How do I know which Class/Topology an amplifier is and uses?

[nyxnyxnyx]

Like many other enthusiasts in this hobby, I don't know much when it comes to practical knowledge and technical features. I see that class A is highly praised in the audiophile circle (despite having read why other classes have their advantages too), but when there are other amplifiers that are not marked as Class A, they often do not mention which class it is, I always found it weird.

So for an uneducated consumer like me, what do I need to learn and view to know what class or topology is used in the amplifier? This is not important but it's just something I think it would be cool if I can realize it for myself instead of having to ask others.

 

[Doodski]

Like many other enthusiasts in this hobby, I don't know much when it comes to practical knowledge and technical features. I see that class A is highly praised in the audiophile circle (despite having read why other classes have their advantages too), but when there are other amplifiers that are not marked as Class A, they often do not mention which class it is, I always found it weird.

So for an uneducated consumer like me, what do I need to learn and view to know what class or topology is used in the amplifier? This is not important but it's just something I think it would be cool if I can realize it for myself instead of having to ask others.

How much do you know about amplifier classes? A, B, AB, C, D, H, N etc etc. Do you understand transistor operation and linearity, switching distortion, saturation and cutoff? That would be a start.

 

[DVDdoug]

If they don't say, it's probably class AB since that's been standard since almost the beginning of hi-fi (for power amplifiers... amplifiers that drive speakers).

But I think most AVRs are class D because you can make a powerful multi-channel amplifier cheaply, and they may not advertise the amplifier class.

Class A, AB, and D are all fine for audio, and any good design will be better than human hearing. Some of those other classes are not suitable for audio, but I don't remember what they all are...

Class A is very energy inefficient. The main output MOSFET (or transistor or tube) burns more power than goes the speaker even when it's idling with no sound. You won't find a 200W class A amplifier. It's OK for preamps and maybe OK for a headphone amp, but for a power amp it's a "dumb design".

On the other hand, class D is very efficient with most of the energy going to the speaker.

Efficiency is important and energy savings is a just side-benefit. The main advantage is that the wasted energy is converted to heat and heat is what burns-up semiconductors. So with a given MOSFET (or other device) and class D you can get more audio power to the speakers and you can get-by with smaller heatsinks. Almost all high-power pro amplifiers are now class D. High-power class AB amplifiers sometimes use multiple MOSFETs in parallel to share the load.

Class D is more complex but since most of the complexity is built-into a microchip it's often cheaper to make a class-D with power and performance similar to a class AB.

class A is highly praised in the audiophile circle

The "audiophile community" is mostly nuts! For the most part they don't trust measurements or blind listening tests and they don't accept that there are real limits to human hearing. And, they tend to use lots of meaningless words that often express a feeling instead of using scientific-engineering terminology like noise, distortion, or frequency response.

And there is a sub-group of "audiophiles" that are fascinated with vacuum tubes and vinyl records, and maybe other nostalgic technology. Tubes can be as-good as solid state electronics but it's more expensive and MUCH more expensive if you want to make a good tube power amplifier. A record is technically inferior to digital audio in every way (noise, distortion and frequency response).

 

[Beave]

If they don't say, it's probably class AB since that's been standard since almost the beginning of hi-fi (for power amplifiers... amplifiers that drive speakers).

Agreed.

But I think most AVRs are class D because you can make a powerful multi-channel amplifier cheaply, and they may not advertise the amplifier class.

I would guess most are still class AB. Pioneer had a few class D models, but Denon, Marantz, Yamaha, Sony, and Onkyo are all class AB as far as I know.


To answer the original question, if the amp is huge, heavy, and very expensive, it's probably some mix of class A and class AB.

If it's pretty small and lightweight for the power it can output, it's probably class D.

If it's in between those two extremes, it's probably class AB.

Edit to add: I'm assuming you mean speaker amps, not headphone amps. For headphone amps, they're generally ALL small-ish compared to speaker amplifiers, so some of my generalizations may not fit. Headphone amplifiers don't need to output nearly as much power as speaker amplifiers.

 

[nyxnyxnyx]

How much do you know about amplifier classes? A, B, AB, C, D, H, N etc etc. Do you understand transistor operation and linearity, switching distortion, saturation and cutoff? That would be a start.

Well do you have any articles or beginner-friendly materials for me to learn? I think I barely know anything about electronics and similar subjects.

If they don't say, it's probably class AB since that's been standard since almost the beginning of hi-fi (for power amplifiers... amplifiers that drive speakers).

But I think most AVRs are class D because you can make a powerful multi-channel amplifier cheaply, and they may not advertise the amplifier class.

Class A, AB, and D are all fine for audio, and any good design will be better than human hearing. Some of those other classes are not suitable for audio, but I don't remember what they all are...

Class A is very energy inefficient. The main output MOSFET (or transistor or tube) burns more power than goes the speaker even when it's idling with no sound. You won't find a 200W class A amplifier. It's OK for preamps and maybe OK for a headphone amp, but for a power amp it's a "dumb design".

On the other hand, class D is very efficient with most of the energy going to the speaker.

Efficiency is important and energy savings is a just side-benefit. The main advantage is that the wasted energy is converted to heat and heat is what burns-up semiconductors. So with a given MOSFET (or other device) and class D you can get more audio power to the speakers and you can get-by with smaller heatsinks. Almost all high-power pro amplifiers are now class D. High-power class AB amplifiers sometimes use multiple MOSFETs in parallel to share the load.

Class D is more complex but since most of the complexity is built-into a microchip it's often cheaper to make a class-D with power and performance similar to a class AB.



The "audiophile community" is mostly nuts! For the most part they don't trust measurements or blind listening tests and they don't accept that there are real limits to human hearing. And, they tend to use lots of meaningless words that often express a feeling instead of using scientific-engineering terminology like noise, distortion, or frequency response.

And there is a sub-group of "audiophiles" that are fascinated with vacuum tubes and vinyl records, and maybe other nostalgic technology. Tubes can be as-good as solid state electronics but it's more expensive and MUCH more expensive if you want to make a good tube power amplifier. A record is technically inferior to digital audio in every way (noise, distortion and frequency response).

Thanks for making it easy for me to read and understand. Back when I first got myself to this hobby the common argument I see for class A is because they "sacrifice" (wasted energy, high heat) for higher sound quality. If there was a similar metaphor for cooking I think it makes sense, but when I read the specs I see that modern amplifiers already reached very low distortion ratio, past the audible threshold for most so that's when I stopped thinking Class A design is the grail.

Just for myself I'm ok with letting my subjective feeling guide me during the listening, but I like to really know what's real and what's not because the further I spend time with this hobby the more sketchy stuff I (or we) found .

 

[nyxnyxnyx]

Agreed.



I would guess most are still class AB. Pioneer had a few class D models, but Denon, Marantz, Yamaha, Sony, and Onkyo are all class AB as far as I know.


To answer the original question, if the amp is huge, heavy, and very expensive, it's probably some mix of class A and class AB.

If it's pretty small and lightweight for the power it can output, it's probably class D.

If it's in between those two extremes, it's probably class AB.

Edit to add: I'm assuming you mean speaker amps, not headphone amps. For headphone amps, they're generally ALL small-ish compared to speaker amplifiers, so some of my generalizations may not fit. Headphone amplifiers don't need to output nearly as much power as speaker amplifiers.

Since I have no knowledge I just assume the class design of an amplifier based on it's maximum output and how hot it runs. I actually have more experience with headphones amplifiers because my living condition does not allow me to fiddle with speakers, but my example in the OP post still stands, most amplifiers I see are either advertised as class A, AB or D. But especially in headphones amplifier market I think the keyword "class A design" shows up way more often.

I've read brief conclusions about Class/Topology design and I can imagine that as long as it's well designed it is going to perform good no matter what class or topology is used. The thing is to the untrained eyes (like me) I can't distinguish a good one from a bad one haha.

 

[Mart68]

Agreed.



I would guess most are still class AB. Pioneer had a few class D models, but Denon, Marantz, Yamaha, Sony, and Onkyo are all class AB as far as I know.

Sony made a class D amp way back in 1977 http://www.thevintageknob.org/sony-TA-N88B.html

I don't know about the others.

 

[MaxwellsEq]

This is tricky. I understand the different amplifier classes because I started tinkering with electronics before my teens, and went on to spend three years at university studying electronics. I then worked on electronic equipment. You can be entirely self taught, but you still need to put the hours in. I believe there are no shortcuts.
The amplifier classes mostly refer to the last stage of a power amplifier, where the device is creating enough voltage and current change to drive an electric motor (e.g. a loudspeaker voicecoil). This is done using output devices such as "power transistors". These devices are not perfectly linear, which means that when they are operating in the middle of their function they don't distort much, but when almost fully switched on or fully switched off they behave in non linear ways (they don't have the same gain as in the middle).
Class A avoids this by ensuring the devices are always in the middle, but wastes energy doing so. Class D adopts a different approach, by switching the devices on and off very fast, and wastes little energy.
To understand Class B, you need to understand "push-pull" operation where one device handles the positive part of the signal and a different device the negative half. In Class B the positive device switches off completely before handing over to the negative device. This is efficient, but means the signal is distorted due to the non linear "off" part of the gain behaviour. Class AB, hands over from the positive device to the negative device before switching off, so is less non-linear, but wastes a bit of energy. In the past, almost all popular brand HiFi amps were Class AB. Class D amps are now becoming popular.

 

[Beave]

Sony made a class D amp way back in 1977 http://www.thevintageknob.org/sony-TA-N88B.html

I don't know about the others.

Cool, I didn't know about that. I didn't know there were any class D amps then.

Sony's recent AVRs, though, at least the ones I've seen, have been class AB.

 

[Tks]

For people that don't know electronics like me. The simplest way is.. If the device clearly has size and weight compared to modern offerings in the same form factor (or the device has heatsinks as a part of the body). Class A, and AB MAYBE for power amps with the aforementioned consideration of form factor. Everything else, is basically lower class. But in reality it doesn't matter since this is the consideration of designers, and not consumers. For consumers the extent at which this is relevant in my view, is simply power envelope (from an efficiency standpoint, meaning do I need a space heater to produce the sound levels I want or not).

As for which class is "best". Obviously the class with higher power efficiency. But this means nothing if there are issues that aren't controlled for said class consideration. What this means (from a consumer point of view), is basically the best "class" is verified per device, and not by class itself. So if the device measures to within specs you expect to get. Then that's the best class. It only gets better when said specs can be met with less downsides by using lower classes (since it's just pure energy efficiency benefit at that point).

As for which class is generally considered the best (in terms of how things have panned out on the market).. No idea, I'm too new to audio to say how things for example like "switching power supplies" have done from a reputation point of view when looking back a decade or something of that nature.

 

[mhardy6647]

Sony made a class D amp way back in 1977 http://www.thevintageknob.org/sony-TA-N88B.html

I don't know about the others.

Sir Clive Sinclair sold them (boards/kits) in the 1960s.

Class D Amplifiers 101

While GaN FETs can be operated up to 100A, 200V, and 100MHz switching frequency, still, no class-d amp either Silicon-based or GaN-based, ever exceeded the 1MHz switching frequency barrier due to diver limitations and output low pass filter for high design problems for very high switching...

www.audiosciencereview.com

 

[Mart68]

Good old Sir Clive. Remember when he used to pop up on 'Late Night Poker'?

Blew his fortune on the C5 electric 'car' disaster and got taken over by Amstrad. Such a shame. I learned to programme on one of his computers along with many other teenagers, his legacy is huge really.