So now I know I have already found high magic in class D, Class AB, class A, and hi power tubes.... I am confident that my discovery of magic OTL will come eventually Saluti, G. |
After a year and a half, I have finally divested myself from a pair of very good sounding Ncore NC1200 Acoustic Imagery Atsahs, but I have not settled in on their final replacement. The original comparison was between the Class D Atsahs and a Class AB McCormack DNA-2 LAE that I own, which SMc Audio upgraded to their Signature Edition in 2014. The SMc-McCormack is an excellent sounding amp and, in comparison to the Atsahs, simply sounded more "real," primarily due to a better portrayal of spacial cues between musicians, a better sense of venue and perhaps a better ability to portray micro-dynamics. In addition to the upgraded DNA-2 LAE, I also have here a pair of Class A Lamm M1.2 Reference monos and, as of Monday, I will have a pair of Class A Clayton M300 monos. I plan to keep either the Class A Lamms or Claytons, and then decide whether I want to keep the Class AB SMc-McCormack too. Reviews have been very positive about the Class D NC1200 amps, and I found them to sound quite nice, with standout features being a dense tonality and excellent (although possibly overdamped with some speakers) bass, as well as several very attractive ergonomic characteristics such as small size, low heat, low energy usage, and zero self-noise. Unfortunately, in comparison to the mentioned Class AB and Class A amplifiers, I felt the Class D Atsahs were lacking that last bit of lifelike ambience, as if music is not being played live or by a band in a studio, but rather as individuals cutting their own tracks and then merging the tracks to make the whole. In my opinion, the reviewer over at Mono and Stereo actually got it mostly right (although too critical), with his review of the Mola Mola Kaluga, where he states, "The familiar music didn`t sound much familiar through the MOLA MOLAs; in the midrange the voices did not posses enough dose of “human touch” to sound real. And he concludes with ....... "As for the KALUGA monos…in my view the time has not yet come. Perhaps many people will find them good in what they do and will happily live with them for many years, but it should be pointed out that class-D amps offer a very different sonic perspective from what one hears live OR with good analog amplification, be it tube or solid state - regardless of the amp`s working class. If the sound of KALUGAs would be declared as very lifelike, then I fear we would be sending a wrong message to the audio amplifier industry, not to mention deny the reality. There is just no way one could consider both, the analog and switching amps equally capable of materialising that grand illusion of performers playing and singing in front of us - this is just impossible due to huge differences in sound." One designer of Class AB amplification once told me, in his opinion, the Class D amps he had heard at that time had been "dynamically challenged." I believe he was talking about that micro-dynamic 0 to 60 thing. Some might call it sounding "overly smooth." Based on my time with the Class D Atsahs and assuming (from the many positive reviews) that NC1200 is at or near the top of the Class D amplification chain, then the current state of Class D amplification has resulted in amplifiers that can sound very good, and that offer excellent ergonomic attributes, but still do not compete in every way with upper level Class AB or Class A amplifiers with regards to creating a musical whole, or a realistic illusion of performers and venue. ���WA�� |
There is only about 1% of 500kHz switching noise on the speaker cable, and that is absolutely irrelevant. Placing an ear next to tweeter proves only that people cannot hear 500kHz (almost complete silence). Modulating 500kHz by the tweeter would require its membrane to move at this frequency - not possible. There is no sizzle of any kind in my class D amp. If anything, class D amps are reviewed as "dark sounding". Yes, higher bandwidth would be always nice, but 65kHz -3dB sounds fine to me (some class D amps go twice higher). |
I have Dynaudio 1.3mkii monitors I've used with my main arc sp16 tube preamp and BelCanto ref1000m amps and also with Newer Bel Canto c5i integrated. With the arc/bc combo the Dynaudios have a bit of bite in the top end and excellent Dynamics at modest to higher volumes. This is in a smaller 12x12 room. At comparable volume with c5i in second system in large family room kitchen area the Dynaudios are smooth as silk. |