There is a common problem of equipment interconnection in the audio system. If the connection is improper, the system index will drop, resulting in noise, and even cause the equipment to not work properly in severe cases. When connecting, do the following:

1. Impedance matching: In the audio system, almost all devices adopt the jumper connection method, that is, the output impedance of the device is designed to be small, and the input impedance is 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, which requires high-quality transmission of the signal, and the change of the load basically does not affect the quality of the signal. 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 equipment is interconnected by jumper connection, which is the impedance matching of audio equipment. When designing a sound reinforcement system, it is generally not necessary to consider impedance issues. However, when the output end of one device needs to be connected to multiple devices, that is, when one signal source drives several loads, an active or passive audio source signal distributor must be used to meet the impedance matching requirements of the device (if it is two devices, Generally, it can be directly and at the output of the pre-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 is 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 larger than that of 8Ω. Two 8Ω speakers can be connected in parallel at the output of the power amplifier, and are in a 4Ω working state. It must be noted that when the speakers are connected in parallel, the impedance will be reduced, and the parallel equivalent impedance should not be less than the nominal minimum output impedance of the power amplifier, otherwise the amplifier will be overloaded and cannot work normally. When using a 4Ω load impedance, the required transmission line impedance is twice as low as 8Ω. In a high-quality audio system, the transmission impedance at 4Ω output should not exceed 0.2Ω (excluding the internal resistance of the amplifier). If the transmission is less than 100m, the cross-section is required to be no less than 9mm2. To reduce its cross-section, it is necessary to replace the 4Ω output with an 8Ω output, and the cross-sectional area of the cable can be halved. It is also required that the contact resistance at both ends of the transmission line be small. When preparing the audio system for a performance, it was found that the noise was too loud. The connectors at both ends of the transmission line were replaced with better gold-plated connectors, and the noise was significantly reduced.

2. Level matching: When the audio equipment is interconnected, the level matching is equally important. If the matching is not good, either the excitation will be insufficient, or the overload will cause serious distortion, which will make the system not work properly. To achieve level matching, it is not only necessary to match under the rated signal signal state, but also not overload when the signal has a peak. A high-quality system crest factor should be considered at least 10dB. Modern audio equipment is designed according to the standard, only need to pay attention to the equipment selection and system tuning to meet the level matching requirements.

3. Balanced and unbalanced: Audio equipment usually has two connection methods: balanced and unbalanced. When there is common mode interference, since the interference signals received on the two balanced terminals have similar values and opposite polarities, the interference signals can cancel each other on the balanced transmission load. Therefore, the balanced circuit has better anti-interference ability. In important performances, try to use balanced input and output.