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
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 amps
you 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.
It may not double power into 2 ohms though, but that’s not important
That 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
:) 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 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.
Sorry, not a "fuser" but I do understand AC circuits. Not so sure you do based on your posts.
People,
shillers and manufactures saying Class-D already great and is better
than the best linear amps, which it’s far from yet.
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.
That Class-D has trouble with low <2ohm impedances,
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 if you accept it for what it is, nothing will be done to fix those inherent problems.
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
own and listen to a pair of direct dac signal feed Hypex NC500 modules
(with no buffers)
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.
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 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!
Good 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 dac
That'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.
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.
George is right. He posts a lot of incorrect, unsubstantiated information that he cannot describe or support in his own words. It is a lot of work to keep correcting that.
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!
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.
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...
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
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:
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.
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 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. :)
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.
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.
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 .
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.
because of my obsession with GaN with it’s ability to have 1.5mhz switching speed the Achilles heel of Class-D
This 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.
Douglas, I hope this tease of yours dies quickly.......What is this mysterious class D amp that you love? Is your mouth tied shut till the review? he he....If you absolutely cannot tell us more.....then when is the review going to be published?
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.
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.
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
@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’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.
georgehifi, perhaps. Comparison would tell. My comment was not meant to be a definitive conclusion, btw. I think that was clear, and that only head to head comparison would reveal distinctions.
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.
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.
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.
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.
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
This 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 forgot dogmatic. If ignorance it is totally wilful. I don't think I could have explained current limiting and power limits and thermal limits any simpler or more completely, or for that matter the impacts of load.
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.
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.
