Connecting wires and connection points in home theater audio system

                 Connecting wires and connection points in home theater audio system

There are many ways to connect a home theater audio system, and different systems and devices have different connection methods. But in general the principles are the same, mainly composed of: sound source + power amplifier + speaker.

1. The current sound sources include various musical instruments, various sound source players and some special sound generators.

2. The power amplifier is composed of various amplifying circuits, which can amplify the signal of the previous stage to drive the speaker of the latter stage.

3. Nowadays, multiple speakers are generally combined to form a speaker, and many types of speakers are also formed.

The above is the simplest set of home theater audio system. Of course, many auxiliary devices have been added to the current system, which we call peripheral devices. Now I usually flexibly match the home theater audio system according to the characteristics of use and customer requirements, but the home theater sound effects produced by the same equipment with different connection methods are also different, so technicians are required to master more knowledge in this area .

Connecting cables and sockets commonly used in home theater audio systems

In the home theater audio system, to achieve contact transmission and communication between devices, it must rely on the connecting tools, which are wires and connectors. It plays a very important role in the entire home theater audio system. Now there are many types of cables and connectors used in professional home theater audio systems. Below we briefly introduce the common types of wires and connectors:

Various wire

1. Professional audio cable

Now there are two-core, three-core, four-core, five-core, etc. audio cables. This kind of cable can be used to transmit high-quality audio signals due to its good shielding effect; now more professional microphones generally use wires with more than three cores. The wire has strong anti-interference ability and can be used for long-distance transmission. Of course, this wire can also transmit other signals, such as the DMX512 control signal of moving lights.

2. Coaxial cable

Generally used in video, there are also some audio cables, because this kind of cable has poor anti-interference ability, and it is not mainly used to transmit audio signals during design, so it is not suitable for long-distance audio signal transmission.

3. Centralized cable

That is, multiple signal lines are wrapped in the same protective tube, which is generally used inside the connection system to reduce the number of independent wires. It is now also used in such special aspects as TV broadcast vehicles, underground pre-buried and other special aspects. This kind of thread is generally processed by professional manufacturers, and the quality is more guaranteed.

4. Optical fiber

A transmission cable commonly used in many recording and playback equipment such as CD or MD, which transmits digital signals. With the popularization of digitalization, the use of optical fiber in home theater audio systems will increase in the future.

5. MIDI cable

It is usually a five-core wire, which transmits information about MIDI, and is now mostly used on keyboards, effectors and other equipment.

6. There are also some special wires

For example, the multi-core network cable originally used to connect to the Internet in the computer song ordering system can now also be used to transmit audio and video to realize the automatic computer ordering function.

Various connectors

1. XLR

Commonly known as Cannon connector (Cannon), this connector is composed of three contacts, respectively 1- Ground ground; 3 is the hot end (+ level); 2 is the cold end (- level), this point should be read clearly in the manual of the equipment.

XLR connectors are the most widely used type of connectors in professional home theater audio systems. They can be used to transmit various audio signals in home theater audio systems. Generally, balanced input and output terminals are connected by XLR connectors. of. In a sense, the use of XLR connectors is also one of the characteristics that distinguish professional home theater audio systems from civilian audio systems. The benefits are:

a. If the balanced transmission method is adopted, the ability to resist external interference is strong, which is beneficial to long-distance transmission.

b. With a spring locking device, the connection is reliable and not easy to pull off.

c. The connector specifies the signal flow direction, which is convenient to prevent errors in connection.

XLR plugs are divided into male plugs and female plugs, and sockets are also divided into male sockets and female sockets. The contact of the male plug is the pin, and the contact of the female plug is the jack. According to the common practice in the world, the male plug or socket is used as the input terminal of the signal; the female plug and socket are used as the output terminal of the signal.

2. RCA

In China, it is commonly known as the lotus head (because some types of RCA connectors look like lotus petals). This type of connector is composed of two contacts, which are the hot end (+ level); Use a coaxial cable to connect, of course, you can also use a multi-core audio cable, which is often used in general home theater audio equipment. Because its length is about 3.5 cm, so I usually call it: 3.5cm plug.

3. TRS

Generally called a stereo connector, it is composed of three contacts, namely: head end (+ level); ring end (- level); ground (Ground), the length used on small headphones is about 3.5 cm, but at most It is still used in professional home theater audio, and its length is: 6.35 cm. At present, most of the high-impedance input and plug-in sockets of professional mixers use this plug, and most other home theater audio equipment also use this port.

4. TS

Commonly known as a monophonic (sound) connector, this connector is composed of two contacts, which are the head end (+ level) and the ground end (Ground). The length of the above two connectors used in professional home theater audio is about 6.35 cm, so I usually call it: 6.35 cm plug. Although the TS connector and the TRS connector have the same length and similar appearance, their specific functions can be different. The TRS stereo connector can use three-core wires to transmit signals in a balanced manner; but the TS mono connector can only use unbalanced signal transmission. Way.

5. MIDI connector

The connector used in MIDI applications has five pins that carry information about MIDI.

6. Speaker connector

Nowadays, four-core professional connectors are generally used, and some use TS mono connectors or other methods.

7. Various adapters

This connector can be conveniently used to switch between various connectors.

8. There are other special joints that will not be introduced here.

Production of various connecting wires

At present, the input and output signal modes of professional home theater audio equipment are basically divided into: Balance balanced mode and Unbalanced unbalanced mode. Of course, signals can be directly fed between balanced and balanced, unbalanced and unbalanced ports; in the case of higher requirements, a special converter must be used to connect between balanced and unbalanced ports. But in actual engineering, as long as the signal line is not too long and the interference is not too large, the balanced port and the unbalanced port can be directly connected to transmit signals normally. In a home theater audio system, in addition to the power transmission line between the power amplifier and the speaker, the signal connection lines between other devices should be transmitted in a balanced manner as much as possible, which can improve the anti-interference ability of the system and increase the signal quality. Effective transmission distance:

A. The signal line between balance and balance:

1. XLR male connector → XLR female connector

This kind of cable is most commonly used in professional home theater audio systems. In terms of production, the three contacts 1, 2 and 3 between the male and female of the XLR are connected respectively. Contact 1 is connected to the shielding layer, and contact 2 is connected to the signal hot end (+ pole), and contact 3 is connected to the signal cold end (-pole).

2. TRS stereo connector → TRS stereo connector

In terms of production, the three contacts of the head end (+ level), the ring end (- level) and the ground (Ground) between the two TRS stereo connectors are respectively connected. In fact, this kind of cable should also be used in large quantities in home theater audio systems, but many sound engineers often use TS mono (sound) connectors instead to save trouble. Balanced transmission becomes unbalanced transmission.

3. XLR male or female connector → TRS stereo connector

In terms of production, the contact 1 (shield ground) of the XLR connector is connected to the ground (Ground) of the TRS stereo; the hot end (+ pole) of the XLR contact 2 is connected to the head end (+ pole) of the TRS; the cold end (- pole) of the XLR contact 3 Connect to the ring end (-pole) of the TRS. This is also a balanced transmission method, which is often used in professional home theater audio systems.

4. XLR male → XLR male or XLR female → XLR female

This kind of line is a bit special, and it is mostly used for signal connection between power amplifiers or between power amplifiers and other peripheral equipment. In terms of production, the three contacts 1, 2, and 3 between the two connectors are connected respectively. On the shielding layer, contact 2 is connected to the signal hot end (+ pole), and contact 3 is connected to the signal cold end (- pole).

Another point, in order to prevent "loop interference", we can leave one of the contact 1 (shield ground) of an XLR connector in a signal line or the ground (Ground) of a TRS stereo connector under special circumstances. Not connected, for example: a balanced cable from XLR male to XLR female, we can leave the contact 1 (shielding ground) in the XLR female connector free to not connect, so as to avoid some interference between devices; The principle of the TRS connector is the same, just leave a ground (Ground) contact free. We used to weld 6 solder joints in total for such a balanced line, but now we can weld 5 solder joints with one vacant line, but this method cannot be used for unbalanced lines.

B. The signal line between unbalanced and unbalanced

Generally refers to the signal line between TS mono (sound) connector → TS mono (sound) connector, which is an unbalanced transmission method. In terms of production, the header between two TS mono (sound) connectors The terminal (+ level) and the ground (Ground) are connected separately.

C. The signal line between balanced and unbalanced

XLR XLR male or XLR XLR female connector → TS mono (sound) connector, this connection method actually becomes an unbalanced transmission mode for signals, and in terms of production, contacts 1 and 3 of the XLR connector are combined to connect to the shield The line is then connected to the ground (Ground) of the TS mono (sound) connector; the XLR contact 2 hot end (+ pole) is connected to the head end (+ pole) of the TS mono (sound) connector. In the professional home theater audio system, this kind of line is often used as the microphone line in the box karaoke system.

D. speaker wire

In the connection between the power amplifier and the speaker of the professional home theater audio system, the resistance of the speaker wire should be as low as possible, and thicker and shorter wires and reasonable wiring should be selected. Today's speakers generally use four-core professional connectors, and power amplifiers generally use four-core professional connectors or binding posts. + pole) and (- pole) are connected correctly. There are also some speakers or power amplifiers that use TS mono connectors and binding posts, and the connection principle is the same. They are all positive to positive, negative to negative. If the speaker is reversed, the phase will be reversed, which will affect the sound quality and stability of the speaker. At the same time, avoid short circuit when connecting, otherwise it will damage the power amplifier equipment.

Generally speaking, the above are the types of connecting cables that we often use in the system. Maybe you didn’t pay much attention to the connection of signal cables and speaker cables before. Take the signal cable as an example: in fact, it is as important as the blood vessels in the human body! And considering stability and long-term, we must use high-quality wires and high-quality connectors, and ensure that they are welded with high quality and trouble-free. Now, no matter how busy or tired I am when I am working on a project, I am used to soldering all the signal connection lines in the system by myself. Like where there will be a landmine on the road, you don’t know when which signal line will fail, so relatively speaking, I can trust the stability of even the worst equipment, but I don’t just trust the quality. Signal cables and speaker cables that are not guaranteed!

Home theater audio system equipment connection sequence

After making various signal connection cables, it is time to prepare for device connection. Now there are many peripheral devices in the home theater audio system, and there must always be a sequence when connecting. Summarize a few simple connection sequences:

1. Bass system equipment connection sequence: mixer (group 1-2)→equalizer→frequency divider→compressor→bass power amplifier→bass speaker.

2. Auxiliary home theater audio system equipment connection sequence: mixer (3-4 groups) → equalizer → delay (optional) → compressor → auxiliary speaker amplifier → auxiliary speaker.

3. The connection sequence of the main audio system equipment: mixer (L-R main channel) → equalizer → exciter (optional) → feedback suppressor (optional) → compressor → main speaker power amplifier → main speaker.

4. The connection sequence of the monitor system equipment: mixer (AUX output) → equalizer → compressor → monitor speaker power amplifier → monitor speaker.

The first connection method above can control the volume of the bass separately, so that we can turn up the volume of the mixing console 1-2 group when we are slow shaking or digo, and turn it down when the singer is singing, which is very flexible. ;The second connection method can also control the sound of the auxiliary speakers; the third main speaker is of course used to output the volume from the L-R output of the mixer; the fourth monitoring system, the standard is to come from AUX Output volume, so that the volume of each channel of the mixer can be flexibly adjusted according to the requirements of the singer or band, but in a smaller home theater audio system, the monitor signal can be directly taken from the main channel signal. Attention should also be paid to the first and second connection methods above: since we have independently output signals from the corresponding output ports at the back to the bass system and auxiliary system in the 1-2, 3-4 grouping, then 1-2, 3- 4 groups should no longer pass through the overall volume output of the mixer, that is, the switches from 1-2, 3-4 groups to the overall volume of the mixer should not be turned on again.

Of course, we still need to flexibly arrange the order of device connection according to the needs and the number of devices. The above order is for reference only.

Equipment Connection Points

The above briefly introduces the types, production and equipment connection sequence of various connecting cables. In the specific connection of equipment, many sound engineers do not know how to do it in the face of various and numerous equipment sockets. It is actually very simple. , you just need to remember the following points:

1. Balance method

Most home theater audio equipment now has balanced ports on the rear panel. We just choose whether to use the balanced line of the XLR connector to connect the device or the balanced line of the TRS 6.35cm stereo connector to connect the device.

2. Unbalance

Although the sockets on the rear panel of most home theater audio equipment are balanced ports, some devices still have unbalanced ports. For example, the output sockets of some electronic crossovers are marked: Balance OUT (balanced output) And Unbalance OUT (unbalanced) output, so we can also use the unbalanced line of TS 6.35cm mono connector to connect the equipment

, as long as the line is not too long and the interference is not too great, this connection is still possible.

3. IN input and OUT output

Some beginners are dizzy when they see so many sockets behind the equipment. In fact, there is a trick: no matter what home theater audio equipment, it can basically be divided into two parts: "IN input" and "OUT output". Just look for "IN and OUT", and don't connect other unfamiliar sockets casually. In short, connecting equipment is like flowing water: the upstream water flows into the "IN input"; the downstream water flows through the "IN input" OUT output" and then flow out, isn't this level-by-level very simple and clear?