I have owned a lot of powerful amps: Krell, McCormack, Aragon, Bryston, etc. Some weighed close to 100 lbs. Can a lightweight Class D amplifier with the same wattage rating drive a speaker just as well as a behemoth Class A or AB amp? Or is there something about current, capacitor reserve, etc. that the class D amps cannot match? My background is not in electronics so it is hard to wrap my head around a 12 lb class D amp being as powerful as a boat anchor in a rack. If you can get a very powerful lightweight class D amp with incredible specs for $1,200 why would you buy a really heavy class A/B amp with specs that are not as good, for multitudes more money?
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Amplifier power: Class A, AB vs D
- Thread starter Hart
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DVDdoug
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It's mostly about efficiency. Class-D sends most of the power to the speakers without wasting energy as heat inside the amplifier.
Class-A is the least efficient, basically generating the same heat when the amplifier is silent as when it's putting-out full power.
Switching power supplies are similar to class-D amplifiers, especially the voltage regulator which switches on & off at a high frequency rather than regulating voltage by turning partially-on. (The energy is stored in capacitors and inductors so the DC power can come-out constantly.) The high frequency much higher than the 50 or 60Hz power line frequency allows the use of a smaller-lighter transformer.
"Audiophiles" like stuff that's expensive and outdated. Some people like class-A tube amps.
Class-A is the least efficient, basically generating the same heat when the amplifier is silent as when it's putting-out full power.
Switching power supplies are similar to class-D amplifiers, especially the voltage regulator which switches on & off at a high frequency rather than regulating voltage by turning partially-on. (The energy is stored in capacitors and inductors so the DC power can come-out constantly.) The high frequency much higher than the 50 or 60Hz power line frequency allows the use of a smaller-lighter transformer.
"Audiophiles" like stuff that's expensive and outdated. Some people like class-A tube amps.
Curious, why so many amps?
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Sounds like a case of chronic "high-end" audiophilia.
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It has been a hobby since 1977, 48 years of dabbling I guess. Maybe that's a part of this hobby, always looking for something better.
Or chasing gremlins....you listed generally good amps, tho, so was wondering what your goal was or if you had failures, or.....these days I wouldn't hesitate to use a class D amp (and do use some). I've got a couple years on ya, started in 72.
Selkirks
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I've owned many big amps ranging from a Bryston 14B3 to dual Pass Labs X-250.5's over the years. Sold my McIntosh, bought a Purifi amp and stopped chasing my tail shortly after. Class D is affordable enough you can try it out for yourself. I don't feel I am missing out on anything, other than staring at the gear I once had laid out on fancy amp stands.
If specs are the same, then the difference is the design, parts, labor and whatever people are willing to pay.
boxerfan88
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In my view:
A is proven tech with excellent performance, but not that popular because of wasted energy (heat).
AB is proven tech and has been performant and shown to be generally reliable over many years.
D is a highly efficient newer tech and had issues (HF performance & noise), which is sorting itself out and maturing over recent years.
Lots of cheap D amps with brick PSUs around ... and slowly moving up into the high performing offerings.
A is proven tech with excellent performance, but not that popular because of wasted energy (heat).
AB is proven tech and has been performant and shown to be generally reliable over many years.
D is a highly efficient newer tech and had issues (HF performance & noise), which is sorting itself out and maturing over recent years.
Lots of cheap D amps with brick PSUs around ... and slowly moving up into the high performing offerings.
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- Thread Starter
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I was always trying to improve the sound as it was not that good as compared to the local audio store. using similar speakers. Turns out it was my room, I had an Eichler house with a 1,000 sq ft living room and it was all glass from floor to ceiling. Hardwood floors. Way to reflective. Never sounded quite right. So most of the audio changing occurred then, Though in retrospect all the amps were fine, the room needed damping and a better shape. I don't think a lot of people realize how important the room is, both dimensionally and damping wise. I auditioned some VMPS RM40 speakers with the late Brian Cheney in an addition at his house that was purpose built for sound. Tweaked to perfection. Maybe the best listening experience I have ever had. RIP Brian, you were a really nice guy.
Yeah fine in the dealers' rooms don't mean much compared to your own. Chasing different amps to resolve....got away from that a long time ago.
Waxx
Major Contributor
Class D amps are mostly rated peak power, not rms power like class A amps (where both are the same in many cases) or class B amps. So you need to have more power reserve on class D than class A or AB.
But once that covered, the only difference is the (harmonic) distortion (concerning sound). Class A is mostly very coloured by harmonic distortion (the warm sound) and has a much higher general noise than modern class D. Some want that, some don't. Technically this is a flaw, but high harmonic distrotion is something we humans tend to love. Class D and certain forms of Class AB are much cleaner in sound, so clean that there is no hearable distortion anymore with the best models.
Class D is due the topology a lot more power efficient than class AB, and even more than Class A and a lot smaller, cheaper to build and running cooler.
So specify the needed power with a class D amp as 2x or 4x what you would use with a class AB amp and the peak vs RMS power will never be an issue. And if you use the right models with sinad above 100dB, then you have an absolute clean sound, that no class A and very few class AB amps can get. And this does not has to cost a fortune, Good top level class D amps can be found under 1K...
But once that covered, the only difference is the (harmonic) distortion (concerning sound). Class A is mostly very coloured by harmonic distortion (the warm sound) and has a much higher general noise than modern class D. Some want that, some don't. Technically this is a flaw, but high harmonic distrotion is something we humans tend to love. Class D and certain forms of Class AB are much cleaner in sound, so clean that there is no hearable distortion anymore with the best models.
Class D is due the topology a lot more power efficient than class AB, and even more than Class A and a lot smaller, cheaper to build and running cooler.
So specify the needed power with a class D amp as 2x or 4x what you would use with a class AB amp and the peak vs RMS power will never be an issue. And if you use the right models with sinad above 100dB, then you have an absolute clean sound, that no class A and very few class AB amps can get. And this does not has to cost a fortune, Good top level class D amps can be found under 1K...
Speakers and their interaction with the room is you are looking for actual improvements in SQ.
Keith
Keith
Plenty of class A amps have no audible distortion, not even close. I'd question 'much higher general noise' too.
I can put the pre on max volume and hear no hiss from the speaker. The measurements back that up too.
No doubt there is some noisy, distorting junk out there in all amp classes, but why would anyone buy them?
No, they are not peak watts. Check out the reviews, power is always RMS in the X axis.
What you mean is that usually class D amplifiers use SMPSs and the latter has little headroom above the max power. But both are measured the same.
Example Apollon NCx500 (class D) + SMPS
Another example Schiit Vidar 2 (class AB) + linear PS.
The first has lower headroom, but still double more powerful. All measurements W RMS.
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Yes fixing room and speakers first usually brings much better results than electronics. It should be prioritized indeed.
I always wondered why all the good class D pack a lot more wattage than seems necessary.
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I can see two reasons: the designs themselves allow for high power output by nature, relative to size and weight. It's an inherent advantage of the technology, so why not use it? You can also save development costs. Why develop a lower power model, when you can offer higher power ones to the target market at highly competitive prices with still good profit? People love big power for little money, even if they don't need it.
And then, headroom. Class D with SMPS typically has virtually none. 500W on the label gets you 500W including peaks, not the 600-800 or something a nominal 500W class AB amp with linear PSU would do. Meaning if you want a "solid" 100-150W like in older times, you better get a 200-250W class D amp for example, which may already sound like way more than needed, but chances are it's adequate instead of too much.
For me personally, the appeal is getting a nicely powerful amp for my money, which is easily powerful enough for driving any speakers I will possibly get in a few years. Who knows which? Perhaps I'll move and suddenly the listening room is much bigger? It's one big worry taken care of: buy once, be done with it for a long time. And still very affordable these days, making it a nonsense idea to buy an amp barely enough for my current speaker/room situation.
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