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How to avoid hum when the audio equipment is connected?

2020-06-23
1. The shell of a properly grounded audio device is generally connected to the power transformer shield of the device. This device shell also has a "ground", which is also different from the other two "grounds". When the "earth" of the earth is relatively disturbing, the "earth" of the device casing can be connected to it to reduce hum interference, otherwise, do not connect it;

2. The power supply of weak signal equipment and the power supply of strong signal equipment are grouped and connected to the weak signal sound source equipment such as CD, deck, effector, mixer, compression limiter and equalizer. The strong signal power amplifier is connected to another Group power connection can avoid the AC noise interference of the conduction mode;

3. Separate the signal ground between two audio equipments with different “ground” potentials to avoid direct connection of the equipment or the formation of ground loops. For example, the externally shielded cable with balanced connection is only grounded at one end, or not at both ends.

4. When designing a clean power supply, a separate power transformer should be designed; when unconditional, an independent set of power supplies can be used to supply power separately from air conditioning, lighting and other equipment; or an isolated power transformer, etc., these are all effective. Measures

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

6. There must be no DC circuit connection between the two audio equipment;

7. The connection of different systems must use a balanced isolation transformer to connect the audio system to the audio system of the TV OB truck; the connection of the system to a large electronic display screen; or the connection to the electronic computer, etc., generally a balanced isolation transformer is required. The common ground of different systems is most likely to cause AC noise interference;

8. The long-distance transmission signal uses the balanced or balanced isolation transformer transmission method, and the short-distance can use the unbalanced type. The transmission method using a balanced isolation transformer generally requires a balanced transformer at both ends, and the shielding layer is grounded at one end or left unconnected. Grounding can play a shielding role, and can also prevent electric shocks caused by equipment leakage. When not grounded, the balance transformers at both ends can play the role of insulation isolation, and the center of the balance transformer is grounded to discharge static electricity;

9. In the case of very serious power supply interference, the equipment is connected in phases to connect the small signal audio equipment and the monitoring equipment power supply, select the one phase of the three-phase power supply with the least hum interference, and the other two phases are connected to the large signal Power amplifier, can reduce the AC noise interference from the power supply;

10. Check if your power supply is not clean;

11. Is it the grounding problem of some equipment?

12. The other thing is to see that there is no interference between the device connections (it is very messy / whether the interface is not soldered);

13. See if it is disturbed by lights (silicon box, signal line):

14. It is usually the problem of the power amplifier if the sound of the sound is relatively loud. If the signal-to-noise ratio of the power amplifier is not very good, it will make a loud noise. First check whether it is the problem of the signal line. Just unplug all the signal lines and turn on the power amplifier. If there is no very loud AC sound in the speaker, it is the problem of the signal line. First, see if the plug has a short circuit and touches the line (take Multimeter measurement is more accurate), if necessary, re-weld the plug. If this does not work, then you have to replace the signal cable. There is still a very loud hum when unplugging the signal cable. That's the problem of the power amplifier. It shows that the power amplifier is relatively poor. To solve this problem, only a good power amplifier can be used.