Products that went out years ago had low performance. During the last 50 years this perception has decreased thanks to progress in technology and technical drawings.
The class d amplifier is an efficient form of amplifier switch. It can reach up to 90 % of its performance; however it generates more electrical interference than other amplifier configuration.
Now class d amplifiers can be found in surround sound home theatre, car audio and even the battery powered hi-fi amplifier.
 |
This type of amplifier is often used in electronic systems, including hi-fi and the PA system (public announces). More and more companies are producing this type of circuit but only some have used it to get high performance audio.
You shouldn’t forget that the "d" of the class d doesn’t stand for "digital", because the operation of the amplifier of the class D is based on analogical principles.
 |
The Class D amplifier is mainly used when the active elements of the power system are operating as saturated or blocked, its operating principle is different: the active components of power generating a square signal of high frequency compared to the input signal that is proportional to the signal amplifier.
A low-pass filter placed in output can keep only the spectral components corresponding to low frequency signal. In fact, the class D amplifier works like a cutter ,that is to say, the output value has either the maximum or 0V. The average power is the audio signal. Just put a crossover lowpass to remove high frequencies.
The problem is that switching, to be inaudible , must be above 20 kHz. The class D amplifier is often used for subwoofers because the bandwidth is low (120 Hz max), it is small and produces less heat. In fact, the efficiency of Class D is superior to Class A, B and AB. Quality can be excellent, but this implies a high switching frequency and a very good filter.
 |
Because the active component is still working there either zero current or voltage drop at minimum, the heating is reduced, the energy loss being carried forward in connections and filters, as well as its high yield class D is an ideal candidate for mobile applications, such as car radios, generally use a topology class D.