Here I want to write a “decoder” to talk about what I think of some basic things, and some most common mistakes.

In fact, the “decoder” often said by enthusiasts is a wrong name. The correct name should be a “digital converter”. English is Digital to Analog Converter, and the abbreviation is DAC. There is no concept of “decoding” here, but the conversion of digital signals to analog signals. The so -called “decoder”, the Dolby surround sound decoding used in AV, that is decoding, but the concept of DAC is “conversion”, not decoding. However, using the word decoder to represent DAC, it has been agreed to become popular for a long time, so everyone can understand.

Since it is the era of digital audio today, all the “sound replay” we use in our lives are digital, which means that the essence is to use binary digital signals composed of 0 and 1 to represent audio. Mobile phones, computers, computer sound cards, TVs (basically all digitalization), portable, recording pens, and the sound replay and recording equipment we use are digital audio and no analog audio. In fact, in addition to enthusiasts, many ordinary people do not know what simulation audio equipment is, simulation audio media. Tape, vinyl records, tape recorders, vinyl singers, and those with audio carriers and equipment have entered the museum, and the lives of ordinary people have nothing to interact.

In the absolute mainstream of this digital audio, all sound recording and playback equipment has a part, a chip, and a circuit, which is the function of “digital simulation conversion”. That is to say, the digital audio signal (Digital) represented by the 0 and 1 binary signals to an analog electrical signal (Analog). What is an analog telecommunications signal? What is the biggest difference between it and digital audio signal? In a word, an analog audio signal is a continuous changing electrical signal. If it is represented by a waveform, it is a smooth waveform. Digital audio signals are only 0 and 1 state, not black or white, and there is no intermediate state. From the perspective of electrical signals, digital audio signals are a series of pulse signals, and the analog audio signal is a non -pulse -type signal that is constantly changing and intensity.

If we observe the surface of vinyl records and watch with a magnifying glass, we can see the actual “ripple” left by the sound. The essence of the sound is vibration, and the vibration of the sound is a series of waveforms. From its essence, the sound is “simulation”. Edison’s initially invented vocal machine and the wax of saved sounds are the waveforms that directly record the sound. From Edison era, to later tapes, LP vinyl records, They are the era of simulated audio. Why was simulated audio replaced by digital audio later? The root cause is the recording, replication and replay of the simulation audio, and there are serious defects -all the simulation recording carriers have noise, and each replication and editing will introduce new noise and new distortion. Even every player will cause wear. After multiple replication and editing of a simulated recording “mother belt”, noise will become very large. My college days were the era when the card tape prevailed. At that time, the people who came at that time knew that every time the tape was copied, the sound quality was obviously degraded. The professional “torture brother” of the fans, even if there is the original tape on hand, will not be copied by the original magnetic magnet. Instead, it will copy a “son belt” first, and then use the son to copy the grandson belt and sell it to the music fans. Essence Why? Because each time the original tape is played, the sound quality will be lost once. After repeated playback, the high -frequency response will be significantly degraded. The “grandson belt” that music fans can buy, and its sound quality has been obviously degraded than the original magnetic bring, but the fans at the time could only listen to such things. This is the pain of simulated audio era.

As soon as the digital audio era, people found that because digital audio is a binary signal composed of 0 and 1, copying is no loss. As long as the data is good, and the sound quality will not be degraded. Digital recorders and CD singers themselves have extremely mild noise in themselves, so digital audio can easily achieve a high signal -to -noise ratio of 90 decibels, which solve the noise problem that has troubled people for decades. Due to the non -contact design of the CD bald head, the playback process is not lost. So in the 1980s, digital audio with CD as the carrier quickly entered people’s lives, and quickly replaced the simulation audio carrier and playback equipment. Of course, there are many enthusiasts who miss vinyl records such as vinyl records now, thinking that they are soft, warm, “simulated” and so on. There are “work” components. Psychology. At the beginning, digital audio replaced simulation audio, very normal and logical, without any wrongdoing or reluctant ingredients. From the perspective of the overall situation, although digital audio is not as “natural” as analog audio (the essence of sound wave vibration is analog waveform), digital audio has huge superiority and should replace simulation audio.

Since digital audio is so good, why does it need a “digital modulus” to convert the digital audio with analog signal? The key is that in the three major parts of the audio system, the two links of the amplifier and speaker can still process simulation audio signals. No matter how we do it, let our ears hear the sound, the speaker must also accept analog electrical signal and emit vibration according to analog electrical signal. If the pulse digital signal composed of a series 0 and 1 is given, the speaker can only emit countless noise. Therefore, the essence of the amplifier is the essence of accepting analog signals and enlarging it, so that the signal strength can reach the degree of driving the speaker. The horn link (including the headset) is also completely “simulated”. Only the audio signal of the analog can be accepted to make a meaningful sound.

Therefore, the sound source must output analog audio signal to give the amplifier. It cannot output digital signals to give the amplifier and horn. Therefore, although we are in the era of digital audio, music is mostly recording, editing, publishing, circulating, and saving in digital forms. Signals so that we can appreciate music. In other words, the entire process of recording and replay is this -the original music sound (simulated sound wave) -The microphone recording (the electro -transformation of the simulation method, the sound wave becomes a continuous analog electrical signal) -D digital recorder records recorded by a digital recorder recorder Come down (the analog electrical signal is converted to a digital signal in this link) -Cing, Publishing (Digital Method) -To Broadcast-DAC Digital Model Transformation (Conversion Return to Simulation Audio Signal) Sound wave).

所以,我们就知道,在所有的能播放数字音频的设备里,从手机、电脑、电脑声卡到电视机、随身听、蓝光机,所有这些设备,里面都有一个部分、一个线路、一个芯片, It is a “digital model conversion” (DAC) work, and the digital audio is converted into an analog electrical signal output. The “decoder” or DAC said what enthusiasts say, but because the enthusiasts pay attention to this part, they think that this part has a great impact on sound quality, so I chose a “decoder” product with a single function of the independent case.

The “decoder” or “digital modulus” or DAC played by the enthusiasts is indeed an important sound source equipment. It belongs to the typical, single -function, and sound quality -oriented device. From a functional perspective, it can be said that it has only one function -converting the input digital audio signal into an analog audio signal output. But in this function, different grades of decoders are completely different and different. The decoder is a high -grade and unprecedented brand in the sound source equipment played by enthusiasts. The price ranges from hundreds of yuan to hundreds of thousands of yuan, with at least hundreds of famous brands.

All the decoders can see the two sets of interfaces on its back. One group is digital inputs, and the other is an analog outputs. Digital signals from digital sources are sent from the digital input port of the decoder. When working, the output signal of the analog output port is received from the later amplifier link, or there is a source speaker.

Digital input ports, the most common are four forms -Optical, coaxial (coax), AES/EBU, USB. Among them, optical fiber ports are generally so -called TOSLINK. There are two 3.5 mm round holes and square mouths (can be converted to each other). The platforms are generally square mouths, and the 3.5mm round holes are used for many portable devices. There are two types of coaxial ports: RCA type and BNC type (cable cables at home are generally the BNC port. See what the connected TV interface will know what BNC is), so the coaxial axis also has two RCA heads and BNC header. In fact, the BNC coaxial port has an advantage, but most equipment is still equipped with a RCA -type coaxial port. The RCA -type coaxial port is exactly the same as the single -end simulation port. Some first burns will be confused. In fact, you only need to see one point: the simulation RCA port must be one pair, divided into left and right (labeled L and R), and the number of numbers, and the number of numbers, the number of numbers, and the digital numbers, and the number of numbers, and the number of numbers, and the number of numbers, and numbers, and digital numbers, and numbers, digital numbers, and digital numbers. There is only one RCA port at the same axle, regardless of left and right.

AES/EBU is commonly known as the “balanced digital port”. It is a three -pin balanced card agricultural port. It is used in professional equipment because it has the advantages of long -distance transmission of anti -interference, but it is rare in home equipment. However, if the user’s device can be connected through AES/EBU, this is still a way to connect it is worthy of priority. The USB port is a digital port that has been popularized in recent years. After all, many people now buy the decoder, and they are connected to the computer through the USB cable. The method of exchangeing data from the USB port and computer has also developed from the early Adaptive Mode (adaptive mode) to the extensive asynchronous mode (ASYNCHRONOUS MODE). In this mode, the built -in clock of the decoder becomes dominant, which reduces the influence of the front -end computer on sound.

If there is no decoder at the USB input terminal -there are two cases, one is an old -fashioned decoder, and the other is a very advanced decoder -you need to connect to the computer, then you can use a product called “USB interface” product connect. The computer USB port receives the “USB interface”, and the USB interface is then received by the coaxial or AES/EBU port. I have introduced this kind of thing before, you can refer to some old texts.

There are two types of decoder’s simulation output port: single -ended RCA output, and XLR output of the balance method. If it is a micro -decoder, it may be loaded with a 3.5 mm analog output. 3.5 mm holes can be made into a headset output, can be made into optical fiber ports, and can be made into analog input or output port. Because its volume is small, it does not take up the place, and it is very common in portable equipment.

Below is the back of the AURALIC VEGA decoder. Its interface is very complete. The numbers and analog interface mentioned earlier are available.

There are a few relatively high -end decoders. In addition to these conventional digital input and simulation output, there is a “clock interface”, which usually uses the BNC terminal, which is also mentioned here.

Among all the decoders, all digital audio devices have a component called “clock”. Its form can be an independent crystal, which can be integrated in the chip, but the role is the same. It determines the “time foundation” of the entire device when working. We know that the principle of digital audio is 44.1K Hertz (CD specifications), or higher frequencies (such as 96K Hertz), “sampling” (Sampling) in continuous changes, get a series of values, replay music, replay music At the time of this, the simulation signal must be rebuilt according to this sampling frequency. In this process, the frequency accuracy of sampling and reconstruction is very, very important, and it will directly affect whether the simulation signal after the reconstruction is accurate. Therefore, the “clock” in the decoder will significantly affect the sound. Many mid -to -high -end decoders now use high -precision crystal. For example, the VEGA decoder mentioned earlier uses the so -called “Filtllo Hotel”, which has the characteristics of femtosecond -grade accuracy and extremely low Jitter, bringing high sound quality.

However, there is another independent advanced product called “Independence Clock”. The representative work is the product of Japanese ESOTERIC, including the world’s most expensive G-0RB super clock with a price of 100,000 yuan. RB is the abbreviation of metal element 缩. This clock uses the observatory atomic clock module in the observatory. With the carefully designed power supply, case, shock absorption, and peripheral circuits, the lowest Jitter in the audio equipment can be achieved. This independent clock device is connected to the decoder with the clock interface through the digital coaxial axis of the BNC terminal. After the connection, the signal of the independent clock replaces the built -in clock of the decoder. This decoder can work according to a clock with higher accuracy and lower Jitter. If the number source and decoder have the clock input interface, then you can connect to the same independent clock, and it will synchronize the entire sound source system to achieve the best effect. Of course, this must be a very advanced system, and the general mid -range system cannot be used. Below is behind the ESoteric G0RB, several groups are clock signal output ports of different frequencies.

Regarding the “decoder”, there are some very common mistakes. I think it is necessary to clarify. Here are some of the most classic examples, and explain it a little.

1) Decoding chip decision theory. Many first -fired burn judgment the decoder: see what decoding chip is used. If they think that they think that high -end chips and more expensive decoding chips, then they think that the decoder is on the upper grade; if the decoding chip used is not expensive, it depends on it. Regarding this issue, I have written a special article. I suggest you take a look at: http://blog.sina.com.cn/s/blog_4e2a0430012e6ws.html. In fact, there are not many mainstream decoding chips. For example There are more and more chip products, and the manufacturer even produces a simple version of the chip supply to mobile phone vendors to enable mobile phones to achieve better sound quality. Recently, the number of manufacturers using Japanese AKM decoding chips has also increased. Some European brands always favor Wolfson’s decoding chip. But there is no reason to say that the overall sound quality of the product using the 9018 decoding chip must be better than Wolfson. Also using the decoder of the 9018 chip, the style and grade of the sound can also be quite different. I have no intention of explaining this question, and it is enough to read that article. There are multiple decisive factors of the sound quality and style of the decoder. It is a systematic engineering, which is definitely not a chip that can be determined.

2) Decoder decision theory. That is, “as long as the decoder is good, it can be ignored in front.” The “front” here refers to the device that provides digital signals to the decoder, or “digital source”. It can be a computer sound card, a CD machine or a CD turntable, a device that can be listened to the device, can be a blue light machine, any device with a digital output port, which can receive a decoder. This misunderstanding has a long history. As early as the period when the CD machine prevailed, some enthusiasts believed that as long as the CD machine was connected to a high -end decoder, it could easily reach the high -level sound quality. Anyway, the digital source only provides a binary digital signal composed of 0 and 1, and it is guaranteed that there is no error code!

音响入门ABC之六——解码器(DAC)

This understanding is completely wrong. A little experienced enthusiasts will notice when playing with the equipment. The same decoder, when it connects different digital source devices, such as different computer sound cards and different CD turntables, the sound coming out can be very different. I tried with a good decoder, and I connected a super rotten DVD machine or a low -end computer sound card to make the digital source. The sound came out was very unpleasant. Replace the number source with a well -quality CD turntable, and the sound becomes very good immediately. Different quality numbers can be very different, and they can be “different from life and death.” Let me say it again, enthusiasts with a little experience in playing machine will soon notice this.

The essence of the problem is that when the CD turntable is connected to the decoder by fiber or coaxial axis, the basis of the digital signal is the clock of the CD turntable, not the clock of the decoder. Even if the clock of the decoder is high and the grade is high, it can only be “corrected” within a certain range, and it is impossible to completely replace the clock of the previous number source. When we connect a very bad DVD machine to a high -end decoder, the digital signal from the DVD machine, Jitter will be very large. After entering the decoder This Jitter’s large digital signal is made of a little positive correction (based on the high precision clock inside the decoder), but it cannot completely rewrite the clock of the previous DVD machine. It also has to follow the bad clock. Some. In this system, the Jitter of the digital signal of the decoding chip finally entered the clock of the DVD machine, the clock of the decoder, and the clock of the decoder. Therefore, we must keep in mind that when the digital audio stream is played, the problem caused by the source (poor digital equipment, high Jitter), the latter link cannot be completely solved. If the signal quality from the digital source is not good, with a high Jitter, the decoder is powerful and the clock accuracy in the decoder is high, and it is powerless.

However, in one case, the clock of the decoder will play a dominant role, which is when the USB asynchronous technology transmission. Most decoders now use the so -called “asynchronous transmission technology”. When switching data with the computer, the clock of the decoder is dominated. In other words, as long as the quality of the decoder is high and the internal clock accuracy is good, then it can basically ensure the better sound quality. What kind of computer is used in front is not too important. Of course, it is not that it is not important. For example, in the architecture of the computer-USB asynchronous transmission-decoder, the USB cable, computer system condition, and computer playback software will still affect sound quality, but these factors generally will not be determined by decision. factor.

音响入门ABC之六——解码器(DAC)

As mentioned earlier, I will repeat it in a simple and practical language: if the digital source is connected to the decoder by optical fiber and coaxial axis, the output quality of the digital source is very important. Quality. A very bad number source is enough to destroy the best decoder. If the computer is connected to the decoder as an asynchronous transmission of USB, the quality of the decoder itself is the most important, although it is not the only influencing factor. In any case, in terms of concept, the decoder is not the only decisive factor in the sound source, not to say that as long as the decoder cattle, the sound source is inevitable; the digital source, decoder, and connection line are played by these factors.

Finally, in summary, in general, in this digital audio era, decoder is still the most important link in the entire “sound source” category, which has the greatest impact on the quality and tone of sound. Finding and having a good quality and style of appetite is important for enthusiasts. In this era we are, especially streaming media playback (played track), there are many forms that can be used: computer+USB decoding, computer sound card+decoding, computer+USB interface+decoding, NAS+decoder, independent player player, independent player player , Independent player+decoding, portable player+decoding, etc. In the future, there may be more types of streaming playback. In the future, the Hi-Fi streaming media play, I personally think that it is a diversified trend. Different people are used to play according to their habits, and there will be no absolute mainstream form. But no matter what form of play, the decoder is the most important link in the sound source system.

(Finish)

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