Many contractors encounter noise when they use pickups. Many situations can cause noises in the recording output, such as interference of the pickup, poor connection of the interface or the connection cable, poor quality of the pickup itself, and the like. For those, how to reduce the noise of pickups, do the following when connecting:
1. Impedance matching. In the pickup recording system, 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. And at the end of the signal level, the signal can be transmitted with high quality, and the change of the load does not substantially 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 satisfied. In fact, the input impedance of the back-end varies greatly. Some equipment rooms are 1k, some are 10k, and the other is 100k. This causes the impedance of the pickup and the back-end input device to not match.
2. Level matching. When the pickup device is connected, the level matching is also important. If the match is not good, either the incentive will be insufficient, or an overload will occur and serious distortion will occur and the system will not work properly. To achieve level matching, it is not only to match under the rated signal state, but also when the signal is spiked, no overload occurs. A good system crest factor should be considered at least 10 dB. Pickups and back-end equipment can be selected in equipment selection to meet the level matching requirements.
3. Balance and imbalance. The pickup device usually has two connection modes: balance and unbalance. When common-mode interference is present, the interference signals on the balanced terminals can cancel each other because the values ​​of the interference signals on the two balanced terminals are similar and their polarities are opposite. Therefore, the balance circuit has better anti-interference ability. The pickups are generally unbalanced transmissions. When there are particularly strong interferences, balanced transmissions need to be used.
4. Shield. The metal shell of the device should be properly grounded, and the grounding resistance should be less than 4Ω. Do not introduce interference noise due to grounding. Strong external high-frequency radio waves will also cause high-frequency wave interference to the pickup system. Especially when wireless transmission is used, external radio waves such as fire alarms and taxi call systems will interfere with the reception of wireless signals. , And produce noise. It is recommended to use wired transmission for work. If the pickup is not grounded well, it will send noise to the next level of equipment, and sometimes it will induce the sound of radio broadcasting. So grounding has a major impact on eliminating noise. There is also a certain technical requirement for this: the grounding point of the pickup should not be connected to the ground of the power supply at the same point, so as to avoid the noise of the power supply network from interfering with the recording system; the grounding wire is preferably a multi-strand textile line, and the area of ​​the welding point To be large enough, it requires good welding and avoids false welding, cold welding, and welding.
Do not use welding oil when welding. Alcohol rosin should be used. If you use welding oil, etc., you should use alcohol to clean the solder joints and nearby circuits to prevent corrosion of components and circuit boards. The shield wiring of the pickup should not be grounded at both the input and output ends to form a ground loop circuit. Grounding; Grounding requires a single point of grounding at the input, because the signal level at this point is small, and the noise level is also minimal. At this point, the ground is grounded, and the noise is short-circuited to ground and removed. If the output is grounded, the signal level is large, and the noise level is also large, so it is not easy to completely eliminate the noise.
In general, the noise problem of the pickup can not be completely avoided. Due to the limitation of the product structure, some electromagnetic interferences are bound to exist. We should pay attention to far away from the radiation source on the placement of the pickups, and do not use the pickups in over-temperature environments. . In addition, as far as possible to ensure the use of a stable place in the city, to allocate a separate socket to the pickup can also to a certain extent to avoid the emergence of current sound.
1. Impedance matching. In the pickup recording system, 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. And at the end of the signal level, the signal can be transmitted with high quality, and the change of the load does not substantially 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 satisfied. In fact, the input impedance of the back-end varies greatly. Some equipment rooms are 1k, some are 10k, and the other is 100k. This causes the impedance of the pickup and the back-end input device to not match.
2. Level matching. When the pickup device is connected, the level matching is also important. If the match is not good, either the incentive will be insufficient, or an overload will occur and serious distortion will occur and the system will not work properly. To achieve level matching, it is not only to match under the rated signal state, but also when the signal is spiked, no overload occurs. A good system crest factor should be considered at least 10 dB. Pickups and back-end equipment can be selected in equipment selection to meet the level matching requirements.
3. Balance and imbalance. The pickup device usually has two connection modes: balance and unbalance. When common-mode interference is present, the interference signals on the balanced terminals can cancel each other because the values ​​of the interference signals on the two balanced terminals are similar and their polarities are opposite. Therefore, the balance circuit has better anti-interference ability. The pickups are generally unbalanced transmissions. When there are particularly strong interferences, balanced transmissions need to be used.
4. Shield. The metal shell of the device should be properly grounded, and the grounding resistance should be less than 4Ω. Do not introduce interference noise due to grounding. Strong external high-frequency radio waves will also cause high-frequency wave interference to the pickup system. Especially when wireless transmission is used, external radio waves such as fire alarms and taxi call systems will interfere with the reception of wireless signals. , And produce noise. It is recommended to use wired transmission for work. If the pickup is not grounded well, it will send noise to the next level of equipment, and sometimes it will induce the sound of radio broadcasting. So grounding has a major impact on eliminating noise. There is also a certain technical requirement for this: the grounding point of the pickup should not be connected to the ground of the power supply at the same point, so as to avoid the noise of the power supply network from interfering with the recording system; the grounding wire is preferably a multi-strand textile line, and the area of ​​the welding point To be large enough, it requires good welding and avoids false welding, cold welding, and welding.
Do not use welding oil when welding. Alcohol rosin should be used. If you use welding oil, etc., you should use alcohol to clean the solder joints and nearby circuits to prevent corrosion of components and circuit boards. The shield wiring of the pickup should not be grounded at both the input and output ends to form a ground loop circuit. Grounding; Grounding requires a single point of grounding at the input, because the signal level at this point is small, and the noise level is also minimal. At this point, the ground is grounded, and the noise is short-circuited to ground and removed. If the output is grounded, the signal level is large, and the noise level is also large, so it is not easy to completely eliminate the noise.
In general, the noise problem of the pickup can not be completely avoided. Due to the limitation of the product structure, some electromagnetic interferences are bound to exist. We should pay attention to far away from the radiation source on the placement of the pickups, and do not use the pickups in over-temperature environments. . In addition, as far as possible to ensure the use of a stable place in the city, to allocate a separate socket to the pickup can also to a certain extent to avoid the emergence of current sound.
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