Just received a new pair of Theta Digital Prometheus mono blocks to replace my Simaudio amps. They were a little more money than some other class d amps,but so far I am very impressed with them.
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?
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I have used the Bel Canto Ref600 mono amps for almost 5 years now, currently driving a pair of ATC SCM 19v2 loudspeakers. 99.9% of the time I don’t detect any issues with their performance. Perhaps that 0.1% anomaly could be attributed to their Class D design, but I can’t say with absolute certainty. What I can say is I agree with what some others have said concerning the synergy between the amps and loudspeakers (a relatively flat impedance curve is optimal), and power source and power cables also come into play. I am pretty discerning and sensitive to the quantity of the sound of my system, and I have tried other amps, but the fact that I continue to stick with the Bel Canto Ref600 mono amps for almost 5 years now speaks for itself. Their sound quality was only reinforced after I purchased their new E1X controller/DAC. So I guess you could say I am biased, but as the old saying goes, “the proof is in the pudding”, and I am really enjoying my system. Happy listening, and remember to enjoy the music! |
if it weren't for efficiency & power, would there be any reason to own a Class D amp?Class D amps rock the category of watts per dollar, which makes them a good choice for powered subwoofers where the goal is control and damping of large drivers while imaging and spatial information doesn't matter. Do they beat Class A in any other categories that count for sound quality?Power and control, both of which are harder to achieve economically with Class A. Otherwise, Class D does not beat Class A in my experience comparing Class A Lamm M1.2s and Clayton M300s with Class D Ncore NC1200 via Acoustic Imagery. I owned all of those amps and compared them directly in my system over an extended period. The Class A amplifiers were way better at portraying music naturally and believably, which seemed to relate to the spatial representation of the individual sounds and instruments. The NC1200 amps also did not beat better Class AB amps, IME. Better sound quality seems to be the current goal of Class D designers, with pockets of manufacturers and owners claiming that certain topologies and products are getting closer or achieving the goal but so far, the marketplace has not seemed to fully agree in the long term. |
Hello mitch2, From some of your past replies on other threads, I remember learning of your disappointments with the performance of some high quality class D amps you've tried in your system. From what I've read, however, the class A Lamm and Clayton amps sound and perform about as good or better than just about any other amps, regardless of amp type. I also believe they're both much more expensive mono-block amps than the Acoustic Imagery and many of the other higher quality class D amps. So, I just wanted to point out that class D amps offer what I believe many would consider very good full range sound quality, typically at a very reasonable price and, therefore, would be considered a better bargain and amp option by those with limited budgets. Yes, the main benefits of current class D amps are still power and control, unsurpassed electrical efficiency, ridiculously low distortion and noise floor levels, extremely small size, weight, operating temperatures and relative price. Sure, their overall full range sound quality may not currently and universally be considered the best in absolute terms. As class D technology continues its steady upward trend in overall full range sound quality performance in absolute terms, however, I believe it currently represents the best, and certainly the most affordable, pathway to high-end sound quality. In my opinion, it'll also likely just be a matter of time before it's universally considered the premiere amp type, especially considering its near-future DSP technology inclusion and potential. It should at least be very interesting. Tim |
Tim Class D absolutely rocks watts per dollar (except of course for gallium-nitride transistor versions) so if they get the other stuff sorted they will be hard to beat. My only comparisons were the Acoustic Imagery Atsah which are a Ncore NC1200 implementation that I owned for over a year, and H20 amps that I had here for a very short time. I was initially impressed with the NC1200 Atsahs because of their dense tonality and hard hitting bass but after a longer period of listening and comparing there seemed to be something just a little off, or missing. It took me a bit to figure out that my issue was with spatial cues that lead to realism. The NC1200 amplifiers were not inexpensive when they first came out and even the Atsahs at the lower end of NC1200 were still $10K. As to Class A, that doesn't necessarily get everyone to the finish line either, even if you neglect the heat and electrical costs. So much is related to amplifier-speaker synergy as well as the types of music preferred by the listener. In my case, the Lamms were not powerful enough to adequately drive my power-hungry Aerial speakers on the rock, pop, and blues music I most often listen to. The Claytons were much closer at 300wpc and they were just outstanding on tone but still displayed a bit of reticence on particularly dynamic passages. There are always trade-offs. My upgraded SMc/McCormack Class AB monos finally gave me enough clean power to properly drive my speakers through the most dynamic music, while also getting me sonically close to the dense tone, staging, and extension provided by the Class A Claytons. They are not necessarily better amplifiers than the Claytons but for my situation, speakers, and musical/listening preferences they are. |
+1 noble100, I was an enthusiast of class D amplification from the start. I replaced my (medium quality) class AB amp (Cambridge A3i) with one of the first class D amps (Rowland 102) based on the one of the cheapest Icepower modules (200ASC) and was very impressed. Recently I replaced it with class AB Benchmark AHB2 rated class A in Stereophile. It is a better (wonderful) amp overall (cleaner, better extensions etc.), but the difference was small, taking into consideration 3x higher cost (in comparison to Rowland that was well made and expensive). Class D technology is only going to improve in time while everything else is pretty much done. There are still some new designs, like my Benchmark AHB2 amps, that dissipate less and have non-recursive NFB, but class D is the future IMHO. |
One of my friends is getting a pair of 48V Desktop Cherrys likely next week. Unless we are in total lockdown, the plan is to try it out at his place, mine and one of our friends in our social bubble. Our friend is running Maggie 20.7s so should be interesting to see how it does. I have wanted to try them out for some time, but wasn't looking for anything new in amplification. |
Hello mitch2, You've utilized quite a few good and varied amps with your Aerial speakers. I've had much more limited amp experience, only using high current class AB amps (Adcom,McCormack and Aragon) initially and then several different high-powered class D amps subsequently with Magnepan speakers, my favorite being my current pair of D-Sonic monoblocks. It seems like class D amps have been a better match with my speakers than they've been with yours. I was actually considering buying a pair of Acoustic Imagery Atsah monoblocks before I decided to go with the DSonic M3-600-M monoblocks because they were almost $7K less expensive and had gotten good reviews here from some members. They've performed great for me,outperforming my former class AB stereo amps in virtually all the sound qualities I consider important. But I'd still love to try out a good quality class A amp with my speakers since I've never used one and mainly out of curiosity about performance differences I'd perceive. OTOH, I'm currently completely satisfied with the D-Sonic class D monos and have no desire to actually switch amps; they're 1,200 w at 4 ohms, have a very low noise floor, are highly detailed, very dynamic, always smooth, natural and never harsh in the treble plus I'm able to leave them on 24/7. Hello kijanki, Yes, I've read several very positive reviews on the Benchmark AHB2 class AB amp. One review that I found very interesting was a review of the AHB2 combined with the Benchmark LA4 preamp.I remember the review because it combined something I've always wanted to try out in my system, a very neutral, detailed, low distortion and low noise amp with a preamp having the exact same qualities. I was seriously considering buying the LA4 preamp to try out with my very neutral, detailed, low distortion and low noise class D amps about a year ago. But I was offered a Mark Levinson S326 preamp, that's also very neutral, detailed, low distortion and low noise, at a very good price and I bought that instead. So, I was still able to try out the neutral, detailed, low distortion and low noise amps and preamp combo concept. It's provided very good results in my system, using mainly hi-res sources through a Lumin D2 dac/streamer. The overall sound is very neutral and detailed but it also really lets the qualities of the recording and music become the focus with a highly realistic and 3 dimensional sound stage that has the musicians seemingly playing in the room. It's very palpable, detailed and enjoyable, especially on good recordings. Tim |
Ric Schultz TweakAudio's newest class D sounds fab. I have his EVS 1200 which is amazing, Keep in mind Underwood HiFi is getting very close to releasing the Voyager GaN amp https://www.underwoodhifi.com/products/lsa-electronics Voyager GAN 200 Balanced Power Amplifier $3,000.00 Our new LSA 200 watts/ch power amplifier, Voyager GAN 200, will ship by the end of 2020. This fully balanced amplifier is a breakthrough product featuring a GAN (Gallium Nitride) FET Output Power Stage as found in products selling for many times our $3,000.00 price. |
I'm not sure that I can help the discussion much, but here you go.... Class A vs Class D. In theory Never switch should be better than switching. Obviously No Switching distortion. With that said, I have owned 3 Pure Class A amplifiers which I loved. Recently, I went on a Class D benge. I purchased 11 amp modules and have built and listened to all of them. I've had Abletec, Pascal, Ice, TPA, TDA, STA modules and maybe more. In every case, the better that I made power supplies the better the amps sound, even low cost STA modules could be quite good. There really can't be an argument that these amplifiers are audiophile quality. Sure, other amps could be your cup of tea, over these, but no doubt, Most (not all) of these amplifiers produce a satisfying amplifier. I have found on at least one of these, I can add a z comp circuit PFFB which stabilizes the frequency response using different speakers. These amps are still developing. Class A and AB won't go away, but I do want to encourage others to leave your bias at home and occasionally take a listen to class D as they continue to develop. |
I have a 40w/ch $85 Fosi Class D integrated amp with Bluetooth in use that sounds really good driving a vintage pair of Boston A40s. Audiophile worthy even, as long as you don’t ask too much of it. Cleaner/Better sounding than most comparable powered vintage receivers for sure. A better power supply would make it even better but add some cost. The TI chip used supports delivering even more power if wired up properly for that. It’s about the size of a pack of cigarettes to boot. So not a lot of bling, but otherwise.... |
mapman"
Hadn’t thought of DSonic in a while but looks like they are still offering a lot of bang for the buck. Nice website.....lots of useful specs and measurements. What Class D modules do they use these days?" Hello mapman, On their current M3a-600-M monoblocks, I know they're using the Pascal Pro2 class D modules, which have the smps built into the module and are the same ones used in the Rowland Continuum 2 integrated amp. I have the slightly older M3-600-M monoblocks and they use the Anaview/Abletec modules. Tim |
Both the switching distortion and non-linear should be addressed. True, the output devices are switching, however, the output devices are unlike other amplifiers as they are not operated in the linear region, which is not actually linear, but operated in saturation. That is a good thing. There is a lot less variability in the saturation region, which leads to less distortion, not more, from an architecture potential standpoint. While technically distortion, the filter is not removing distortion in the the sense of a standard linear amplifier which would be distortion in the audible band, but harmonic products above the audible band.
I also understand the weaknesses somewhat. 1. Non-linear & lots of distortion that needs to be cleaned up with an output filter. |
Hello atmasphere, As I understand class D technology as a layman, timlub could be referring to 1 of 2 different possible types of distortion: 1. Distortion caused by the output transistors not turning on and off quickly enough- Most current class D amps utilize MOSFET transistors that have a limit to how fast they can switch from completely off to on and vice versa. Any lag time between the transistor being fully in the on or off state is termed 'dead time' and can cause signal distortion. 2. Distortion caused by the carrier frequency being too low- This is a possible form of distortion that georgehifi claims is audible but has never provided any valid evidence to support his claim. Basically, he claims the ultra-sonic frequencies (typically in the 300-600 kHz range), that class D amps modulate to carry the audio signal and subsequently completely filter out the frequency leaving just the signal, are too low and somehow affect or distort frequencies in the uppermost audible frequency range. He claims carrier frequencies need to be above at least 1 mHz in order not to affect or distort frequencies in the audible range. I've never subjectively perceived any distortions or sonic artifacts on the many class D amps I've owned or heard. However,I know some amps are beginning to utilize the newer, ultra-fast switching GAN output transistors and I believe at least 1 company, Technics, offers a class D amp model with a carrier frequency above 1 mHz. Tim |
@noble100 OK- I just wanted to be clear on what was meant by 'switching distortion' since that's not an engineering term at all! Artifacts from dead time show up as harmonic and intermodulation distortions, so a class D amplifier can easily be compared to other amps on that basis. IOW, on its own 'switching distortion' has no meaning. With regards to the switching frequency, with the current state of affairs with switching devices, its actually easier to make a low distortion amplifier when the switching frequency is less than 1MHz. This is because the amplifier has to meet certain standards for RF radiation- various countries have specs for how much RF noise can be tolerated. The faster you go, the difficulty in getting the amp to behave in this regard goes up on an exponential curve! Its quite a feat that Technics was able to switch so fast, but in reading their ads for the amp, I suspect a bit of marketing hype is also involved. The problem with a low switching frequency is probably that of bandwidth, but class D amps can have a way of getting around that, since it is possible to add enough feedback to allow the amp to compensate for phase shift that would otherwise plague an amplifier with bandwidth from only 20Hz-20KHz. In a nutshell its really dangerous to make blanket statements about 'all class D amplifiers' just as it is about 'all tube amplifiers' or the like- there are often many exceptions. |
Hello all. I'm not able to be on here as much as I used to, but I will answer when I can. @atmasphere Hi Ralph, You are correct, I don't necessarily use engineering terms, but that may be because I am not an engineer. I have posted in the past that As much as I do know and practice about speakers, I've spent my adult life working on, building, modifying and designing speakers, I found that I was only touching the surface with amplifiers. I was out of place in some more technical conversations... So I decided to learn. 6 or 7 years ago, I started buying bad amplifiers, repairing and rebuilding and in general just learning about amplifiers. I have repaired or rebuilt maybe a dozen old classics and today am fairly competent doing most repairs or modifications on amplifiers. Compared to those builds, my class D quest has been fairly simple. I have been purchasing class D modules and doing changes. With these modules, I built with linear supplies and switching supplies, both when hefty enough supplies were used would produce quite good results.... I started mostly just upgrading parts on these boards to very high quality parts. I have done very few circuit mods, but I have done a couple. Many of these amps do a good job. |
I cannot hear any trace of harmonic distortions on the 3rd or any other partials when I play music with my class D Rowland M925 monos or class D Rowland Daemon integrated.... Nor do they intermodulate. They are as sweet and stunning as can be. As fashionable as it might be, generalization is a dangerous tool. Best to avoid the infimous logical trap of "1, 2, 3.... 99, 100". Like with any other class of operation, the performance of class D amps can be evaluated only one amp at a time... And only through actual listening to boot. There is a huge variation of audible performance characteristics and tonal qualities amongst amps to make any sweeping proclamations one way or another. Regards, Guido |
guidocorona: "I cannot hear any trace of harmonic distortions on the 3rd or any other partials when I play music with my class D Rowland M925 monos or class D Rowland Daemon integrated.... Nor do they intermodulate. They are as sweet and stunning as can be." +1 guidocorona I also hear no traces of harmonic distortions on the 3rd or any other partials when I play music with my, much less expensive, class D D-Sonic M3-600-M monos or 2 other class D amps that I formerly used for music but currently use for HT 5.1 surround sound, an Emerald Physics EP100.2-SE and a Class D Audio SDS-440-CS, which are both excellent performing and very reasonably priced stereo class D amps. In general, I view class D amps as an excellent alternative to the more traditional ss and tube amp types that represent a bit of a revolutionary approach and a breath of fresh air. They're the very competent, silent, efficient, straight talking and cool running guys in the amp neighborhood who just even handedly and confidently tell us what's what without distortion or ever getting overheated. No, they don't all sound the same, not everyone likes them, some refuse to even listen to them, some are prejudiced or jealous and others just bad mouth them out of habit. But these confident, competent and cool guys don't care. They know how good they already are, that they're constantly only getting even better and that their technological future is bright. Tim |
I should however like to point out that as with any other class of operation and topologies, class D amps range from the marvellous to the horrid. When I visited RMAF a few years ago, there was an equal proportion of class D amps and tube, class A, and A/B that left me befuddled for their total lack of musicality, be their tone dull and wooden, or acrid and shreaky. Bottom line... Let’s use our ears when choosing an amp best for our music genres, and avoid preconceived abstractions. Old and trite urban legends are bound to drive us down some suboptimal path. G. |
Bottom line is until we can get rid of the nasty 3rd harmonic distortion in class d our ears will always prefer the cozy 2nd harmonics that tubes generate@kw6 Actually the human ear/brain system treats the 3rd harmonic the same as it does the 2nd, in that its relatively inaudible and adds to a bit of what audiophiles call 'bloom', 'warmth' and the like. The other odd ordered harmonics are not so benign! |