Class D
I’m listening to Class D Bel Canto ref1000m amps into kef ls50 metas as I type. Magic. Plain and clear. You can reach out and touch it! Fed by mhdt Constantine DAC into Audio Research sp16 preamp. Having heard Atmasphere amps at various shows, I’d say Class D fits right in in regards to sound and is a natural addition to the product line. |
@atmasphere , Ralph, would you ever get caught building a class D amplifier? Seems like the antithesis of what you are all about. Class D amps can sound very good but there is no magic there, not like your amps, Pass amps or John Curl amps. I have never heard Boulder or Constellation amps. With good speakers it is that magic that counts. So what if it is harmonic distortion. Us audiophiles just want to be happy and a great amp is like catnip. Class D amps just do not get me high, at least yet. |
I believe you would have, if the one/s you heard used the GaN technology to it’s fullest, which is to be able to increase the switching frequency 3 fold to 1.5mhz like Technics did with the SE-R1 and maybe in Feb 2021 the SU-R1000. Then the "switching noise output filter" can also be set higher and so eliminates most of the switching frequency noise left at the speaker terminals. Without introducing phase shifts back down into the audio band, like what happens with lower 600-800khz switching frequencies/filters. EG: in red https://ibb.co/vvwzGV5 Cheers George |
ricevs, I'm just ebullient due to the performance. Forgive me, I won't talk about it anymore. ;) The article should be coming sometime in the first quarter of 2021. Still some important system building to do for an attempt at ultimate build, performance, etc. No, it's not Exogal. However, I am using the Exogal Comet DAC with it a lot, with spectacular results. |
because of my obsession with GaN with it’s ability to have 1.5mhz switching speed the Achilles heel of Class-DThis really isn't correct. You can get vanishingly low distortion with less than half that speed; alternatively you can go a 1.5MHz using MOSFETs as they are plenty fast enough. GaNFETs have other advantages completely unrelated to their speed, although you can run them with slightly less deadtime. The thing is, if you run at 500KHz, the deadtime (being a constant) has 1/3rd the significance that it has at 1.5MHz. |
georgehifi has been talking up GaN for a long time. If I am not mistaken, the new Technics integrated uses GaN chips. Interesting assertion, Mike. I have concluded much the same with a different class D! Now, which is superior? My class D, or yours? I did not hear anything from the Gan amps at AXPONA that would make me think they are superior to the one I am using. You are hurting your reputation with such an open-ended assertion. Imo, the problem isn't so much what you said in regard to other classes of amps; it's what you asserted in regard to other class D amps. Imo, unsupportable and a mistake. :( It's not too late to walk it back. In regards to the emergence of the superiority of class D, however, you are correct. With amps like this, it's a new era. |
These AGD amps have been very highly reviewed. Yeah they may well be. I was the first to bring them up on Audiogon, because of my obsession with GaN with it’s ability to have 1.5mhz switching speed the Achilles heel of Class-D But Audiogon don’t need dealers propaganda shilling to say how good they are. They need owners to do the personal reviews or mags like Stereophile . |
You can read all the reviews here. https://agdproduction.com/category/reviews/ Hope everyone enjoys, especially George. |
First off Im going to let you know about an amp company that makes such a stunning GaN amp, that I immediately negotiated the USA Dealer position . It is nothing like any of you have yet heard and I stake my name on it . The AGD Production amps are capable of delivering 32A of current on the $7500 model and 50A on the $18K model. They switch at 800Mhz. They are the only GaN amps where the MOSFET is designed for HiFi ground up. The other amps are using GaN devices optimized for battery chargers. These amps caught me off guard with their performance. Ill keep it short and sweet because talk is cheap , everyone says the same thing and the proof is in the listening. My guarantee is that it will outperform any other amp in existence sonically. A AB, D it does not matter. Im not here to tease or play games , Ill put my money where my mouth is. Rarely done in this industry. an open invitation to try it in your home and if it is not the most incredible sounding amplifier you have ever heard, then return with no restock fee. I dont know how else to do this as its the only meaningful way I can see for people in the market for a $7500 to $20K set of monos of the latest cutting edge amp tech to realize this new level of listening. If anyone has ideas on how to do this most effectively please share. Perhaps I start a thread dedicated to these new creatures. Bring your Gryphon, Boulder, EDGE.. It wont matter. Again, I am not on these forums enough to know the proper way to tell folks to do a demo or to pose a challenge or whatever. Ill just say that AGD Production makes amps that are a bold departure into perfection from what we are used to. |
Class D is the future and continues to improve as solid-state did and tubes over time did. My next amp will be class D of some sort, no longer going to want to lift my 100 lb McIntosh amp which is superb. It will be sold at local pickup only at a reduced price. Just reality of age. Walter at Underwood going to be releasing a class D amp with the newest technology for $3,000. Cherry Class D, Merrill class D, and one or 2 others. |
I do not think I have ever been more excited by the prospects of amplification in the industry than now. There are wonderful things coming for the hobbyist! There is no reason that most participants here cannot all have fundamentally superior sound in the next 2-3 years, due to developments in amps. :) |
I have run D-Sonics Class D M3a-1500M monoblocks with Maggie 3.7i's for about a year now. They are very good. I have tried McIntosh, Bryston and these are far better. Way better than I would expect for under $3000. monoblocks. I even ran them in my reference system that I run MC 601's and Sonus Fabers....Mc's better in this rig but the D-Sonics performed way better than you would think for about 1/5th of the price. With the Maggies, in a very large room, they are outstanding! |
I love the scientific talk of why one Amp might be better than another and if money was no object I could see this discussion going on forever, some for and some against. Without more information though (budget) I will answer as to my personal experience and limited amount of funds. To start out I assume that you have one of the original PSB Stratus Gold's as written about here: https://www.stereophile.com/content/psb-stratus-gold-loudspeaker-specifications The set from the early nineties does dip below 4 Ohms but does not go below 3 Ohms and should be no problem for most well respected Class D Amps. The later set though from the late nineties does dip about an Ohm lower and in a lower frequency range making these I would say, harder to drive. I have Tekton Double Impact speakers (I did purchase the upgrade package and the 4 ohm version) and though there is not an awful lot of information out there on the impendence curve of these speakers I have found them hard to drive at mid to high volume with the limited amount of money that I have to spend on this hobby. I finally settled on the Peachtree Nova 300. It sounds fantastic and is in all in one box unit that is rated into 2 ohms. I can now crank it loud enough that you can here it inside my neighbors house and it runs somewhat cool. It will get warm with prolonged high volume listening, this leads me to believe that these speakers demand more current than we are lead to believe. If you are worried about it just step up to the the Nova 500. I have found many places that will let you do a free home trial or in some cases just pay the restocking fee if you do not like it. I would say for the money they are hard to beat with versatility and sound from a "1 box does it all" stand point. https://www.peachtreeaudio.com/collections/amplifiers/products/nova500 |
I purchased a Rotel RMB-1575 just as a first plunge into the class D world. It’s 250 watt x five channel in 8 ohm, 500 watt @ 4 ohm. My RBH Reference gear is four ohm. This amp could destroy my basement with freakish volume and all the while, cool to the touch. I drove a twin pair of reference subs that use twin 10” reference drivers as well. Shakes the foundation. It’s 18 lbs, makes no sense to have that kind of power and the sound is absolutely beautiful. |
No, I’m not pairing the Scintilla with the SE-R1 - that’s why I said "OR" not "AND". I meant a system with either of those pieces is simply more than "decent" - much more. I know what works great with Scintillas and class D, as I noted above. And I know of old school amps that work great with them as well. Yes, I’m referring to the 1-ohm version. Staying on topic... |
As good as I like to say Class-D gets with the Technics SE-R1, I still don’t think it’s a good amp for driving the Scintilla’s 2ohm load, compared to big linear bi-polar amps, that can really dump many more amps (current), especially when the Scintilla’s are in the better sounding 1ohm mode. I head them at the Apogee/Krell dealer 20 years back, Len Wallis Audio, driven by a pair of these Krells, and the sound was to die for, speakers disappeared and had a sound stage and depth you felt you could walk into and greet the artists. https://i1080.photobucket.com/albums/j329/ALE7575/stereogear3_zpsc311def0.jpg 475W into 8 ohms 850W was available into 4 ohms I measured 1060W into 2 ohms, the AC line in our Santa Fe office was sagging significantly for this measurement. Cheers George |
madavid0: Something to keep solidly in mind when reading about how wonderful this or that class D module is that the commentator probably doesn't have even a decent system and his standards are very low. That seems to be the general rule with people praising class D. A bold and laughable generalization. If you consider a system with an Apogee Scintilla or Technics SE-R1 "decent" then you don't know much. If your argument is based on a low end VTV without even a linear ps, then you know even less. Note: I had to edit this as it was removed by the moderator. I didn't realize there are some here who are so sensitive! |
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Isn’t Jeff Rowland (hardly a bargain basement brand) still using Pascal modules?Y Yes, which are just tweaked Chinese Sanway subwoofer module’s, and Red Dragon use them also at 1/5th the price. 1st pic is the $10k JR Contiuum S2, 2nd pic is the module in the Red Dragon, the rest are $100 Chinese Sanway Audio sub woofer/PA modules https://www.china-sanway.com/ https://www.reddragonaudio.com/products/s500?variant=969867425 https://ibb.co/TwL29tF https://ibb.co/m56rBry https://ibb.co/LZ2br14 https://ibb.co/CnDG1pr https://ibb.co/27HJ0v5 Cheers George |
Something to keep solidly in mind when reading about how wonderful this or that class D module is that the commentator probably doesn't have even a decent system and his standards are very low. That seems to be the general rule with people praising class D. You'll rarely hear anyone say, for example, they liked this or that module over their old Pass, Mark Levinson, Esoteric, Solution, Gryphon, Boulder, etc, etc. It's also bottom-tier entry level products. I'm currently evaluating a VTV Purifi, and it's frankly not impressive. I'm not saying horrible, but my Odyssey amps (Stratos, Kismet) are better, and Odyssey is in no way a high-end amp. |
I smell another fuserGood job. Did not know this characteristics of yours. My neighbor also has 2 Vizslas. People, shillers and manufactures saying Class-D already great and is better than the best linear amps, which it’s far from yet.Ignore them and move on. you are a **** why bring that up if you know the answer already.To make people aware of your agenda and why your keep barking. But your smelling characteristic is something that you should use to search for people with COVID. That way you can stop the spread. But no need, I go direct into my Class-D’s from my dacThat's what I thought, but wanted to confirm. @douglas_schroeder You might not be aware that georghifi is also a big A-SO (anti-snake oiler). In fact he might be the biggest A-SO in the industry, from down under. That's how he smells people :-) You are free, of course, to argue, defend, your product as you see fit. :)It's called fierce arguments that are futile. But I am a bit disappointed in his response to my post. I was expecting him to call me sunshine. I like it when he tries to defend by calling people names. It will get funny from here. |
I don’t know your DAC, but I hope it has very low output impedance. The NC500 without buffers needs a low impedance source or you will degrade its performance.Are you blind as well as deaf? You are free, of course, to argue, defend, your product as you see fit. :)I don’t have to it speaks for it’s self. Unless ****** like milpai bring for no reason it into a Class-D amplifier thread but to try to cause a fight and you following like a rat up a drain pipe, just like "fusers" do! |
Ah, well, I'm starting to have some perspective here. I was unaware - never bothered to care or look - to discover georgehifi is an industry member who sells his own attenuator. Well, NO WONDER there are issues here, and ferocious debates in regard to class D! georgehifi, please accept my apology; I thought you were a curmudgeon with a bad attitude toward the industry. You are free, of course, to argue, defend, your product as you see fit. :) I'll recuse myself at this time on further comment on class D in general as compared to other genres of amps. I will have plenty to say about that in the article. I most definitely am checking into an aftermarket fuse for this class D on review. Already spoke with the manufacturer to get info on the value of fuse to acquire. :) |
I smell another fuser Sorry, not a "fuser" but I do understand AC circuits. Not so sure you do based on your posts.
May want to check out some tests at audiosciencereview.com With the exception of the Benchmark, nothing out there matches the best Class-D on many critical specifications.
Nope, but you do have trouble understanding how Class-D amplifiers work, and amplifiers in general as it relates to loads. I can and have talked in great details the real limitations of Class-D amps as it applies to low impedance loads. I Challenge You to do the same. and that it’s switching frequency is too low for it’s output filter to remove completely without introducing large phase shift down into the audio band. And wrong again. Been fixed for over 5 years now. Sorry that your information is dated and you don't understand enough about amplifier design to know how this works. can your attenuator drive Class D amps you are a **** why bring that up if you know the answer already. If they have >33kohm input impedance buffers it can Why do you keep posting wrong information? But no need, I go direct into my Class-D’s from my dac I don't know your DAC, but I hope it has very low output impedance. The NC500 without buffers needs a low impedance source or you will degrade its performance. |
I don't know what his agenda is, but given he spreads grossly false information and refuses, absolutely refuses to educate himself such that he understands the statements he makes, I don't get it at all. Come on George several messages above I went into great detail about what EPDR is and how that impacts a Class-D amplifier. I went into great detail about hard current limiting and explained why the watts don't double at 2ohms. I think I made it simple enough that many people can understand. Tell me, at this point, who do you think people are going to believe, someone who goes into great detail to explain the process, relates it to actual amplifiers, and uses actual numbers to back up their arguments, or someone who can't do any more than link to an article on Stereophile that they don't even understand? I will address one other thing on Class-D amplifiers, thermal shutdown. Class-D amplifiers will often shut down early in amplifier tests when the current load is high and continuous. Why is that? This is actually a design choice. The market, at least initially for Class-D, is compact, light weight, efficient amplifiers. Sure, there is a portion of the market who is quite happy with an 80lb monoblock Class-D, but for the most part, that is not the market, even in audiophile land. People want a powerful, efficient, and still compact amplifier. That puts limitations on the size of the heatsink. Most Class-D amplifiers don't use any more than the small aluminum plate heatsink they are built with. As well, for good circuit operation, the switching devices are small and surface mount to keep parasitics low. Unlike a linear amp, you can't mount those transistors at the end of inches of wire or PCB trace if you want good performance. Now sure, you could design a system, easily, but more expensive, where you could effectively couple to a large heatsink and keep the circuit compact, but that would greatly increase implementation difficulty and cost. I did a prototype once using a heat pipe assembly designed for a PC. Now I think we all know that the ratio between the peak wattage and the average wattage is quite low. 20:1 or even higher is typical. So even though you may be hitting 500W peaks, 10-20 watts may be your average. Most Class-D amplifiers, knowing their target market, take this into account. Class-D amplifiers are already efficient, so creating a design that allows very high peaks, does not require a design with high quiescent power draw and dissipation. Since it is not needed, it is not included. That works great for music, but does not work great when someone is trying to run continuous tones for maximum wattage testing. |
It may not double power into 2 ohms though, but that’s not importantThat more fake than anything! :) sheesh. In case you didn't mean that as a joke (because its pretty funny): Think about it- if an amp has an output impedance (Purifi for example) that is lower than a foot of 14gauge wire, how is it really going to be affected by a 2 ohm load? The answer is it isn't. Now the power supply might not support the current the amp would demand at full power, but all that means is you would clip the amp at some point. When that happens, simply turn down the volume. Why is this so hard to understand?? The idea that you can make a self-oscillating class D amp oscillate when in fact they already oscillate for a living is rubbish. Maybe you can explain that?? When an amplifier is oscillating, another way to put that is its Phase Margin has been exceeded. This simply means that there is so much phase shift at some high frequency that the negative feedback applied is now positive feedback- and presto! The amp oscillates. If you don't believe me on this, read the works of Norman Crowhurst. You can find his books on Pete Millet's excellent resource site:http://www.tubebooks.org/technical_books_online.htm Now I doubt you'll be doing you're homework, but I provided the link so you or others can, so you or others can follow along. So try this on: In a self oscillating class D amp, the phase margin is exceeded ***on purpose***. The oscillation is used as the switching frequency. Its got a certain elegance, but now that you brought it up, one of the advantages is that its quite literally impossible to get it to oscillate any more than it already is. So its impervious to load conditions in that regard. |
I smell another fuser So what bothers George?People, shillers and manufactures saying Class-D already great and is better than the best linear amps, which it’s far from yet. So what is your agenda?That Class-D has trouble with low <2ohm impedances, and that it’s switching frequency is too low for it’s output filter to remove completely without introducing large phase shift down into the audio band. And if you accept it for what it is, nothing will be done to fix those inherent problems. The Technics SE-R1 and maybe the SU-R1000 has done something about the switching frequency, but still the 2ohm load capabilities are not yet fixed, if you check independent tests. can your attenuator drive Class D ampsyou are a **** why bring that up if you know the answer already. If they have >33kohm input impedance buffers it can But no need, I go direct into my Class-D’s from my dac I own and listen to a pair of direct dac signal feed Hypex NC500 modules (with no buffers) with very big linear supplies, into my second system, which speakers are a nice benign 6ohm load. |
I fail to understand one thing - people spend "their own money" to buy the class D amp they like. So what bothers George? Don't know what he is trying to achieve jumping on all the Class D threads and making a mess. The only reason I can think of is - his light attenuator must not be compatible with Class D and hence he does not want people to adapt them. George, can your attenuator drive Class D amps? I might look into Purifi or GAN based amp if I upgrade in the future. So what is your agenda? |
A typical response from a snake oil "fuser" https://forum.audiogon.com/posts/1572264 |
Just like *****, into protection mode for his own interests, the new Class-D must be coming soon. It may not double power into 2 ohms though, but that’s not importantThat more fake than anything! Most Class-D’s, independent tests, can’t better the 4ohm wattage with the 2ohm load, if they don’t turn off first, let alone double it. That’s how "strangled" they are for current. With regards to that bit about ’oscillate’: most modern class D amps already oscillate as part of their modus operandi. You can’t somehow make them oscillate *more*; the idea is rubbish.No you are. You know exactly what was meant by that, don't play the arrogant card, just another ***** side step to protect an upcoming Class-D from you |
As said in my first post, they don’t give it as they either turn off going into protection mode, or they are current starved into 2ohms, or the worst oscillate.This is fake news. If you have a class D amp, and a speaker that dips to 3 ohms or even 2 ohms, don't worry- just hook it up. EPDR won't be an issue- the output impedance of any modern class D amp is only a few milliohms; what's happening at 2 or 3 ohms is thousands of times higher impedance and the amp won't care. It may not double power into 2 ohms though, but that's not important except at clipping. What's important with most speakers is the amp behave as a voltage source, which it will do just fine. With regards to that bit about 'oscillate': most modern class D amps already oscillate as part of their modus operandi. You can't somehow make them oscillate *more*; the idea is rubbish. |
No, not on my end. An amp that can easily handle a Scintilla, not just handle but do it beautifully, is a breeze with any other speaker. Several users on the old Apogee forum agree and they are fanatical about their Apogees! I was less fanatical for mine especially when they needed restoration and I had to let them go - along with the amp. Price is not bad at around $3500, if I recall. Problem is Henry Ho is tough to get a hold off, as it seems this is a sideline for him. I can pass along his email to anyone interested. |
