Class D Technology

Just my opinion, but all you guys out there claiming audible switching noise are a little misguided.

Speak for yourself Kimosabe.

You probably missed the part where I mentioned we have a class D amp in the works, right?

Seanheis 1,

If you're only interested in sound quality and nothing else, you're likely missing the finer points of a good class D amp.  IMHO, the ONLY good point of a class A amp is its sound quality.  If you would list all the pros and cons of a class A amp, the only pro would be sound quality. ALL the other factors  you could think of when buying an amp would be on the con side, and I mean EVERY SINGLE factor you can think of:
Most expensive to buy
Most electricity consumed to operate
Most of the electricity inputted is converted to heat and wasted.
Nuclear reactor type heat  produced in your listening room
Huge due to huge heat sinks required to try and prevent nuclear fusion from occurring.
Constant high heat reduces reliability and life span.

Put it this way: would you only pick a life partner based on looks? Would you ignore the fact that she required a very large payment to even consider you? Required expensive gifts to keep dating? Raised the temperature 20 degrees every time you were near her? Occasionally pooped in your bed blaming the high heat that she was the cause of and requiring expensive 'repairs'? Grew to enormous size and weight in an attempt to dissipate her excess heat through an increase in surface volume like a hippo?  Okay that's enough, I can't think of many more analogies or are they metaphors? I think you get the picture.

Sure, looks/sound quality is important but I suggest you might be happier with a woman/amp that is only one of the most beautiful in the world but not quite THE most beautiful but is your best friend,  low rather than high maintenance, a toned and healthy size and weight rather than extra large and heavy, generally has many more pros than cons. Besides, the higher quality class D amps currently sound strikingly similar to the higher quality class A amps.  I think you'd be pleasantly surprised if you gave a good one a try, I know I was.

Okay, that's the gist of it but I wrote more specifically about my experiences with class D in the book below:  

  
I've become  a big fan of class D amps for several reasons:

1. They are extremely quiet, having THE HIGHEST S/N Ratio and THE WIDEST DYNAMIC RANGE of any amp type, with almost no audible background noise and highly detailed.  I can turn my volume control to maximum without any source playing, put my ear an inch from the tweeter panel of either speaker, and there is absolutely no sound. Is this possible with a class A amp?  This is very important because it enables sound to emerge from a dead silent background which enables very fine details to be distinguished, including the all important spatial cues required for good sound staging. I believe the quietness of these amps is the root cause of their excellent detailed nature; this is my theory but it has been proven to me repeatedly through my actual listening experiences.  I know my music well and I can easily discern a redbook CD from a hi-resolution 96/24 digital recording mainly based on the low level of background noise, high level of detail, lack of the 'loudness wars effect' and the very life-like attribute of having THE greatest dynamic range of any amp type. 
I also found it is now much easier to discern audible differences between different speaker, interconnect and power cables and other upstream issues with these class D amps than with any of my previous class A/B amps I've used.
Contrary to comments by previous posters, I have never heard any 'switching noises', they are the quietest amps I've ever heard (not heard?).     

2. They are very powerful and good ones are very stable into very low impedance speaker loads.
My main speakers are relatively inefficient (87 db at 1 watt)  Magnepan 2.7qrs. that can dip a bit below 4 ohms.  I'm currently driving them with a pair of D-Sonic M3-600 monoblock class D amps rated at 1,200 watts @ 4 ohms.  These amps are rated as stable down to 1 ohm.  All tube amps, and many class A and A/B amps, are not capable of driving speaker loads that dip to a dangerously low 1 ohm (almost a complete short) as some more exotic speakers do at specific frequencies.

3.  They are very neutral in their overall tonal characteristic, not adding or subtracting anything audibly that I can perceive.

I had previously always paired decent class A/B amps (McCormack and Aragon) with a good tube preamp (VTL 2.5 with NOS Mullards) to achieve the slightly warmer sonic characteristics I favored.  Initially, I paired my class D monos with the VTL and it sounded very good.  But, after extensively comparing my system's sound with and without the VTL, I decided my music sounded just as rich, sweet and dimensional  without the added tube coloring so I sold my beloved VTL to a friend.  I don't want to portray the sound of these amps as 'tube-like', but the natural sweetness and richness of good music and instruments played well is definitely conveyed if the recording is well done and the recording captured it. 

I think it's important to note that most of the newer class D amps rely heavily on feedback circuitry that constantly compares the signal accuracy at the input stage to the signal accuracy at the output stage going to the speakers, making adjustments as needed to ensure the accuracy prior to releasing the signal to the speakers. This is likely a major factor in the generally neutral nature of the best class D amps.  Those using tube preamps need to choose carefully since the tube preamp's sound will be passed through faithfully without any alteration and the differences in sound qualities between preamps and tube swaps will be readily apparent and distinct.  

In my listening experiences, tube and class A amps tend to have a sound more to the warm side of neutral, which I previously thought I preferred to neutral.  Class D amps are closer to the classic audio amp ideal of a 'straight wire with gain' than any amp type I've listened to.

4.  They excel at dynamic range so much I feel the need to mention it again.


My system is a combination 2-channel and 5.1 HT surround system used about equally between both.   I use an Oppo BDP-105 as a 2-ch preamp, 5.1 surround processor and as a wireless DAC.  I run JRiver on a laptop that wirelessly streams music files from a Synology 20 TB NAS to the Oppo DAC. My entire CD collection, along with numerous 96/24 hi-res digital WAV files are stored on the NAS.  All amplification is class D:

D-Sonic M3-600M monos power my front Magnepan 2.7 mains
A bridged Emerald Physics 100.2SE powers my Magnepan CC-3 center
A stereo ClassDAudio CS440 powers the Infinity in-ceiling rears.
A Dayton Audio class A/B amp powers 4 Audio Kinesis subs configured in a distributed array bass system. I'm currently searching for a good class D amp that can handle 4 subs @ 4 ohms to replace the Dayton that came with the distributed array sub system.

The video connections from the cable box to the Oppo to the tv are all HDMI. The audio cabling is all run directly from the Oppo to the amps, XLR for the D-Sonics and RCA for all others. All of the class D amps have the same neutral, ultra quiet, detailed and highly dynamic sound quality that seems to be charactaristic of good class D amps. The ability of these amps to go from quiet to loud for both music and HT audio is very good and can be even startling on well recorded content, an obvious improvement over my previous class A/B amps.

5.  They are space and energy efficient.

My previous main amp was an older class A/B Aragon 4004  that was very big (19"W x 14.75"D x 6.75"H), weighed 76 lbs, got warm-hot to the touch, was inefficient and put out 400 watts @ 4 ohms. This amp had to be replaced due to leaking caps in the power supply section.  My current D-Sonic monos are small (7.25"W x15"D x4"H), weigh about 10 lbs. each, never get more than mildly warm, are very efficient and put out 1,200 watts @  4 ohms which has had a very positive effect on the performance of my inefficient panel speakers.
After switching my previous 3 class A/B amps for class D amps, I would estimate my monthly average monthly electric bill decreased between $30-$40 varying by the season.  I've always left my amps on 24/7 for both types unless I'm away for a day or more. I think that's fairly significant savings, especially projected over a full year.
The switch also allowed my audio gear to be streamlined due to the new equipment occupying roughly half the space. The top shelf of a new much smaller rack containing just my Oppo straddled by both D-Sonic monos on small maple isolation stands with all remaining gear located in an enclosed shelf below. Aesthetically a breath of fresh air with less gear, less visible gear, with a more pleasing symmetry, better air circulation and minimal heat.

In conclusion, I think we can all agree that there are many tube, class A, and even some class A/B, amps that achieve a stellar performance level when properly matched to quality speakers.  I have no doubt because I've personally listened to many examples.  However, I also have no doubt that high quality class D amps can achieve similar stellar performance levels when properly matched to quality speakers but I realize everyone is not ready to acknowledge this quite yet.  Resistance could be due to deeply held beliefs in the superiority of certain amp design types or perhaps a reluctance to concede a relative equal status to such an upstart newcomer.  But, after reading this thread and listening to some of the comments, it seems increasingly obvious to me that many have simply not heard a high quality class D amp driving a pair of high quality speakers and how closely it approaches the sound quality of even the best of the class A amps.  

And you don't need to believe me when I proclaim my opinion that class D is the likely wave of the future in high end amp design not only due to its excellent sound quality but also due to its many ancillary benefits such as lower weight, smaller size, lower heat, higher reliability, lower maintenance costs, lower R$D costs due to amp module designers/manufacturers taking on this responsibility and lower production costs caused by completed amp sellers simply buying the amp modules they prefer from 3rd parties.  All you need to do is look at the many stalwart amp manufacturers (Jeff Rowland, Theta, Mark Levinson, Audio Research, Rotel, NAD, Technics, Yamaha, Marantz, Cary, Halcro, etc.) that are now offering class D amps.  They're doing this because they've compared the sound quality of their traditional amp designs to the ever increasing and improving class D amp module typologies and decided they offer high quality sound along with many ancillary benefits:

Amp module designers assume many R$D costs=Lowered internal R$D costs
Lowered heat=Increased reliability=lowered warranty repair costs and increased company amps'  reputation as being reliable 
Lowered weight/size=lowered shipping costs
Higher efficiency=lowered customer electricity usage=a 'greener' product
Increased amp module suppliers=freedom of company amp designers to tailor sound to their preference via amp module selection and design of custom input stages
Other likely benefits I'm not thinking of right now because I'm tired

It is evident there is a slew of benefits to traditional amp sellers increasing class D offerings with minimal associated risks that could result in a class D wave of the future and the proverbial win-win situation between amp sellers and amp buyers that I believe has already begun.

Sorry my post turned out so lengthy but I was trying to be as thorough as possible,
    Tim
 
      

     



 

 



















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One heck of a lot of information, too much for my poor head!
I am in the market for new amplification, moving on from my trusty Krell KAV250 and was considering giving class d a try again. I say again as about 3 years ago i tried a pair of bel canto 500m mononblocks and found them to be so cold and sterile that I could not stand them.
So have class d moved on since these or should I stick to a monster class a like a bat vk500 or ml product?

@uberwaltz

Keep your Krell KAV250 (nice amp) for a while yet, read my reasons here.   
https://forum.audiogon.com/discussions/class-d-technology

Cheers George

A standing ovation to Noble100 ’s post . Claps !