How to quickly and efficiently eliminate the noise in the professional sound audio system?

As we all know, in speaker sound systems such as stage performances and live sound reinforcement, the noise problem is a common and very headache problem. The noise generated by a set of sound systems is not the same. It may come from many aspects. The sound engineer should analyze and judge the more complicated situations, and deal with them separately. General noise may come from three aspects: one is the improper connection of the equipment; the other is the inherent noise of the equipment itself; the third is the interference noise of the power supply.

Tip 1: Eliminate noise caused by improper connection of equipment

In the audio system, there are widespread problems with the interconnection of equipment. If the connection is improper, the system indicators will decrease and noise will be generated. When connecting, do the following:

Impedance matching: In the line array audio system, almost all equipment adopts a jumper method, that is, the output impedance of the equipment is designed to be very 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, requiring high-quality signal transmission, and the change of the load basically does not affect the signal quality.

When the signal source is designed as a constant voltage source, or the load is much larger than the internal impedance of the signal source, the above requirements can be met. In fact, the impedance of professional audio equipment is designed according to the above principles, and the device interconnection adopts a jumper method, which is the impedance matching of audio equipment.

When designing a sound reinforcement system, there is generally no need to consider impedance. But 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 used to meet the requirements of device impedance matching (if there are two devices, Generally, it can be directly connected to the output terminal of the previous equipment).

The power amplifier and the speaker are connected according to the nominal output impedance and the input impedance of the speaker. 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 4Ω working state.

Tip 2: Eliminate the inherent noise of the device itself

The audio system is composed of multiple devices, such as microphones, DVD decks, mixers, effects, equalizers, compressors, exciters, electronic crossovers, power amplifiers, speakers, etc. Each device has It may be the source of noise. In order to discover and determine which unit the noise is generated from, it is necessary to detect the inherent noise of each unit.

Turn on the audio system: the boot sequence is step by step in the order of the signal flow. After turning on, there is noise from the speaker. First of all, 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 produced by the wireless microphone receiver: if there is still noise, it proves that the noise is not produced by the wireless microphone receiver. You can check other units.

Secret Three: Eliminate the interference noise of the power supply

Noise interference of light thyristor: On the stage, the most interference from power supply noise is the noise from light thyristor, because the brightness and intensity of the lights in theaters and dance halls are not changed 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 sinusoidal waveform in the power supply is changed into a sawtooth-like shape, and obvious 50Hz ripples are generated in the power supply. When it is manifested in the sound system, obvious noise appears. In order to eliminate the interference noise of the thyristor, the most effective way is to provide two phases of the three-phase power supply for light use, and use the other phase as a dedicated audio system. In this way, the interference of the light SCR can be avoided.