What class of amplifier has the most high definition sound ?

Just so we are clear- there are classes of amplificationandthere are types of amplifiers.

The class of operation has mostly to do with how the output devices in the amp are turned on and how long they are on. In this regard both solid state and tube amps can be class A, class AB, class B or D (yes, you can build a tube amp that is class D). Class C is not used for audio- its typically used for radio frequency transmitters.


A *type* of amplifier has to do with its topology (circuit design) and often what sort of devices it uses in the output section. For example an SET is a type of amp using entirely single-ended circuitry and a triode for a power tube. An OTL is a tube amp that does not use an output transformer. There are single-ended solid state amps (ala First Watt amps from Nelson Pass) and most solid state amps are output transformerless, so the OTL moniker is usually reserved for tube amps. These days all class D amps are solid state, but they can have half-bridge and full bridge configurations.

What a can of worms.  Synergy is the real quest.  It's mating the loudspeaker to a power amplifier that has the right chemistry.  Certain combinations or one particular amplifier are/is pure magic while others are simply pitiful. 

1. OTL
2. Really good switching amps ONLY with linear power supplies. SMP’s will foul up the entire presentation.
3. Superior A/B solid state amplifiers

Lots of excellent input here, especially M Green, and George

IME, the interaction with the room plays a very significant roll

I am blessed and cursed with a large room (~ 19 X 35 X 12 i. The blessing is virtually no boundary interference. The curse- finding a amp/speaker combination that will properly energize the room without going overboard

I just replaced a excellent Audio Alchemy 175w/ class D stereo amp with PS Audio M700 monos which only have ~ 200 hours on them (bought them slightly used). Even stone cold, they did a better job of energizing the room (I could better hear deep background low level tinkly things, like in the opening of Famous Blue Raincoat Joanne of Arc, BUT, I think I really need to double their ~ 350/700w to get the full texture

Speakers are Emerald Physics KCIIs @  92dB with Clarity cap and Wire World upgrades +. even though a very benign load, I am told the KCIIs love some power. To compensate, I have  2 SVS Bash amp subs (Ultra and Plus), but their volume control is way too coarse at lowest volume they come on too much, so very hard to blend  

IN MY ROOM I probably need Ice EDGE power @  ~ 1200w to properly energize the room

There's hardly a consensus about Deviolet amps. Those things evoke some real hate. 

I have a new definition.  With research (listening research) and a budget that matches your research, it is the amp you bought given the rest of your equipment.

Would like to know where the Devailet amps score in this? (Class A in parallel with Class D).For those familiar with them please chime in.

OTL -  Atma Sphere

almost all audiophile preamps are pure class A. just sayin'.

You can listen to an amp that that tested off the charts in the lab, has the greatest reviews, in your setting sounds sub par. I think end of the day, it’s the pairing, room, setting, and the hearing and how one process the sound and the music. I’ve had $$$ amps and tried low wattage boutique amps that sounded better, to MY ears. I’ve had arguments with friends that tell me I’m foolish for spending what I did on gear, and say their blu tooth speaker sounds great.  End of the day, there are more factors to the equation.

The amps that shine in class A are the pre-amps .

Hi there
We can get the most natural sound from class A amplifiers. They have "soft" distortion spectrum and they are stable for pulse signals because of stable power consumption. But they produce some specific problems too. Open my page in LinkedIn (Vladimir Benkhan). There are couple articles about it and a description for simple class A amplifier.

Give Spectral a try. There are a number of reasons you may find it rewarding. Resolution combined with macro and micro dynamics. Utterly uncoloured. They are fanatics; and Professor Johnson has never been influenced by money or short term gain. It’s a very unusual company; a pure pillar of truly high end audio. 

A. Nothing is better, except maybe single ended class A.

soix, I concur; we are not in disagreement. We may vary on what we feel the degree of contribution the amp (whatever type) and the system contribute, but both are critical to desired outcome, and everyone will have their favorite genre of amp. Absolutely, the quality of the amp in the chain is critical! And, people will feel strongly about the genre of amp they think is superior. 

I have heard many SOA contenders & with a compatible pair of speakers nothing has ever matched the purity of an OTL.  I remember the first time I heard a Futterman.  It was certainly dirty sounding (enough to disqualify it in many ways),  Even so it had a purity in the upper midrange in particular, that was unequaled by any objective or subjective standard. End of story. By any amplifies.   A high quality OTL wiil far surpass it.  I don not own an OTL.  The speakers required are not anything I've encountered so far.  Nevertheless it is & no class of amplifier I've heard comes up to that standard. None.  Although there are some pretty wonderful ones for other kinds of systems that overall may be better compromises.

+1 @douglas_schroeder -- but the fact remains, when all other pieces of the audio system are dialed in and set, the amp choice still matters. As with everything in audio, the chain is only as strong as its weakest link. And you can carry that down to the design of the amp itself. No matter what class of amp, all the other design parameters and choices affect the final outcome. So while I might prefer the strengths of a Class A amp in general, I’ll take a well-designed Class AB amp over a poorly-executed Class A amp hands down.

@ vt4c
+1 Focusing on bias class is a waste of time. Find a good pairing with your speaker is more important. Difficult speakers will reduce the choice of amplifiers. 

(Except for this last sentence ... ¨ Shun those 85dB speakers.¨ in which I also believed until after years of owning a pair of passive ATC20s, decided to hook them up to a Mastersound parallel SET 20w/channel integrated and was pretty surprised. Speakers are 8 ohm nominal though and the Mastersound has some pretty hefty transformers.)

But getting back to OP,  comment by  georgehifi ...¨ Best, least coloured, fastest, cleanest, most dynamic a Class-A OTL tube amp, trouble is the speakers they love to drive are the "polar opposite" if full range 20hz-20khz.¨ ...seems to hold true with the  high efficiency speakers I´ve heard. For whatever reason lower efficient speakers have always appeared less colored.

Still miss my Celestion 600s (Stereophile measured them at 81db/1w/1mt. back in the day I believe), even with their lack of bass, but most definitely not my pair of Klipsch La Scalas which they replaced.

D_Schroeder wins #micdrop - BOOM!

What class of amplifier has the most high definition sound? 

The one that you want, but don't own. ;) 

Having built all manner of audio systems I assure you that the caliber of the system build has as much influence upon performance as the amp (or class of amp) itself. 

Georgehifi: Best, least coloured, fastest, cleanest, most dynamic a Class-A OTL tube amp, trouble is the speakers they love to drive are the "polar opposite" if full range 20hz-20khz.

+1 for the first part of that sentence.

I love my Atma-sphere MA1 amps. Clean OTL class A. I had the marvellous Krell FPB600 but have not looked back (much).

Speakers? You can get them. OTL amps can play the full frequency scale ok if the speakers are matched. And if the speakers aren't tuned to the amp, you can forget most of the discussion about amp quality, class A B or what.

For OTL you need easy to drive speakers, 8 ohm is marginal, speakers should be 12 ohm or more, OTL loves 16 ohm speakers with 90+ sensititvity. If not, your money on the OTL amps are wasted, you will get good but not excellent sound. 

I bought Audiokinesis Dream Maker speakers, and have been very happy with this combination.

Wrong question. It is related to results but does nor answer your question.
Operating class is not a value graduation, while applicable to RF amps not so directly with audio. All low level stages are operating in class A, i.e. full current, they only need to amplify voltage with no demamds for power. Only the output stage adds current to the formula. Here the biasing class determines the zero signal current of the output stage. Biasing needs to overcome device non-linearities at lower idle current. More current is more heat and power wasted, less for output. Heat loads increase adding demands for heat sinks and bigger power supplies.
So there are tradeoffs. 5W class A or 15W class AB?  Class D is not a biasing class, just a diffent amp architecture. Output stage is like switch mode powersupply, either fully on or off. The magic happens at the input where the switching levels are determined. Anything other than pure DC in the power supply will end up in the output just like any other amp class. 
Focusing on bias class is a waste of time. Find a good pairing with your speaker is more important. Difficult speakers will reduce the choice of amplifiers. Shun those 85dB speakers.
Good dynamics means high efficiency with budget in mind.  

Ear 868 preamp,Ear 509 power or 890,.
Audio Note M5 and GamuT D 200i
Integrated: Gryphon Diablo 300, Isoteric 03/05.
Zanden.

Transformers provide nonlinear frequency response, not second harmonic distortion. One sucks, the other rocks. Why wouldn't you want to just connect the output devices directly to the speaker? That just sounds smart on it's face!

Class D amps take some meat off of the bone. It can come off as crystal clear, defined, and completely quiet between notes (inky black) but to my ears that sound signature is the result of removing a tiny amount of the music from the source. My guess is that its a product of the output filter, a tiny amount of the good leaving with the bad.

"a tiny amount of the good leaving with the bad."

The bad being "switching frequency noise".

Trouble is, there’s still a lot of the bad left behind, with today’s Class-D topology.

Best, least coloured, fastest, cleanest, most dynamic a Class-A OTL tube amp, trouble is the speakers they love to drive are the "polar opposite" if full range 20hz-20khz.

Cheers George

I'm pretty sure it's the tubes that do that, as it's been claimed the transformer's job is to strangle things. You have to pay attention around here.

Good job transformers, whatever the hell it is you do...

They provide the even ordered harmonics (distortion) that makes tube amps sound so nice. 

This thread,
Pit of misery,
Dilly, Dilly!

If my SEP (that's right, P!) amp is being strangled by the output transformers (or is it the input transformer acting in a co-strangle mode?) it must be consensual and a good thing somehow as it's the best sounding amp I know of, or certainly have ever heard in my various systems over the years. Good job transformers, whatever the hell it is you do...

I would say that Class D and Class A tube amps (excluding OTL) have an opposite sound signature. 

Tube amps add some meat to the bone.

Class D amps take some meat off of the bone. It can come off as crystal clear, defined, and completely quiet between notes (inky black) but to my ears that sound signature is the result of removing a tiny amount of the music from the source. My guess is that its a product of the output filter, a tiny amount of the good leaving with the bad.  

@sacresta, I think I know what you mean by high definition and pure. That was my first reaction when I first heard a Class D integrated. It was a Primare I32 and it may have been due to their unique and proprietary implementation of Class D. I've never heard any other Class D, so I can't say; but defined and crystal clear was the way I described it. As a frame of reference, to me most tube amps sound sweet and mellow.

I read all this stuff about Class A and thought it was overblown, so finally bought the 8-watt Pass Amp Camp Amp from diyAudio store. Built it, used a Marantz receiver to drive it, and thought, hmmmmm, that’s pretty sweet. Not much volume into 89-dB speakers, but very “natural.” That’s my adjective for a sound that approximates an acoustic sound. A piano sounds like a piano, not a keyboard.

so I built another ACA for monoblocks, so now 15 watts a channel and good volume. I really like my Rogue Sphinx Class D into Magnapan 0.7s, and also my old Marantz, but I will say there’s something special about Class A. My experience.

@georgehifi -- have u looked at Audiokinesis?

I believe in Dilly Dilly.  

If there was a magic bean, don’t you think we would all have one?  Many choices, many tradeoffs and associated gear is among them.

The unstated inference is that anyone who agrees with what the magic bean happens to be, is dumb if they can afford it and don’t own it.

I found the match I like for my planars and understand others enjoy their amp for efficieny speakers.  There is no one size fits all “best”, no matter how much money you throw at the issue.  For those of us on a budget the choices are fairly proportional to the budget size and associated gear.

There are many great combinations at a variety of price points.  But alas, there is No magic bean.

what class of amp is the High Definition kind?

short answer? The High Dollar kind.

almost invariably greater fidelity goes hand in hand with more investment. despite ‘class’.

A, A/b, D, Hybrid, Tube amps which have an enormity of classes based on their output tubes, all have different levels of audio definition, or resolution. as the entry fees escalate in each camp, usually their resolution increases commensurately. there are over achievers and we all seek them out, but usually, more money means better most often. 

 the buyer beware note here is that it will take more than just an amp to realize the amps true abilities.

there needs be a great source, and of course, great speakers, or at least very competent ones.

a pair of Hiesenberg monos at $100K running into a pair of say, Joeseph Audio Pulsars isn’t gonna express the entire bandwidth as revelatory as they would with say, a pair of Legacy Aries.

amps are key, but so is the rest of the rig.

The question does hinge somewhat on what you intend to drive. A SET can measure great into a 16 ohm resistor. It would crap it's pants driving my Focal speakers though. 

I don't consider feedback a universal evil. Like anything else, it requires proper execution. 

Class D is out of the question, DOA, given it's gratuitous complex distortion at low power levels. Class A simply destroys class D at 1 watt where a huge amount of detail resides. 

I would say it somewhat differently - tubes presenting harmonically correct soundscapes.

Only Class-A OTL's, anything with an output transformer is hamstrung.

Cheers George 

I would say it somewhat differently - tubes presenting harmonically correct soundscapes.

To win, you:
 
1. can't have an amp with crossover distortion (sorry class AB)
2. can't have an amp that isn't linear & has an output filter (sorry class D)
3. can't cheat and use a bunch of feedback to lower distortion. (sorry class AB & D).

What we are left with is Class A solid state for accuracy (pure sound?) and tubes for adding those lovely harmonics that give us that deep and wide sound stage, extra decay, and rounded notes. 

sacresta OP
Ok guys, my question was focused in experience and sensitivity to pure sound.

"Pure Sound"?? Class-A OTL tube wins, with heavy proviso's on what they can drive. After which come Class-A solid state, which can drive most things if good designs. 
SET and all other tubes are governed by their output transformers, they are not "pure in sound" and have colourations.

Cheers George

Class A wins

It doesn't matter for as long as you plug them in Furutech duplexes because this completely eliminates all distinctions.
 Everyone knows that Class A is best.

I can't believe no one got that.......

Oz


Heh, I got it.....dilly dilly. My CD player says on the front :"vacuum tube reference CD player" but I don't know what the reference was. I sometimes listen to it , though.

Dilly Dilly

That is not  clear  cut at all, a SET tube amp with very efficient speakers may have the best purist  midrange,  and a big solid state amp  may have the best dynamics or Bass. The speaker 
and type of music too come into play.  The correct answer is
No amplifier is the best under all circumstances .

"They" say that SET amplifiers are the best but since I have no experience with them I cannot confirm or deny it. But "they" say lots of things that may or may not be nebulous. In general I consider vacuum tube amps to be superior for audio reproduction but others swear by solid state. I suspect it all comes down to individual ears as I’ve proffered before.....different folks hear differently just like how some folks can see better than others. Perhaps one day we can all be able to say "I see the light."

Ok guys, my question was focused in experience and sensitivity to pure sound.
Class A, A/B, D ? High definition or pure sound are subjective concepts.

I didn’t ask for brand or speakers quality. I said compatible system!

Thanks you all.

Only opinion:
High efficiency speakers with a First Watt amp.  

The question was about the *class* of amplifier. And -- if cost i no object and all other variables held constant, class-A, no question.  But it has many downsides, mostly size, heat and cost int he real world.
For small signals anyone who doesn't design class-A is crazy. For big power amplifiers there are many trade-offs. Note there are also sliding scales.
Class D, an entirely different type of "class" has huge potential but still needs refinement. Modern GaN is already helping.
But among A, AB, C it is clearly A.  That said i always design high bias AB for bog amps.