How are the various parts of the audio system connected?

Posted by hw on March 25th, 2020

Mixer connection

When it comes to the audio system, of course, we will first think of the mixer. There are many ways to describe it. The most appropriate thing is to compare the mixer to the heart of an audio system. How the blood circulation of this heart directly affects the whole System performance. In the image, the mixer is like a large water treatment tank. We input a variety of sound source signals into this large pool like flowing water, and then reasonably process the various kinds of water flowing in the pool. Flowing out from different channels, the whole process is as simple as that. Therefore, the connection to the mixer is nothing more than two parts: input and output.

(I) Line connection of the input section of the mixer

The input signal of the mixer is roughly divided into two types: low-impedance microphone signal input and high-impedance line signal input. In fact, we can think of the difference between low resistance and high resistance as the difference in water pressure or flow velocity. For example, the high-impedance input has a high level, as if the water pressure is large and the water flow is rapid. It is appropriate to input directly into the pool of the mixer. The low resistance input level is low, as if the water pressure is very low and the water flow is very slow. It is not suitable to directly input into the pool of the mixer. We need to add a pump to the large pool to reduce the low resistance and low water. Increase the pressure to make the water flow faster! Therefore, the low-impedance input channel of the mixer has built-in special circuit amplifiers to amplify the low level to a proper level. In this way, the characteristics of low-resistance signals and high-resistance signals should be well understood by everyone.

Only after distinguishing between high resistance and low resistance, can you choose the correct cable for the corresponding connection. Generally, the input jacks of the mixer can be basically divided into three types:

1. TRS: High impedance input part usually uses 6.35cm TRS stereo connector for balanced input, try not to use 6.35 TS mono (sound) connector for unbalanced input, and most of the audio source playback equipment we use now, such as: The output signals of VCD, DVD, MD, MP3, etc. and most instruments are usually high impedance signals.

2. XLR: While low-resistance usually uses XLR XLR connectors for balanced input, most wired microphones now usually use low-resistance jacks to connect to the mixer.

3. RCA: If some mixers have TAPE recording input, it is usually connected by RCA lotus connector.

Issues needing attention in the signal input section of the mixer: The input signal of the mixer can be roughly divided into low-impedance and high-impedance input, but how to accurately define whether a signal is low-impedance or high-impedance requires flexibility. For example, according to the standard, electronic keyboards, electric basses, electric guitars, etc. are high-impedance signals, which can only be input to the mixer with a 6.35 plug. Large, coupled with system interference such as lighting, the background noise of this signal line is already very large, even if no sound source signal is input, when the gain of the input channel of this line is turned on on the mixer, there will be A lot of background noise, as described above: this line is a river, and now there is too much sediment in this river, at this time there is still a lot of noise in this line, and the line is over there The volume of my musical instrument has been turned to the maximum and can no longer be increased, that is, the river can only put you so deep in water, what should I do? If high-impedance signal input is used, the water in the river has not increased, and the water quality cannot be changed. Of course, the sound quality cannot be changed. If a signal is input from the low-impedance jack with a Cannon plug, a little shallow water in the river will pass through the low-impedance amplifier Zoom in, so that the water is deeper, the water quality is better, and the sound quality is better. It doesn't seem to be true, everyone can try it. I have done a lot of projects now. The bands basically use Cannon jacks to input from low resistance. Although the surface looks irregular, it is actually a helpless way to reduce the noise of the band. So we still need to be flexible and find the best working method in practice.

This image was provided by registered user "sastchina", copyright statement feedback

(Two) the line connection of the mixer output section

There are many sockets in the output section of professional mixers, and each has its own division of labor. Unlike the input section, which has many sockets, it is relatively simple. Therefore, be careful when connecting output signals. Generally, the main output part of the mixer refers to the total volume output, group volume output, AUX output, etc. Generally, the output part of the mixer can be divided into 6 parts by function:

1. Group output: If we control the volume of the subwoofer through 1-2 group alone, then we can only output audio signals from the corresponding output jacks of the mixer 1-2 group. Most of the output ports of the group output use TRS Stereo jacks are used for balanced output. Of course, some use the XLR jack.

2. Main channel output: The L-R main channel usually adopts XLR XLR balanced output. Some small mixers also use TRS stereo jacks instead.

3. AUX output: The AUX output in the mixer is most commonly used to output vocal effects. The second is to provide monitoring signals to bands or singers. Of course, it is also used for other purposes, such as recording and auxiliary speakers. Signals, etc. AUX usually uses TRS stereo jack output signals.

4. Direct output section: There is a “Direct Direct Output” jack in each input channel of a more professional mixer. This jack can be provided to other equipment for recording and monitoring. Each channel of the mixer is usually The signal is output using the TRS stereo jack. For example, a performance TV station needs to broadcast live, and the site must also broadcast live. If there are 20 channels of audio signals, then we can input these 20 channels of audio signals into the TV mixer first, and then use the direct output of the TV mixer The jack inputs these 20 channels of audio signals to the mixer for live performance. Of course, for the sake of safety, these 20 channels of audio signals are first adjusted by the signal amplifier distributor, and then distributed to the TV mixer, live performance mixer, backup emergency mixer, recording mixer or other Equipment, etc.

5. Recording output: Most of the analog recording output signal jacks use RCA lotus connectors. If it is a digital signal, other digital output methods such as fiber optics and firewire may be used.

6, INS plug-in jack: This jack in the mixer is between input and output, it uses a TRS stereo connector for connection. Many audio engineers may not use INS insertion and insertion. It can insert a peripheral device into an input channel, group channel, or main (left and right channel) of the mixer, and separate the sound signal of the inserted channel. For processing. When using the TRS large three-pin stereo connector to connect, the method is to output the signal from the TRS large three-pin stereo plug head, connect to the input of the device to be inserted, and then send the signal from the output of this device to the TRS large three-pin. The ring end of the stereo plug then flows into the mixer. For example, we can use this method to insert an equalizer into the 1 and 2 microphones of the mixer, which is equivalent to cutting off the water pipe of the 1 and 2 microphones, adding a water processor (equalizer), and then inputting Mixer, this way to adjust the sound effect is better.

The above is the connection of the mixer. Regardless of the input part or output part of the mixer, the sockets and signal connection methods used are basically these kinds, but they must be correct when connecting.

 Connection of equalizer and limiter

1. Equalizer: The main function of the public equalizer is to adjust the tone, adjust the sound field, and suppress acoustic feedback. Therefore, the equalizer is almost an indispensable device in the current audio system. At present, the input and output parts of the equalizer are all used. Balanced socket, it is best to use the balanced line of XLR connector when connecting, of course, you can also use the balanced line of TRS connector.

2. Compressor: Compressor is a device for processing audio signals, which can compress or limit the dynamics of audio electrical signals. In fact, our main function when using a limiter is to let it compress high-level signals, which can protect its lower-level audio equipment. It can be said that in a complete set of audio equipment, in addition to the mixer and equalizer, the limiter is the most important peripheral device. Therefore, under normal circumstances, the limiter should be placed in front of the power amplifier. Behind. For connection, balanced lines of XLR connectors or balanced lines of TRS connectors can be used.

Electronic crossover connection

Electronic frequency divider refers to an audio peripheral device that can divide the audio signal in the 20Hz-20000Hz frequency band into suitable and different frequency bands, and then send them to the corresponding amplifiers to promote the corresponding speakers. At present, the input part of the electronic frequency divider is relatively simple, but the output part is more complicated: there are treble output, midrange output, bass output, etc. Do not confuse the output of the bass signal with the output of the treble signal when connected, inversely the treble signal is given to the woofer and the bass signal is given to the tweeter. In this way, there may be no sound in the sound system because the frequency is not correct , Or they will burn out speakers and other equipment! The electronic frequency divider can use the balanced line of the XLR connector or the balanced line of the TRS connector on the connection surface.

Connection of feedback suppressor

In terms of equipment connection, balanced lines using XLR connectors or balanced lines using TRS connectors are also used. The connection methods can be roughly divided into the following three types:

1. The serial devices are connected in series in the audio system like equalizers and other peripheral devices. The advantage of this connection is that the connection and operation are very simple and suitable for simpler systems. However, the disadvantage is that when this connection method is used to suppress the acoustic feedback of the microphone, it will also affect other sound source signals that pass the feedback suppressor.

2. Use the INS plug-in / plug-out interface in the mixer channel to connect the feedback suppressor in series to the corresponding channel separately. The advantage of this connection is that the feedback suppressor can be adjusted to the maximum without having to take into account the impact on other Sound source. The disadvantage is that with this connection method, a feedback suppressor can only control up to 2 channels of the mixer, and the equipment utilization is too low.

3. Use the INS plug-in / plug-out interface in the mixer group to connect the feedback suppressor in series to the corresponding group channel. The advantage is that the microphones programmed into the group can be processed centrally without affecting the group. To other audio sources. In general, since this method can make full use of the feedback suppressor, it is currently the most commonly used connection method.

Delayer connection

The delayer can delay the audio signal, and it is generally used in some systems with large sound field space and requiring multiple groups of speakers to disperse the sound. Because in such a system, sounds are emitted from speakers at different positions and arrive at the listener's ears in order, in order to ensure the consistency of the sound image, increase the readability of the sound, and avoid the turbid sound , Flanging and trailing, we need to use delayers for related processing. Regarding the determination of the delay object, who is the delay? It's actually very simple, just need to figure out the following three points:

1, the first is people-oriented, no matter how many, the best audio equipment also serves people, so in a sound field, we must first take the audience as the benchmark.

2. The second is based on the main sound source, which is usually where the main speakers and the main stage are located. Ideally, the sound from the main sound source should be directly transmitted to the audience's ears. However, due to the energy, range, directivity, and evenness of the sound pressure of the sound field, most of the indoor sound reinforcement systems now need to add auxiliary supplementary sound boxes that are closer to the audience.

3. The third point mainly refers to these auxiliary supplemental sound boxes that are relatively close to the audience, that is, speakers that may require delay processing.

In most cases, the first factor is identified, the main sound source of the second factor is determined, and then the supplementary sound box of the third factor is delayed. The speed of sound is about 340 meters per second, so the delay time is calculated based on the distance between the auxiliary speaker of the third factor and the main speaker of the first factor. Knowing the delay object can correctly connect the delayer. The connection is basically like an equalizer and other peripheral devices. It is connected in series with the signal channel that needs delay in the audio system. The balance line using XLR connectors or the balance of TRS connectors Line for connection.

Exciter connection

An audio exciter is actually a harmonic generator, an audio processing device that uses human psychoacoustic characteristics to modify and beautify sound signals. The exciter generally has the following three connection methods:

1. It can be connected in series with the signal channel that needs to be excited in the audio system like an equalizer and other peripheral equipment. For example, in a mixer, the 1-2 group is human voice. If you want to excite the human voice of this group You can connect the exciter to the 1-2 group channels of the mixer using the plug-in / plug-out interface.

2. For comprehensive processing, it is sufficient to connect an exciter in series with the mixer's main volume output channel or other group output channels.

3. The exciter can also send signals from AUX like effects, and then return to the mixer, so that you can adjust which channels need to be stimulated, and how hard they need to be processed, which is actually more flexible.

In terms of signal connection, the exciter is also connected by balanced lines of XLR connectors or balanced lines of TRS connectors.

Digital effects connections

Effects are audio peripherals that process and produce various sound field effects. They are generally used to process human voices. In most sound systems, if the human voice is not processed by the effects, it will become full and lack brightness. That is: dried up without moisture. Now the latest effects have used digital processing chips, so we also call them: digital effects. The effects are relatively less connected to the sound system like peripheral equipment such as equalizers. Generally, the signal from the mixer's AUX is sent to the effect's input interface, and then the signal is returned from the effect's output interface to the adjustment. In the sound stage. In terms of signal connection, most use TRS connector balanced lines for connection, and a few professional effects also use XLR connector balanced lines for connection.

Amplifier and speaker connection

Everyone should be familiar with this, but just pay special attention: the signal line of the power amplifier should use balanced lines as much as possible, so as to minimize noise. Many audiophiles like to provide one or two signal lines to multiple amplifiers, but if there are more than four amplifiers, it is recommended to use a signal amplifier to separate a sufficient number of signal lines without attenuation for each amplifier to be used separately. This can reduce system noise, reduce hidden dangers, and improve the signal-to-noise ratio. In terms of power transmission, try to use thicker and shorter speaker wires and use reasonable wiring to shorten the distance of the speaker wires, and pay attention to the positive and negative electrodes to avoid short circuits.

Issues for device connection:

1. Pay attention to the power supply: the audio equipment must have a dedicated power supply, which must be separated from the power supply of the light, and the light prefers a lower voltage, but the audio requires a standard voltage. With a dedicated power supply, you also need a stable and reliable power outlet. You can use the "power sequencer" as much as possible. Although the cost increases, the stability and ease of use are improved. In short: It is critical to properly and securely connect the power of all audio equipment. It is also important to note that some imported equipment will have 110V and 220V selection switches in the power supply part. In China, be sure to select the 220V position before you can connect to power.

2. Pay attention to the grounding of the equipment: It is very important to properly connect the ground wire to all audio equipment. Good grounding can reduce the interference of equipment signal transmission and improve the stability of the equipment. It should be noted that the grounding wire should be made according to the grounding standard of lightning conductors. That is, the conductors buried in the underground must be rust-proof, have good contact, and be buried deep. Do not share them with the three-phase power line. Not only does it not reduce the noise in the sound system, it also easily damages the equipment.

3. Pay attention to selecting the appropriate connection signal cable: For an audio equipment, we can use XLR XLR balance cable to connect, do not use TRS balance cable; if you can use TRS balance cable, do not use TS mono unbalanced Cable connection; when there is no way, you can use TS mono unbalanced cable to connect the device.

4. Pay attention to the inversion and short circuit of the signal: The short circuit of the signal line often causes silent failure, but it is very troublesome to check, unless each signal line is removed and tested with a multimeter, so be careful when welding the wire.

5. Pay attention to the length of the signal line: When connecting devices, use shorter signal lines as much as possible to save costs and reduce line resistance and interference. Under normal circumstances, the signal line using the balanced transmission method can reach a maximum length of about 300 meters, while the unbalanced line cannot do long-distance transmission.

6. Pay attention to the level of the device: If the +4 and -10 or -20 level switches are on the rear panel of the device, we normally put it in the +4 position, which is the standard level.

7. Pay attention to pass-through: Many devices have a Bypass button. The device usually does not work during pass-through, so we should pay attention to check this button. Inversely, if we make the compressor pass-through not work, then The equipment behind the limiter has lost its protection.

8. Be careful of misoperations: Because there are many devices and many buttons, misoperations are easy to occur. For example, some electronic crossovers have a “× 10” button. Be careful not to press it easily. For example, if our crossover point is adjusted at 200Hz, pressing this button 200 × 10 will become 2000Hz, so we must avoid misoperation.

With good equipment and correct and reasonable connection of them together, the effect of this audio system will be perfect.