When purchasing an audio amplifier, one important criterion to consider is the amplifiers wattage. The wattage describes how much power the amplifier can deliver to some speakers. Usually, and manufacturers will specify the total wattage. In order to determine the wattage per channel, you simply divide this number by the number of channels.
Let’s say for example that you purchase 100 what amplifier. If the amplifier is a stereo amplifier then you will have 50 Watts per channel. However, keep in mind that they are different ways of specifying amplifier wattage. Usually the RMS wattage is the most reliable means for determining the amplifiers performance. To determine how powerful an amplifier you will require, investigate the type of speakers that you have.
Speakers usually have a wattage rating printed on them. However, the wattage that you actually need also depends on your listening environment as well as the sensitivity of the speakers. Different speakers will become loud to a different degree depending on their sensitivity given a fixed wattage.
Also, if you set up speakers in a noisy environment then you will need to drive them harder. However, also pay attention to the speaker impedance. Speakers with a high impedance are usually much harder to drive for an amplifier because the voltage swing is larger. If you have a small amplifier that works with a 12 fold supply voltage then you are very limited in how much wattage the amplifier can deliver to some speakers. In this case, you will want to have speakers with a low impedance.
Also, pay attention to the power supply that is bundled with the amplifier. The power supply has a voltage and amperage printed on it. If you multiply these two numbers, you will be able to determine the wattage that the power supply can deliver to the amplifier. Obviously, the amplifier will not be able to exceed the wattage of the power supply. In fact, some portion of the wattage delivered by the power supply is wasted inside the amplifier. As a rule of thumb, you should estimate that the amplifier can use of between 50 to 90% of the power supply wattage.