Failure of conference audio equipment

When the conference system audio equipment problems, what should be done? Now, the small edition for you to briefly introduce, conference audio equipment in the event of a fault, how to distinguish and clean up.

Discrimination and elimination of voiceless sound problems in conference system

1. Check whether all the equipment is open, whether the volume control button of each equipment has been adjusted to the appropriate position, whether the channel channel switch on the mixer has been turned on, and whether the connection lines have been connected correctly and reliably.

2. If it is still silent, it should be checked step by step. It can be checked step by step from the back to the front or from the back in the early years. In the early years of backward inspection, the first thing is to use the earphone to check whether the signal has entered the mixer, and then can be used voltmeter, multimeter step by step to check, until the detection of a silent level and to determine whether the equipment has no output, is still a problem in connection. If the equipment is defective, it should replace the spare equipment to rescue the emergency; if the peripheral equipment appears defective, in the absence of spare equipment, the peripheral equipment will be able to skip the defective directly. For example, if the equalizer is faulty, the input line plug from the input to the equalizer can be pulled out and added to the input socket of the latter level equipment; if one of the input channels of the mixer is faulty, the input channel can be changed all the way until the activity is finished and then the equipment can be replaced; if the connection line is faulty, the input socket can be changed first in case of emergency. Spare lines, and then repair equipment and connection lines when available. As for equipment, if you are not familiar with the internal structure and principle of the equipment, do not simply start to repair, to avoid minor hair lesions into major problems when using a capacitive microphone, you should also check whether the phantom power is added.

Two. Discrimination and elimination of hum in conference sound system.

Humming is often due to poor grounding or incorrect, the system equipment is not in the same power grid, ground potential caused by severe difference, and the connection of the shielding layer off welding or shielding wire is not connected correctly to form a ground current loop, will also cause humming. Therefore, we should focus on these aspects, if necessary, should block the use of audio transformers, so that the front and rear equipment between the "ground" disconnection, and the signal is still dredged. Especially when the two systems are connected, the ground potential between the two systems is often different, sometimes even very severe, because the two systems do not use the same power supply, and then there is a significant hum. The reason for this is very simple to distinguish, as long as the connection between the two systems between the signal line plug off from a system, the hum will disappear immediately. If it is confirmed that the hum is caused by the difference in the ground potential between the two systems, the "ground" between the two systems can be blocked, usually by adding a blocking audio transformer to meet the technical requirements of the intended blocking audio transformer:

(1) the one or two winding is made of the same standard wire, and the number of turns is 1:1.

2. The impedance and output impedance of the input are both 600 ohms.

(3) the harmonic distortion is not greater than 10%.

(4) frequency response is better than 0. 5dB in 40Hz~16kHz range.

The best power is not less than 100mW.

Three. Discrimination and elimination of chopping and abandoning in conference sound system

The first step is to check whether the clipping indicator is on or not. If the clipping indicator is not on one after the other, it is possible to select a central device to reduce the volume by several dB. After adjusting the volume controller several times, you can tell which level the clipping comes from. Generally speaking, if the clipping is caused by the strong signal, the volume level should be lowered on the front-end equipment. If the equipment is defective (such as abnormal operation power supply in the equipment or open circuit of negative feedback channel, etc.), the equipment must be replaced.

Four. Discrimination and elimination of noise in conference sound system.

When the operation of each device is in line with the standard, the problem of noise is often the most common problem. If the connection line is short-circuited, the plug and socket are not well matched, the connection virtual welding and so on, after judging that the connection line is no problem, then suspect the equipment, check that the equipment has a fault, and then replace the equipment. If the noise is small and the acoustic field is severe and uneven, the phase of the loudspeaker should be taken into consideration.

Five. Disturbing noise in conference sound system

Sometimes the sound of radio stations and other disturbing sounds can be heard in some area's sound reinforcement system. For example, the disturbing sound from radar, high frequency heat exchanger and electric welding machine is called noise. Sometimes when a sound reinforcement system is installed, the announcement of interstitial murmur in the speaker can be heard during debugging, and even the sound of broadcasting station can be heard. These sounds are often due to the strong (modulated) high frequency electromagnetic waves in space. The high frequency inductive electromotive force (EMF) occurs when the sound reinforcement system accepts these modulated high frequency electromagnetic fields. The high frequency signal is then demodulated by a circuit consisting of non-linear components such as crystal diodes, crystal triodes, field effect transistors, integrated circuits, etc. in an amplifying system. The audio modulation signal parasitic in the high frequency signal is demodulated. Here is the high frequency signal phase. When the modulated carrier signal, and the audio signal parasitic in these high-frequency signals is equivalent to the modulated wave signal, if our sound amplification system planning is not in place, it is possible to radio high-frequency scrambling signal through the connecting line more accepted, and then because of the non-linearity of the amplifier circuit, these will be. High-frequency radio signals are demodulated, then sensible audio scrambling signals occur, and finally broadcast in the loudspeaker system.

The first way to solve this problem is to choose a balanced connection in the system planning. All audio lines to the power amplifier input end should be selected with excellent shielding function, and the length of the connection line should not be too long, outstanding grounding. When all these methods are in place, and when the disturbance signal is presented, it should be considered to participate in the RF filter. Now many peripheral devices have RF filter circuit at the signal input end, which can press the RF signal, but the mixer and other equipment have no RF filter circuit at the input end. Considering that the lowest carrier frequency of the FM wave is 535 kHz, it is advocated that the - 3dB frequency of the RF low pass filter should be 400 kHz, which is 20 times higher than the highest frequency of the audio, and will not affect the transmission of the audio signal. Of course, it is not enough to lower the frequency than 40 kHz, but at least 200 kHz. RC can be used to form resistance-capacitance low-pass filter, LC can also be used to form a filter, the low-pass filter connected to the input of the mixer, especially the small signal source and the mixer connected to the input.