How to quickly eliminate the noise in the professional performance sound system

　　In professional performance audio systems such as stage performances and live sound reinforcement, noise is a common and very headache problem. The noise generated by a set of professional audio system is in different conditions. It may come from multiple aspects. The sound engineer should analyze and judge the more complicated conditions, and deal with them separately. According to past experience, general noise may come from three aspects: firstly, the equipment is not properly connected; secondly, the disturbing noise of the power supply; and finally, the inherent noise of the equipment.

　　1. Eliminate the inherent noise of the equipment

　　The professional performance audio system is composed of multiple devices, such as microphones, DVD decks, mixers, effects, equalizers, compressors, encouragers, electronic crossovers, power amplifiers, speakers, etc., each Equipment may be the source of noise. In order to find and judge from which unit the noise is generated, it is necessary to detect the inherent noise of each unit.

　　Open the professional audio system: the order of starting is opened step by step in the order of the signal flow. After turning on, there is noise from the speaker. First, you can turn off the power of the wireless microphone receiver to identify whether there is noise. If the noise disappears, it proves that the noise is generated by the wireless microphone receiver. If there is still noise, it proves that the noise is not generated by the wireless microphone receiver, and other units can be detected.

　　2. Eliminate the disturbing noise of the power supply

　　Noise interference of light thyristor: On the stage, the most disturbed by power supply noise is the noise from light thyristor, because the light and dark, intensity changes of theaters and dance halls are not achieved by changing the voltage of 0 ~ 220V. , But through the electronic circuit to control the conduction angle of the thyristor, change the conduction area of the sine wave of the alternating current, and realize the change of the control power transmission.

　　Therefore, the sine f sine wave in the power supply is changed to a shape similar to a sawtooth wave, and obvious 50Hz ripples occur in the power supply, which shows obvious noise in the professional audio system. In order to eliminate the disturbing noise of the thyristor, the most effective method is to provide two phases of the three-phase power supply to the light, and use the other phase as a professional performance audio system, so as to avoid the light thyristor. disturb.

　　3. Eliminate noise caused by improper connection of equipment

　　In the professional performance audio system, there is a common problem of equipment interconnection. If the connection is improper, the system indicators will decrease, noise will occur, and the equipment will not work properly in severe cases. The following points must be done when connecting.

　　Impedance matching: In the professional audio system, almost all devices use the jumper method, that is, the output impedance of the device is planned to be small, and the input impedance is very large. This is because in the system, unless the signal is transmitted over a long distance, it is generally treated as a short line. Moreover, the signal level is low, and the signal is required to be transmitted with high quality, and the change of the load basically does not affect the quality of the signal.

　　When the signal source is planned as a constant voltage source, or the load is much larger than the internal impedance of the signal source, the above requirements can be satisfied. In fact, the impedance of professional audio equipment is planned according to the above principles, and the jumper method is used for the interconnection of the equipment. This is the impedance matching of professional audio equipment.

　　When planning the sound reinforcement system, it is generally not necessary to consider the impedance problem. However, when the output of one device needs to be connected to multiple devices, that is, when a signal source drives several loads, an active or passive audio signal distributor must be selected to meet the requirements of the impedance matching of the device (if there are two devices, Generally, it can be directly connected to the output terminal of the front-end equipment).

　　Professional performance audio amplifiers and speakers are connected according to the nominal output impedance and the input impedance of the speakers. The output impedance of the power amplifier has two types, 4Ω and 8Ω, which can be connected to 4Ω speakers or 8Ω speakers. When connected to a 4Ω speaker, the output power of the power amplifier is greater than that of 8Ω. Two 8Ω speakers can be connected in parallel to the output end of the power amplifier, which is a 4Ω working condition.

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