Selecting the power amplifier mainly depends on parameters such as output power, frequency response, distortion, signal to noise ratio, output impedance, and damping coefficient.
(1) The unit of output power is W. Due to the different measurement methods; there are some different names, such as rated output power, large output power, music output power, and peak music output power.
The peak power is the larger music power that the amplifier can output when the amplifier volume is adjusted to a large value within the allowable distortion condition.
The rated output power refers to the larger output power when the distortion is less than a certain value, which is also called the larger useful power. Generally, the peak power is greater than the music power, and the music power is greater than the rated power. In general, the peak power is 5-8 times the rated power.
(2) Frequency response: indicates the unevenness of the level gain within the operating frequency range of the power amplifier. The straightness of the frequency response curve is expressed in decibels (dB). The frequency response of a home Hi-Fi amplifier is generally 20 Hz to 20 kHz, and 1 dB. The wider the frequency response range is, the better.
(3) Distortion: The ideal power amplifier should be to amplify the input signal without change. In fact, the amplified signal of the power amplifier is compared with the input signal, and different degrees of distortion are generated. This distortion is distortion expressed as a percentage, the smaller the value, the better. The distortion of the power amplifier includes harmonic distortion, intermodulation distortion, cross distortion, clipping distortion, transient distortion, and transient intermodulation distortion.
(4) Signal-to-noise ratio: refers to the ratio of the signal level to the various noise levels of the power amplifier output, expressed in dB. The signal-to-noise ratio of a typical home Hi-Fi amplifier is above 60 dB.
(5) Output impedance: The equivalent internal resistance exhibited by the speaker.
(6) Damping coefficient: refers to the ratio of the load impedance of the power amplifier to the actual impedance of the power amplifier. A large damping coefficient means that the output resistance of the power amplifier is small, and the output impedance of the power amplifier directly affects the low-frequency Q value of the speaker system, thereby affecting the low-frequency characteristics of the system. It is generally desirable that the output impedance of the power amplifier is small and the damping coefficient is large. The damping coefficient is between tens and hundreds, and the damping coefficient of professional power amplifiers can be as high as 200 or more.
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