Digital Amplifiers / Class D

A Class D amplifier, often incorrectly called “digital,” amplifies the signal by switching: instead of allowing transistors to conduct continuously as in Class A or A/B, it makes them switch very rapidly between on and off, then a filter reconstructs the audio waveform at the output. The original signal remains analogue; only the switching is binary, hence the misleading “digital” label. The advantage lies in efficiency: Class D reaches 85 to 95% where Class A/B peaks much lower, with little energy lost as heat. This results in a compact chassis, low heat dissipation, high available power and modest power consumption, including in standby. Long criticised for treble deemed harsh and a particular sonic character, modern Class D has bridged most of the gap thanks to refined modules and careful output filtering, to the point where it compares favourably with good Class A/B designs. Its firm, well-controlled bass is due to a high damping factor. Some nuances remain depending on the implementation, with the quality of the module and power supply mattering more than the class itself. This design is used in a large share of high-power units: the power amplifiers category benefits from compact yet powerful formats. This amplifier drives a pair of passive floorstanding or bookshelf speakers and belongs to the integrated stereo amplifiers category.