What does class A, B, or A/B mean?

[L.J.]

I've been reading threads and I'm wondering what does class A, B or A/B mean. Just curious.

Thanks

[Glen B]

I've been reading threads and I'm wondering what does class A, B or A/B mean. Just curious.

Thanks

See the following link for an explanation of amplifier operating classes. Although it describes the operation of tube amplification, the principles are identical for solid state devices.
http://www.duncanamps.com/technical/ampclasses.html

[RGA]

Hmm think of it like a letter grade rating

Class A is the best (usually the best but occassionally bested by A/B on a good day when the moon is blue)
A/B is not quite an A so it's next best (some pretty good ones)
Class B is in last place and is worst. (Enter most Receivers and Naim)
Class D is lousy
Class T is marketing drivel


Generally speaking as silly as the above is stated -- in my epxerience it holds true of most of the stuff I have heard..

If you can put SE after the class A you're (Super Excellent)

And if you can put SEP after the class A you're (Super Excellent Posh)

And if you can put SET after the class A you're (Super Excellent To-the-max)

http://www.tpub.com/neets/book7/25e.htm

And from the Class A SET guru's perspective http://www.triodeandco.com/levelsystem.html

[theaudiohobby]

Hmm think of it like a letter grade rating

Class A is the best (usually the best but occassionally bested by A/B on a good day when the moon is blue)
A/B is not quite an A so it's next best (some pretty good ones)
Class B is in last place and is worst. (Enter most Receivers and Naim)
Class D is lousy
Class T is marketing drivel


Generally speaking as silly as the above is stated -- in my epxerience it holds true of most of the stuff I have heard..

If you can put SE after the class A you're (Super Excellent)

And if you can put SEP after the class A you're (Super Excellent Posh)

And if you can put SET after the class A you're (Super Excellent To-the-max)

http://www.tpub.com/neets/book7/25e.htm

And from the Class A SET guru's perspective http://www.triodeandco.com/levelsystem.html

You really need to listen to a lot more amplifiers, your SET guru is simply trying sell product like every other bloke/gal, the blurb is marketing hot air, it is called market differentiation.

A Class A topology simply consumes more power, it has been demonstrated again and again that well designed Class AB amplifiers are as good. It is simply impossible to build good Class A amp with reasonable power (5Wpch SS amps anyone) as cheaply as an equivalent Class A/AB, as a result the entry point of Class A amplifiers is much higher, you are not going to see a Class A amplifier at NAD320BEE prices or Rotel RA-01 prices, it ain't gonna happen and those cost savings are reflected in the sound, there is no free lunch.

Class D amplifiers is making inroads because they generally handle adverse loads better than the more traditional topologies at a more modest cost, hence their increasing popularity amongst planar speaker owners.

The sound of an amplifier is largely determined by its load handling xteristics ( impedance, disortion spectrum etc.).

[Feanor]

Hmm think of it like a letter grade rating

Class A is the best (usually the best but occassionally bested by A/B on a good day when the moon is blue)
A/B is not quite an A so it's next best (some pretty good ones)
Class B is in last place and is worst. (Enter most Receivers and Naim)
Class D is lousy
Class T is marketing drivel


Generally speaking as silly as the above is stated -- in my epxerience it holds true of most of the stuff I have heard..

If you can put SE after the class A you're (Super Excellent)

And if you can put SEP after the class A you're (Super Excellent Posh)

And if you can put SET after the class A you're (Super Excellent To-the-max)

http://www.tpub.com/neets/book7/25e.htm

And from the Class A SET guru's perspective http://www.triodeandco.com/levelsystem.html

Our guy askes what A, B, A/B mean: you tell him which sounds best -- in your own opinion, of course.

Speaking of opinions, mine is that my "Class T", (Tripath) amps sounds great. Tripath is a proprietary technology that is a significant variant on the established PWM, (pulse width modulation), approach. Just "marketing drivel", no! Better than others? Not necessarily, but like I said ...

[Feanor]

"Stupid, expired technology" ...

[Geoffcin]

Our guy askes what A, B, A/B mean: you tell him which sounds best -- in your own opinion, of course.

Speaking of opinions, mine is that my "Class T", (Tripath) amps sounds great. Tripath is a proprietary technology that is a significant variant on the established PWM, (pulse width modulation), approach. Just "marketing drivel", no! Better than others? Not necessarily, but like I said ...

He's already proven beyond a doubt that his opinion is worthless when it comes to amps or speakers.

[L.J.]

Interesting stuff. Thanks for the links and replies. I will have to give the articles a couple of more go overs to get a better since of it.

So from what I could grasp. The class A seems to be on top when it comes to sound, I believe the words no distortion and highest fidelity were used, but the least efficient.

So how important is efficiency?

[RGA]

He's already proven beyond a doubt that his opinion is worthless when it comes to amps or speakers.

Really You've proven that. Man when one posts humour you guys are just so one track minded -- everything is an attack on yor penis. LOL. Not there is much there it seems.

[BRANDONH]

I've been reading threads and I'm wondering what does class A, B or A/B mean. Just curious.
Thanks

Class A amplifier - Class A operation is where both devices conduct continuously for the entire cycle of signal swing, or the bias current flows in the output devices at all times. The key ingredient of class A operation is that both devices are always on. There is no condition where one or the other is turned off. Because of this, class A amplifiers are single-ended designs with only one type polarity output devices. Class A is the most inefficient of all power amplifier designs, averaging only around 20%. Because of this, class A amplifiers are large, heavy and run very hot. All this is due to the amplifier constantly operating at full power. The positive effect of all this is that class A designs are inherently the most linear, with the least amount of distortion.

Class B amplifier - Class B operation is the opposite of class A. Both output devices are never allowed to be on at the same time, or the bias is set so that current flow in a specific output device is zero when not stimulated with an input signal, i.e., the current in a specific output flows for one half cycle. Thus each output device is on for exactly one half of a complete sinusoidal signal cycle. Due to this operation, class B designs show high efficiency but poor linearity around the crossover region. This is due to the time it takes to turn one device off and the other device on, which translates into extreme crossover distortion. Thus restricting class B designs to power consumption critical applications, e.g., battery operated equipment, such as 2-way radio and other communications audio.

Class AB amplifier - Class AB operation allows both devices to be on at the same time (like in class A), but just barely. The output bias is set so that current flows in a specific output device appreciably more than a half cycle but less than the entire cycle. That is, only a small amount of current is allowed to flow through both devices, unlike the complete load current of class A designs, but enough to keep each device operating so they respond instantly to input voltage demands. Thus the inherent non-linearity of class B designs is eliminated, without the gross inefficiencies of the class A design. It is this combination of good efficiency (around 50%) with excellent linearity that makes class AB the most popular audio amplifier design.

Class AB plus B amplifier - Class AB plus B design involves two pairs of output devices: one pair operates class AB while the other (slave) pair operates class B.

Class D amplifier - Class D operation is switching, hence the term switching power amplifier. Here the output devices are rapidly switched on and off at least twice for each cycle. Since the output devices are either completely on or completely off they do not theoretically dissipate any power. Consequently class D operation is theoretically 100% efficient, but this requires zero on-impedance switches with infinitely fast switching times -- a product we're still waiting for; meanwhile designs do exist with true efficiencies approaching 90%.

Class G amplifier - Class G operation involves changing the power supply voltage from a lower level to a higher level when larger output swings are required. There have been several ways to do this. The simplest involves a single class AB output stage that is connected to two power supply rails by a diode, or a transistor switch. The design is such that for most musical program material, the output stage is connected to the lower supply voltage, and automatically switches to the higher rails for large signal peaks. Another approach uses two class AB output stages, each connected to a different power supply voltage, with the magnitude of the input signal determining the signal path. Using two power supplies improves efficiency enough to allow significantly more power for a given size and weight. Class G is becoming common for pro audio designs.

Class H amplifier - Class H operation takes the class G design one step further and actually modulates the higher power supply voltage by the input signal. This allows the power supply to track the audio input and provide just enough voltage for optimum operation of the output devices. The efficiency of class H is comparable to class G designs.

http://www.audiolab.com/glossary/#C

My QSC SRA 6322 is a class H