Introduction of circuits and parameters in the
1. Some circuits in professional power amplifier (1) The power capacity of the power supply circuit is large, and a toroidal transformer is commonly used, commonly known as 'ring cattle', and a large-capacity filter capacitor, called 'big water pond', to ensure sufficient power supply at the peak of the working instant. High-power devices such as final-stage power tubes (commonly known as Sanken and Toshiba pair tubes) use products with a maximum current and withstand voltage higher than the rated value. In the output stage with severe heat, a larger heat sink is required for heat dissipation , Most will also use cooling fans for forced air cooling. (2) Various protection circuits, such as DC protection, short circuit protection, overheat protection, sensitive overheat management system, input (output) overload protection, soft start protection, active limiting protection, etc. 2. The main parameters of the power amplifier Select the power amplifier mainly depends on the output power, frequency response, distortion, signal to noise ratio, output impedance, damping coefficient and other parameters. (1) Output power The unit of output power is W. Due to different measurement methods, there are some different names, such as rated output power, maximum output power, music output power, peak music output power. Some manufacturers of fisheye mixed beads often use this to confuse users. Peak power refers to the maximum music power that the amplifier can output when the amplifier volume is adjusted to the maximum within the allowable distortion. Rated output power refers to the maximum output power when the degree of distortion is less than a specified value, also known as the maximum 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 to 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 household Hi-Fi amplifiers is generally 20 Hz to 20 kHz, ± 1 dB. The wider the frequency response range, the better. (3) Distortion The ideal power amplifier should amplify the input signal without change. In fact, the amplified signal of the power amplifier compares with the input signal and produces different degrees of distortion. 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, crossover distortion, clipping distortion, transient distortion, transient intermodulation distortion, etc. (4) Signal to noise ratio Refers to the ratio of signal level to various noise levels output by the power amplifier, expressed in dB. The signal-to-noise ratio of general household Hi-Fi amplifiers is above 60 dB. (5) Output impedance The equivalent internal resistance presented to 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 will directly affect 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.