Gear & technology
Class D
Also called Class D amplifier, switching amplifier, digital amplifier
A Class D amplifier switches its output devices fully on and off at a very high rate and filters the result back into an audio signal. It is over 90 percent efficient, which allows small, cool-running amplifiers with hundreds of watts.
The "D" is just the next letter, not "digital", although the technique is sometimes called that. The output stage produces a train of pulses whose width follows the music; a filter removes the switching frequency and leaves the amplified waveform.
Early Class D amps had a reputation for a hard treble, but modern modules from Hypex, Purifi and ICEpower measure as well as the best Class AB designs and are used in active speakers, subwoofers and compact integrated amps. Whether any audible difference remains is argued; the measurements say very little does.