Amplifier Class
Amplifier class describes the operating method of an audio power output stage.
Class A keeps its output devices conducting throughout the signal cycle; Class AB varies conduction with level. Class D uses switching. Classes G and H vary supply arrangements to improve efficiency. These classes differ from tube versus transistor technology.
Amplifier Class — Power Amp
For a power amplifier, the class belongs to the speaker-output stage, including on a hybrid with tube input stages. It helps explain operating efficiency and heat generation.
A Class AB amplifier can operate in Class A over an initial power range without being Class A throughout. Compare the full-power class and any stated Class A range separately; single-ended and push-pull describe another aspect of topology.
Amplifier Class — Subwoofer
For an active subwoofer, the class describes its built-in power amplifier. Efficient switching stages can deliver substantial bass power with less heat than less efficient designs at comparable output.
The class does not specify acoustic output, bass extension or the limiter behavior. Keep it separate from rated amplifier power and the enclosure and driver design.
Amplifier Class — Headphone Amp
For a headphone amplifier, the class describes the stage supplying power to the headphones. It can affect idle consumption and heat as well as how the stage operates with signal level.
Compare the stated operating class at the relevant output conditions. A tube circuit or balanced output is not itself an amplifier class, and class alone does not establish noise or distortion performance.