(1) Improper grounding
In an audio system, the entire system must be properly grounded. The grounding resistance should be less than 4 ohms. Otherwise, the induced charge generated by the devices in the system due to various radiation and electromagnetic induction will not be able to flow to the ground, thereby forming a noise voltage superimposed on the audio signal.
Grounding noise is caused when there is a ground potential difference between the wires of different devices due to the difference in grounding resistance, or when there is a loop in the ground inside the system. When two different audio systems are connected to each other, it is also possible that noise is generated by directly connecting the ground lines of the two systems.
(2) Noise generated by electromagnetic radiation interference
Spurious electromagnetic radiation interference in the environment, such as high-frequency electromagnetic wave radiation interference of communication equipment such as mobile phones and walkie-talkies, electric pulse interference such as elevators and air conditioners, and radiation of thyristor rectifier control equipment for studio lighting control, which are directly mixed and transmitted through the transmission line to form the noise in the signal.
(3) Circuit noise inside the equipment
When one device works alone, the electrical noise generated by the internal electronic components can reach the required standard, but after cascading multiple devices, the noise will increase cumulatively and form serious noise in the system.
(4) Noise generated by power supply interference
The urban power grid has formed a serious interference source due to the joint access of various lighting equipment, power equipment and control equipment. If the lighting control equipment, air conditioner, motor, etc. connected in the same power grid will generate spikes, surge currents, and ripple voltages of different frequencies on the power line. Break into the power supply of the device through the power cord. There will always be some interference noise voltage that cannot be effectively filtered out by the power supply circuit of the audio device, which will inevitably generate noise inside the device.
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