Listen to and enjoy the sound of music or to increase the sound of a device such as a home theater, you will need an amplifier. On the market, there are different models of amplifiers whose mode of operation is generally identical.
The basic principle of an amplifier
The operating principle of an audio amplifier takes into account the frequency of the current with a transformer. Today, there are two types of power, namely switching power and conventional power. For the first power category, the usual frequency is converted into a higher frequency by chopping or chopping with a high-frequency oscillator driving the switching circuit. In the case of a conventional power supply, the transformer lowers the voltage of the electrical network so that output is rectified.
The functions present on an amplifier
Most amplifiers work at fixed gain”, More clearly, the amplification ratio between the input signal and the output signal must be constant. The level of the input signal will have to be adjusted by one or more pre-amplifier stages to prevent saturation of the amplifier. These stages have an adjustable gain and give the possibility of adjustment of the signal level before amplification, that is, to adjust the final volume. You will regularly see an abstract scale of 0 to 10 indicating the attenuation in decibels of the signal. Also, the balance has the role of balancing the sound level between two channels, that is to say, the left and the right. The simultaneity of serious and acute levels is used to compensate, at low volume, what your hearing does not perceive thanks to a filter called “Loudness.” Depending on the amplifier you have chosen, you can mitigate the sensation of Rumble or hum with specific filters, such as when you listen to vinyl.
- The solution in technical jargon sounds like this: Since you put a DC offset on it. Here is the translation. It is always a fixed value added to it. In the example shown here it is enough to add 2 (-2 + 2 = 0). Usually more is added (2.5 or 3). The fixed value has a name: DC voltage, the wave is an AC voltage. And in the end, only the changing part “AC voltage” is released on the speaker.
- There we have an amplifier. Since everything in the jargon must have its name, someone decided that it had to hear the name “Class A.” Of course, a “Class A” amplifier as a device consists of many more components, but to understand the actual principle, I did not mention a few details …
- An important feature of the “Class A” amplifier must be mentioned in any case: The thing is a heater! How so? Well, yes, it was the water turned up a little, so that afterward the sound can be perceived as a change. That is, there is always some water flowing even if there are no sounds to amplify.
- Unfortunately, since a transistor is not a proper conductor, the electrical current must fight against resistance. The transistor warms up. This heat has to go away from the transistor. Otherwise, it burns it. Therefore, transistors, if they have to work properly, screwed to metal pieces, called heat sink (or radiator, it depends on the direction of view). The size of the piece of metal estimates how much power it will burn.
- The second drawback is that only ON transistor is working. It would be better if two could share the work. Sure, says the management, we could see still someone to side, then you could work in parallel. But YOU need soviet space with your radiator… Um, heat sink. If there is a second, who needs so much space again… Sorry but that’s the building … um, housing too small.
- To get out of the problem case “heating” and the associated “power limitation,” technicians were asked (as always) to find a solution. The simple idea of the technician (concept “Class B”): How about if we would split the work meaningful? Looking at the wave, one could reinforce the upper hump and the other the lower valley. The advantage of this solution: the annoying direct current that always flows, could be eliminated. That would also make huge heating … um, the heat sinks superfluous.
- Now, the physics of transistors has taken a little pity on the often-freezing women. The technicians were warned that the transistor always needs a little push to work. Because just before “not work,” i.e., 0, the transistor stops its work. Since the technicians need two transistors for this concept (one for the hump, the other for the valley) creates a kind of death zone, where no one works. To overcome this, a little “Class A” concept is mixed in there will be some tension added and a little electricity will flow (yes, the heating is back!). Since the voltage is low, the current remains small. Thus, the mission is (almost) fulfilled. This mixture is logically called the “Class AB” concept.
All good? Goal achieved? Yes, the goal of reducing the heat output (power dissipation) has been achieved. It only costs gains small inaccuracies at the transfer point between the two transistors.