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Class D Technology

So I get the obvious strengths of Class D. Efficiency, power output & running cool which allows for small form factors. I also understand the weaknesses somewhat. 1. Non-linear & lots of distortion that needs to be cleaned up with an output filter. 
So my question is, if it weren't for efficiency & power, would there be any reason to own a Class D amp? Do they beat Class A in any other categories that count for sound quality?  
seanheis1
georgehifi's avatar
georgehifi
10,312 posts
 
no human has ever claimed to hear these affects or even describe what these affects would sound like.
Plenty have with saying, hard sound, soft sound, lacking in harmonic structure, dead gaps between notes (no harmonics) like the amp has been turned off.
There are many that hear these effects, myself also, but like I said before I "could" live with the Belcanto Ref600's, with their in house special filter for the switching frequency, but they were driving an expensive two way with a very benign 8ohm Raven ribbon tweeter load.

Cheers George 
guidocorona
4,298 posts
 

The concerns of the OP and of George are correct, at least from a historical point of view.... When I first started looking at class D amps, in the middle of the last decade, there were many examples of class D amps which were either sounding dark, or limited in the harmonics of the upper frequencies, or harsh, or high-fiish, or a combination of several of the above undesirable characteristics.... For Example:



* Flying Mole -- All the delicacy of music reproduced with 150grit sand paper!


NuForce Reference 9 SE V2 monoblocks -- Clean but quite climical, even after 1K hours break-in... And treble was clinky and limited.


Red Dragon monos -- Both harsh and dark at the same time... Quite an achievement!


Wyred4Sound monos -- Listened extensively at RMAF several years in a row... Harsh and fatiguing to the point of non-listenability.


Rowland M501 monos Powerful, but lacking subtlety.


Bel Canto Ref1000 Mik.1 -- Better than the above, but still somewhat rough in the treble... Note that the problem simply does not exist on the Mk.2 version.


Rowland M302 stereo -- Sweet and delicate, but will little macrodynamics... And just slightly cold.


But... The World has moved along... A dozen years have gone by, and modules and device designs have evolved enormously in the land of class D amplification, starting with the Rowland M312 stereo, and the Bel Canto Ref1000 Mk.2 monos: products that simply... Make real music.


Today, amps like the Bel Canto REF600 monos and the Merrill Teranis stereo based on Hypex NCore NC500 modules, once appropriately broken in -- yes I insist it is needed -- make extremely fine music for their quasi entry level pricepoints, without pretending  to achieve the ultimate subtlety of reference level amps.


But if one were keen in hearing what musical refinement has been achieved by current reference-level class D amplification without audible compromises, please have a listen at least to some of the amps that have captured my heart over the last few years:


* Merrill Veritas monos based on NCore NC1200.


* Rowland Continuum S2 integrated -- Based on Pascal M-Pro2.


* Rowland M825 Stereo -- based on NC1200.


* Rowland M925 monos, based on NC1200.


* Bel Canto Black -- based on customized NCore modules.


And there are more marvellous class D devices, which I have not had the fortune to audition at all price points.


Are all current class D amps today superb music makers? That is unlikely.... For example, last time I heard W4S -- admittedly this was 3 years ago -- the sound of my music camples: piano, string sextet, Diana Krall, orchestral, and vocal + sax was still so harsh to give me an "ear bleed".... But by now, W4S may very well have matured as well.


Please note that exactly like proclaiming that all class D amplifiers are inherently flawed constitutes a logical fallacy, so would be the assertion of the opposite... Reality is, that with all topologies, some amps will meet our particular taste in music reproduction, some will miss by a country mile, and some will be somewhere in between.


G.

   

 

 



      

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georgehifi's avatar
georgehifi
10,312 posts
 
modules and device designs have evolved enormously in the land of class D amplification
I say more of a gradual upwards evolvement, with tweaks and band aid filtering, no real technical breakthroughs.

The only one I know who is stretching out for real progression is Technics with their SE-R1, with the supply finally of newest technology to double the switching frequency, with this latest device from EPC Corporation Inc. Who invented the Mosfet Power Transistor years back.
This is where the real evolvement for Class-D will come from the manufactures of the components, not the manufacturers of the amps.

In a way it’s up to the audiophiles to get them to use this new technology then the price will come down for something like the $30k Technics through demand of those components and other device manufactures copying them.

http://epc-co.com/epc/GaNTalk/Post/13752

http://www.technics.com/us/products/r1/se-r1.html

Cheers George



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noble100's avatar
noble100
2,419 posts
 
Hi Guido,

     Very good summary of the evolution of class D over the last few decades.  I've become familiar with your thorough knowledge of most things class D over the last few years and I'll take your word for it that early class D amps did suffer from some of the ills that the op and george have discussed..  Luckily, I avoided the early disappointments by not using class D until the last 2-3 yrs.  I've experienced no high frequency harshness, brightness or any other negative treble qualities and thought they were referring  to more recent class D amps.

     I'm not a fan of  bright sounding amps of any type and, if any of the class D amps I currently use shared any of those qualities, I would not have kept them and definitely would not be recommending them to anyone.

 Guido said::     

"Please note that exactly like proclaiming that all class D amplifiers are inherently flawed constitutes a logical fallacy, so would be the assertion of the opposite... Reality is, that with all topologies, some amps will meet our particular taste in music reproduction, some will miss by a country mile, and some will be somewhere in between."


     I agree with your summation completely.I think you're correct, the reason I enjoy my current D-Sonic M3-600M amps so much is because they match my taste in musical reproduction so well:

Very good bass response that is deep, solid but also nuanced when required.

Very low noise floor that enables details to be heard.

Powerful for good dynamics and a relaxed and effortless quality on all content that allows music to sound very natural and life-like.

Dense, solid and stable imaging that allows for the illusion of a 3-D sound stage both laterally and front to back.


A smooth mid-range and treble that also manages to be highly detailed.

A generally accurate and neutral presentation that is capable of conveying warmth when it's contained in the music and captured on the recording.

     This is a summary of what I hear when I listen to my class D amps.  It is a combination that suits my tastes well but I realize may not suit others tastes and I realize not everyone will even .hear the same qualities from these amps in their system and room.  as I do in mine, it's to be expected.


Tim       

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