An article for newcomers who want to play with audio systems
Time:2023-08-16
Views:662
1. The development history of sound technology.
The development history of sound technology can be divided into four stages: electronic tubes, transistors, integrated circuits, and field-effect transistors.
In 1906, American De Forrest invented the vacuum transistor, pioneering human electroacoustic technology. After Bell Labs invented negative feedback technology in 1927, the development of sound technology entered a new era. Representative examples such as the "Williamson" amplifier successfully applied negative feedback technology, greatly reducing the distortion of the amplifier. By the 1950s, the development of electronic tube amplifiers reached a climax, and various types of electronic tube amplifiers emerged one after another. Due to the sweet and mellow sound of electronic tube amplifiers, they are still favored by enthusiasts to this day.
The emergence of transistors in the 1960s opened up a wider world for audio enthusiasts. Transistor amplifiers have the characteristics of delicate and moving sound, low distortion, wide frequency response, and dynamic range.
In the early 1960s, the United States first introduced a new member of sound technology - integrated circuits. By the early 1970s, integrated circuits were gradually recognized by the sound industry due to their excellent quality, low price, small size, and multiple functions. Up to now, thick film audio integrated circuits and operational amplifier integrated circuits have been widely used in audio circuits.
In the mid-1970s, * * * produced the first field-effect power transistor. Due to the fact that field-effect power transistors have both the pure thick and sweet sound of electronic tubes, as well as the dynamic range of 90dB and THD<0.01% (at 100kHz), they quickly became popular in the audio industry. Many amplifiers nowadays use field-effect transistors as the final output.
The development of sound technology has gone through the historical period of electronic tubes, transistors, and field-effect transistors, each with its own characteristics in different historical periods. It is expected that the mainstream development of audio technology in the future will be digital audio technology.
Introduce the specific meaning of dB
The unit dB is a widely used unit in electronics, which is a relative unit for measuring and comparing the power, voltage, and current of a system. Later, due to technological advancements, it was realized that human response to sound varies logarithmically, So there was a unit called Bell, which is the name of the inventor of the telephone. Its expression is: Bell=lg (P/Po) P is the measured power Po is the reference power, and Bel is the logarithm based on 10. In practice, it was found that Bel is too large, so one tenth of it was taken as a new unit, which is decibels (dB). Divide Bel by 10 to obtain dB. The expression is: dB=10lg (P/Po), dB=20lg (E/Eo), dB=20lg (I/Io)
2. What is Hi Fi? What kind of audio equipment is Hi Fi?
Hi Fi is an abbreviation for High Fidelity in English, which literally translates as "high fidelity". Its definition is: a playback sound that is highly similar to the original sound. So what kind of audio equipment is the playback sound of Hi Fi? It is still difficult to reach a definitive conclusion so far. Professionals in the audio industry use various instruments and methods to detect various indicators to determine the level of Hi Fi in equipment, while audio enthusiasts often use their own ears to determine whether the equipment meets their desired Hi Fi. To determine the high fidelity level of playback sound, it is not only necessary to have high-performance equipment and software, but also to have a good listening environment. Therefore, there is still a difference between objective testing and subjective evaluation in how to accurately measure the Hi Fi level of audio equipment.
3. Main technical indicators of the audio system.
The overall technical performance of the audio system depends on the performance of each unit itself. If the technical indicators of each unit in the system are high, then the overall technical indicators of the system are very good. Its technical indicators mainly include six items: frequency response, signal-to-noise ratio, dynamic range, distortion, transient response, stereo separation, and stereo balance.
1、 Frequency response: The so-called frequency response refers to the frequency range of sound equipment during playback and the relationship between the amplitude of sound waves and frequency. Generally, this indicator is measured with a frequency amplitude of 1000Hz as a reference, and the frequency amplitude is expressed in decibels (dB) using logarithms.
The overall frequency response of the audio system is theoretically required to be between 20 and 20000 Hz. In practical use, due to reasons such as circuit structure and component quality, this requirement is often not achievable, but generally it must reach at least 32-18000Hz.
2、 Signal to noise ratio: The so-called signal-to-noise ratio refers to the ratio of the playback sound of the sound source software by the audio system to the new noise generated by the entire system. The noise mainly includes thermal noise, AC noise, mechanical noise, and so on. This indicator is generally measured as the logarithmic ratio of the rated output power of the playback signal to the system noise output power without signal input in decibels (dB). The signal-to-noise ratio of a general audio system needs to be above 85dB.
3、 Dynamic range: The dynamic range refers to the logarithmic value of the ratio of the maximum undistorted output power of the audio system during playback to the system noise output power at rest, in decibels (dB). Generally, sound systems with good performance have a dynamic range of over 100 (dB).
4、 Distortion: Distortion refers to the change in certain parts (waveform, frequency, etc.) of the original audio source signal after the audio system replays it. The distortion of audio systems mainly includes the following types: 1. Harmonic distortion: The so-called harmonic distortion refers to the sound produced by the audio system after playback, which has many additional harmonic components compared to the original signal source. This additional harmonic component signal is a multiplication or division of the signal source frequency, which is caused by the nonlinear characteristics of the negative feedback network or amplifier. The harmonic distortion of the high fidelity audio system should be less than 1%.
2. Intermodulation distortion: Intermodulation distortion is also a type of nonlinear distortion, where two or more frequency components are mixed in a certain proportion, and each frequency signal is modulated with each other. After passing through the playback device, a newly added nonlinear signal is generated, which includes the sum and difference signals between each signal.
3. Transient distortion: Transient distortion, also known as transient response, is mainly generated when a large transient signal is suddenly added to the amplifier, resulting in signal distortion due to the slow response of the amplifier. Generally, the amplifier‘s ability to follow transient signals is expressed by observing whether the envelope waveform of the amplifier‘s output signal is similar to the input square wave waveform after the input square wave signal passes through the playback device.
5、 Stereo separation: Stereo separation refers to the isolation between the left and right channels in a stereo sound system, which actually reflects the degree of crosstalk between the left and right channels. If there is significant crosstalk between two channels, the stereoscopic effect of replaying sound will be reduced.
6、 Stereo balance: Stereo balance represents the difference in gain between the left and right channels in a stereo playback system. If the imbalance is too large, the sound image positioning of the replayed stereo will be offset. The stereo balance of a general high-quality audio system should be less than 1dB.
4. How is the range and audio range of sound replayed by the audio system divided? How does each frequency band perform on music?
The range of playback sound in a sound system can generally be divided into eight ranges: subwoofer, bass, mezzo, mezzo, alto, alto, treble, and ultra high. The audio frequency range can generally be divided into four frequency bands, namely the low frequency band (30-150Hz); In your frequency band (150-500Hz); Medium to high frequency range (500-5000Hz); High frequency range (5000-20000Hz).
Among them, the frequency range of 30-150Hz can represent the low-frequency components of music, allowing the viewer to feel a strong and dynamic feeling.
150-500Hz frequency band: capable of expressing the expressive power of a single percussion instrument in music, it is the part of low frequency that expresses the power.
500-5000Hz frequency band: mainly expresses the clarity of the singer‘s language and the expressive power of the strings.
5000-20000Hz frequency band: mainly expresses the brightness of music, but too much can cause the sound to burst.
5. What are the commonly used terms for audio enthusiasts.
Audio enthusiasts often use abstract terms, such as:
1. Neural line: mainly refers to the signal line that transports low levels (millivolts, microvolts) and small currents. The general neural wire is used for both audio and video purposes, while the plugs at both ends of the higher-level neural wire are gold plated RCA plugs, and the surface of the wire is coated with anti-static protection layer.
2. Fever line: mainly refers to the signal transmission line of a speaker with a large cross-section and a large number of strands. High quality fever wires are made of materials such as oxygen free copper.
3. Burner: The so-called burn-in period of a machine is similar to that of a mechanical machine, which means that after the sound equipment has been working for a certain period of time, the temperature inside the machine is the same as the ambient temperature, so that the working state of the amplifiers at all levels reaches the optimal point. At this time, the playback sound is the best. 4. Moji: The so-called Moji originates from the English word "Modify", meaning to modify or modify. Fans replace or modify the components or circuits within the audio system to upgrade it, which is called a motorcycle.
5. Explosion: The so-called explosion refers to the deafening atmosphere generated by the sound equipment when the music reaches its climax during playback.
6. Bile machine: Bile machine refers to an amplifier made of electronic tubes. The warm and transparent sound quality of electronic tube amplifiers remains unforgettable to the older generation of enthusiasts.
7. Stone machine: The so-called stone machine refers to an amplifier made of transistors.
8. Gallstone machine: refers to a sound equipment made by mixing electronic tubes and transistors. Generally, electronic tubes are used as front-end amplifiers and transistors as back-end amplifiers.
9. Ring transformer: The so-called ring transformer refers to a ring transformer, which has less magnetic leakage compared to ordinary transformers.
10. Large pond: A large pond refers to a power filter capacitor, typically 10000 μ Large capacity capacitors above F.
11. Beautiful sound: Refers to the playback sound quality of sound equipment that is very good and meets the requirements of high fidelity.
12. Resolution: Refers to the transparency of the playback sound of audio equipment, giving people a feeling of "clear and bottomless".
13. Dyeing: The so-called dyeing refers to the sound that is not present in the playback sound due to the resonance of other objects or materials caused by the vibration of sound waves during the playback process. It is harmful to the playback effect.
14. Microphone: Refers to various microphones.
15. Supplements: Refers to high-quality components used in the renovation of audio systems. 6. How should speakers be placed?
The correct placement of speakers is one of the factors for achieving good playback results, and the following issues must be noted when placing them:
1. The distance between two speakers should not be less than 1.5-2 meters and should be kept at the same level. The distance between the left and right sides of the speaker and the wall should be the same. There should be no debris in front of the speaker, as shown in Figure 2 (a). Sound P10.
2. The tweeter unit of the speaker should be kept at the same level as the ear of the listener, and there should be a 60 degree angle between the listener and the two speakers. There should be some space left behind the listener, as shown in Figure 2 (b). 3. The walls on both sides of the two speakers should be acoustically consistent, that is, the reflection of sound waves by the walls on both sides should be the same.
If the directionality of the sound waves in the speaker is not wide, the two speakers can be placed slightly inward, as shown in Figure 2 (c).
5. For small speakers, if you feel that the low frequency is not enough, you can place them near the corner of the wall.
7. What issues should be noted when connecting audio equipment?
The coordination between different levels of audio equipment is more important. Improper connection not only affects the playback effect of the equipment, but also damages the equipment.
1. Basic requirements for equipment connection:
(1) Signal level matching: When connecting audio equipment, it is important to pay attention to the differences in input and output signal levels between each equipment. If the level of the input signal of the previous level equipment is too high, it will generate nonlinear distortion. Conversely, it will lower the signal-to-noise ratio of the playback system and even fail to drive the amplifier of the next level equipment. Therefore, when matching, it is important to note that the level difference between equipment should not be too large. If there is a signal level mismatch in actual use, it is necessary to reduce the input signal level through a attenuation circuit or increase the input signal level through an amplification circuit. For general dynamic microphones, the output voltage is a few millivolts, so a primary amplification circuit is required to amplify the signal and send it to the preamplifier circuit. For recording consoles, CD players, and LD players, the output signal level can reach 0.755-1V or above, so it can be directly fed into the preamplifier.
(2) Impedance matching: In Hi Fi audio equipment, for example, the output impedance of transistor power amplifiers is low, while the output impedance of electronic tube power amplifiers and other equipment is high. If their impedance does not match when connected to the speaker, it will cause uneven distribution of output power of the amplifier, or the transient characteristics of the speaker will deteriorate due to excessive damping.
There are generally two types of impedance matching connections: balanced and unbalanced. The so-called balanced type refers to the equal impedance of the two shielded wires transmitting signals to the ground. The so-called unbalanced type refers to a two core shielded wire, one of which is grounded. When the balanced output is connected to the unbalanced input, it must be matched by adding a matching transformer.
2. Connection method of connectors: In Hi Fi audio equipment, the connection of the equipment relies on various connectors. There are several commonly used connectors, as shown in Figure 4. Sound P14.
(1) Two core plug: mainly used to transmit signals between various equipment and as an input plug for microphone input signals. According to its diameter, it can be divided into three types: 2.5mm, 3.5mm, and 6.5mm
(2) Lotus plug: mainly used as an input and output plug for circuits between audio and video equipment, as shown in (b) in the figure.
(3) XLR plug: mainly used for connecting microphones and amplifiers, as shown in (c) in the figure.
(4) Five core socket (DIN): mainly used for connecting cassette recorders and amplifiers, it can concentrate stereo input and output signals on one socket.
(5) RCA plug: RCA plug is mainly used for the transmission of video signals in equipment.
(6) F, M plug: It is mainly used for the input and output of RF signals in audiovisual equipment, as shown in (f) in the figure.
8. What is the "OFC" fever line? What is the fever line of "6N" and "7N"?
OFC "is an abbreviation for" OxygenFreeCopper "in English, meaning" oxygen free copper ". As is well known, gold and silver in metals have the lowest electrical resistivity and the best conductivity. However, if gold and silver are used as the production materials for fever wires, their prices are very expensive and not acceptable to most enthusiasts. Copper, as a commonly used metal material, has good conductivity and is widely used. However, due to its high content of impurities, most of which are oxides, its conductivity is affected. What is currently commonly used? Quot; The "OFC" of intelligent fever line Wire, which uses high-tech methods such as electrochemical method, PN junction implantation method, and isotope irradiation modification method to change the metal structure of copper, creating a unique metal structure on the surface of the copper wire, making the surface of the same copper wire suitable for transmitting frequency signals above 5000Hz, while its center is only suitable for transmitting frequency signals below 5000Hz, so that high and low frequencies do not interfere with each other, which is beneficial for improving playback sound when transmitting large signals Improve the clarity of playback and improve the sound quality.
"6N" and "7N" are used by enthusiasts to indicate the purity of fever wires made of oxygen free copper materials. Because the beginning of English "9" is the letter "N", for convenience, enthusiasts use "N" to represent "9", and the number before "N" indicates how many "9" there are. For example, "99.9999%" can be represented by "6N", which means its purity is 6 9s. The larger the number before N, the higher the purity of the fever line.
2、 What is the difference between a combination sound system and a sound system?
Answer: The so-called combination sound system is commonly referred to as a set of machines, and the various equipment in its sound system has been selected and assembled by the manufacturer, and cannot be disassembled casually. Due to the fact that manufacturers cater to the needs of the majority of consumers by considering the aesthetic appearance and diverse functions of their audio systems, while having average requirements for components and circuit structures, the playback sound quality is also relatively average, and it is only suitable for general consumers to use.
For audio enthusiasts and some professionals in the audio industry, the sound quality of a combination audio system cannot meet their requirements. They believe that even high-end combination audio systems can only perform at a medium to low-end level. Therefore, enthusiasts often freely choose and combine according to their own hobbies and the characteristics of various equipment playback, so that the playback sound of the equipment has a certain personality. The sound combination mainly focuses on whether the sound quality of the equipment can express the connotation of music and certain content that enthusiasts need, while the appearance and function of the equipment are secondary.
Of course, in order to achieve the best and most reasonable sound combination, one must also possess certain knowledge in music, electronics, acoustics, and other aspects.
3、 Home Theater
1. Overview of Home Theaters
In recent years, a strong AV whirlwind has swept abroad, and a more enthusiastic and popular AV fever than HI-FI has quickly emerged in China. This refers to creating a perfect home theater center at home - a home theater. Home cinema is a highly perfect combination of digital technology and analog audio technology that brings the audio effects that can only be enjoyed in the cinema to life in your home. You can taste fragrant cocos, listen to wonderful music, and indulge in karaoke with a wide variety of programs such as CDs, LDs, VCDs, DVDs, VCRs, and BS. You can also enjoy Dolby‘s directional logic surround cinema effects, immerse yourself in the cowboy style of the vast North American grasslands, and enjoy the magnificent style of the Alpine winter ski resort, Experience the thrilling scene of gunfights and battles; Feel the beauty of the future world in mythical science fiction films to the fullest All of these are the supreme enjoyment that home theaters bring to you. How to configure an ideal HI-FI sound combination or home theater?
2. Basic configuration of home cinema
Firstly, we pursue high-definition visual effects, so we must have a high-definition large screen color TV, usually 25-34 inch color TV. Imported brands such as Panasonic, Sony, Hitachi, Toshiba, and Philips are all your top choices. Of course, you can choose our domestic TV. If conditions permit, we can choose a better rear projection large screen color TV (50 inch), and even a projector, Form a true home theater.
How can we not pursue high fidelity sound effects when appreciating high-quality images? And for this premise, we need an efficient sound combination. In order to have visual enjoyment, we choose audio and video sources such as LD, VCD, DVD, etc. In fact, we can purchase compatible machines to save money and be practical. Audio is the focus of home cinemas, and AV amplifiers with Dolby‘s directional logic surround digital processing must be selected (specifically introduced later). There are a total of six speakers in home cinemas, including front left and right speakers, rear speaker speakers, and beautiful and quiet speakers. Is it possible to use the elegance and elegance of my elder brother‘s work, and to use the beauty and beauty of my garden? Is it necessary to maintain a clean and lively environment in order to purchase 5 sodium beer? In a home theater, unlike a sound combination, a home theater can create a sense of being in the scenery, which is due to the surround effect of the home theater. Let‘s introduce the surround sound field below.
Surround sound is the ability to reproduce the direction of each sound source in the original signal during playback, giving the viewer a sense of being surrounded by sound from different directions. The current surround sounds include Dolly Surround, Dollypro logic, THX, Dolby AC-3, and more.
(1) The playback form of Dolby surround sound is still stereo, only decoding the signals from the left and right channels through a matrix to obtain a surround sound channel.
(2) Dolby‘s directional logic surround sound utilizes a 4-2-4 encoding system, which produces four channels that provide accurate positioning.
(3) The THX (Tom Holman "experiment) system, also known as THX, was developed by Lucasfilm in the United States A home theater system developed by the company. It can create a cinematic effect in a general listening environment. The format of the THX system is designed for independent six channel wide screen stereoscopic cinemas. Compared to other sound systems, the most obvious feature of the THX system is that the sound is more natural and clear, with a strong sense of stereoscopic effect. The positioning of the sound image is very accurate, and it can generate a comprehensive dynamic range and frequency response, allowing the viewer to hear the same playback effect from any position in the listening environment.
The listening environment set by the THX system is that the front left and right speakers are the main channel of the full frequency band, and the middle channel speakers are located at the back of the screen, which can generate sound sources in three directions: left center, center, and right, to achieve accurate audio image positioning. The surround sound field is generated by the two speakers behind it, which can create an ideal diffuse surround sound effect. In order to enhance the low-frequency shock, THX has also added a subwoofer to create grand scenes in cinemas.
The biggest feature of the THX system compared to other audio systems is its unique control circuit, which mainly consists of a rebalancing circuit, a decorrelation circuit, and a tone matching circuit. The input dual channel signal is first decoded by the Dolby decoder, and then compensated for the imbalance of sound in different listening environments through a rebalancing circuit, thereby eliminating various noise in the signal. Then, the surrounding sound is divided into two unrelated outputs through the relevant circuit, driving the left and right surround speakers respectively to produce a diffusive surround effect. In order to generate a complete sound field, the voice matching circuit can keep the sound transmitted as it is, so that the replayed sound maintains the same voice color from the front main channel to the rear surround channel. The playback frequency response of the left, middle, and right channels of the THX system reaches 20Hz~20kHz; The frequency response of the surround sound channel can reach 100Hz~7kHz. THX has high requirements for decoders and speakers, and its speaker performance in the left, center, and right directions must be consistent. There are only a few companies producing THX products internationally, so the price is relatively high. If the THX system is used for playback, the playback software must be encoded according to the THX standard, otherwise it will not produce the THX effect.
(4) AC-3 surround sound is a new generation of Dolby digital surround sound developed by Dolby Company in 1991. (AC refers to AudioCoding) This Dolby AC-3 surround sound has 6 completely independent channels, including full band left, right, center, left surround, right surround, and a subwoofer channel below 120Hz, hence it is also called 5.1 channel. In the AC-3 specification, the subwoofer is 10dB larger than other full band channels to obtain impressive low-frequency information. AC-3 can also use the strong sound pressure of other channels to mask the noise of other channels. Due to this masking effect, Dolby AC-3 achieves unprecedented digital audio compression efficiency, making the sound quality more realistic. Digitized audio effects, including a wider dynamic range, all channel frequency response exceeding 20KHz, higher S/N ratio, fully independent 6-channel high-power output, without the problem of weak rear surround output.
Performance Comparison between Dolby AC-3 and THX
THX is a playback system that presents better results in the sound recorded by Dollysurround (similar to George Lucas‘ studio). It is basically a four channel Dolby surround sound, which means that the rear surround sound is still a single channel, only 7kHz frequency response sound image, rather than stereo sound. THX only made some adjustments using unique equipment: adding an extra subwoofer output; Simulate surround sound as body sound; Make corrections in the high pitched area.
The Dolby AC-3, on the other hand, uses a new sound processing system -5.1 channels from the beginning of recording. Compared to the AC-3‘s subwoofer, the THX‘s subwoofer output is an independent channel that enhances the bass effect during recording, and its content is completely different from the main five channels; The bass of THX is separated from the original four channel analysis, and is not a special sound effect recorded on a separate track. There is a significant difference between the two.
The launch of AC-3 is aimed at pursuing more realistic and faithful sound effects to the director‘s intentions. It is a product of the new era and will not immediately replace the Dolby surround decoder. These two new and old systems will inevitably have a buffer period coexisting, but in the future, home cinemas will definitely be dominated by Dolby AC-3.
(5) What is DSP sound field processing technology?
The full name of "DSP" is "Digital SoundField Processing". It is a new sound field processing system developed and produced by * * * Yamaha Company in the 1980s. The so-called sound field processing technology refers to the processing of sound wave reflections and residual signals from various occasions of singing and performance, forming different sound field characteristics data. It is packaged in a large-scale integrated circuit (DSP), and when replayed, the corresponding simulated sound field data is called up through the DSP circuit, which can more conveniently simulate various on-site effects. Therefore, adding DSP‘s live sensing signal to the signal that already has Dolby directional logic decoding will create a more magnificent sound field.
DSP software is divided into two categories: one with live characteristics and the other with surround sound characteristics. The former is used to process character dialogue and background music, while the latter is used to generate surround sound effects. Currently, DSP software generally has the functions of these two types of software.
On AV amplifiers with DSP sound field processing, the symbol "NATURALSOUNDDIGITALSOUNDFIELDPROCESS" is generally marked.
Currently, there are two main types of DSP sound field processing circuits. The commonly used method is "serial processing", which generates left, center, right, and surround sound signals after being processed by the Dolby decoder. Only the surround sound signal enters the DSP processing system, and the surround sound processed by the DSP can generate various simulated sound field effects. Another method is the "serial control method", where two DSP systems process left, center, and right sound field signals and surround sound signals respectively, so that the front and rear sound fields generated by simulation are mutually expanded, resulting in a complete simulated sound field. Its playback effect is better than the "serial processing method", but the circuit is more complex.
DSP sound field processing technology can generally generate the following analog sound fields: HallAinEurope: European Concert Hall A (2500 seats) HallBinEurope: European Concert Hall B (2000 seats)
HallCinEurope: European Concert Hall C (1700 seats)
HallDinU.S. A: US Concert Hall D (2600 seats)
HallEinEurope: European Concert Hall E (circular 2200 seat)
LiveConcert: Live Concert
Church: Church effect
LargeChapel; Cathedral effect
Afterflow: Evening effect
RealRoom: Standard Listening Room
SpaceFlange: Highlighting Space Effects
On the Town: urban street effect
RockConcert: Rock Concert
JazzClub: Jazz Music Club
ConcertVideo1: Concert Video
Classic/Opera
Recital: Solo Solo
ConcertVideo2: Concert Video
Pop/Rock: Pop/Rock music
Pavilion: Midsize Stadium
TvTheater: Television Theater
MonoMovie: Mono Movie
Variety/Ports: Sports programs
MovieTheater1: Cinema
70mm Spectacle: 70mm thriller movie
70mm Music: 70mm music movies
MovieTheater2: Cinema
70mm Adventure: 70mm action movie
70mm General: 70mm storyline movie
DolbyProLogicSurround: Dolby directional surround sound
(6) What is an SRS system? What is its basic working principle?
Generally speaking, only when the number of replayed channels reaches six or more can the human ear obtain accurate spatial distribution of the sound source. Although Dolby surround sound greatly improves the sound image positioning effect of replayed sound, its software still needs to undergo Dolby encoding to obtain Dolby effect, and the price of Dolby playback systems is also higher.
The biggest feature of SRS (Sound Retrieval System) is that with only two speakers, it can generate a live experience and surround sound that is basically the same as the actual live effect from ordinary dual channel programs, and is not limited by the listening environment. SRS has no requirements for sound sources, it can process and replay single and dual channels, Dolby encoded software, and other sound sources.
The basic principle of SRS is to utilize the auricle effect of the human ear, which means that during playback, regardless of the position of the speaker system, the human ear feels that the sound originates from the spatial direction corresponding to the frequency response, regardless of the location of the speaker. According to this principle, the SRS system uses circuits to modify the replayed sound, compensating for the difference between the frequency response of the replayed sound and the auditory frequency response of the human ear, so that the replayed sound forms a complete sound field replay system in terms of human psychology and subjective perception.
3. AV amplifier
AV amplifiers are the system center of home cinemas, which integrate audio and video signal control into an integrated audio-visual equipment. Compared with commonly used ordinary amplifiers, AV amplifiers mainly have Dolby directional logic surround decoding, AC-3, DSP, digital sound field processing, AM/FM digital tuning reception, and multiple sets of audio and video I/O interfaces. Some AV amplifiers also have SVIDO interfaces
4. Speaker
The speaker is the most important mouthpiece in the entire system.
Performance indicators of speakers
(1) If the sensitivity is marked with 87dB on the speaker, it means that a pink noise of 1W is directed towards the speaker, and the sound pressure value received one meter directly in front of the speaker is 87dB. From another perspective, the size of sensitivity reflects the difficulty of pushing the speaker, and it is best to have a sensitivity of over 87dB. This type of speaker is easier to push, and the requirements for the power amplifier are not too high.
(2) Impedance refers to the resistance value of a speaker at a frequency of 1Kz, usually 4 or 8 ohms, but also 5, 6, 10 ohms, etc. In fact, the impedance of a speaker changes with the working frequency, usually low in the low frequency range and high in the high frequency range. The ideal state of the speaker should be as small as possible with changes in operating frequency.
(3) When we buy a speaker, we usually see the words "how many watts to how many watts" on the nameplate. Its meaning is: the previous value refers to the minimum continuous power that drives this pair of speakers. Only when this power is reached can the speaker enter its optimal state, and the indicators also meet the requirements. The following numbers refer to the maximum power that the speaker can withstand, beyond which the unit may be burned. (4) Frequency response refers to the frequency range that a speaker can operate in. Generally, we require a full frequency range of 20Hz~20KHz, but there is usually attenuation at both ends. Of course, we require a wider frequency response, but it must also be flat, and at least the attenuation at both ends does not exceed 3dB to be meaningful.
（1） Left and right channel main speakers (20Hz~20KHz): During playback, they mainly reflect the size and depth of the audience‘s front sound field, and represent the left and right front sound field signals in the playback field. They play a leading role in the playback process. When playing storyboards with Dolby decoding in the AV system, the left and right channel main speakers represent their background music. The positioning is required to be equal to the height of the television.
（2） Middle speaker (40-20k): The middle speaker mainly displays the dialogue of characters and the sound in the middle during the playback process. The center speaker is generally placed on top of the television. There are two types of center speakers: one bass and two bass. The former should be placed vertically, while the latter should be placed horizontally.
（3） Surround speakers (40-10k) are mainly used to represent the sound behind the playback field. Only with surround speakers can the audience feel surrounded by the sound field, especially when playing war movies. When the plane flies from behind to the front, the surround speakers can give the audience an immersive feeling. The height of the surround speakers is usually 70 centimeters higher than the listener.
（4） When the dynamic signal is re amplified or a climax occurs in a feature film, the playback of the subwoofer (50-150) can make the viewer experience a towering momentum. Due to the directionality of the bass, the subwoofer can be placed freely, usually between the main channel and the surround speaker. 4、 Introduction to World Famous Brand Equipment
AV amplifier:
DSP: MARANTZSR73.SR82.SR92
KENWOODKR-V6070.KR-V7070KR-V8070
YAMAHARXV-890RXV-690RXV-2090
PIONEERV504
TEAC3020
JVC508808
DENONAVC-2000BAVC2500BAVC-2800
THX: KENWOODKR-X1000
ONKYOTX-SV828
AC-3ANSONICKR-TX1000
YAMAHADSP-3090
KENWOODKR-V3090
DENONAVC-3800AVR3600
In terms of domestic production: Yadun, Bada, Tianyi, Zhongshen, Dongpeng, Desai, etc.
In terms of equipment:
1. American JLB, EV, BOSS (PhD), AR, ACOUTECHLABS (Yadick), BOSTON (Boston), SOURCE (Sounce) and other speakers, as well as equipment such as INFINITV (Yanfei Lish), MCINTOSH (McIntosh), Lion Dragon, Crown, etc. Its characteristic is that it has a large dynamic range and better performance in music dynamics, making it more suitable for playing music with a strong sense of rhythm. 2. UK TANNOY, WHAREDWARO, B&W, MISSIO, NROGERS, MONITOR, as well as KEF speakers and equipment such as HARBETH, CELESTION, NAD, and QUAD. The characteristics of British equipment are: delicate expression of music details, exquisite manufacturing techniques, and more suitable for playing symphonies.
3. * * *‘s equipment in China is mainly based on packaged machines, such as Sony, Jianwu, Shanshui, Aihua, etc. The equipment mainly includes ACCUPHASE, DENON, TEAC, YAMAHA, ONKYO, MARANTZ, AKAI, LUXMAN, and CEC*** The characteristics of AV equipment are its high manufacturing process and extensive use of functions, especially in terms of advanced technology in AV equipment, making it more suitable for playing pop music.
4. ELAC (Italy) VISATON (Weishatong) HECO (Germany), etc. The playback sound of German audio equipment is relatively soft and natural, and the production process of the equipment is relatively high.
The main Danish equipment includes AVANCE, DANTA, DYNAAUDIO, DALI, JAMO, etc. Its characteristic is that the manufacturing process is also relatively fine, and its playback can better express the connotation of music.
6. Canadian equipment has a relatively small market share in China. Currently, popular PSB speakers have average craftsmanship but excellent performance, with a clean and sharp sound.
Of course, the quality of various audio equipment is mainly determined by various factors such as personal preferences and understanding of music, and cannot be generalized. In terms of speakers: Tianlang from the UK, VIFA from Denmark, and Proud Poetry from France
Made in China: Nanjing, Nanjing, Shanghai, Feile, Henan, Xin, Guangzhou, the Pearl River, Shanghai, Yindi, Zhuhai, Huiwei, Chengdu, Xinda, etc
Sound cable: Mecca Luhua (* * *) Osonic (* * *) Budweiser (USA) First class ELEO (Germany) Sandfish (UK) Thunder (China) Teflon (China), etc
Signal Line: Monster (USA) AR (USA) Economic and Practical Akihabara (* * *. Assembled in Shenzhen)
In terms of material selection:
Capacitors are one of the most important components in sound systems, and to achieve good sound quality, we must choose good capacitors. For example, ELAN high-speed electrolytic capacitors, which are our most commonly used and recognized best electrolytic capacitors, Panasonic gold electrolytic capacitors, * * * chemical capacitors, Dutch Philips capacitors (which are most suitable for filtering capacitors with good elasticity), Rubycon ruby capacitors (which are very common capacitors on the market), There are also ROE supplementary capacitors from West Germany, polypropylene capacitors such as WIMA from Germany, RIFA from Sweden, EC from the United States, MPK from France, etc
The resistor uses the original high-precision five ring resistor from Philips in the Netherlands
Potentiometers also play a crucial role in sound systems. We can choose * * * ALPS potentiometers, which are recognized as high-quality products in the sound industry. Taiwan‘s Zhengxin 16 model and domestically produced Fengzhisheng are also good choices
We choose a ring type transformer, and if possible, we can choose an E-type transformer
The signal line inside the machine must be shielded
We choose * * * TDK as the filter
It is best to choose gold plated connectors to ensure good contact. High content solder wire should be selected, preferably silver containing
In terms of earphones: the world famous Deep Sea Sear (the cheapest one is over 300 yuan), Germany‘s Bayer Power, Triangle Iron (* * *), Boss (Ph.D. America). They are all professional earphones in the world. Suitable for us to use are several affordable and high-quality earphones such as Sony, Panasonic, AIWA, etc
Several high-performance power amplifier chips suitable for our production
TDA1521/TDA1514A
TDA1521/TDA1514A are two chips specially designed and launched by Philips Netherlands for low distortion and high stability of digital audio playback. So the sound quality used to connect the CD player directly output is particularly good.
The parameter is: TDA1521 has an output power of 2 when the voltage is ± 16V and the impedance is 8 Ω × At 15W, the distortion at this time is only 0.5%. The working voltage of TDA1514A is ± 9V~± 30V. When the voltage is ± 25V and RL=8 Ω, the output power reaches 50W, and the total harmonic distortion is 0.08%. The input impedance is 20K Ω, the input sensitivity is 600mV, and the signal-to-noise ratio reaches 85dB. Its circuit is equipped with waiting and quiet states, with overheating protection, low offset voltage and high ripple suppression, and extremely low thermal resistance, with excellent high-frequency resolution and low-frequency force. Its timbre is transparent and pure, the bass is full and thick, and the treble is clear and lively, with a strong electronic tube charm.
The above two amplifiers have relatively few peripheral components and are "foolproof" type amplifier chips, which are very suitable for beginner enthusiasts to assemble. As long as you follow the circuit diagram and do not need to debug, you can achieve good results. Due to the relatively low input level of the chip, we do not need a preamplifier in production, as long as it is directly connected to our computer sound card, optical drive, and walkman. The famous computer multimedia speaker Ranger also uses these two chips. LM3886
LM38863TF is a high-power audio amplifier chip launched by NS Corporation (National Semiconductor Corporation) in the early 1990s.
The main parameters of the chip are: the continuous output power reaches 68W (peak 135W) when the working voltage is ± 9V~± 40V (recommended ± 25V~± 35V) RL=8 Ω. If the output power when connected to a BLT can reach 100W, and its distortion is less than 0.03%, its internal design has a very complete overload protection circuit. I am also using the chip, which has a very sweet tone, rich sound quality, and a strong electronic tube flavor, making it suitable for playing softer music.
NS Company also has familiar chips such as LM1875, LM1876, and LM4766, among which LM4766 is the latest, designed for dual channels and includes protection circuits for overvoltage, undervoltage, overload, and over temperature. Its output power is not less than 2 × 40W. Deep and elastic bass with a daring style.
TDA7294
TDA7294 is a novel DMOS high-power integrated power amplifier circuit that was launched by the famous SGS-THOMSON Microelectronics Company in Europe in the 1990s on the Chinese Mainland. It sweeps away the raw, cold, and hard tones of linear integrated amplifiers and thick film integrated amplifiers in the past, and is widely used in the HI-FI field, such as home theaters and active speakers. The design of this chip focuses on timbre and combines the advantages of bipolar signal processing circuits and power MOS. It has characteristics such as high voltage resistance, low noise, low distortion, and extremely friendly playback sound; The short-circuit current and overheat protection function make its performance more perfect.
The main parameters of TDA7294 are: Vs (power supply voltage)=± 10~± 40V; Io (peak output current) is 10 amperes; Po (RMS continuous output power) is 70W at Vs=± 35V and 8 Ω, and 70W at Vs=± 27V and 4 Ω; The music power (effective value) is 100W when Vs=± 38V and 8 Ω, and 100W when Vs=± 29V and 4 Ω. The total harmonic distortion is extremely low, only 0.005%.
In addition, SGS-THOMSON Microelectronics also has several representative power amplifier chips, such as TDA7295TDA7296TDA7264, TDA2030A (which is commonly used in our McBlue subwoofer), etc.
LM4610N
LM4610 is a high-quality DC controlled audio circuit from National Semiconductor Corporation of the United States. It is a stereo integrated circuit that utilizes DC voltage to control tone, volume, and channel balance, and has 3D sound field processing and equal loudness compensation functions. The circuit controls smoothly and smoothly, with natural and smooth sound quality, clear high-frequency, and excellent analytical power. The generated 3D surround sound field has a strong sense of three-dimensional space and surround, and the subjective feeling is similar to the effect of SRS.
The main electrical parameters of LM4610N are as follows: it has 3D sound field processing function and loudness compensation function. Loudness compensation is aimed at reducing the sensitivity of the human ear to high and low frequency signals when the volume is low. Therefore, it moderately compensates for the high and low frequency ends at different volumes, so that the human ear can always hear a flat and balanced response at any loudness. Its voltage range is: 9V~16V (typical 12V, current 35mA); The distortion is only 0.03%; Signal to noise ratio up to 80dB; The frequency bandwidth reaches 250kHz, and the volume is adjusted to 75dB; Balance adjustment is 1-20dB; The range of tone adjustment is ± 15dB; Maximum gain 2dB; LM4610N has the advantages of high input impedance (30 Ω) and low output resistance (20 Ω).
The use of LM6410N tone control circuit plays a prominent role in improving sound quality, enhancing low-frequency dynamics, and enhancing three-dimensional spatial sense. It can be said that LM4610N is a high-quality product for assembling power amplifier systems or replacing tuning parts.
BBE technology
BBE is a patented technology for sound enhancement and improvement. Its full name is Barcus BerryElectronics, which is a new technology launched by BBE.sound in the United States in 1985. It has been widely used since its emergence, such as foreign Panasonic and Sony, as well as new generation color TVs such as TCL, Skyworth, and Lehua in China. BBE technology has also been widely used in recording and recording, and some radio stations such as Canadian broadcasting companies, Swiss International Broadcasting, Korean Broadcasting, and the NHK government‘s broadcasting and television systems have all applied this technology.
High resolution BBE circuit XR1075
XR1075 is the latest high-resolution BBE chip launched by XEAR Company in the United States. On the basis of XR1071, a new bipolar technology is adopted, which reduces the noise figure and total harmonic distortion of the chip. The chip size is smaller, and the peripheral components are further simplified. The high and low frequency extension, high frequency analysis force enhancement adjustment range, and low frequency compensation range are both wider than XR1071. High frequency adjustment range -0.5~+13db, low frequency compensation adjustment range -0.5~+13db
Digital subwoofer processor M51134P
M51134P is a specialized subwoofer detection and enhancement circuit developed by Mitsubishi Corporation for AV audio and video systems. Its internal components include frequency detection, regulator, level detection, low-pass filtering VCA voltage controlled amplification, etc. The principle is to use digital filtering to detect the level of the low-frequency components in the input signal, strengthen the corresponding low-frequency components, and perform low-frequency dynamic expansion (also completed by a voltage controlled amplifier). Its principle is different from the general low-pass filter form of the bass enhancement circuit. The heavy bass effect provided by M51134P has a strong sense of shock, especially the sound of thunder, artillery, explosions, etc. M51134P only detects signals below 120Hz. If there are no components below 120Hz in the input signal, there is no output.
Latest standard virtual Dolby surround sound chip QS7779/QS7785
QS7779/QS7785 is a single-chip virtualized surround sound processing circuit launched by Qsound Audio Laboratory in Canada. It is currently recognized in the industry as the virtual Dolby surround sound chip with the closest processing effect to natural sound! QS7779 adopts a 2 in 2 out method, while QS7785 adopts a 2 in 5 out method. Both of them include Dolby directional logic and DVD (AC-3) mixed signal decoder, using Qsound Lab‘s patented QSurround virtual surround technology and authorized by Qsound Lab. The main functions of this chip are: (1) If the input is a regular stereo signal, Then perform stereo effect enhancement: (2) If the input is a 2-channel matrix encoded signal (Dolby directional logic or mixed AC-3 signal), first decode it, and then virtualize it into a 2-channel or 5-channel output.
Main features of QS7779:
1. Equipped with Dolby directional logic and DVD (AC-3) mixed signal decoding output, using 2 speakers to achieve virtual surround sound.
2. Signal to noise ratio 11db, dynamic range 110db
Main features of QS7785:
1. Equipped with Dolby directional logic and DVD (AC-3) mixed signal decoding output, the solved surround signal is a 2-channel full frequency band, which is the same as AC-3 surround sound and superior to Dolby directional logic system.
2. The front adopts 3D stereo enhancement technology, and the rear adopts 3D synthetic virtual surround technology. There are two enhancement methods (low enhancement and high enhancement), with center output and bass enhancement functions.
3. Use 5-channel surround sound or 2-channel output.
4. Signal to noise ratio 11db, dynamic range 110db
Operational amplifier
We commonly or commonly use: 4558 (which is relatively cheap and usually used for some Walkmans). NE5532 was once known as the king of operational amplifiers AD712K. AD827 (very good operational amplifiers are difficult to buy on the market, it is said that orders also need to wait for three months, and the market price is about 100 yuan per piece). The above are dual operational amplifiers, and there are also four operational amplifiers such as TL084.LT058, etc