1、 Judgment and sentence of humming in conference audio system.

The hum is often caused by poor grounding or improper grounding of the system equipment which is not on the same power grid, serious difference in ground potential, and the current loop formed by desoldering of the connected shielding layer or improper grounding of the shielding wire. Therefore, it is necessary to focus on these aspects and add audio transformer for isolation when necessary, so as to disconnect the "ground" between the front and rear equipment while the signal is still unblocked. Especially when two systems are connected, the ground potential between the two systems is often different due to the fact that the two systems do not use the same power supply, sometimes even very serious, resulting in obvious humming. For this reason, it is very easy to judge that as long as the signal wire plug between two systems is unplugged from one system, the hum will disappear immediately. If the hum is confirmed to be caused by the different ground potentials of the two system power supplies, the method of isolating the "ground" of the two systems can be adopted. Usually, the isolation audio transformer is used to achieve the technical requirements for the isolation audio transformer:

① The ratio of the number of turns of the wire with eye size for the primary and secondary windings is 1:1

② Both input impedance and output impedance are 600 Ω

③ Harmonic distortion is not more than 10%

④ Frequency response is better than ± 0.5dB in the range of 40Hz-16kHz

⑤ The power should preferably not be less than 100mW

2、 Judgment and elimination of clipping loss in conference audio system

First, check whether the clipping indicator on each device is on. If the clipping indicator is not found to be on continuously, you can select a device in the middle of the system to reduce the volume by several dB to determine whether the clipping distortion is present in front of the device or just behind the device. In this way, you can determine which level the clipping comes from after several adjustments to the volume controller. Generally speaking, if it is true that the signal is too strong to cause clipping, the volume level should be lowered on the previous level equipment. In case of equipment failure (such as abnormal working power supply in the equipment or negative feedback Tonglu open circuit, etc.), the equipment must be replaced.

3、 Judgment and elimination of low voice in conference audio system

Under the condition that the operation of each equipment conforms to the specifications, the low sound often causes problems in the connection lines. If the connection is short, the plug and socket are poorly matched, and the connection is faulty, suspect the equipment after determining that there is no problem with the connecting line, check which equipment has failed, and then replace the equipment. If the sound is low and the sound field is seriously uneven, consider whether the phase of the loudspeaker is connected incorrectly.