Sorry, @zappas for derailing your thread, but @georgehifi has been on a one man crusade or spreading misinformation w.r.t. Class-D amplifier. He single handedly has spread more misinformation on this topic on this site than everyone else combined.
Class D
Been thinking of trying a D amp to reduce clutter. Most that I see are not rated at 2 ohms. My PSB Stratus gold's will drop to 3 ohms or lower at some frequencies. So my question is will these types of amps handle this impedance ?
Thanks in advance. Chris
Thanks in advance. Chris
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Given his comment about 1GHz for Class-D, that statement you just made is obviously not true. I would say it is self evident to someone who understands the technology with any degree of competence (that would exclude George), that Atmasphere and I, on this area, seem to know far more. I am sure there are areas of circuit design that Cyrill is more competent than I. I am also pretty confident there are areas where I am more competent, and again, that ludicrous GHz comment makes me question who is the high powered technical talent at Soulution. A link to a website proves nothing. Let’s do a little digging ...
Darn, I must be clairvoyant! ... or just experienced enough to know people who really know what they are talking about and those that do not? Then again, based on his work experience which has been more on the business side, less on the technical, maybe I was giving too much credit? Experience
I will give him props, even if just repeating what his designer said, Cyrill Hammer: For a “solid-state” amplifier design the speed (e.g., bandwidth) of amplification is one of the most important criteria. This speed or bandwidth has nothing to do with the MHz-range frequencies that can be reproduced by such an amplifier; the bandwidth is required to make the “feedback loops” of solid-state designs work properly. Hey @atmasphere , sound familiar? ... of course, I take exception to their claims to be pioneers in either recognizing this or designing with this in mind. A friend did an app-note in the 90’s on a current feedback audio power amp topology that accomplished this. Of course op-amps have been doing this for quite a few decades as well. |
I think Cyrill Hammer (of Soulution) https://soulution-audio.com/ knows more about solid state circuit design in his little toe than you and ralph combined could wish to know in your lifetimes. |
in the GHz range or even GHz. You really think these don't say the same? He clearly said, "or even GHz". That is a silly statement that shows a clear lack of understanding of the fundamental way in which Class-D works. The PUTZ is you George and that is being kind. Is that the level of name calling YOU need to use when you have absolutely 0 ability to form a proper argument? That says far more about you than about me. As Atmasphere has clearly said, and as actual measurements have shown, you don't need multi-MHz and certainly not GHz switching speeds to not have phase shift or switching noise in the audio band. YOUR knowledge is evidently sorely lacking in this area. Common sense would tell you that signa-delta DACs don't need to "switch" in the GHz range in order to not have switching noise in audio band. It should tell you that. What that tells you is a mystery. |
needing switching in the GHz range is really quite laughable. There you go again, he said "that provide switching frequencies of several MHz or even GHz.""Even" is the word there sunshine, looking towards the future would be even better to have ghz when technology allows, to get rid of every little trace of switching noise, without any phase shift anywhere near the audio band. Stop being such a putz. |
@georgehifi, You have proven repeatedly you don’t have anywhere near the knowledge to make a comment on someone’s credentials. Your continued lack of understand of even the most basic aspects of amplifier operation, class-D operation, and even basic electricity make your comments on this topic meaningless. However, someone with a basic knowledge of signal processing, the math of signal processing, noise sources in a switching amplifier, or the basic math defining their performance, or say the related math of DACs would know that a comment about needing switching in the GHz range is really quite laughable. That tells me he really does not know what he is talking about and is just making an off the cuff comment or parroting someone similarly unqualified to make a comment. It is not healthy to put on a pedestal people who simply reinforce your biases without ascertaining if they truly have relevant knowledge in the topic of discussion. You don’t have any reason to place high value in Cyrill Hammer’s knowledge w.r.t. Class-D. Based on the public information, which we can assume we both have equal access to, I don’t perceive anything in his experience set that would make me place high value in his opinion on this matter, unlike say Bruno Putzey who has shown repeatedly, both a high understanding, and an ability to move the technology forward. |
I like my class D NAD M27 amp. It sounds amazing and is dead black quiet. Highs, mids, bass is all steller. It is solid trouble free, built very well and runs cool. Not looking back. I tried D-Sonic as well. It sounded amazing but I had an issue with one channel and it was solid, well built to. I will stick to class D and don't see any issues. I also have a vintage Sansui AU11000a in my stereo setup which I bought new in 1977 which sounds sweet and warmer but I like both. Sansui runs quite warm. |
I don't see anything in Cyrill Hammer's bio that would suggest the extensive knowledge in signal processing or advanced control theory or even ultra high speed switching for analog reconstruction that would make his opinion any more valid than many many others, and perhaps less. That GHz comment really makes me suspect his depth of knowledge on the topic is really quite weak. |
If Class D was even 10% as bad as he makes it out to be it would be a non-issue.Laugh all you like, Putz! Like I said you are the rumour spreader, not once have I said Class-D is bad, if fact I’ve praised the Hypex NC500 with linear power supply monoblocks (given the right loading) that I own in my second system. Class-D has yet to reach the same sound quality as good linear amp in the upper mids and highs. What you need to get right, is that I say Class-D the way it’s used (except for the Techincs SE-R1) has problems that MANY hear in the upper mids/highs, the deaf may not hear it. And this is a long way being fixed in the Technics SE-R1 by having a 1.5mhz switching frequency/low order output filter instead of 400-600khz as all are today. And those that are, or going to use the GaN transistor technology have the chance "to use 1.5mhz", but don’t, probably because they don’t have the R&D knowledge skill of Technics behind them to do it. And btw Cyril Hammer was the first to say this, even before GaN transistors were released to the market. And has more solid state knowledge in his little toe than some "tuber" here saying anything else. Cyrill Hammer (Soulution) "if you want to have your Class-D product performing at the cutting edge it is not possible with todays known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz." |
Has anyone reported back in detail about these? https://www.starkesound.com/detail.html?id=47 BTW, they don't use any of the off-the-shelf modules. https://hometheaterhifi.com/reviews/amplifier/power-amplifier/starke-sound-ad4-320-power-amplifier-review/ |
Correct, if you want big Class-D wattage at 4ohms the get a Behringer 6000watter for just $599USD! for 6000watts! With DSP!!!! https://www.parts-express.com/Behringer-NX6000D-Ultra-Lightweight-Class-D-6000W-Power-Amplifier-with... Cheers George |
while they sounded fine, they did not have the depth, or crunch of a nice class A/AB amp. high priced amps are paying for the same old routine. Crown makes great class D amps, as does QSC, your paying for the name and advertiising, not sound. get a nice class AB amp and have enough power and great sound for 20 years! even my old class H amp would smoke any class D amp made. dont believe the advertising, and smokescreen reviews. |
If Class D was even 10% as bad as he makes it out to be it would be a non-issue.You are the rumour spreader, not once have I said Class-D is bad, if fact I’ve praised the Hypex NC500 with linear power supply monoblocks (given the right loading) that I own in my second system. Class-D has yet to reach the same sound quality as good linear amp in the upper mids and highs. What you need to get right, is that I say Class-D the way it’s used (except for the Techincs SE-R1) has problems that MANY hear in the upper mids/highs, the deaf may not hear it. And this is a long way being fixed in the Technics SE-R1 by having a 1.5mhz switching frequency/low order output filter instead of 400-600khz as all are today. And those that are, or going to use the GaN transistor technology have the chance "to use 1.5mhz", but don’t, probably because they don’t have the R&D knowledge skill of Technics behind them to do it. And btw Cyril Hammer was the first to say this, even before GaN transistors were released to the market. And has more solid state knowledge in his little toe than some "tuber" here saying anything else. Cyrill Hammer (Soulution) "if you want to have your Class-D product performing at the cutting edge it is not possible with todays known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz." |
Gotta say, the energy and vitality George brings to discussions about Class D makes it seem rather personal. As if Class D killed his dog, and he is John Wick. If Class D was even 10% as bad as he makes it out to be it would be a non-issue. Class D would be dead and none of us would listen to it, and no one would need to bash it. It would be it's own worst enemy, and attract flies and locusts whenever anyone turned a Class D amp on. But yet, here we are. |
he needs extraordinary proof to support his claimsI know you don’t believe them, just look at the Technics SE-R1 at what it does and the press reviews it gets of it sound quality. Which rids the Class-D bugbear of many that say the uppermids/highs are the problem with Class-D. And what designers of higher standing than you quote. Just one of those quotes from Cyril Hammer probably one of the best solid state designers in our lifetime with Soulution Audio amps https://soulution-audio.com/ Cyrill Hammer (Soulution) "if you want to have your Class-D product performing at the cutting edge it is not possible with todays known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz."Now we do have those devices in the GaN, but so far the only one using those 1.5mhz switching speeds is in the Technics SE-R1. All the rest, including you are not using the GaN technology to it fullest. You started with a clean design slate, you should have utilized the GaN to it fullest, but you state you didn't. maybe you just didn't have the ability to do it like Technics design brains trust team do. |
Yes like the ones and their lackies pushing yet to be released commercial products, with fanciful claims that will only be proved right or wrong "if" given access to by independent measurement testers.To be clear here, the 'fanciful claims' were made by Bruno Putzeys, a good 15 years ago with the introduction of his UcD module. And again with his Hypex and Purifi modules. These devices have been measured many times. Any of the claims I've made are a subset of those by Bruno. So really the extraordinary claims are at this point coming from George. And to trot out yet another worn trope, he needs extraordinary proof to support his claims (beyond just wilful ignorance). So far, not seen it. |
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Really, do you really want to embarrass yourself yet again?? Calling me a fuser. What a laugh. Everyone who has read my posts here knows you are lying, but you are still upset I have shown you don't know how electricity actually works. Oh well. As well, it is time you stopped this classless attack on Atmasphere who has been pretty much right on the money with everything he says. Your comments about "product protection" are something you should be embarrassed as an adult to make. Atmasphere is just too nice to say what he probably really wants to. |
Every one knows "global feedback" is not a good thing in any amp, it’s a "sound sterilizer" and should only be used very sparingly if possible, just to clean things up a little, and preferably use only "local feedback".Actually 'everyone' does not know this about feedback and I think this is where your misunderstanding originates. For many years, feedback did do exactly as you said. This isn't to say that 'every one knows "global feedback" is not a good thing in any amp' but it is to say that there was a known problem but no good solutions. This had been true for about 60 or 70 years, so you shouldn't (and probably won't) feel too bad about being ignorant of advances in the technology. Now I've mentioned this before and I'll wager it went over your head. But nevertheless: It has to do with something called Gain Bandwidth Product. The math gets tricky, but in a nutshell you can sort of equate GBP to feedback as gasoline is to a car. When you run out of gas, the car stops, when you reach the limit of the GBP, you run out of feedback. This means that where ever that limit is, your feedback goes to zero. You need GBP well into the MHz region to support feedback going up to 20KHz if you're going to use a lot of feedback. The more feedback you use, the more GBP you need to have. Well guess what? Nearly all solid state and tube amplifiers made up until about 15 years ago or so lacked the GBP to allow for a lot of feedback at higher frequencies. Put another way, this causes the distortion to rise as frequency rises. To get around this problem most amps are measured at 100Hz; this sweeps the dirt under the rug. You don't see how the distortion is in fact higher at more critical frequencies like 5KHz. So at 100 Hz the feedback is adequate in almost any solid state amp, which is why they have a reputation for good bass, and this creates the idea that they must be OK elsewhere too. But we've been hearing the brightness and harshness for decades- in fact that is why tubes are still around. Now how it works otherwise with feedback is if you add a little, it seems to help, you add more and the benefit diminishes, as higher ordered harmonics are added by the process of the feedback itself- and this is the cause of harshness and brightness in most solid state amps (and tube amps too- this is why feedback has a poor reputation). But this does not happen to infinity. It turns out that if you can get enough gain, if you run about 35dB of feedback this will allow for the circuit to compensate for the effects of the feedback itself. IOW, you'll have low distortion at higher frequencies. Normally getting this sort of gain is hard, because your open loop gain is killed off by the feedback you have- and any power amp will need about 25 dB of voltage gain to be practical, and higher powered amps (which are likely to be used on low efficiency loudspeakers) might need 30 or 35dB. Well if you have 35dB to start with (and 40dB is better) that means you need at a minimum 60 dB of gain in the circuit open loop. That's a lot- and you run into something called 'Phase Margin' that limits how much feedback you can use before the amp goes into oscillation. The semiconductors needed to make this sort of gain possible in a traditional design have not existed until fairly recently. But you have to know what you're doing even if you have the devices in your hand. One amplifier of 'traditional' design that actually does have the GBP and feedback to pull this off is the Benchmark. It is a very rare exception in this regard; obviously John Siau knows his stuff. Class D amps have an advantage here though. If you give it so much feedback that it oscillates, you can use that oscillation as the switching frequency. All you have to be careful about is that it always find the same 'solution', the same switching frequency. But now at audio frequencies you have consistent feedback even at 20KHz; and this easily corrects for phase shift caused by the output filter (which is included in the feedback loop so as to allow the feedback to do its job). This is all standard control theory. I don't expect you to know it because its clear you don't have an engineering degree. But you don't (and I'm sure you won't) have to trust me on this- its easy enough to find on the web if you cause your hand to move and search for it. |
Oh George, I don't think you know the meaning of the world troll. I am sure I upset a lot of people here. It comes with the territory. They, like you, spew how you want the world to work or believe it works, I have the knowledge and experience from research to practical to know quite well how all this "audio stuff" works, right from recording tech all the way to small details in reproduction. That is the benefit of actually doing research (real research, like in a lab), and developing products instead of whatever you do. Your position on Class-D is laughable. Atmasphere has explained in detail, at a simple level you can understand, why so much of what you say is wrong. I have explained, in terms simple enough for you to understand, what so much of what you say is wrong. Yet you refuse to take even 5 minutes to understand, thinking that reading an outdated effectively graph in Stereophile gives you more knowledge than people who have actually designed amplifiers, who understand both the math (mainly control systems theory), the electronics, and the practical implementation details. But no, you are a greater expert than us, even though you can't even begin to explain the simplest details about your claim. I would go back to making yourself useful trolling fuse threads, and let people who know what they are talking about talk about class-D. There are no doubt people on Audiogon more knowledgeable on some areas of audio than I am, but I expect the people you claim are "upset" don't fall into that category. I am quite happy for Atmasphere or Duke to correct me, I would rather be shown wrong so others can learn, and mislead people. That is my character. What is yours? |
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No I defiantly don’t sunshine, but as you said "Decades behind"!!!!Decades! Really! It is also not that either, again just furphy from someone in product protection mode. As you say you’ll get around that problem with "global feedback", you can throw all the "global feedback" you want at it, to fix the phase shift problem. Every one knows "global feedback" is not a good thing in any amp, it’s a "sound sterilizer" and should only be used very sparingly if possible, just to clean things up a little, and preferably use only "local feedback". Which won’t help your plight as you’ll need a stack of "global "feedback" that has to incorporate even the speaker output filter into it, to try to remedy this kind of phase shift problem down to 1khz 40 degrees out of phase, and 70 degrees!! at 10khz (in red). https://ibb.co/vvwzGV5 And to those many that complain about it, this is why you have this concern with Class-D sound in the upper/mids and highs. And a 1.5mhz switching frequency goes a long way to remedy it (without throwing stacks of feedback at it), like they used in the 55kg $KKKKK Technics SE-R1, and hopefully next month in the far more obtainable and affordable SU-R1000 integrated. Cheers George |
The 1200AS 2 is still the current Class-D module from ICEPower, what have you been sniffing.Nothing but air. However if you are suggesting that this amplifier is representative of all class D amps you would be committing an excellent example of the logical fallacy known as Guilt By Association, and it works like this: 'Because this particular amplifier has significant phase shift at 20KHz and is class D, therefore all class D amps have significant phase shift at 20KHz.' Because its a logical fallacy, this idea is false. Obviously ICEPower has chosen a different set of parameters for what they feel is important, which with a short look at their website, appears to be public address. At any rate there are class D amplifiers that have less than 1 degree of phase shift at 20KHz. OK George- that one is debunked. Please proceed to the next. |
But don’t send that tired link about an amp that is obviously decades behind us.The 1200AS 2 is still the current Class-D module from ICEPower, what have you been sniffing. https://ibb.co/vvwzGV5 https://icepower.dk/products/amplifier-power-modules/as-series/ |
Once again, straight into product protection modeThis statement is false. I've simply been engaged in correction of misinformation. That is why I used the phrase fake news. But I could use others- ignorance comes to mind. Misleading. Deceptive. And so on. But since I don’t know/understand why you insist on posting incorrect information, I don’t use the word ’deceptive’ although due to the tenor of your posts I’m often tempted. Again for the umpteeth time: READ UP ON THIS STUFF. Parading the same rubbish over and over isn’t winning you any accolades and isn’t impressing anyone that you know what you’re talking about. Its easily shown that its not product protection, for the simple fact that whether my company produces an amp or not, what I have stated remains factual. Its not like our amp somehow makes it true. It may be that you won’t get this simple fact as this has been gone over and over again and you seem to hang on to the same mythology in the face of facts (just like that same person you alluded to in your post above). Please consider just reading and educating yourself. You might find it worthwhile. If you need links to articles I can provide them. OTOH if you can find anything that debunks my comments, please produce them; I’d be interested to see. But don’t send that tired link about an amp that is obviously decades behind us. |
You can easily put together a couple of icepower 500 watt monoblocks for about $800 as mentioned by Erik: https://forum.audiogon.com/discussions/how-to-diy-yourself-very-nice-class-d-monoblocks When completed they look strikingly similar to the aforementioned d Sonics class d m3a 1500s, inside AND outside. |
This is fake news.Once again, straight into product protection mode, just like someone else that abuses this tiresome saying. Hope independent tests from the likes of Stereophile will sort out your furphy’s. https://en.wikipedia.org/wiki/Furphy |
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The ’switching noise’ of any class D amplifier is a sine wave at the switching frequency. If the filter is properly designed, the sine wave is quite small and low power- it has to be so because the amplifier can’t interfere with other services, like AM broadcast (1.5MHz is at the top of the AM band). But an amp that is switching at 600KHz will have the same amount of noise and 600KHz is in the AM broadcast band too- the same rules apply. An amplifier is an unintentional radiator. FCC (and others) will only test conducted emissions at <=30MHz. Radiated emissions is tested at >=30MHz. The noise would be a square(ish) wave as the transistors are hard switching. It would become a sine due to the output filter.
This is very much not the case. Most are based on modules, and those modules are not designed with thermal paths / heat sinks that will allow full power continuously or more specifically high current continuously. That's fine since music doesn't work that way. The devices normally used are not the absolute lowest RDSon, but more so tuned for good switching performance. When they heat up a lot of course, that RDSon goes up. |
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.This is fake news. Let’s, once again, unpack and debunk this rubbish to set the record straight. The ’switching noise’ of any class D amplifier is a sine wave at the switching frequency. If the filter is properly designed, the sine wave is quite small and low power- it has to be so because the amplifier can’t interfere with other services, like AM broadcast (1.5MHz is at the top of the AM band). But an amp that is switching at 600KHz will have the same amount of noise and 600KHz is in the AM broadcast band too- the same rules apply. Phase shift is indeed a consequence of using a filter. But it is incorrect to assume that because a filter is used, even one of a low frequency like 80KHz, that there will be phase shift in all examples of class D amps that have a filter set this low. This is because some class D amps are of the self-oscillating variety, and self oscillating class D amps run a prodigious amount of feedback. They do this as part of their switching scheme but that is not why so much feedback is used. The thing about feedback is that its application causes distortion while suppressing the innate distortion of the circuit in which its used. The distortion generated by feedback tends to be higher ordered harmonics, which is audible as harshness and brightness, due the ear being keenly sensitive to these harmonics. It is that sensitive because it uses them to sense sound pressure. But if you use enough feedback (north of 35dB) you can not only suppress the distortion caused by the application of feedback, but you can also correct phase shift. This is why self oscillating class D amps with a switching frequency of 500KHz and a filter set at 70KHz can have less than 1 degree of phase shift at 20KHz- quite unlike the amp depicted at the link which George put up in his last post- and I might add, knew that this was the case. Amps that have less then 35dB (which includes about 99% of all solid state amps ever made) will have some brightness and harshness due to that lack of sufficient feedback. This is why class D. @mijostyn We’ve been working on a class D project of our own design for about 4 years. In November of 2019 we were awarded a patent in the field. Our prototypes make 100 watts into 8 ohms with 200 watts into 4 ohms and 400 watts into 2 ohms (sorry George) no worries, if given enough current in the power supply (the GaNFET output devices are rated 35 amps). When testing traditional solid state amplifiers the FTC requires that the amp be preconditioned at 1/3rd power for an hour and then the amp can be tested for as short a time as possible to get the full power specs. This is done because traditional solid state amps will overheat if you run them at full power for a long period of time and usually that’s only a few minutes. Our amp (and I assume for most class D amps this is true) can be operated at full power all day long and you can hold it in your hand- they get warm but not hot. We don’t know where this will lead, but we have a goal and now we’re seeing if it can be achieved. |