High end Class D amps?

The way to tell people who know and don't know what they are talking about is by the detail and depth of their posts.  Ralph, jaytoy, and I talk about architectural specifics about Class-D, even where the filter is placed. We talk about device operating region. We talk in numbers specific to Class-D.   One other person here who has a bugaboo and about Class-D and I think Ralph in general does not.  I would argue that he cannot, and if he educated himself, he still would not be able as he would see his errors.

As Ralph has pointed out, there are many ways to skin the Class-D cat. High frequency open loop is just one method. Claiming it is the best is like claiming tubes of solid state is the best.  We know many do it, but it is purely dogmatic.  Implementation details can push either in a direction of like or dislike for a given person.

Tim also clearly laid out what I would agree w.r.t. modern high end class-D. It is targeted towards very neutral. Many don't like that.  I am finding the Cherry very neutral. It does appear to have a better supply than what you are using.  I have heard your present Odyssey a few times, one of my friends bought on reviews and did not keep it.  I can see the allure, but it was not for him and and if you like that sound, the Cherry may not be your cup of tea, and I can't recommend one that will be, though they may be out there. 

Here are the class D I tried.
Old ICEPower: Unlistenable junk. To be fair I didn't burn it in much (didn't know about burn-in back then).
DriveCore 2: Very poor.
Pascal (newer version forget the designation): Very tight control good imaging but also empty and not pleasing. MAYBE it needed more burn-in but I was running into the return widow.
Cherry: Decent in some ways, couldn't compete with my linear amp. Actually I just moved it back into my main system to contrast and compare again now that I have new pre and source gear.
Technics GaNFET: Dry, sterile, boring. Burned it in for over a month. The cheap integrated unit.

I haven't owned any Hypex amps. I've listened to some at shows but I do realize those are poor environments for critical listening.  There was one nCore 1200-based unit I thought MAYBE warranted further listening but that was based on the "wow" factor of high-end class D's first impression.

How many class D do I have to listen to? Is there a The class D which disproves the "myth"? Did I just happen to miss the good ones?

@atmasphere, and @tweak1, Tweak1 is also getting Walter's Voyager GaN amp as well as having Ric's modded 1200AS amps, Ralph he deserves to be in your Beta testing.

George is correct. Lack of switching bandwidth is the problem. I know Bruno Putzeys claimed differently in an old interview, but he's mostly a self-promotor so no one should take what he says as gospel truth.

For the record, Bruno Putzeys is the one that made self-oscillating class D amplifiers a reality, a practical thing. That's a pretty big deal; if you work out the math for that you are doing quite well. You better be good at calculus with multiple variables! He also is able to show the measurements to back up what he says about how the technology works. Attacking Bruno is really done at your own peril!

By 'switching bandwidth' I think you must mean 'switching frequency' since 'switching bandwidth' isn't a thing. And in this regard your statement is false. Based on the rest of your comments I would venture that you simply haven't heard everything that's out there, and just like traditional solid state amps and tube amps, there is a tremendous variance in class D implementation!


You might think of it this way: digital has come a long ways since 1981 when it first started showing up. Its common now to see scan frequencies of 192KHz; class D amps are commonly switching well over double of that. At the current state of affairs, the practical upper limit is around 600-700KHz before you really start to get into troubles with radiation and oscillation issues- the fact that Technics seems to have gone well past that says a lot about their engineering expertise. But Technics has to switch faster, since (if their claims are correct) their circuit is zero feedback, so they have to raise their filter frequency quite a lot in order to avoid phase shift at audio frequencies. Also for the record, self oscillating class D amps don't have to do this- their filter frequency can be lower since they can run so much feedback that it is able to correct for phase shift. 
@tweak1 Thanks for your offer!

Ralph, if GFi is right, that you are close to releasing your class D, I volunteer to compare/comment on it vs my much beloved EVS 1200, dual mono IcePower AS 1200 modules with lots of Rics pixie dust. My speakers are EP 3.4s 12' concentric driver with polyester tweeter. Digital is a Oppo 105 with upgraded LPM, Furutech rhodium IEC with silver tail to LPM and ground, plus jumper to replace 110/220 switch. Series 8 WireWorld ICs and Series 7 speaker cables. CorePower 1800 into 20 amp dedicated line

madavid0:
" I don't think you guys really appreciate how deadly to euphonics that traditional class D output filter is. I didn't start out hating class D I developed that position after being burned many times being told this or that class D module was the revolutionary savior of the topology. I remain interested in GaNFET because it seems like that is what will finally be able to pull class D into the realm of quality audio."

Hello madavid0.

     I believe the most prominent characteristic of the newer, good quality class D amps is neutrality, with no euphonics or anything else added or subtracted.  In my experience, this high degree of neutrality is very revealing of everything upstream, even interconnect and power cable quality levels and differences are more easily detected.  
     I know that Bruno Putzeys, the inventor and designer of the Phillips ucd, Hypex Ncore and the most recently the Purifi class D modules, has stated that he has steadfastly maintained a goal of optimum neutrality in all his modules in order to appeal to the largest number of potential customers.  Based on my experience, the designers of most other class D amp modules, such as TI, Anaview/Abletec and Pascal, have apparently maintained the same neutral presentation goal.
     As to your statement " I don't think you guys really appreciate how deadly to euphonics that traditional class D output filter is.", I don't know where you read this, why you believe it or what class D amps you've listened to, but it's definitely not true with my class D monoblocks.  These are good quality units and, as I stated above, their primary characteristic is a completely honest neutrality, like the traditional audio ideal of a 'straight wire with gain'. 
     It is definitely true that this level of neutrality very distinctly and articulately portrays the quality level of both the recording and the music but there's absolutely no elimination or theft of 2nd or 3rd harmonics and euphonics taking place.  If the music contains these euphonic qualities, and the recording is of sufficient quality to have captured them, then they are faithfully amplified and reproduced.
     I happen to appreciate and prefer utilizing very neutral and revealing  amps in my system while understanding that numerous others seem to prefer a bit of flavoring.  However, I believe this is a topic best left for a separate thread.

Tim

@audio2design Okay what class D amp today can beat my Stratos? I can’t have fatiguing sound. Does the little Cherry just lack juice? My speakers are ProAc D30R.

Edit: it's a Stereo Maraschino with an external power brick, less than the 48V listed on the website but I forget the exact value.

You have absolutely no idea, your burying your self with your own brand of **** ****

I generally think of the Odyssey units more as PA amplifiers than serious audiophile gear. Throw lots of brute force at a problem, but not a lot of finesse ending up with a "warm" but bloated sounding box.  If that is the sound you like, then I am not surprised the Cherry was not to your liking. It is transparent, not "euphonic".

 Bruno is a promoter, but unlike many in the audio industry, actually has the technical chops to put something together.


Switching frequency was important 10+ years ago before people figured out putting the filter inside the feedback loop.

The claim the output filter is "deadly" to euphonics, again is "old" knowledge, see last comment about the placement of the filter in new higher end class-D amplifiers, not to mention a bit better practical understanding of how to tune class-D filters, however, keep in mind the filter is to keep ultrasonics out of the speaker.

George is correct. Lack of switching bandwidth is the problem. I know Bruno Putzeys claimed differently in an old interview, but he's mostly a self-promotor so no one should take what he says as gospel truth.

I tried the low-end Technics integrated which only had around 800 or 900 kHz of bandwidth and was generally unimpressed even if it wasn't terrible. There is going to be a huge difference between that and the SE-R1 which I haven't listened to.

I also own a Cherry amp, the older lower end one with the external power brick. I was told Cherry was the revolution of class D, etc etc. It wasn't THAT bad, but it didn't hold a candle to my Odyssey Stratos. It's currently on PC speaker duty.

I don't think you guys really appreciate how deadly to euphonics that traditional class D output filter is. I didn't start out hating class D I developed that position after being burned many times being told this or that class D module was the revolutionary savior of the topology. I remain interested in GaNFET because it seems like that is what will finally be able to pull class D into the realm of quality audio.

George is coming from a position of near 0 experience

Really??? so you think a Class-D with a tube rectified power supply and a chassis stuffed with pillow fill is the answer to the woes Class-D has?. Good luck with that sunshine.

I tried to tell you the answer, with higher switching frequency (3x the norm at 1.5mhz) using GaN output transistors as Technics did with the $$$$$ SE-R1 so that then switching frequency output filter can then be set also 3 x higher thus stopping any phase shift down to 1khz as it is now with all Class-D’s
  
As for driving low impedance combined EPDR even lower, not even the GaN can compete with bi-polar A/B amps there, they still rule the roost.   

Cheers George

George is coming from a position of near 0 experience with actual class-D amplifiers and I expect almost 0 experience at the architectural / design side of amplifiers at all.  He only knows what he reads, with limited direct listening experience.  Because he does not have the right experience or knowledge, he misinterprets what he reads and draws erroneous conclusions.  He is not "holding his ground", he is standing in one place stomping his feet up and down.  

As others have pointed out, there are Class-D amplifiers that sound excellent, and not just the one that george is enamored with, and likely only from knowing 1 raw specification about that amplifier. George isn't calling anything out.


I am currently listening to a Cherry amplifier and I must say, I am rather impressed with it.

madavid0141 posts12-01-2020 11:20pmI don't know it seems to me that George is coming from a position of a lot of experience and the fact that he's holding his ground here suggests to me that he's on the right side while you guys are just compensating with confirmation bias and group-think. Many people don't care at all about what is true, only that they feel good about something, so when someone is willing to call out something as being garbage many people won't want to hear it.

Nothing worse than high functioning trolls.

another good discussion thread devolved and down the toilet

except for us bored souls who habitually hang out here, who in their right mind would come here for some real insight and good info -- and read this mean spirited crap???

especially people who are ’in the industry’ -- why would you pollute your own backyard?

leaving aside the obvious trolls who have nothing better to do than post 300+ posts in 45 days since joining, zero transactional feedback, no system disclosed, stirring the pot every post?

Swing and a miss...

I don't know it seems to me that George is coming from a position of a lot of experience and the fact that he's holding his ground here suggests to me that he's on the right side while you guys are just compensating with confirmation bias and group-think. Many people don't care at all about what is true, only that they feel good about something, so when someone is willing to call out something as being garbage many people won't want to hear it.

No, no, it’s not the Tri-Art class D Amp

Yeah well that’s a beauty

No, no, it's not the Tri-Art class D Amp, as lovely as that little number is.

after reading this thread and its recent entries i have to agree with doug s when he says

Especially since audiophiles love to jump to contusions

LOL

Douglas .. fair enough. Please let us know about the new amp when the time comes...

klh007...thanks for the link...

Typical response from a fuser. 
https://i.dailymail.co.uk/i/pix/scaled/2013/12/18/article-0-1A2B262D00000578-818_636x382.jpg

"True, I can take that one both ways.
He does trash his reputation when he’s product protection mode, as there's not much new tube amp sales going on anymore."

I was actually speaking about you George. I think that you were being unreasonable, and in this case, made yourself look bad. 

This goes beyond Dunning-Kruger it is just bizarre. We aren't arguing over something subjective or subject to opinion. This is clear cut, basic operational details.  It is almost at conspiracy level.  I don't understand it.

@aolmrd1241, This is just speculation, but I looked at Doug's equipment list for a recent review and this was the last piece listed in amps,   Tri-Art Audio Series B 60W Class D with Tube Linear Power Supply,  link;  https://www.triartaudio.com/?page_id=3997      
Single ended Class D, 60WPC, I can't find a price?

True, I can take that one both ways.
He does trash his reputation when he’s product protection mode, as there's not much new tube amp sales going on anymore.

You really don't need to trash George. He takes care of that himself.

Amazing.
@atmasphere ,
Dunning-Kruger effect seems to sum it up nicely.
Bob

I currently don’t make, sell, or market any amplifiers and have no skin in the game either way.

You are delusional, I didn’t say you. Go back and read.

But then you are a 50’s kind of guy and you don’t hear too well anymore

George, as a simple tip: the ability to admit that you were wrong is a strength, not a weakness.

Ralph lay off protecting, you do the same with preamps.

The answer is simple: Gain knowledge instead of made up stories.

These are words of someone either in denial or in product protection mode.

George, as a simple tip: the ability to admit that you were wrong is a strength, not a weakness.


In my quote above I was simply stating a fact. My advice is to study how class D amps work (the theory is simple) and keep in mind that with any current output device (MOSFET or GaNFET; the difference between them these days is slight) the output impedance is going to be lower than any traditional solid state amp, often by a couple of orders of magnitude. As I mentioned earlier, the PuriFi modules (not made by me, so clearly not in 'product protection mode') have output impedances that are tricky to measure as they are about the same as a few inches of 12Ga wire.


So this is not about denial, its physics. When you have an amplifier with an output impedance that low, it pretty well makes no difference what phase angles the speaker has nor its impedance, since both are several **hundred** times more than the output impedance of the amp. This simply means that the amp will be able to make constant voltage into that load.

I currently don’t make, sell, or market any amplifiers and have no skin in the game either way. I do understand quite well amplifier topology though.

georgehifi, given your obviously thin educational knowledge w.r.t. amplifier topologies and again obviously without the practical experience to compensate for that knowledge gap, perhaps you should be giving pause to the fact that people with far more knowledge of amplifiers theoretically and practically are all telling you you are wrong. Not just one, but everyone.

The answer is simple: Gain knowledge instead of made up stories.

These are words of someone either in denial or in product protection mode.

I made a general statement, and I am not prepared to discuss at length. I have made a general observation, and that observation will be shown true or false over time as I build systems, but usually my first instincts have been correct.

Regarding comparison to the XA200.8, I have not done direct comparison yet, but I will. One of the XA200.8 has been back to Pass Labs for repair following my bone headed blowup wherein a metal plug of an IC was touching the output. Amazingly, the amp survived another four weeks before giving up the ghost. It's not back yet, so no chance to compare.
I attest to the sensational service of Pass Labs; no arguing, no bickering, no guilt trips, no plea for me to cover return shipping, which would have been expected, given I hurt the amp; just, "We'll arrange pick up, get it done and back to you." That is a big part of why they are world class!

For any kind of meaningful conclusions, several systems have to be made. This amp is very different from the XA-200.8, but so far to my ears, as legitimate. I think this may settle out like the two motorcycles I own; Yamaha Stryker and Yamaha FJ-09; two very different rides, but I love them equally. I am not of the school where there is only one form of excellence in amps and systems.  (If you are, great! So be it.) I have built too many rigs and used too many speakers, such that I do not wish to limit myself to one expression of fine audio.  :)  However, I do try to maintain a high standard for excellence across a variety of systems.

Especially since audiophiles love to jump to contusions, I usually withhold names of equipment before the time is right (publication). Sorry; sometimes you just have to wait.  

How can anyone believe that "any" Class-D driving a pair of Wilson Alexia etc etc could possibly do anywhere near the sonic job that an amp like Gryphon Antllion or similar could do.
Especially in the lower bass where the Alexia's are 0.9ohm loading presented to the amp.

The answer is simple: Gain knowledge instead of made up stories.

georgehifi,
There’s no way to know how Ralph’s new class D amp will sound, or how it might compare to a Gryphon, or similar amp; but we do know that he has a pretty stellar reputation for the OTL amplifiers that he has produced to date, so I am going to bet that his class D amps will be something special. Customers will decide if that’s the case.

Hello georgehifi,

     Hey, maybe douglas_schroeder has found your first class D amp?
     If so, welcome to the club!  But I think we're gonna need a bigger bandwagon.
Love,
 Tim
XOX

And there it is, Ralph's new Class-D release must be soon as he's gone into full product protection mode.
 
How can anyone believe that "any" Class-D driving a pair of Wilson Alexia etc etc could possibly do anywhere near the sonic job that an amp like Gryphon Antllion or similar could do.
Especially in the lower bass where the Alexia's are 0.9ohm loading presented to the amp.

Cheers George

The LKV Veros costs 10K.  Is that it?

10K class d is paying for a name, and aesthetics.

 800$ class D amp is smart buy.

 Don’t let the sheep make a line you can’t help but follow.
 Happy hunting.

As with any audio component these days, it's possible to get pretty good quality for a modest sum (say, under $1K for most component types). Clear improvements beyond this quality require considerably higher investment. 

Consider a simple component like a film cap. A cheap no-name 1uF cap will cost about $0.30 qty 1 at retail. Stepping up to a better quality WIMA will increase the price to $0.50. Moving up to a SoniCap will increase the price to close to $10. A Miflex KPCU copper foil cap will increase the price to close to $75. 

Multiply this by the hundred+ components in a given product and you can see how the build cost for high end products can quickly escalate. 

Whether these "upgrades" result in sound quality improvements that are worth the incremental cost is up to the customer, but since there is a fairly robust market in high-priced gear, many people believe it is. 

But saying that you are just paying for name and aesthetics is just not true. Class D amplifiers can benefit from judicious use of higher quality components and more sophisticated design approaches as much as any other product.

Now you go find a Class-D that will keep pushing even more current into that kind of loading like a good bi-polar amp can.

You mean like, *most* class D amps?? Because its most of them.

@jaytor  I've found that dealing with George means you have to accept that Dunning-Kruger is at play.

10K class d is paying for a name, and aesthetics.

 800$ class D amp is smart buy.

 Don’t let the sheep make a line you can’t help but follow. 
 Happy hunting. 

Hey Douglas..does this class d amp you speak of sound better than the Pass Labs XA200.8 you recently reviewed? 

Hello douglas_schroeder,

   I've been reading your professional published audio reviews and your occasional posts here for years.  I've always respected your knowledge, experience and opinions as well as your abilities to articulate sound quality and performance characteristics and differences.
     So the above is all true and I respect your judgment.  Now, would you please not keep us in suspense any longer and spill the beans on the identity of your newly discovered class D high quality performer?

Thanks,
  Tim

As to OP's question,  the answer is yes, as of December of 2020. I am using one that qualifies.  How many are there, I do not know. This one is not "close", it's clearly superior to most class A and A/B I have used. Tonally superior to the tube amps I have used. Bonus is that price per Watt is low. Win, win, win...

This is very basic stuff.

Which I sorry to say you don’t understand.
If you knew the difference of current ability between complimentary Mosfets v complimentary Bi-Polars into low impedances like the Alexia’s etc etc we wouldn't be having this, and you will see how misguided YOU are.

And as for the title to this thread "High end Class D amps?" here is the only answer so far to that title
https://forum.audiogon.com/posts/2057327.

You see @georgehifi, @jaytor understands quite clearly how your term EPDR has no meaning effectively for Class D as well as how your metric of doubling in output power at half the output load impedance has little meaning for Class D. You do not. You don’t appear to possess adequate knowledge in this area. This is very basic stuff.  Please research amplifier topologies more if you have the skill set and you will see how misguided you are

This argument seems kind of silly. As with class A and class A/B, a class D amp's output power at any given load impedance is limited by its voltage and current capabilities. 

In class A and class A/B amps, the output transistors are dissipating power proportional to the bias current and voltage across them. Most class A amps (although not all) are set up with enough bias to operate in class A only into 8 ohms, switching to class A/B into lower impedance loads. With adequate heat sinking (and a big enough power supply), their thermal capabilities can generally support enough current to double power into 4 ohms and again into 2 ohms (and some even again into 1 ohm), since the voltage across the output transistors carrying the current is lower when they are delivering the maximum current. 

This is where EPDR comes into play, because if the phase angle requires high current while the output voltage is still low, the thermal limits of the amp can be quickly exceeded. 

Class D amps operate differently, since the transistors are almost always either in saturation (where maximum current is flowing, but with very little voltage across them) or turned off (where no current is flowing). The only time they are dissipating significant power is when they are switching from on to off or back (this is obviously a simplification). but this is a small percentage of the time. This is how class D amps can be so efficient. 

But there is nothing about class D amps that would prevent you from building an amp that doubled power as you halved impedance. It's just that there is not the same benefits to do this as their might be in a class A or A/B amp. The amp is not going to run much more efficiently at half the rail voltage like a linear amplifier will. 

Since most speakers are nominally 8 ohms (or slightly less), most class D amplifier designs are optimized for this load.  But that doesn't mean you couldn't build amp to do what you're describing. The Hypex and Purifi modules, for example, can be operated at a lower voltage with the same high-current power supplies to create an amp that can easily achieve what you are talking about.

If you ran a Purifi module at around 35v, it would be limited to about 30w into 8 ohms, 60w into 4 ohms, 120w into 2 ohms, and could probably achieve 240w into 1 ohm. But why would you want to do this since you could achieve almost the same power into 1ohm and get over 200w into 8 ohms without generating much heat by using a higher voltage supply.

I will state again. You clearly do not understand what this term EPDR means.

You have no idea, https://imgbb.com/Zzsqsr0 
If you have, stick one on your test bench and watch what happens with the same input to the wattage figures under 8ohm 4ohm 2ohm and 1ohm loading. Until then please take a pill, and push your Class-D out there beliefs to ones that will believe it.

I will state again. You clearly do not understand what this term EPDR means. It had absolutely no meaning for a class D amplifier as it does not work in the linear range.  The only figure that matters is lowest impedance which in most speakers occurs where Class D amplifiers have very low output resistance.

Your request for tests from 8 to 1 ohm is meaningless and again has no relation to EPDR and a Class D amplifier.

Whether they current limit or not is representative of maximum power and designed thermal limits. What matters is THD at those power levels.

Until you increase your knowledge of Class D amplifiers and this term EPDR as it applies to amplifiers I feel this conversation will go no where. Unfortunately your knowledge in this area is not sufficient for us to have a meaningful conversation.