The tuner needs to know the music characteristics of each link, the frequency of the easiest feedback and the resonance point of the venue in order to control the volume of each song and balance them. In addition, we will use effects to improve the unused vocals and musical instruments, and be familiar with the functions and limitations of each piece of equipment, so as not to cause distortion and other adverse effects. The quality and reliability of the selected equipment must be ensured, and the possible failures should be prepared in advance, and effective remedial measures should be taken in time. Sometimes it is necessary to complete the preparation work a few hours before the performance. Although the time is tight, for the sake of safety, each signal line must be picked up in person to be assured. ?
This article can be read and referenced by beginners, amateur audio enthusiasts, and dance hall ringers. If there are deficiencies, please give criticism and correction. ?
First, the power amplifier (ROWER AMPLIFIER)?
Professional amplifiers need to work continuously for a long time in large-scale activities, but also withstand the vibration and impact during transportation. Therefore, compared with amplifiers for general audio, professional amplifiers pay more attention to the durability and structural reliability of long-term use in design. Amplifiers have an important influence on the sound quality of sound reinforcement, accounting for about 30% of the total sound equipment. Therefore, in order to give full play to the performance and role of audio equipment, we must pay attention to the quality of the amplifier. Otherwise, high-quality sound reinforcement systems will not work. There are three types of power amplifiers:
1? Single power amplifier;
2? Mixer + power amplifier integration;
3? Speaker + power amplifier integration. ?
Monolithic amplifier: This power amplifier is an independent component. You can combine the sound system according to your own plan. Generally, one power amplifier is composed of two channels. ?
Mixer + power amplifier integration: This power amplifier is simple to connect and easy to operate, and small and medium-sized sound reinforcement systems are often used. ?
Amplifier + speaker integration: Due to the consideration of the matching of the amplifier and the speaker, it is simple and convenient to use, and is mostly used for monitoring speakers and keyboard musical instrument speakers. When the amplifier is connected to the amplifier and the amplifier is connected to the amplifier, the impedance matching between them (impedance in ohms) must be considered. Impedance matching means that the rated output impedance of the power amplifier should be equal to the rated impedance of the speaker. The power absorbed is the largest. If the rated impedance of the speaker is much smaller than the rated output impedance of the power amplifier, it will cause a sharp increase in the operating current, which in turn will damage the speaker and the amplifier. When one channel of the power amplifier drives two speakers, the total impedance of the speakers will become smaller, and then the load impedance value of the power amplifier will become smaller, and the power amplifier will be overdriven under the condition of near short circuit. Therefore, when the amplifier is connected to the speaker, it must be noted that the input impedance value of the speaker must be within the load impedance range of the amplifier. ? Power matching: In principle, the rated output power of the power amplifier should be equal to the rated power of the speaker, but since the power amplifier tube will have serious nonlinear distortion after overload, it is usually intentional to increase the rated output power of the amplifier so that it is greater than the rated rating of the speaker power. The correct connection should be: the output power of the power amplifier is 30% greater than the nominal power of the speaker. If the power of the speaker is too small than the power of the power amplifier, you should be extra careful when using the power amplifier. The volume should be adjusted gradually from small to large, and it should not be too large, otherwise the speaker will be damaged. In actual work, the output power of the power amplifier is relatively large, which is beneficial to improve the sound quality. In addition, the dynamic range of the sound source is very large, so pay attention to the damage of the speaker caused by the momentary overload of the power amplifier. ?
The average output power refers to the power that works continuously for a long time. Peak power refers to the maximum power withstand in a short time, it is much larger than the rated power. The output of the sound reinforcement is determined by the power amplifier. A concert of a certain size must have a certain power, and the standard is one watt per person. The power will vary depending on the type of concert, the size of the venue, the reverberation, and the number of speakers. ?
Total power / output power of one power amplifier = number of required power amplifiers?
Bridge output: Bridge output is a method used for mono amplification of a stereo amplifier. It is a circuit form used to obtain a large power output, also called BTL mode. ?
The principle of the bridge connection method: A channel is used to amplify the positive half cycle signal, and B channel is used to amplify the negative half cycle signal, so that the output gets doubled power. ?
Bridge connection and specific steps: When two channels of a power amplifier work separately, the rated output power of each channel is 400W \ 4 ?, which is the ordinary stereo connection. When a larger rated power output is required (below 400W), the bridge connection method can be used:
1. Set the mode switch to the "BRIDGE" position;
2. The signal is input from channel A;
3. The power is output from the "+" terminals of the two channels, the channel A is the output "+", and the channel B is the output "-". ?
Amplifier output level display: The display is a color light-emitting diode trapezoidal group, which is used to instantly display the level height of the power amplifier. The normal level is green; when the power amplifier requires continuous high-frequency signals, the level signal is yellow; when the audio signal of the music peak or drum is played, the red LED flashes (and sometimes flashes). The above is normal. ?
If the red LED is always on, it means the power amplifier may be overloaded. This situation often occurs when multiple speakers are driven by one power amplifier, and the system should be reconfigured to eliminate this overload phenomenon. ?
Peak amplifier display (PEAK): When the peak diode of PEAK flashes, the gain control should be lowered. ?
Amplifier protection display (PROTECTION): During some faulty operations, the built-in protection circuit of the amplifier will be automatically disconnected, and the protection display will flash. After the faulty operation is eliminated, the protection indicator will go out. ?
Second, the mixer (MIXER)?
The mixing console is divided into: recording studio and stage dance hall. ?
The role of the mixer is:
1. Pick up the signal and amplify;
2. Perform pitch equalization of high, medium and low bass as required;
3. Send the signal to the left and right bus or group control as required;
4. Artistically process the signal sent to the auxiliary bus;
5. Perform output control as required. ?
The mixer can be divided into an input unit and an output unit. ?
(1) Input unit
The input unit is an important part of the mixer. The input unit is a shunt parallel circuit, each of which is roughly the same, and can generally be divided into the following parts. ?
A. Input selection section
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 on the attenuation switch. At this time, a 20dB attenuator is inserted between the preamplifier and the input socket to avoid overload. ?
C. Input gain control (GAIN)?
The sound sources of the mixer are: microphone, musical instrument, magnetic tape, effect device, sound reinforcement equipment, etc. Because their output levels are different, in order to be able to match them, it is necessary to use gain control to adjust the input sensitivity on the mixer. If the input signal is too large, clipping distortion will occur. Conversely, if the input signal is too small, the noise will not be controlled. Gain control is used to ensure that the mixer works within a fixed dynamic range. The method of expressing the level of gain control level on the panel is based on 0dB = 775mV, and it is set at different positions according to the size of the output level of the sound 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 (general audio)?
D. Signal input jack?
Divided into low-impedance balanced input (LO-Z XLR) and high-impedance unbalanced input (HI-Z two-core). ?
The connection method of general musical instruments and audio equipment is unbalanced, and one end of the signal "+" and "-" is shared with the shield layer of the signal line. For example: a core shielded wire, the core wire is the signal "+", the shielded wire is the signal "-" and the ground wire. This is less than the induced noise of parallel lines without shielding, which belongs to the easy-to-type incomplete shielding. ? The input and output of professional audio equipment are balanced, the signal is divided into "+" and "-" transmission, and then the shielded wire is connected, "+" and "-" use independent ground wires, and the plug uses the XLR plug of XLR. ?
E, overload (CLIP)
The overload indicator is used to warn the input signal of instantaneous overload. The indicator light will illuminate when it is 3dB below the peak level (the level at which the signal is excessively distorted), which is helpful for setting the position of the gain switch. ?
F, input equalization part?
The input channel equalizer is used to correct the timbre of the input signal to achieve the standard effect. Because it is a single-channel control, the mixer can perform equalization control on each channel without interfering with each other. The equalization is divided into: high frequency (HIGH), intermediate frequency (MID), and low frequency (LOW). ? 0 position is flat; + direction (gain), + 15dB (enhancement 5 times);-direction (attenuation), -15dB (attenuation 5 times). Continuously adjustable. ? Equalizer generally uses high-frequency (10kHz), midrange (the center frequency of the equalizer can be freely set between 350Hz-5kHz), bass (100Hz) three-band equalizer. ? Because each frequency band has independent control, you can carefully adjust the input signal, and then make a bold attempt to adjust the timbre, and effectively remove unnecessary components such as howling and noise. ?
1. High frequency: 10kHz ± 15dB / slope? Affected area: higher harmonics in the treble area of ​​the instrument. ?
Gain effect: The metallic sound increases, the timbre is relatively sharp, the gain is too much, and the noise can be clearly heard. ?
Attenuation effect: It can effectively remove the hissing sound. If the attenuation is too much, the transparency in the high-pitched zone will be lost. ?
2. Intermediate frequency: 3kHz ± 15dB / peak?
Affected areas: musical instruments, treble areas of vocals. ?
Gain effect: The sound is bright, the texture is hard, too much gain is susceptible to fatigue. ?
Attenuation effect: The balance of the music will tend to bass, including the sound will also feel the same. ?
IF: 1kHz ± 15dB / peak?
Affected areas: musical instruments, midrange of vocals. ?
Gain effect: The outline of the timbre is clear, the pan is protruding forward, and the head of the drum is strengthened. ?
Attenuation effect: panning. ?
Intermediate frequency: 500Hz ± 15dB / peak?
Affected area: musical instruments, mid-bass range of vocals. ?
Gain effect; the tone is thick and powerful, and too much gain will cause the phone tone. ?
Attenuation effect: The sound head is hard, the balance tends to be high, and the texture is too thin for thinning. ?
3. Low frequency: 100Hz ± 15dB / slope?
Affected area: Bass area of ​​the instrument. ?
Gain effect: The sound is thick and the gain is too much, the tooth sound is not clear. ?
Attenuation effect: the sound is relatively easy, the tooth sound is good, and the background noise and hum can be effectively removed. ?
G. Pan?
The pan 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 positioning of the pan position of each input channel signal between groups 1-2 and 3-4 is also determined by this knob. If the knob position is in the middle, the pan position is also in the middle. Turn the knob to the left to locate it in group 1 or 3. Rotate the rudder to the right and position it in groups 2 or 4. ?
H. Monitor and send (MON / SEND)? Monitor and send is used to control the level of the input signal on the monitor bus. This control is not controlled by any control switch on the channel (including channel volume control) except for gain control. . Therefore, the transmission signal is relatively independent of the main bus signal. ?
I. Effect sending (EFX / SEND)?
It includes all peripheral devices and is used to determine how many signals from internal effects or external effects are added to the input signal. It is affected by equalization and volume attenuator, because each channel has its own effect transmission, so through adjustment, some channels can produce effects, while other channels do not produce effects. ?
However, it should be noted that the internal effect and the external effect share the same transmission control, so they should have the same sound source. ?
J. Pre-monitor switch (PFL / CUE)?
When this switch is "ON", the signal of each input channel can be monitored in the headphones and confirmed on the level meter. The priority order of the monitoring switches must be firmly remembered.
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