The whole reason for existence of Class D is efficiency.

....

If Class D were perfect, it would have swept the world and there would 
be no other class in common usage. I'll tell you about the three major 
problems of Class-D amplifiers in a moment, but first, here's a 
question: how do you make an efficient radio transmitter? Answer: start 
with a Class-D audio amplifier. Yes, the high frequencies involved in 
Class-D amplification readily propagate as radio waves, potentially 
causing interference with radio receivers and other equipment. You might 
think that the solution would be to enclose the amplifier in a 
substantial steel housing. But that's not where the problem manifests 
itself — it's in the cables. The filter that is supposed to remove the 
high-frequency components and leave only the audio signal is quite 
shallow in slope — 6dB or 12dB per octave — so there's quite a lot of RF 
energy still getting out. Clearly, manufacturers take care to improve 
the situation and remain within allowable limits, but it is a problem 
inherent to Class D.
Class D without the filter. Lab Gruppen's 'Class TD' technology extends 
Class D with a claimed sonic performance equivalent to Class AB, but 
with Class D's superior performance in terms of efficiency and low weight.

  The second problem of Class-D is that the last thing the signal sees 
before it reaches the loudspeaker is the filter. A passive filter made 
from capacitors and inductors expects to see a certain load on its 
output. Even just looking at the resistance of a loudspeaker and 
ignoring its capacitance and inductance, loudspeakers come in 2(omega), 
4(omega) and 8(omega) nominal impedances, and the filter will work 
differently according to the impedance of the loudspeaker. Taking 
capacitance and inductance into account, the impedance will vary 
according to frequency. So the filter design is suddenly very much more 
complex: an amplifier that performs differently for different speakers 
is going to be a problem.
Thirdly — not finally, but enough for now — a Class-D amplifier has a 
relatively poor damping factor. The damping factor is the ratio of the 
impedance of the loudspeaker to the output impedance of the amplifier 
(it's a little more complex than that, but let's not get bogged down 
with details). In simple terms, it's a measure of how well the amplifier 
can control the movement of the diaphragm of the loudspeaker. A good 
amplifier doesn't just give it a push and hope for the best; it senses 
where the diaphragm is from moment to moment and controls its position. 
To do that, a high damping factor is desirable, and, as mentioned above, 
a simple Class-D amplifier has a low damping factor.

Clearly, advanced technology can be applied to ameliorate these 
problems, but because of them Class-D amplification is used mainly in 
applications where efficiency, weight and small size are important. 
These include live sound, in-car audio and compact portable systems.

Clearly, there is more to know. For instance, it's important to know 
that the switching frequency must be very high to achieve the necessary 
resolution. A switching frequency of around 300kHz, which is around 15 
times the highest audio frequency of general interest, is typical. The 
dynamic range and signal-to-noise ratio of the Class-D amplifier are 
controlled by the switching frequency — the higher the better. Clearly, 
the greater the rate of pulse generation, the more closely the pulse 
width will be in proportion to the instantaneous signal level. However, 
the drawback of increasing the switching frequency is that the amplifier 
will be less efficient. Optimum efficiency would be achieved if the 
transistors could switch instantaneously, so that they were in either 
their fully on or fully off states, where almost no power is consumed. 
But in the real world it takes a little time for the voltage to swing, 
and during that time some power is dissipated. So the more often the 
swings take place, the more opportunity for waste. Even so, the 
efficiency of a practical Class-D amplifier can be better than 90 
percent, which is significantly better than a Class-AB design (78.5 
percent at best and typically closer to 50 percent).

http://www.soundonsound.com/sos/jun06/articles/loudandlight.htm

On 05/02/2013 08:25 AM, Dainiushas wrote:
> tu čia stebuklines pasakas kažkokias seki. šiaip jau
>
> On 2013.05.02 07:56, Signalizacija wrote:
>> Dar karta kartoju. Klausai , kalusyk, bet nerikia kist D klases kai
>> kazkokio stebuko. Pats aiskiai parasei, geris gabarituose ir energijos
>> panaudojime. Deja tuo tas geris ir baigiasi.
>>
>>
>> On 05/01/2013 09:17 AM, spakainas wrote:
>>> Ale tu žiūriu vis nepasimokai, negana o.autos'uose grybą pjauni, tai dar
>>> ir kitur ateini pasišiukšlint.
>>>
>>> 2013.04.30 22:52, Signalizacija rašė:
>>>> Nu maladiec, kad pacitavai kazkoki reklamini straipsniuka
>>>> Klausykis savo lengvo ir ekonomisko stepro, ziurek lcd plastmasini
>>>> vaizda, apsikabines gumine bobike :)
>