When it comes to sound system, of course, we will think of mixer first, and there will be many descriptions about mixer. The most appropriate method is to compare the mixer to the heart of the sound system. The blood circulation of this heart directly affects the performance of the whole system. Figuratively speaking, the mixer is like a large water treatment pool. We input all kinds of sound source signals into this big pool like running water, then treat the incoming water reasonably in the pool, and finally flow out from various channels. The whole process is as simple as that. So the connection with the mixer is nothing more than two parts: input and output.
(1) Line connection of the input part of the mixer:
The input signals of the mixer can be roughly divided into two types: low-resistance microphone signal input and high-resistance line signal input. In fact, we can regard the difference between low resistance and high resistance as the difference of water pressure or water flow speed. For example, the input level of high resistance is high, just as the water pressure is high and the water flow is urgent, so it is appropriate to directly input it into the pool of the mixer, and there is no need to add any link in the middle to adjust the water pressure and water flow speed; However, the level of low resistance input is low, just as the water pressure is very low and the water flow is very slow, so it is not appropriate to directly input it into the pool of the mixer. We need to add a water pump to the large pool, increase low resistance and low water pressure to speed up the water flow! Therefore, a special circuit amplifier is built in the low-resistance input channel line of the mixer to amplify the low level to an appropriate level. It should be well understood that the characteristics of water are used to describe low resistance signals and high resistance signals.
Only after distinguishing between high resistance and low resistance can the correct wire be selected for the corresponding connection. Generally speaking, the input sockets of the mixer can be basically divided into three types:
1, TRS: The high impedance input part usually uses the 6.35cm TRS stereo connector for balanced input, and the 6.35 TS single tone (sound) connector should not be used for unbalanced input. However, the output signals of most audio playback devices we use now, such as CD, VCD, DVD, MD, MP3 and most musical instruments, are usually high impedance signals.
2.XLR:XLR cannon connector is usually used as a balanced input with low resistance. At present, most wired microphones are usually connected to the mixer with low resistance sockets.
3.RCA: If there is a mixer with recording input, it is generally connected with RCA Lotus connector.
Problems needing attention in the signal input part of mixer: As mentioned above, the input signal of mixer can be roughly divided into low resistance input and high resistance input, but how to accurately define whether a signal belongs to low resistance or high resistance requires flexibility. For example, according to the standard, electronic organ, electric bass, electric guitar and so on. It is a high impedance signal and can only be input into the mixer with a 6.35 plug. But in some places, the connecting line from the stage to the mixer is too long and the line resistance is large. Coupled with the interference of lighting and other systems, the background noise of this signal line is already very large. Even if there is no sound source signal input, there will be a lot of background noise when the gain of this line input channel is increased on the mixer. As mentioned above, this line is a river, and now there is too much sediment in this river. At this time, a lot of noise on this line remains unchanged, and the volume of the instruments on the other side of the line has been adjusted to the maximum, which means you can only put so much water into the river. What should I do? If a high impedance signal is input, it means that the water in the river has not increased, the water quality can not be changed, and the sound quality can certainly not be changed; If the signal is input from a low-resistance socket with a gun plug, a little shallow water in the river will be amplified by a low-resistance amplifier, so that the water depth is deeper, the water quality is better and the sound quality is better. It doesn't seem true. You can try. Many projects I am doing now, the band basically uses cannon sockets to input from low resistance. Although it looks irregular on the surface, it is actually a helpless move to reduce the noise of the band. Therefore, we should be flexible and find the best working method in practice.
(2) Connection of mixer output circuit:
At present, there are many sockets in the output part of professional mixer, and each has its own division of labor, unlike the input part, although there are many sockets, it is relatively simple. Therefore, be careful when connecting the output signal. Usually, the main output parts of the mixer still refer to total volume output, grouped volume output and auxiliary output. Generally speaking, the output part of the mixer can be divided into six parts according to the function:
1. Grouped output: If we control the volume of the woofers individually by grouping the woofers into 1-2, then we can only output audio signals from the corresponding output jack of the mixer 1-2. Most of the output ports of grouped output use TRS stereo sockets for balanced output, and of course some use Cannon sockets.
2. Main channel output: The L-R main channel usually adopts XLR Cannon balanced output, and some small mixers are also replaced by TRS stereo jacks.
3. Auxiliary output: The auxiliary output in the mixer is most commonly used to output to the voice effect device, followed by providing monitoring signals for bands or singers. Of course, it also has other uses, such as recording, as an auxiliary speaker signal. AUX usually uses TRS stereo jack to output signals.
4. Direct output part: The professional mixer also has a "direct output" socket in each input channel, which can be provided to other devices for recording and monitoring. Each channel of the mixer usually uses TRS stereo socket to output signals. For example, if there are 20 audio signals, we can input them into the mixer of the TV station first, and then use the Direct output jack in the mixer of the TV station to input them into the mixer of the live performance. Now, of course, for the sake of safety, these 20 sound source signals are adjusted and distributed through the signal amplification distributor, and then sent to the TV station mixer, live performance mixer, standby emergency mixer, recording mixer or other equipment respectively.
5. Recording output: RCA Lotus connectors are mostly used for general analog recording output signal sockets. If it is a digital signal, other digital output modes such as optical fiber and firewire can be used.
6.INS plug-in socket: this socket in the mixer is connected between input and output through TRS stereo connector. Many sound engineers may not know how to insert ins. They can plug peripheral devices into the input channel, grouping channel or main channel (left channel and right channel) of the mixer, and independently process the sound signals of the inserted channels. When using, use TRS big three-core stereo connector to connect. The method is to output a signal from the head end of TRS big three-core stereo plug and connect it to the input end of the equipment to be inserted, and then send a signal from the output end of this equipment to the ring end of TRS big three-core stereo plug, and then flow into the mixer. For example, we can use this method to insert an equalizer into the microphones 1 and 2 of the mixer, which is equivalent to cutting off the water pipes of the microphones 1 and 2, adding a water processor (equalizer) and then inputting it into the mixer, so that the timbre adjustment effect is better.
The above is the connection of the mixer. Whether it is the input part or the output part of the mixer, the sockets and signal connection methods used are basically these kinds, but attention should be paid to the correctness when connecting.