The interference in the home listening environment is generally not very serious. Because there is no braking of large-capacity electromechanical equipment on the same line, there is no large anti-electrode impulse of the inductive component. The most common interference is electrical interference such as the 1KW air conditioner and the hundreds of watts of refrigerators on the same line and the flashing of the fluorescent lamps. Of course, these interferences can make the listening device unusable when the situation is particularly serious. In addition, sound interference, radio interference, etc. will affect the listening effect.
1. Power interference
The above-mentioned air conditioner, refrigerator, fluorescent lamp opening and closing circuit forms a spike on the power line, which enters the rectified power source through the power transformer of the audio device, affecting the operation of the audio device, thereby generating acoustic interference, for this kind The interference phenomenon must be overcome by the following measures:
(1) Insert an anti-jamming network at the input end of the sound to filter out the back-potential interference during braking.
(2) When possible, use an independent power line, and the audio equipment is connected to the home network using a small-capacity voltage regulator.
(3) The isolation transformer is used to filter the high-frequency interference by the leakage magnetic reactance to reduce its influence.
(4) The method of separately supplying power by the acoustic power amplifying unit to reduce the influence of the instantaneous load of the power amplifier on the preamplifier.
(5) When the power amplifier unit is powered separately, pay attention to the grounding wire of the circuit such as the phono head, the card holder, the CD player, the intermediate frequency balance circuit, and the reverberator, which cannot be mixed with the power amplifier. After their grounding wires are put together, they are connected to the power amplifier unit.
2. Radio interference
Ordinary rooms are usually surrounded by electromagnetic fields. The high-frequency magnetic field flashing by the fluorescent lamp, the radiation of the welding machine around the village, and the high-frequency electric field such as wireless communication will affect the sound reception. The high-frequency induction at the connection cable or the joint will also cause interference. In order to reduce these interferences, it is necessary to reduce the interference. Take the following measures:
(1) Shield the audio equipment. The cables of fluorescent lamps, air conditioners, and refrigerators are twisted and routed so that their electromagnetic induction cancels each other or minimizes the influence.
(2) The power cord of electrical equipment is laid with an electrician pipe.
(3) The connecting line between the audio equipment should be grounded in addition to the shielding.
(4) Audio and video cables should be as far away as possible from lighting wires or other power cables without shielding.
3. Audio interference
In the audio pickup and karaoke singing, the audio in the listening room or the external audio will affect the listening effect, and measures should be taken to avoid the sound source interference.
4. Method of forming and eliminating noise
The noise in the sound amplification process can be divided into white noise, pop sound, hum, and induction sound. These noises are deeply unpleasant to the listener. Therefore, in addition to using various noise reductions and blanking circuits, other measures must be taken to eliminate them. The method is as follows:
(1) White noise is an irregular continuous rustling sound. This is the thermal noise generated by the original device. Only when the original is found and replaced, the problem can be solved.
(2) The popping sound is a kind of intermittent slap sound. This is caused by circuit flashover, capacitor leakage, and poor soldering. Therefore, it must be searched step by step to eliminate such failures.
(3) The hum is a low-pitched humming sound, which is caused by poor power supply filtering. Therefore, it is necessary to strengthen the filtering, re-adjust the grounding arrangement and use the decoupling filter, so as to effectively solve the problem. .
(4) Inductive noise is a harsh humming sound that comes from electromagnetic induction inside the machine or electromagnetic induction due to poor shielding of the input preamplifier. The solution is to shield the input lines of the preamplifier stage and the pickup head, and to isolate the magnetic ring electromagnetic field of the switching power supply from the preamplifier as much as possible.
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