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High end Class D amps?
Just an observation and a question. Are there 'high end' Class D amps out there that are just as good as Class A, A/B amps? I realize that's a sensitive question to some and I mean no disrespect---but whenever I see others' hifi systems on social media, all of the amps are A or A/B. There's always Pass, McIntosh, Moon, Luxman, Accuphase, etc. Where are the Class Ds? For folks out there that want more power for less efficient speakers and can't afford the uber expensive Class As, A/Bs, what is there to choose from that's close to those brands? Thanks
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The idea that Class D amps are overly load sensitive was true with early implementations. We are way beyond that now. Take a look at this page about the PuriFi modules. With a 2-ohm load, the THD+N stays below 0.01% up to full rated power. And to those who say, "The only good ones are made by XXXX." Really? You've heard EVERY Class D amplifier out there, and under a wide variety of circumstances? |
I'm liking my Bel Canto monoblocks. They have all the power and all the detail and none of the coloration and distortion. Works for me. I have used them now with two different tube (valve) preamps. I've used them with my Acoustat speakers and it really brought them to life. I use them now with Goldenear Triton Ones, which can handle but do not need that much power (partly because they have class D amps built in for the low end) and that sounds great, too. Keep in mind that I upgraded from Adcom, if that helps. |
This is a smoke screen, they are still "basically" the same, with the same glaring problem, upper mid/highs phase shift, because of the "switching frequency noise filter" on the speaker outputs. The only REAL gains so far have been with GaN output devices, and the only one to utilize the 3 x higher switching frequency that they can operate at, is Technics with the SE-R1. And because of it their "switching noise output filter" is 3 x higher also, therefore there is 3 x less switching noise present at the speaker output at 20khz, and then also 3 x less "phase shift" going back down into the audible upper mid to high frequencies. Until other Class-D manufactures have done this, they have clearly NOT turned any corners, but just taken small sideways manoeuvres to make buyers think they are being innovative. Cheers George |
Class-D wattage instead of doubling for each halving of impedance load actually gets goes backwards when they see 2ohms and worse if there is any - phase angle involved, because they can’t deliver the current like a good bi-polar linear Class-a or a/b amp can.This statement is false. The limitation of a class D amp is similar to what is is with any amp- how big are the heatsinks, how much current can the output devices handle, and how much current is available from the power supply. The output impedance of any modern class D amp is only a few milliohms (the Purifi module' output impedance is lower than a foot of 18ga wire). So it can double power from 1 ohm to 0.5 ohms as long as the current doesn't exceed the limits of the output section. The real issue is the filter; lowering the load impedance lowers the effective 'Q' of the filter, IOW it flattens out the filter response. So as the load impedance is reduced, the 'residual' (which is the sine wave remnant of the switching frequency) will increase in amplitude. For any speaker this isn't a problem as the residual is very small on any competent class D amp. One thing I find reprehensible is the way the big names have added all kinds of tweaks to Putzeys’ design (op-amps, power supplies) that are completely unnecessary, or even cause spec deterioration, so they can charge more.The reason everyone has different input circuits is because the module itself doesn't have one. Its input impedance is about 2,000 ohms- most preamps and sources would fall flat of their face driving a load like that. When you're designing a module, there is only so much gain you can get out of it, and you have to use an input circuit called a 'comparitor' which tends to have that low input impedance. So some sort of buffer is typically needed. You are correct that this can color the sound if not implemented correctly. Bruno of course has a recommended circuit, but its not cast in stone that it be used. |
This statement is false. The limitation of a class D amp is similar to what is is with any amp- how big are the heatsinks, how much current can the output devices handle, and how much current is available from the power supply. This statement is just by someone protecting their yet to be released Class-D. If you say then put big heatsinks and power supplies on it if you want them to be able to drive the many hi-end speakers with low bass impedance combined with large amounts of - phase shift. (smoke screen, using small form factor as the excuse) Lets see if the yet to be released class-D amp can truly double from 8 to 4 to 2ohms, without understating as many now do the 8ohm to make the 4 and 2 look good, thank god for Stereophile pulling them up (but quietly) on this understating 8ohm wattage practice Everyone knows that Class-D can’t do the wattage doubling act below 4ohms, it’s shown in every "legit independent test review", mostly by not even giving! the 2ohm figures. And certainly not like the better complimentary bi-polar linear amps can, when driving speakers that have hard loads, like the Wilson Alexia etc. |
FWIW, I've been using a "Parasound ZoneMaster 2350" class D power amp and "Parasound NewClassic 200 Pre" and have been thoroughly impressed. Matched up with Audiolab CDT600 and Polk Lis15 + Velodyne sub is giving me the best sound I've owned (or can afford right now). Maybe not quite Audiophile territory, but I'm smiling all day as I work/listen from my home office. |
Hello, Stereo Elleven sells Jeff Rowland. Very nice amps. Not sure on your budget. Someone mentioned the NAD M33. NAD under rates their power so you should be good to go. The M33 is hard to find right now. If you cannot locate one locally or if you are in the Chicago area. https://holmaudio.com/nad-electronics/ |
I got a pair of Jamo 707i speakers that are 4 ohms and seemingly a bit difficult to drive. i tried a few integrated options that just didn't sound great. I got the Crown XLS 1002 amp and really liked it and felt like all the criticism was misplaced about the Class D bandwagon. I think it sounds decent with that speaker. However, I got a pair of Tekton Lores and they really exposed the crown. It is loud and clear etc but very very linear. when I switched up the xls 1002 with a nearly 20 year old class A - Acurus M100 i could definitely hear a distinct difference with the more open soundstage. I just purchased and hooked up a brand new parasound 2250 v2 A/B and it sounds great but to be honest i am struggling to hear much difference between the 20 year old Acurus M100 and the parasound. The XLS 1002 was absolutely "good enough" until I realized it wasn't. |
i had not heard class d that i thought could equal class a/b until i bought a devialet unit, which sounds really excellent devialet calls what they do a 'hybrid', using a regular class a section to slave the class d section - i am not technically equipped to understand or describe that in detail but i can say it makes no apologies to the best class a/b amplification i have ... hegel, naim, audiosector, primare etc etc |
This is a smoke screen, they are still "basically" the same, with the same glaring problem, upper mid/highs phase shift, because of the "switching frequency noise filter" on the speaker outputs.This statement is false- they are not 'basically' the same at all. Bruno Putzeys has shown that you can run enough feedback in a class D amp that it can correct for phase shift at high frequencies that would otherwise be the result of limited bandwidth. To do this the amp has to have more than 35dB of feedback. Any less and the phase shift will show up. In this way the bandwidth of the amp can be limited to 20KHz and yet no phase shift in the the audio band. Normally you need lots of bandwidth (usually 10x the frequency of concern) to prevent phase shift. With traditional solid state and tube amps, this much feedback would likely result in oscillation due to phase margin issues. A class D amp can take advantage of this because the oscillation is welcomed- and is used as the switching frequency. This type of class D amp is known as 'self-oscillating'. The pulse of the switching frequency is then converted to a triangle wave, and compared to the input signal to create Pulse Width Modulation (PWM) for signal encoding. Its a neat trick- and then you don't have any of the issues described in the quote above. |
The Starke Sound AD4.320 is on a "Black Friday" sale for a preposterous price of $839. It is as good as the Purifi Audio modules in the NAD M33 that are getting great reviews. I own both and ordered another Starke today. Check it out! For a review, Google "Starke Sound AD4.320 review." Don't let you preconceptions cause you to miss out on the latest developments in amps. Outstanding specs. Outstanding sound! |
Theta, ATI, and Legacy all have really nice Class D amps that have rave reviews. I'm a class A A/B guy but I'd take any of these over most amps aside from the likes of Pass Labs, Mark Levinson, and Lexicon. I run all Klipsch Pro Audio speakers with sensitivities around 105-108db. I ended up with a Butler TDB3150 and it sounds great. I'm happy with it. It was a big difference from my Bryston 8B-ST's. |
I used a NAD M22v2 for a couple of years. The NAD M22v2 build quality is superb. It's the only class D that I've ever owned. The SQ was quite good and it drove my Tannoy DC8Ti 89db speakers with ease. I replaced it with a BHK 250 and of course there's no comparison. The BHK 250 is better in every way. Being a hybrid amp at more than twice the price, I'd expect that and have not been disappointed. I plan to keep the M22v2 and use it in a secondary system with a tube pre amp. |
Some helpful insight here. Just starting to explore adding a sub to my system and wondering whether Class D is the way to go. The sub will run with an active crossover and is 94db efficient with a stable 8ohm load +\- 1db. I like the idea of a small mono block like the D Sonic but would appreciate opinions on whether Class D would be good in this application. |
class d greatest strength is outstanding bass, so yes on that front I'm running a pair of Swarm subs with a class D amplifier, to break up the standing waves in my room. My main speakers go down to 20Hz so I didn't need 4 subs. Its amazing how well it works- the bass is absolutely consistent everywhere in the room now (a lot of bass was absent at the listening chair prior, with too much bass elsewhere in the room). |
dodgealum Just starting to explore adding a sub to my system and wondering whether Class D is the way to go. jjss49 class d greatest strength is outstanding bass, so yes on that front Definitely the way to go, but there is a proviso, so long as the bass (sub) loading is "not too" much below 3-4ohms with high EPDR (-phase angle), "if not so" then Class-D’s high point is it’s bass and it’s claim to fame. You’ll see that Class-D’s output impedance is measured in milliohms, not in 1/10’s of ohms like Linear amps. So for the same given subwoofer load a Class-D amp has a multitude better "damping factor" (woofer control) than a linear amp can do. But saying that into a hard bass frequencies "loads" like a Wilson Alexia etc that have of 0.9ohms (EPDR), a linear amp like Gryphons etc etc will wipe the floor with the Class-D in the bass, because the Gryphon etc can do far more current into that 0.9ohm bass speaker load. So you have a two edged sword for bass, "control" (damping factor) and (current drive), and it all comes down to what the load is that the sub is presenting to the amp, to which will sound the better for the bass, Class-D or Linear (Class-A,A/B) Then you have to ask, which bass is the better designed, one that's an easy load or one that's a ***** to drive, I generally find the latter to give the better sounding bass when driven right, as they have usually been developed to the max, and the down side is a hard to drive impedance loading for an amp to see. Cheers George |
Hello dodgealum, It sounds like you already have picked out the sub you want to use and it's a high efficiency passive sub, with passive meaning it has no internal amplifier. I just have a few suggestions for you based on my fairly extensive experience incorporating 1-4 subs in my system utilizing Magnepan main speakers with a rated bass extension of only 35 Hz: 1. A pair of subs will perform roughly twice as well as a single sub in virtually any room and system. The bass will be smoother, faster, more dynamic, as powerful as the source material calls for and with a greater sense of ease, more detailed and better integrated with your main speakers regardless of their speaker type. 2. The bass will likely sound more detailed and natural to you if you power your sub or subs with a class AB amp instead of a class D amp. The reason is due to the extremely high rated damping factors of most class D amps, often rated above 1,000 while class AB amps are typically rated in the 100-400 range. The higher the rated damping figure of an amp, the more precisely it is able to control the starting and stopping of the sub's transducer, which I believe is a normal dynamic cone woofer in your sub. This precise control is usually considered a beneficial quality in a sub amp. But if the amp's rated damping factor is excessively high, such as over1,000 on some class D amps, then the amp has the capacity to very suddenly and abruptly stop the woofer as the woofer travels along its normal in and out or up and down path motion. The audible result, of a woofer suddenly and abruptly stopping along its path, is that the normal, natural, slow and gradual decay times of deep bass notes are truncated. This premature ending of normal note decay times are more noticeable and annoying, of course, on certain types of instruments, certain types of music and in the deeper keys. The main point being your music will be audibly less natural and enjoyable, less so on most rock music than on other types of music in my experience. What's a viable solution? I'd suggest you use a good quality but reasonably priced mono class AB sub amp like the Dayton SA1000 for about $300-400 from Parts Express or some other retailer, use a pair of good quality subs and optimally position each in your room, and in relation to your designated listening seat, by utilizing the 'sub crawl method' (which you can google for details). Best wishes, Tim |
I come from the audio objectivist camp, so for me this analysis is pretty easy. I’m looking for a wire with gain. Coloration should not come from my equipment. Most companies are relabeling common modules, and for good reason. The modules available off the shelf now are astoundingly good. Three vendors come to mind right away Hypex, Purifi, Icepower. If you look at these companies’ modules you’ll see their specs show up everywhere in high end audio manufacturer’s spec sheets. Once I realized this I purchased Hypex modules packaged by kjfaudio.com I’ve been extremely happy with them powering driving a variety of speakers. https://www.kjfaudio.com/hypex-amplifiers/ https://audiosciencereview.com has a list of all the Hypex module resellers. The price range covers a full factor of 10. There is no value add that can cover all of that. Snake oil runs expensive though :-). A unique product that stands out to me is Orchard Audio Starkrimson(formerly BOSC) monoblocks. These are amazing devices and I can’t recommend them highly enough. Everyone who is serious about class D power should consider them. https://orchardaudio.com/shop/ols/products/bsc-mplfr |
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blurion:"
Great discussion and I've learned a lot from this---some of you have commented that class Ds is good for better bass. Why is that? You wouldn't get good bass from class A or AB?" Hello bluorion, I suggest you read my last post on this thread from earlier today that covers this subject a bit. In general, solid-state (ss) amps reproduce deep bass frequencies better than tube amps. A good indicator of an amp's bass reproducing ability is its Damping Factor, which basically measures its ability to control, or start and stop, the bass driver. The higher the number the better its control. Class D amps usually have much higher damping factors than the other amp types; class D amps can be rated in the low thousands, class A and AB are typically rated in the low hundreds and tube amps even lower. Bass frequencies also require more current or power to reproduce than higher frequencies because the bass drivers typically have more mass and, therefore, require more energy to start and stop. There's also the matter of personal preferences in bass reproduction. For example, an apartment dweller may want to keep the bass down since bass sound waves can vibrate room boundaries(floor, ceiling and walls) and a portion of the in-room bass will be audible to the neighbors. OTOH, some weirdos who live in houses, such as myself, even believe the accurate reproduction of the bottom 2 octaves in music, about 16-32 Hz, is the main quality that separates a decent home audio system from a very good one. Some of these complete whackos even utilize 4-sub distributed bass array (DBA) systems to achieve this ultra accurate and ultra realistic in-room bass reproduction. Weirdos! Tim |
this is a good discussion i too am interested (in a more technical, geeky way) to understand WHY a class D amp delivers higher damping factor (let’s use that as a proxy for bass control and quality) than a similar class AB amp using standard transistors be they mosfets bipolars etc etc... let’s say the power supply quality is the same and the input stages are well designed... the switching amp or transistor effectively ’gates’ the power supply from the speaker load at the various frequencies asked of it, per the input signal why is it that the class d module does it better than a well designed set of transistors, with a higher degree of control/accuracy? |
The best amplifier I’ve heard is in class AB, bettering other much more expensive class A, AB and D amplifiers. I have had class D amplifiers which better class A and AB amplifiers. I have also had various D amps which vary widely in sound quality. So what I’m saying is that there is no such thing as a better class. It really is not as simple as which class. |
These are the most interesting Class D amps I've yet come across, using
Korg Nutube buffer, which emulates a triode. https://atm-audio.com/class-d-amplifier/ Unfortunately, they don't seem to have made it to the US yet, but if Nord, Apollon and March have, surely they will too. |
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@noble100 Thank you for that information---so would it make sense to add a class D power amp to a class AB integrated with a pre-out to get more power if needed? I realize that may sound weird but if you have a 100wpc integrated, for example, and need more power for a pair of low efficiency speakers, adding a 200+ wpc class D would be ok? |
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bluorion:"
@noble100 Thank you for that information---so would it make sense to add a class D power amp to a class AB integrated with a pre-out to get more power if needed? I realize that may sound weird but if you have a 100wpc integrated, for example, and need more power for a pair of low efficiency speakers, adding a 200+ wpc class D would be ok?" Hello bluorion, Yes, I believe that would work, however, it's not ideal and I think there are a few details you need to consider: 1. It's important to impedance match, which means ensuring the input impedance on the class D amp or amps you're using are at least 10x more than the output impedance of your integrated amp's pre-outs. 2. It's very important that you really love, not like, I said love the sound of the integrated amp's pre-out section because the majority of, if not virtually all, good quality class D amps are neutral in the extreme. Good quality class D amps, in general, are very low distortion and very low noise system components that you'll definitely perceive as not adding or subtracting virtually anything from the inputted signal or signals. The good ones function very much like the audio ideal of 'a straight wire with gain'. I know you stated you wanted to use the pre-out section of an integrated amp, in effect using the preamp section of the integrated amp as your preamp. But I don't recall you stating why you want to do this or which brand and model you own or plan to use. Can you please clarify? Tim |
Finally I own a pair of Nuprime Ref.20 Class D with some modifications (silver wiring, Duelund Bybass caps, WBT Silver binding posts...) They are amazing. I feel no need to go back to Class A - but to be honest before I met them by chance never thought about class D. I shared the same prejudice about Class D. Lacking Detail, thin shrill Highs... The Nuprimes Evos are even better. Hopefully I get the chance to grab a pair in the near future. The only non Class D Amps that would be on my wish list are Boulders. But - to be honest are financially out of range and wouldn't work with my Plixir power conditioner. I own a full MSB Signature V frontend (CD and Dac), modified Pioneer/TAD S1 Speakers, cabling is Neotech 1001. Sorry if my english isn't perfect - I live in Germany |
Based on
boomerbillone's comments on the Starke AD4.320 in this thread, and the very aggressive Black Friday pricing of $839, I bought the amplifier and it was delivered Wednesday. I let the Starke AD4.320's burn in for about 20 hours and spent a few hours tonight comparing it to the PS Audio M700's which are Class D monoblocks costing $3000 and a Stereophile A rated choice. The M700's are rated at 700 watts into 4 ohms vs the AD4.320's 430 watts bridged into 4 ohms. I listened on the Magnepan 3.7's and the amps were driven directly by a SMSL SU-9 DAC streaming over bluetooth and level matched to pink noise at 75 dB. I fried my Roon Core a couple of days ago and couldn't stream via USB. Bottom line is I really liked the AD4.320's. The have a very dynamic, rich sound while still being very detailed and quite a large and deep sound stage. Bass is tight and impactful without exaggeration. Midrange is warmer than the M700's which tend towards a little dryness. Highs are bright and detailed without any harshness. The AD4.320's struck me as bringing some of that subtle magic that a good set of tubes in my Freya Preamp can offer over its solid state modes. I usually found the AD4.320's to be more engaging and dynamic than the M700's. I generally have preferred the M700's to my Parasound A21 class AB amp with the Maggies except in the mid-range vocals and I think the Starkes bring some of that better midrange while having great bass and dynamics. For the Black Friday sale price of $839 I have no qualms about recommending the AD4.320's and to my ears they punch way above that price. Very fun to listen to. I would love to hear the opinion of some of the more experienced ears on here that have actually heard the amp rather than just get flamed by all the Class D haters. |
@noble100 Hi Tim---thanks for the info. I don't consider myself a new audiophile per se, but in the past, I didn't really pay much attention to specs like I do now. I was a young 20-something back then and just bought what sounded good. As I've gotten older, I've become more interested in what matches better with what and I'm trying to learn from all you guys. So now I have a Luxman 505UXii integrated with a pair of Dynaudio S40s as well as pair of Tekton Lore References. I alternate b/w the Dyns and the Lores depending on my mood and musical tastes. I love the Luxman but I at times I wish it had some more punch or something. I caught a video on YT recently that had a new Luxman connected to a Pass amp (I think)---I can't seem to find it now. Anyway, it got me thinking about higher output class Ds (like 200+ wpc) and wondered how that would go. I really appreciate everyone's input and suggestions. |
The Japanese company Spec design very well regarded Class D amps that are apparently very valve-like in tone, though they are not the mega-watt things that a lot of people seem to use Class D for. I have 300W Class D amps in each of my semi-active speakers and they work brilliantly at driving bass. But the passive end of the speakers I prefer driving with Class A.. It is the perfect combination. |
These things are great https://6moons.com/audioreviews/acousticimagery/1.html The company went under. They sound in some way better than my 50K VAC amp. Please give them a listen. |
