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To know the power amplifier better it is beneficial to understand the concept of a power amplifier first. In general, an amplifier’s main purpose is to take a weak signal and make it strong enough to drive a speaker. In such a case the power amplifiers do get the necessary energy for amplification of input signals from the AC outlet. It is practical to understand that no amplifier is 100% efficient, so some of the energy from the wall outlet is wasted. The amount of energy wasted by an amplifier shows up in the form of heat. Heat is harmful for any electronic equipment and to avoid that most of the amplifiers in the 200 watt and up per channel range have forced air cooling to prevent excessive heat buildup during the process. Practically many power amplifiers will suffer some or the other energy loss but it can be avoided if the power amps are operated within their recommended power ratings. Mostly all the power amplifiers have a defined power rating and the units of power are called watts. This power rating of an amp can be stated for various load impedances in this case the units for load impedance are ohms. The most common load impedances in a power amplifier are 8 ohms, 4 ohms, and 2 ohms. In general the power output of a modern amp is usually on the higher side when lower impedance loads are used on it. In a power amplifier the rated power output is taken as its maximum output but that doesn’t mean that the amplifier can only be used at this output. Let’s make it clear with an example, if an amplifier is rated at 300 watts, the output can vary between zero and this maximum rated value. In such a case the chances are that the amplifier can probably put out more power if the input signal is overdriven, however in such a scenario the quality of the output may tend to degrade rapidly.
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