How to avoid "AC sound" when connecting audio equipment

　　1. The enclosure of reasonably grounded audio equipment is generally connected with the power transformer shield of the equipment. The enclosure of this equipment also has a "ground", which is different from the other two "grounds". When the "ground" of the ground is interfered, the "ground" of the equipment shell can be connected to it to reduce the AC acoustic interference, otherwise, it should not be connected.

　　2. The power supply of weak signal equipment and the power supply of strong signal equipment are connected in groups. The weak signal sound source equipment, such as CD, card holder, effector, mixer, compression limiter and equalizer, are connected with one group of power supplies. The strong signal power amplifier is connected with another group of power supplies, which can avoid the AC noise interference of the power source in the conduction mode.

　　3. Separate the signal ground wires between two audio equipment with different "ground" potentials to avoid direct connection of equipment or formation of ground loop. For example, the external shield wire of balanced connection is grounded at one end only, or both ends are not grounded.

　　4. When connecting clean power supply to power supply, separate power transformer shall be designed; An independent group of power supply can be used to supply power when there is no condition, which is separated from air conditioning, lighting and other equipment; Or the use of isolated power transformers, these are effective measures.

　　5. The use of floating grounding means that the point potential is the same as the ground, which is zero potential. But this point is not directly connected with the ground. It is the point where the potential of audio equipment circuit to ground is zero. There is an impedance between the "ground" and the actual ground, and it is high impedance, which can overcome common mode interference.

　　6. There shall be no DC circuit connection between two audio equipment.

　　7. The connection of different systems must use balanced isolation transformer to connect the audio system with the audio system of the TV relay vehicle; Connection between the system and large electronic display screen; Or the connection with the electronic computer shall be connected with the balanced isolation transformer. The common ground of different systems is the most likely to cause AC noise interference.

　　8. Balanced or balanced isolation transformer transmission mode is used for long-distance transmission signal, and unbalanced transmission mode can be used for short distance transmission. The transmission mode using balanced isolation transformer generally requires a balanced transformer at both ends. One end of the shielding layer is grounded, or it can be suspended in the air. Grounding can play a shielding role and also prevent electric shock accidents caused by equipment leakage. When not grounded, the balance transformer at both ends can act as insulation and isolation, and the center of the balance transformer is grounded to discharge static electricity.

　　9. In case of serious power interference, the equipment shall be connected in separate phases to connect the audio equipment with small signal and the power supply of monitoring equipment. The phase with the least AC acoustic interference among the three-phase power supplies shall be connected, and the other two phases shall be connected to the large signal power amplifier to reduce the AC noise interference from the power supply.

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