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Why do so many prefer the sound of "Class A" amplification vs. "linear" amps?

Vacceo

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Agree with that. Problem is when you see differences in the measurements it is most time hard to correlate to what you hear. Historical there is IMO confidence that a pleasant sounding amplifier should have the distortion harmonics profile dropping off gradually and as fast as possible.
Pleasant or unpleasant is up to the listener. That's why I prefer transparent systems, so I can get my choice of distortion from the source itself (I love high distortion as part of the music creation, no need to add extra sauce).
 

Steven Holt

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How much better is one another thing.
Doodski, are you sure that you were hearing the amp, and not the speakers? That is, did u check the 'sound' of the amp using two different sets of speakers?
 

GXAlan

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Themaltrack is way too slow to be effective for distortion cancellation at audio frequencies. Its only pupose is to help stabilising the operating point of the amplifier when the amplifier heats up. However is has nothing to do with the "Class-A sound"
Agreed. What I am saying is that half of the Class A sound is better engineering overall independent of the Class A vs AB crossover distortion.

I agree. If you hear a difference, if it does not show on measurements, it's psychoacoustical, not in the reproduction chai

Right. What is interesting is that it can show in measurements of music that does not show up “obviously” in 1 kHz test tones or traditional multitone tests.
 

Steven Holt

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I'll put in my two cents, for what it's worth. When I was coming up in this hobby, the best amp was considered one of 'a straight wire with gain'. Maybe that's why people like class A, it's the closest you can get to that ideal. I do understand that things have changed slightly since then.
 

tmtomh

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It’s rare to find a pure class B amp nowadays. With Class AB amps, you are running class A at low power anyways.

Take a look at my three generations of Marantz measurements as well as Amir’s PM-90 review which showed vanishly small differences.

This is the most important point IMHO: the overwhelming majority of Class A vs Class AB listening comparisons that people do, and that they have been doing over many decades, are meaningless regardless of whether they are blind or sighted, because the vast majority of the listening has likely been done with the Class AB amps operating in Class A mode. So in practice, most folks have been comparing Class A to Class A.
 

Doodski

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Doodski, are you sure that you were hearing the amp, and not the speakers? That is, did u check the 'sound' of the amp using two different sets of speakers?
We used Energy Pro22, Energy Reference 22 and the KEF 104.2 and did a listen both in the repair shop and at home because 2 of us techs bought and used the same class A amps at home. The Pro22 and the Reference 22 are revealing speakers in that they sound good with a average amp but if using a really good amp they perk up and come alive. I wish I still had the class A amp in mind because with all the excitement in the magazines of the time, all the listener tests and my own tests showed that it is a very smooth amp. Almost tube like. I suspect the amp is colored but if it is they did a wonderful job of smoothing things out and making it a high power class A.
 

Piere

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This is the most important point IMHO: the overwhelming majority of Class A vs Class AB listening comparisons that people do, and that they have been doing over many decades, are meaningless regardless of whether they are blind or sighted, because the vast majority of the listening has likely been done with the Class AB amps operating in Class A mode. So in practice, most folks have been comparing Class A to Class A.

What do you mean by that? A class-AB amp has an optimal bias point where cross-over distortion is lowest. That is indeed slightly in class-A. But that does not mean most folks who are comparing class-AB amps are actually comparing class-A amps. Only amps that are intentional highly biased, like Krell (and most so called class-A), are working in class-A at low levels. But when the output crosses the bias level they move over into class-B. As far as I know there is no clear different naming for regular low biased class-AB and high biased class-AB. The latter is brutally called class-A most of the time.
 
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Vacceo

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I'll put in my two cents, for what it's worth. When I was coming up in this hobby, the best amp was considered one of 'a straight wire with gain'. Maybe that's why people like class A, it's the closest you can get to that ideal. I do understand that things have changed slightly since then.
Ideally, an amp replicates a signal only increasing its amplitude. If there is a way to archive that using less power, less physical space and there is no audible difference even if the replica is less perfect (but there is no way we can notice with our own hearing organs), I'm all for efficiency.

In a nutshell: there is no inherent advantage in practical terms for a class A.
 

Doodski

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In a nutshell: there is no inherent advantage in practical terms for a class A.
It sounds about right on. Class D has achieved a high state of readyness and just needs market penetration and familiarity now with the general public. That new high power unit with 2 Ohm drive is far out and for the price it's expensive but it will save energy and sound good doing it.
 

Vacceo

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It sounds about right on. Class D has achieved a high state of readyness and just needs market penetration and familiarity now with the general public. That new high power unit with 2 Ohm drive is far out and for the price it's expensive but it will save energy and sound good doing it.
I'm not denying that decades ago things were different. But I see no point on further developing a steam engine to move a locomotive when you have electric engines.
 

Peluvius

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I'm not denying that decades ago things were different. But I see no point on further developing a steam engine to move a locomotive when you have electric engines.

Unless you are building a nuclear submarine ;)
 

tmtomh

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What do you mean by that? A class-AB amp has an optimal bias point where cross-over distortion is lowest. That is indeed slightly in class-A. But that does not mean most folks who are comparing class-AB amps are actually comparing class-A amps. Only amps that are intentional highly biased, like Krell (and most so called class-A), are working in class-A at low levels. But when the output crosses the bias level they move over into class-B. As far as I know there is no clear different naming for regular low biased class-AB and high biased class-AB. The latter is brutally called class-A most of the time.

Yes, I understand that the biasing affects when an AB amp will switch to Class B mode. But even an AB amp that switches to Class B operation beyond 1 watt is going to spend a heck a lot of its time in Class A mode. For amps that switch to Class B at 5 watts and 10 watts, they will spend even more time in Class A mode - especially if we consider that when the whole thing of Class A sounding better than Class AB began a few decades ago, when speakers were generally more efficient than they are now. That Class A vs Class AB idea also was created in a time before the internet.

So with that in mind, I think it is reasonable to hypothesize that a large proportion of the Class A vs Class AB listening tests (almost all sighted) that were conducted and publicized by reviewers and other influencers, were done with the Class AB amps spending most or in many cases all their time in Class A mode.
 

Peluvius

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Doodski

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How do they get 115dB spl at 4 meters with 100w at 87dB sensitivity? Even if the amp gets 400 wpc at 2 ohm, it doesn't compute....let alone making an amp recommendation based on 8 ohm for a 3 ohm nominal speaker? What am I missing?
I don't get the specs either. All I remember in the day was that the rumor mill stated these require a beast of a amp. :D
 

Chrispy

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I don't get the specs either. All I remember in the day was that the rumor mill stated these require a beast of a amp. :D
Yeah those speakers definitely have that reputation, often pulled up as an excuse for needing an amp with that kind of capability :) Have always wondered how many are actually in use, tho...
 
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