Tuning beginners must: mixer knowledge (MIXER)
The mixing console is divided into two types: recording studio and stage ballroom.
The role of the mixer is: 
1. Pick up the signal and stop zooming in;
2. Stop the pitch balance of high, medium and low sound as required;
3. Send the signal to the left and right busbars as needed or stop the group control;
4. Stop the art disposal of the signal sent to the auxiliary bus; 
5. Stop output control as requested. 
The mixer can be divided into an input unit and an output unit. 
The input unit input unit is an important component of the mixer. The input unit is a shunt parallel line. Each path is roughly the same. It can be divided into the following parts.  A. Input selection local 1.TAPE: tape 
2.MIC: Microphone
3.LINE: Line 
B. Input attenuator (PAD)
If the level of the microphone or line input signal is too high and the gain control cannot be adjusted, turn the attenuation switch open. A 20dB attenuator is inserted between the preamplifier and the input socket to prevent overload. 
C. Input Gain Control (GAIN)
The sound source of the mixer is: microphone, musical instrument, tape, effect, sound reinforcement equipment, etc. Since their output levels are different, in order to match them, the gain control is applied to the mixer to stop the adjustment of the input flexibility. If the input signal is too large, clipping distortion will occur. If the input signal is too small, the noise will be uncontrollable. Gain control is used to ensure that the mixer works within a fixed dynamic range. The representation of the gain control level on the panel is based on 0dB=775mV and is set at different positions depending on the output level of the audio source. 
The input signal and gain level are shown in the table below. 
Gain (dB) 〓 Input signal  -60 ~ -50 〓 low level microphone  -35 〓 high level microphone (capacitor), electronic musical instrument  -20 〓 low level line (normal sound). 
D. Signal input jack
Divided into low-resistance balanced input (LO-Z card) and high-resistance unbalanced input (HI-Z two core). 
Ordinary instruments and sound equipment are connected in an unbalanced manner, and one of the signals "+" and "-" is common to the shield of the signal line. For example: a core shielded wire, the core wire is the signal "+", and the shielded wire is the signal "-" and the ground wire. This is less inductive noise than the unshielded parallel line, which is an incompletely shielded type.输入The input and output of professional sound equipment are balanced. The signal is transmitted by “+†and “-â€. In addition, the shielded cable is connected. The “+†and “-†use independent ground wire, and the plug uses the XLR plug. 
E. Overload (CLIP)
The overload indication is used to signal the input signal 霎 when the signal is overloaded, and the indicator light will illuminate 3dB below the level of the peak (signal over-extension distortion level), which is convenient for assisting in setting the position of the gain switch. 
F. Input balance local 
The input channel balancer is used to stop the correction of the tone of the input signal to achieve the specification effect. Because it is single-channel control, the mixer can stop the balance control for each channel without interfering with each other. The balance is divided into: high frequency (HIGH), intermediate frequency (MID), and low frequency (LOW). 0 position is flat; + direction (gain), +15dB (enhanced 5 times); - direction (attenuation), -15dB (attenuation 5 times). Continuously adjustable. The  balancer is usually a high-pitched (10 kHz), mid-range (the center frequency of the balancer can be set freely between 350 Hz and 5 kHz), and a low-frequency (100 Hz) three-stage balancer. Because each frequency segment has independent control, it can stop the input signal to be carefully adjusted, and then make a bold attempt to make the sound color, and effectively remove unnecessary components such as howling and noise. 
1. High frequency: 10 kHz ± 15 dB / slope impact area: the higher harmonics of the instrument's high range. 
Gain effect: The metal sound is increased, the tone is sharper, the gain is too much, and the noise can be clearly heard. 
Attenuation effect: It can effectively remove the hum, and if the attenuation is too much, the transparency of the high-pitched area will be lost. 
2. Intermediate frequency: 3kHz ± 15dB / peak 
Area of ​​influence: musical instrument, the high-pitched area of ​​the human voice. 
Gain effect: The tone is bright, the texture is hard, and the gain is too much to feel tired. 
Attenuation effect: The balance of music tends to be low, including sound and the same feeling. 
IF: 1kHz ± 15dB / peak 
Area of ​​influence: instrument, the midrange of the vocals. 
Gain effect: The outline of the tone is clear, the pan is convex forward, and the drum head is adjusted.
Attenuation effect: The sound is retracted.
Intermediate frequency: 500Hz±15dB/peak influence area: instrument, middle and low range of vocals.
The gain effect; the tone is thick and powerful, and the gain is too high to present the phone tone.
Attenuation effect: The sound head is hard, the balance tends to be high, and the texture is too thin.
3. Low frequency: 100Hz ± 15dB / slope affected area: the bass area of ​​the instrument.
Gain effect: The sound is thick and the gain is too much, so the tooth sound is not clear.
Attenuation effect: Sound is easy, tooth sound is good, background noise and hum can be effectively removed.
G. The pan sound phase knob is used to adjust the left and right balance of the signal, and the position is after the channel potentiometer level adjustment. And the position of the acoustic phase between the first input group and the third to fourth groups is also determined by this knob. If the knob is in the middle, the pan position is also in the middle. Turn the knob to the left and position it in 1 or 3 groups. The knob is turned to the right and positioned in 2 or 4 groups.
H. Listening and sending (MON/SEND)
The monitor sends a level value that controls the input signal on the monitor bus. This control is not controlled by any control switches on the channel (including channel volume control) except for gain control. Thus the transmitted signal is relatively independent of the main bus signal.
I. Effect sending (EFX/SEND)
It includes all peripheral devices that are used to resolve internal effects or external effects to participate in the input signal. It is affected by the balance and volume attenuator. Since each channel has its own effect transmission, it can be adjusted to make some channels produce effects, while other channels have no effect.
However, be aware that internal and external effects share a single send control, so they should have the same sound source.
J. Pre-monitoring switch (PFL/CUE)
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