Multiplex input signals are amplified, mixed, processed and distributed, and sound quality modification and sound effect processing are carried out. It is an important equipment for playing and recording in modern radio broadcasting, stage ballroom sound reinforcement and sound program production.
The mixer can receive multiple input sound source signals with different impedances and levels, amplify and process these signals, and then mix, redistribute or recombine the signals according to different volumes, thus producing one or more outputs. Through the mixer, you can also monitor various input signals.
When dry goods arrive, the main functions of the mixer must include:
1. Signal amplification
In the mixer, input signal sources (microphone, tape recorder, CD player, tuner, electronic musical instrument, etc. ) it's all enlarged. Because their levels are different, for example, the signal of the microphone is a few mV to 200 mV, while the signal of the CD player can reach 1000mV, which requires the mixer to amplify various signals with different sizes to different degrees, so that the amplitudes of various signals are finally similar to facilitate the follow-up.
At the same time, in order to adapt to the different levels of the input signal, the input end of the mixer is usually equipped with high-level and low-level sockets. The former mainly receives large signals output by tape recorders, CD players and tuners, and of course can also receive strong signals returned by reverberation devices. The latter receives a weak signal from the microphone for full amplification, and the gain of the amplifier can be adjusted and controlled.
2. Signal processing
The most basic signal processing of mixer is frequency equalization processing. Each input channel is equipped with a frequency equalizer (EQ) to enhance or attenuate different frequency components of the sound according to the requirements of the program content, thus beautifying the timbre of the sound source.
In addition, frequency adjustment can make up for the "defects" of sound and improve the quality of audio signals, thus achieving the basic requirements of frequency balance. In modern audio equipment, multi-band frequency equalization equipment is also specially equipped.
In addition, the mixer also controls the volume of each input channel signal to achieve volume balance; There is a filter in the input channel to eliminate some noise in the program signal; The audio signal is processed by delayed reverberation to make it have a certain reverberation effect.
A "compression/limiter" is set to compress or limit the dynamic range of the audio signal, so as to reduce the relative variation range between the maximum level and the minimum level of the signal, thereby reducing distortion and noise. Modern audio equipment also has special effects processor, auditory exciter, compression/limiter, expander and other equipment to choose from.
3. Signal mixing
The mixer has multiple input channels or ports, such as microphone input connected with wired microphone, line input connected with active sound source equipment, breakpoint insertion connected with signal processing equipment, signal holding, etc.
Finally, there may be only one or two main signals output by the mixer, which requires the mixer to mix the input signals of these ports into one or two signals according to a certain proportion after technical and artistic processing. Therefore, signal mixing is the most basic function of mixer. In this sense, the mixer is also a "mixer".
4. Signal distribution
The mixer not only has multiple inputs, but also has multiple output channels or ports. In addition to mono output and stereo main output, there are monitoring, auxiliary and grouping output. Therefore, the mixer should allocate the mixed input signal to each output channel according to different requirements.
For example, it is necessary to apply reverberation effect to the sound of a certain road, so besides sending the sound of passers-by to the main output, it is also necessary to take out (distribute) some signals from this road and feed them into the auxiliary output channel connected to the reverberator. After the speech is processed by the reverberator, it is sent back to the mixer and mixed with the main output of the mixer to hear the reverberation effect.
The sound image localization of stereo mixer is another typical application example of signal distribution. It uses the audio-visual potentiometer on the input channel of the mixer to adjust the signal distribution ratio in the left and right channels of stereo output, so as to obtain different signal strengths and realize audio-visual positioning control.
It can be seen that the mixer is essentially a matrix, and it also has auxiliary functions such as monitoring, display, grouping, remote control and intercom. The mixer can independently monitor each input signal or output signal, and can also selectively monitor mixed signals, providing a basis for system tuning;
The mixer is equipped with a volume meter or a digital light-emitting diode indicating light beam, which is used to indicate the strength of various signal levels, so that Andhadhun can intuitively detect the signal levels while monitoring, thus judging whether all components in the mixer work normally;
There is also a special communication microphone interface on the mixer, which can connect a mobile microphone for audio operators to talk with performers. When the intercom switch on the mixer is turned on, other microphones are connected from the program transmission system to the communication intercom system.