The power amplifier power supply filter capacitor has three functions: 1. Filter the pulsed DC power obtained after rectification to reduce AC interference. 2. High-speed power supply. 3. Provide access for audio signals. The filtering effect of the capacitor on the power supply only shows whether there is AC interference to the power amplifier; the energy storage function of the capacitor can provide power for the transient high current needs of the power amplifier, but the transformer power is insufficient to charge it in time, and its energy storage function It is not obvious; and it provides a path for the audio signal to affect the sound quality and tone color.
The positive half-cycle audio signal in the figure is an example. The signal is divided into two channels through the power amplifier tube, emitter resistance, speaker, and ground. One part forms a loop through a power transformer and a rectifier tube, and the other forms a loop through a filter capacitor. Obviously, the transformer inductance is very large, which is not conducive to the passage of the high-frequency part of the audio. It can only pass the low-frequency audio signal with very low frequency and only provide a path for the sub-bass. More audio signals, especially the high-frequency part of the signal, pass The power filter capacitor forms a loop. The capacitor and the transformer secondary complement each other, providing a frequency band path from DC to high frequency for audio.The role of power supply filter capacitor