One of the most important equipment in the entire sound amplification system of the mixing console is the command center of the audio system. It has multiple input channels (up to 60), which can simultaneously input signals from multiple audio equipment and control the level of each signal; Mix in proportion; Adjust and process the timbre of each channel's signal; Provide output signals for different purposes at line level, such as recording output, sound amplification output, monitoring, etc; There are many types of mixing consoles that display the levels of various signals, and can be divided into two categories according to their purposes: recording and production mixing consoles and performance mixing consoles. The recording and mixing console is one of the most important equipment in the entire sound reinforcement system, serving as the command center for the audio system. It has multiple input channels (up to 60), which can simultaneously input signals from multiple audio equipment and control the level of each signal; Mix in proportion; Adjust and process the timbre of each channel's signal; Provide output signals for different purposes at line level, such as recording output, sound amplification output, monitoring, etc; Display the levels of various signals, etc.
There are many types of mixing consoles, which can be divided into two categories according to their purposes: recording and production mixing consoles and performance mixing consoles. The technical specifications of the mixing console used for recording production are high, requiring it to have good noise reduction effect, large dynamic range, and strong output interface flexibility. At present, newer digital recording and mixing consoles are also used in some recording occasions, which realize the remote control and automatic control functions of the timing console.
The technical specifications of the functional mixing console are high, requiring it to have good noise reduction effect, large dynamic range, and strong output interface flexibility. At present, newer digital recording and mixing consoles are also used in some recording occasions, which realize the remote control and automatic control functions of the timing console.
(1) Channel input control section
Channel input is an important component of a mixing console, and the number of input signals can generally be divided into several to dozens according to different usage requirements. Although mixing consoles have a wide range of functions, the basic working principles of each one are generally similar. They all consist of input parts, signal gain control, frequency equalization, and signal level control.
There are both high impedance (Hi Z Line In) and low impedance (Lo Z Bal In) interfaces through the input section. The high impedance input interface is mainly used to input devices with high output levels, such as music synthesizers, effect processors, etc. The low impedance interface is mainly used for inputting microphone signals. There is also a line/microphone (Lne/MIC) conversion switch in the input of the mixing console to select the input of one of the different signals.
If there is no such switch in some mixing consoles, the microphone is usually directly plugged into the high impedance input interface, and the machine will automatically disconnect the low impedance input interface. The phantom power supply in the signal input section can provide a working voltage of 48V, which is used to supply devices such as condenser microphones that require external working voltage.
Attention should be paid to the matching of impedance and voltage levels between the interfaces of the mixing console and the connections between various devices. To achieve optimal impedance matching, the input impedance of the mixing console should be about 5 times greater than the output impedance of the signal source. If the general signal source equipment has balanced output, it can be connected to the mixing console in a balanced manner. If the signal source equipment has unbalanced output, it can be connected to the mixing console in an unbalanced manner.
After the input signal enters the mixing console, the first step is to control the level. Due to the varying levels of signals input to the mixing console by various devices, it is necessary to control the signal levels in order to match the mixing console. If it is a high-level signal input, after control, the maximum peak value of the signal should not exceed the dynamic range of the mixing console to avoid clipping distortion. If it is a low-level signal input, after control, increase the amplitude of the signal level to avoid generating significant noise. Therefore, gain control systems (Gain) are installed in the mixing console, and by adjusting the knob, the signal source signal can be selected between 60~-20dB. For example, the level gain of a low-level microphone is -60~-50dB, the level gain of an electronic musical instrument is -35dB, and the general instrument gain generally needs to be used in conjunction with the peak and limit indicator lights when controlling usage. When the voltage level of the material transmission line is -20dB
When the input audio signal is overloaded, the peak indicator light will light up 3dB before the occurrence of clipping distortion to remind the tuner to adjust the Gain knob appropriately to reduce the gain of the input signal. In the actual tuning process, if the input signal level needs to be at the maximum level, adjust the Gain knob. If the peak indicator light is lit when the signal peak appears, it is normal, indicating that the gain control is in a better position.
On some mixing consoles, limit indicator lights are used instead of peak indicator lights. If this light is on during operation, it indicates that the input signal overload has reached its limit. The Gain knob should be adjusted immediately to reduce the gain of the input signal. Therefore, during normal operation of the mixing console, the limit indicator light should remain off at all times.
There is also an equalizer (EQ) in the channel input section of the mixing console, which is used for frequency equalization of the input signal to make the reproduced sound more perfect. Due to the single channel control of the input channel, the mixing console can perform frequency equalization on each signal without interfering with each other. Generally, there are 2-4 equalizer stages in the mixing console, with the most common being a 3-stage equalizer, which can adjust the high-frequency (High) 10kHz, intermediate frequency (Md) 350Hz~5kHz, and low-frequency (Low) 100Hz respectively.
When adjusting the equalizer, attention should be paid to:
High frequency mainly reflects the brightness and clarity of sound, but if the gain of high frequency is adjusted too much, it will produce metallic sound, which is relatively sharp. If the high-frequency gain is adjusted too small, it will reduce the resolution (transparency) of the sound.
Mid frequency represents the intensity of sound, and the performance of human voice mainly relies on mid frequency. If the gain of the intermediate frequency is adjusted too much, it will make the sound harder. If the gain adjustment of the intermediate frequency is too small, it will make the sound too thin.
Low frequency mainly reflects the contour of sound, the richness and richness of sound, and the degree of mixing. The low-frequency range of sound is mainly represented by low frequency. If the low-frequency gain is adjusted too much, the sound will become thick and the clarity will decrease. If the low-frequency gain is adjusted to be small,