Class D amps seem poised to take over. Then what?

It amazes me how someone can say a Class-D like the AGD has no limitations into one of the hardest know speakers to drive, and for it to sound it's best.

You are correct.

Also to date they do stand apart design wise Merrill does also atmosphere from what i'm reading has spent many hours designing their Class D offering which i'm sure will be a great sounding amp.

But in the end it's the SQ, one can have the best parts but if you do not know how to maximize what you have best parts means little.

You know as i do from experience and living with the AGD's that they are great sounding, Alberto has taken advantage of what he has at his disposal. It does not take long after talking to him that he is the real deal and a very intelligent person when it comes to design and parts implementation. His upper end amps have a clear cover so one can see his design also in the so called tubes. He is very proud and deservedly so of his creations.

Some talk negative about the amps but do they have any experience with them? It's like me telling you how your care drives even though i have never been in the make or model, it also takes time to familiar yourself with a product to maximize it's potential.

It amazes me how some can form an opinion out of the air.

earlflynn, thanks for the response. I totally understand passion,and brand loyalty.  I'm a motorcycle enthusiast. I ride Victory bikes. I was also in an MC where everyone else in the club rode HD. While we used to bust each other's stones, it never got to the point of hostility.  I guess when you can only see written words,sometimes what is meant to be passion,comes off as pompous.  

rh67
Would you agree that the actual GANfet used in AGD amps is proprietary? The comparison has been made to Nelson Pass acquiring all available SITs. Although Nelson does not hold the patent on SITs as does Alberto on the AGD’s GANfet.
One reason I bought AGD is because I was convinced that they stood apart from all other Class D.
That all the others used variations of existing technology (chips).

@georgehifi - wouldn’t it depend on the original rating at 8ohms, the power supply rating that feeds the class D modules?

No, although it to needs to be beefy, look at any Class-D that has been independently wattage tested into 8ohm 4ohm 2ohm regardless of powersupplies (most won’t get test into 2ohms), they are fets, and fets can’t do doubling of 8 to 4 to 2ohms (current) like complimentary bi-polars (bjt) can do like in the the Gryphon Antillion, bigger Krell, D’Agostino Boulder, etc etc etc

Also look at my post in the  "Pass X260.8 vs Bryston 7B3" thread

Cheers George

@georgehifi - to be clear here, I saw the post after mine (above this) and I wasn't be combative, I was giving you the benefit of the doubt.

I know a bit more than Ohms laws, so I have genuine interest as to the limitations. Which there very well may be.

WOW! You know what my system sounds like yet you have never heard it.

Now your a mind reader knowing what i will say next. Bravo!

I was in the industry for many decades, building and designing, amps, pre amps and speakers so it's easy for me to tell who's winging it and those who know their stuff, keep winging it george i know better.

@georgehifi - wouldn’t it depend on the original rating at 8ohms, the power supply rating that feeds the class D modules?

I’m not pretending to know, I’m just posing the question: if the power supply is engineered to supply enough current at 1ohms impedance seen by the amplifier, where is the limitation?
Could it not be possible, to double to 1ohm?
Is it a lack of efficientcy, I mean there’s less loss by creating heat.

It might be a lengthy topic to answer, if you know of an article I could read about it perhaps?

I hate it when people talk about subjects they know nothing about.

You need to hate yourself then, as you have no idea about the performance of Class-D even when using GaN Fets into 8 4 2 and 1ohm at it’s "current ability" (wattage doubling) at these loadings. And how those Wilsons demand it to get the best out of them.
Next you’ll say an OTL of Ralphs can drive those Wilsons to their best properly, because they too will stay stable into them and not oscillate.🤷‍♂️

I have been selling audio for along time now and we have heard this type of rhetoric before. A few decades back a person buys a cd player and claims to the world that the turntable will now be obsolete, more recently another person bought a streaming device and declared to the world once again the turntable will be obsolete. The names change but the story its still the same. Very seldom do our customers every make a request for a certain class of amplifier, instead  their decisions are based on how it sounds with their equipment and room. Class D amps have made themselves known in the huge audio equipment landscape, are they going to make everything else obsolete? History says no. For us the problems we have encountered with class D is reliability and repair

Never entirely but for the most part, class D is too attractive an option to audio manufacturers with it's cool running efficiency, compact form factor, etc.
Properly implemented, it's increasingly recognized as being as good or better than the alternatives, despite myths to the contrary.

atmosphere
+1.

George
What you posted shows lack of knowledge. Your talking about products that you have zero knowledge about, why say anything at all?

I hate it when people talk about subjects they know nothing about.

Good stuff. Thank you @atmasphere

...yes, but is Class D stable into 2 ohms?

Yes, depending what most meanings of the word 'stable' are. Yes, a class D will not go into oscillation when presented with a 2 ohm load (instability can result in oscillation- so that's one meaning of the word...). Yes, a class D amp can easily double power into 2 ohms or even 1 ohm, since its actual output impedance is probably only a few milliohms (our Beta production amps have an output impedance of about 10 milliohms).


With an output impedance like that, of course an amp can double power. But we also have to be clear about what limitations exist. The limitations are the ability of the heatsinks to get rid of the additional heat, the current available in the power supply and the ability of the output devices to handle that much current. So most class D amps might be able to double power into 2 ohms, but maybe not at full power.


One limitation with GaNFETs is the heatsink- because their appearance has a lot in common with a postage stamp, there's not a lot of methods available to couple them efficiently to a heatsink. And that heatsink has to be very effective at moving heat away from the device. This is (IME) the biggest limitation of GaNFETs; on the case of our design, the heatsink simply isn't fast enough to move all the heat away from the devices if operating at 2 ohms to full power (which would be 800 watts). The output devices are rated for the current, no worries there and its no problem putting in a power transformer that has enough current.


But are they stable? Certainly! For that matter so are any of our tube OTL amplifiers (in that they too will not oscillate when presented with an adverse load) although they certainly won't double power. So what this question really points to is the ability of the amplifier to behave as a voltage source (able to put out the same voltage regardless of load) and so long as you don't ask it to make full power into the load, almost any class D will do that like a walk in the park.


But at the same time its important to know that  **ANY** amplifier driving a low impedance like that will not really be able to strut its stuff. All amplifiers make higher distortion when driving lower impedances; from a high end audio point of view where its all about getting closer to the music, this is the Thing You Don't Do if you want your stereo to sound like real music- the additional distortion will manifest as harshness and brightness with a loss of detail.

Keep your Dingos away from him

What does that even mean?
@georgehifi - I read the book written by the Chamberlain's lawyer, and learnt a lot about Dingos, they are most closely related (genetically) to the timber wolf. Highly intelligent is accurate. I've only ever seen them in zoos, never in the wild, even when I drove around Oz.

"Then what?"
A: GaN

Don’t have to, the AGD is just GaN based Class-D slid into a "bogus" empty tube envelope, which uses (horror) the base pins for all it’s contacts 🤦‍♂️

And there no way the AGD can do what say the Gryphon Antilion can do into the Alexia, Alex, or XLF’s bass, if you do own any of these, they go down to 0.9ohm EPDR (Equivalent peak dissipation resistance). It’s a measurable fact.

Don’t get me wrong, I never said it won’t sound any good, just not the very best for those speakers. And if I had the money for them I’d have the money for the best amp also.

Cheers George

I said the AGD's sound better than SOME 40-50k amps. It's also not my opinion alone i have had many bring their mega buck amps into my system and most are shocked at the SQ of the AGD's most leave scratching their heads in disbelief.

By your comment you must have heard the AGD's so what's YOUR take on the SQ?

Guarantee put a Gryphon Antilion stereo or monoblocks on them and you'll change your mind in an instant.
And if you don't there's something seriously wrong.

Cheers George

My AGD Audion’s drive Wilson’s effortlessly even the large XLF’s. I own Wilson’s no issue at all. And the $7500 AGD's sound better than some 40-50k amps.

The Merrill amps double power to 2 ohms.....who cares? about one ohm except for those that have overpriced big speakers that only the 1% can afford?  You really need to try the Lii drivers on an open baffle.  You can use 10 watts and play way over 100db.  Those Wilson's etc. are boat anchors.  You buy a $100K speaker and you have to buy a $40K amplifier to run them....crazy.  A pair of 99db Lii 10 inch full range drivers are $1300 a pair delivered.  Make an open baffle with wings and you have flat to 40hz bass.....and then in a few months (after you have picked your jaw off the floor) you add a supertweeter....then later add some woofs....and you have better sound than a Wilson big heavy boat anchor.

hshifi:  The NAD M27 uses nCore amplification, not the same as the NAD M33.

A lot of scintilla owners went from the big krell amps to the H2O and said it was way better.

FACT!!!!
No way can ANY Class-D compete with doubling of wattage into impedances 8 > 4 > 2 and 1ohm (current ability) like BJT amps Gryphon Antillion, bigger Krell, D’Agostino Boulder, etc etc etc can

Class-D "may" not blow up, because of severe current limiting at 2 and 1ohm but they can’t drive into those low impedances like those BJT above amps can.
Anyone who says they can is just shilling for sales.

A friend Edgar Kramer, editor/owner of Soundsatge Australia has the Wilson Alexia MkII, and no Class-D he’s tried and reviewed and I’ve heard at his house has sounded any where near as good on them, as his Gryphon Antilion does, especially in the bass where those Alexia’s are 0.9ohm loading.
I will also say the Technics SE-R1 which I rave about is also in that same situation, as GaN Fet like Mosfets output stages can’t do current like BJT’s can into low impedances, 1 or 2ohms

Cheers George

yes, but is Class D stable into 2 ohms?


Yes, they are stable into 1ohm, the H20 amp that Henry used to make was used with the apogee scintilla.  

Grannyring,
I am 100% sure it will sound different. Every single thing you do changes the sound including jacks, wire, solder, chassis vibrations, etc. But, yes, they are using the exact same modules (except that Rouge is using mono modules and Legacy is using one half of a stereo module (exactly the same thing). Yes, you can see pics of the inside of the Legacy amp that verify this fact. Legacy are not doing anything to the modules....they do not touch them......it is quite clear from the pics. They do have a separate ground wire running from each module and they do scrap away the anodizing where they ground (standard practices). Basically, they are stock IceEdge modules in a box.....same as Rouge Audio. What I am 100 % sure of is that with my mods either amp will sound way, way better.....but still slightly different from each other.

https://systems.audiogon.com/systems/5078
Pic #11 shows the best interior shot. Click on the pic again to make it larger.....you can clearly see the amp channel on the top of each module is not hooked up in any way.  Totally stock stereo modules using just one channel for more power and better separation (same as using mono modules).

George,
Wrong, many class D amps are fine with 2 ohms (stable and otherwise) and one of my customers is driving 2.4 ohm Thiel 3.7s ......Fremer drove his 1.4 ohm Wilson Alexx with the IceEdge module without a hitch. Time to tell the truth, dude! Yes, some class D amps are not designed with big enough power supplies to drive 2 ohms or less. After all, how many speakers go down to 2 ohms or less.....mostly the big expensive ones that only the 1% can afford and with 97+db speakers like the incredible sounding Lii Audio drivers.....those big expensive boxes are now boat anchors.

jbhiller
I’ve tried a couple class D units. They were good but not great to me. I’m game to try some more.

If you can get hold of a Technics SE-R1 flagship or at least it’s cheaper integrated the SU-R1000
The SE-R1 addresses the "Achilles Heel" of Class-D, (ultra sonic switching noise down into the audio band) Technics takes it up 3 x higher and so filters it up 3x higher also, which results in 3 x less switching noise in the audio band.
It’s been said the SU-R1000 integrated does it also, but not confirmed by Techinics.

These are the only Class-D’s so far to take full advantage of the GaN Technology’s far higher ability to be able switch 3 x higher.
Other manufactures using GaN are only half exploiting it, and still using the old 3 x lower switching frequency, like all other Class-D’s do since the 90’s, so really not much advantage using GaN if not used like Technics have.

This top pic is what the switching noise looks like on the output of a Class-D going to the speakers a 10khz square. https://ibb.co/qBnNwVJ
Now Stereophile use an "AP (Audio Precisions) temporary test bench filter" on the output to give the illusion of a cleaner bottom pic, and they never give the top pic anymore, this is done in my view as to to not freak potential; buyers out.

Cheers George

...yes, but is Class D stable into 2 ohms?

Sadly not, like good Class-A/B's can be using BJT (bi-polar) output stages, especially in current delivery.

Cheers George

.
...yes, but is Class D stable into 2 ohms?

I’ve tried a couple class D units. They were good but not great to me. I’m game to try some more. 
Anyone try a class G amp?  I had a Creek class G. Very cool topology: first 25 watts was all Class A and the switching side kicked in north of that to output 170 watts into 4 ohms. Sounded lovely with PSB Imagine T2s. But I went horns and tubes.   

Oh, and I had my first class D amp way back when. 1965 or so.

The Sinclair X20. 

http://www.vk6fh.com/vk6fh/sinclairX20.htm

Built it myself, I did. If you soldered a short wire to the collector of the driver transistor, you could pick up a distorted version of what I was playing (from a self-electronic'd reel to reel) at intervals all the way up to about 30MHz on the AM band for quite worrying distances. So I put it in a metal box.

It had a class A front end, so it must have been good...

What's after Class D?

Well, as usual, probably improvements on what we've got. Sounds like GaN (Gallium Nitride) transistors can handle very high voltages and very high current and very high frequencies. Perhaps useful for class A, A/B, G etc - because they cmight vastly reduce output delta t, so feedback works better -  but almost certainly wonderful for D. Much better edges, so fewer errors for the system to compensate for.

And, of course, all this hifi stuff is for pleasure. It's nice to know that product X has immeasurable distortion under all circumstances, but of you prefer listening to product Y, then go for it. I prefer Burgundy, but there are those who drink Bordeaux. Neither I nor they word - or rather should - argue that my preference is 'the absolute best'; just that 'I prefer'.

It's true that many designers want accuracy first. Good! But if you prefer the sound of something else, go for it.

But don't tell me that you're right and I'm wrong for enjoying my Kii Threes. 

@ricevs 

Are you 100% percent sure the Rouge ICE amplifiers will sound the same, as good, as the Legacy amplifiers that Doug reviewed? Have you seen inside the Legacy amps? Is it possible they have performed some upgrades or other power supply changes etc? 
Looking at the Rouge amplifier now.  Thanks! 

I have had my AGD Vivace amps now for a month or so. I have sold my Luxman M600-a class a 30 watter plus some other ss and tube amps. I did not think it could get better-I was wrong. Try some diff class d amps. I tried some a few years back and that was terrible. The AGD and Merrill companies seem to lead the pack-both sound very good but the AGD is just a step above in my opinion. 

Class D amps today are so much better than the ones 5-10 years ago. That has been said for the last 30 years. 

Tweak1, I mentioned just Sugden for some good reasons, firstly they made the world’s first pure class-A transistor amplifier, they are regarded as the benchmark for class A, and seeing as I own one and it’s my last amplifier I’ll buy. 

Children......go to your room until you know how to play.  So much ego, so little agape.

Everyone has the ability to choose love at any time.....and every second even.  Please choose to only share when you have something that contributes to the advancement of audio and the soul.  Every word you think, say and write affects every single person on the planet.  That is how powerful we are.  May all be blessed....may all find the love and joy that is always present.

Yet again with a personal attack🤷‍♂️

There you go again, do you not get it? 

YOU ATTACK PERSONALLY !!!

If you have none, try giving some electronic technical proof for your arguments quoted from someone else, instead of attacking personally.  

Pour another glass of that Vegimite moonshine.
You'll feel better soon enough. 🥃

You’re the one who brought up the topic of fuses.

Yes "fuses and other snake oil" not people, big difference!!!!!! and you bit and attacked me and my dog personally, and yes I consider my Dingo a person.
You choose attack the members/people/dog, probably because you have no electronic knowledge you can call on.

 

What we're often hearing from many higher priced class A/B and good quality class A amps, are amp designs that intentionally emphasize or overemphasize the even ordered harmonics, which tends to be perceived by humans as a warm coloring added to the music that many individuals prefer.
     Better class D amps generally have a very accurate, detailed and neutral sound quality, with little to nothing added or subtracted to the musical signals that results in a very high degree of faithfulness to the recorded music. This is something one needs to experience to make sure they enjoy this type of amp design and sound signature, since it equally and accurately reveals good and poor quality recordings without prejudice. You may prefer some added coloring either through the amp or via tubes in the dac or preamp. You won't know for certain until you hear the differences between them with music that you're very familiar with.

Very well said. It's all about the implementation and the expectations.

All the best,
Nonoise

Hilde45 and douglas_schroeder,

     Very good points that I routinely notice in others, and previously noticed in myself, when it comes to many individuals' reactions to the sonic and other perceptions of class D amps and new experiences.
     I've been happily aboard the D train for over a decade now and consider my current class D monos, a pair of D-Sonic M-600s, as the best amp(s) yet to drive my inefficient Magnepan speakers that have had a msrp of under $10K. 
     Please understand, I'm not claiming they can't be bettered by other class D, class A or tube amps. I'm just claiming they represent an excellent solution for a combo music and ht system like mine, especially when considering the multiple benefits of sound quality performance, high power, high electrical efficiency and generally reasonably low prices.
    Just a few responses to previous posters on this thread:

daydream16: " what about class d and difficult loads like magnepans? Are they capable of driving them as well as class a-b. This is the internal debate I am having right now as I am putting my system together with  magnepan 1.7’s in mind."

     I've owned various models of Magnepans and they're not actually a difficult load, mainly stable at just under 4 ohms throughout the entire frequency spectrum.  I do think they generally sound more natural, alive and dynamic with increased wattage/power but power is cheap with class D.  However, there are significant differences in class D sound quality between amp brands and models.  I've found the better ones are distinguished by their smoother midrange and treble performance which typically carry higher price tags, but not always. 

lucky_doggg7: " When I think Class D, I automatically think of the good stuff like Devialet, Linn Amps, and Bryston (sp?) amps.  I have a very nice pair of Audio Research DS450M monos that I really like.  These are fairly powerful, meaning 450 wpc into 8 and 650 wpc into 4 so no lack of power there, and since these are ARC amps, I know it’s good stuff.  They’re even voiced with the ARC house sound.  As an added bonus, they don’t cook the entire place after an hour or two of listening like my Pass monos do so they’re good on electricity use, and low on heat generation."

     What we're often hearing from many higher priced class A/B and good quality class A amps, are amp designs that intentionally emphasize or overemphasize the even ordered harmonics, which tends to be perceived by humans as a warm coloring added to the music that many individuals prefer.
     Better class D amps generally have a very accurate, detailed and neutral sound quality, with little to nothing added or subtracted to the musical signals that results in a very high degree of faithfulness to the recorded music.  This is something one needs to experience to make sure they enjoy this type of amp design and sound signature, since it equally and accurately reveals good and poor quality recordings without prejudice.  You may prefer some added coloring either through the amp or via tubes in the dac or preamp. You won't know for certain until you hear the differences between them with music that you're very familiar with. 
     One more personal and additional musing on my class D amp experiences:

I always assumed I preferred a bit of added coloring with my class D amps and originally used a a VTL preamp, with a set of expensive NOS Mullard tubes swapped out for the original OEM tubes, to attain a smoother and more dimensional midrange and treble on my music.  I've since discovered I can attain he same result using a high quality, accurate and neutral solid state preamp in combination with my high quality, accurate and neutral class D amps.  This does, however, require the compromise of only playing high quality recordings.  I don't consider this a deal breaker yet but others may feel otherwise, depending on the quality of their recordings.

FWIW,
  Tim

@rocray It is kinda like the Ford vs Chevy, Ferrari vs Lamborghini, Ducati vs Honda (Ducati wins every time).

People like what they like and can be quite passionate about a brand or a system.

I learned to fly in J3 and love tail draggers with a high wing, others swear by low wing tricycle I gear AC.

It’s what you know and what evokes passion, emotion, loyalty.

Not numbers on paper or noise in a forum or trade rag.

Just my take.

All noise, when a subject is attacked for being snake oil, voodoo or whatever, that is fair game and keeps the shillers down.

Now georgie, since when is a discussion on Class D a snake oil or voodoo themed topic? You’re all over the place. Haphazard. You're the one who brought up the topic of fuses. 

But you then retaliate by attacking the poster or in the last case their dog personally.

What you need to learn is the ability to recognize snark (humor) when it’s deployed as a means to combat your strangeness.

And that’s where the difference is, and why you get deleted more than anyone on Audiogon.🤦‍♂️

Far from it, sunshine. 😄

All the best,
Nonoise

Honest question. Why is there so much controversy over amplifier topology?  I mean, there are a bunch of choices in this hobby that are very subjective.  You would think this was a cable thread. I don't understand that whole thing either.