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Why does even digital audio deteriorate? Part 2

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Why does even digital audio deteriorate? Part 2

Digital Audio

I am not an audiophile, and I am not the type that is very demanding to listen, which is why I am not aware of so-called pure audio.
So I didn’t know Mr. Kanai at all, but he seems to be famous for that source.

Digital Audio

The reason I met Mr. Kanai was because I saw the serialized article “What is the definitive SACD born in the” Kaimaru Room “” from the “Ken Fujimoto Weekly Digital Audio Lab” which I have long subscribed to ? , this article was really interesting.

This is an interview article about the production process of Emi Fujita’s (Le Couple) work “Manzanilla Best Audio”, but it is very easy to understand the difference in mindset between the production side and the actual listener. I think .

Anyway, the content on Mr. Kanai’s HP was scaled content for me.
It’s a good opportunity, so I’d like to change my mind a bit.

Especially around surround sound, you need to study.
I cannot understand it at all because I have not tried surround sound as a real experience.

I am also very interested in SACD, but I am very concerned about buying a PS3 because I do not have a playback environment.

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Why does even digital audio deteriorate?

Digital Audio

It is not limited to DTM and DAW, I think if you are a musician you may have noticed the deterioration in sound quality.

Digital Audio

For example, change the shield to a higher one or allow it to be bypassed entirely when the effector is not in use.
When it comes to old stories, record without ping-pong as much as possible.

I don’t think the deterioration in sound quality bothers me, but I’m obviously not afraid of losing sound, so I’m careful.
But, it is simply an analog of the story in, don’t use your mind as I don’t say anything about digital audio.

Why?
That’s because I couldn’t fully understand the concept of “digital data degradation”.

When it comes to guitars, it’s easy to see that upgrading the various effectors and protectors between the guitar and the amp, and the protector that goes to the amp’s audio I / O “improves the sound.”
It is an analog signal.
But I couldn’t quite understand the history of changing the Firewire cable connecting the audio I / O to the PC to improve the sound quality.

It does not matter if it is via the Internet or copying from a medium, but when you think about it normally and transfer data digitally, there is no deterioration.
To be precise, transmission loss always occurs, so the signal itself deteriorates, but when the data of the transfer result is considered as the center, the picture is that the transfer retries increase rather than deteriorate, and on the user side. From the point of view, I don’t think it can be said that the transfer time has increased and the data has deteriorated.

If the transmission loss is very large, the file itself may be corrupted, and in the case of data to be processed in real time, the transfer may not be on time and the processing may result in an error, but it is transfers normally. In that case, I thought it was digital data that the data should be the same before and after the transfer, no matter how much transmission loss occurred or how long it would take …
(This is just my own expectation. I don’t know if it fits).

Also, in terms of sound, there are two patterns: deterioration of the analog sound quality, which is literally “deterioration” that produces sloppy sound like “thinning sound”, and noise mixed in the transmission path. I think that in the case of a digital data error, it is not a level that says “the sound is bad”, but it becomes a choppy sound or a loud sound that can only be called noise.

Even in digital, analog affects sound quality

analog digital

Audio network audio for PC

analog digital audio

Whether you listen to music or watch videos on television, it is becoming more and more common to use digital data as a sound source.

With the improvement of the quality of communications, such as optical lines on the Internet, the amount of information is increasing and the enjoyment and choices for users are increasing.

However, whether you listen to music on a smartphone or PC audio, the sound quality of subscriptions differs by high resolution, but analog is really important to fully bring out the high quality of the source of sound.

Analog opinions that are not anti-digital

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Analog opinions that are not anti-digital
At first glance, the difference in the amount of digital information appears to be the deciding factor.
CD player whose analog circuit influences the sound.

At first glance, the difference in the amount of digital information appears to be the deciding factor.

Digital sound sources (software) that started with CDs are now changing for downloads and stories.

Music data has an Internet environment and digital devices, such as PCs, network players, and transmitters, receive digital signals and a DA converter converts them to analog.

The analog signal converted from digital is amplified by the amplifier and sound is output from the speaker.

Recently, it seems that the digital sound source in the smartphone is popular for products that play music directly from the speaker via Wi-Fi or Bluetooth, but in fact, the Bluetooth speaker has a DA converter that converts digital to analog. ..

Analog-Digital Processing

Analog-Digital Processing

Digital vs Analog

A digital signal is obtained from analog or is directly synthesized into digital (in electric musical instruments).

DIGITAL ANALOG AUDIO

Converting from analog to digital involves two basic operations: sampling and quantizing. Discretization is the replacement of a continuous signal with a series of samples of its instantaneous values taken at regular intervals. According to the Kotelnikov-Chenon theorem, a discrete signal can be completely restored later, as long as the sampling frequency is at least twice the upper frequency of the signal spectrum. The samples are then quantized according to level: each of them is assigned a discrete value closer to the real one. The precision of quantization is determined by the bit width of the binary representation. The higher the bit depth, the more quantization levels (2N,

The audio CD format has a sampling frequency of 44.1 kHz and 16 bits. This gives 44 thousand samples per second, each of which can take one of 216 = 65536 levels (for each of the stereo channels).

In addition to the 44.1 kHz / 16-bit format, others are used in digital recording. Studio recording is generally done in 20-24 bit, then the data is converted to audio CD by recalculation. The extra bits are then discarded or (better) rounded, sometimes pseudo-random noise is added to reduce quantization noise (dither).

The most advanced custom audio formats are DVD Audio and Super Audio CD (SACD). DVD Audio adopts the MLP lossless data compression algorithm developed by Meridian. And SACD, unlike other formats, does not use pulse code modulation (PCM or PCM), but one-bit encoding of the DSD (Discrete Pulse Width Modulation) stream. SACDs come in single or double layer (hybrid) discs with a normal CD layer.

The most popular audio medium today is compact disc, despite certain limitations in sound quality seen by audiophiles. The reason for them is in the low sample rate: for an accurate reconstruction of signals near the upper limit of the audio range, a filter that is not physically workable is needed (its impulse response covers the negative time area). This is compensated to some extent by digital filtering with higher sampling and bit depth. The data on the disc is redundantly encoded (Reed-Solomon code) to ensure smooth playback in real time.

Broadband communication is required for digital audio transmission, especially for uncompressed high definition multichannel transmissions.

Figure: 1. Digitizing an analog signal and obtaining digital samples on CD Audio and SACD (right)

DIGITAL AUDIO TRANSMISSION

The communication lines for digital audio transmission can be cables, optical lines, and overhead radio.

For the transmission of PCM signals over wired lines, AES / EBU (balanced, coaxial), S / PDIF (unbalanced coaxial) interfaces have been developed, which provide transmission of various signals (clock frequency, digital word rate, channel data) over a cable. Inside the devices, these signals are transmitted separately, at the output of the transport mechanism they are encoded and at the input of a digital-to-analog converter (in two-block systems) they are separated again in a digital receiver.

Typically, a high-quality coaxial cable is used for digital audio transmission. There are also S / PDIF converters for fiber optic lines: AT&T ST and Toslink (the latter is standard in consumer equipment). And also, for the use of twisted pairs in Ethernet cable networks. The medium of distribution for compressed audio in the form of archived files is the Internet.

Like any digital signal, digitized audio is distributed and switched by special devices: distribution amplifiers, matrix switches, and conventional.

There is one factor that negatively affects digital signals, and often negates almost all of the advantages of digital audio over analog, including the ability to repeatedly copy, stream, and archive programs without any loss of quality: we are talking about jitter. Jitter is jitter, or the uncertainty of a transition from 0 to 1 and vice versa.

Differences between analog and digital audio

Differences between analog and digital audio

Analog and Digita

Very often we hear definitions such as “digital” or “discrete” signal, how is it different from “analog”?

Actual] Difference between Analog and Digital Signal with Examples - ETechnoG

The difference is that the analog signal is continuous in time (blue line), while the digital signal consists of a limited set of coordinates (red dots). If everything is reduced to coordinates, then any segment of an analog signal consists of an infinite number of coordinates.

For a digital signal, the coordinates along the horizontal axis are located at regular intervals, according to the sampling frequency. In the popular audio CD format, this is 44,100 points per second. Vertically, the precision of the coordinate height corresponds to the digit capacity of the digital signal, for 8 bits it is 256 levels, for 16 bits = 65536 and for 24 bits = 16777216 levels. The greater the bit depth (the number of levels), the closer the vertical coordinates will be to the original wave.

Analog sources are cassette tapes and vinyl. Digital sources are: CD-Audio, DVD-Audio, SA-CD (DSD) and files in WAVE and DSD formats (including those derived from APE, Flac, Mp3, Ogg, etc.).

Advantages and disadvantages of the analog signal

The advantage of the analog signal is that it is in the analog form that we perceive sound with our ears. And although our auditory system converts the perceived sound stream into digital form and transmits it to the brain in this way, science and technology have not yet reached the possibility of connecting players and other sound sources directly in this way. Currently, this research is being actively carried out for people with disabilities, and we exclusively enjoy analog sound.

The downside to an analog signal is the ability to store, transmit, and replicate the signal. When recording on tape or vinyl, the quality of the signal will depend on the properties of the tape or vinyl. Over time, the tape will degauss and the quality of the recorded signal will deteriorate. Each read gradually destroys the medium and rewriting introduces additional distortion, where additional deviations are added by the next medium (tape or vinyl), devices for reading, recording and transmitting a signal.

Making a copy of an analog signal is like taking another photograph to copy a photograph.

Advantages and disadvantages of a digital signal

The advantages of a digital signal include precision when copying and transmitting an audio stream, where the original is no different from the copy.

The main disadvantage can be considered that the digital signal is an intermediate stage and the precision of the final analog signal will depend on how detailed and precise the coordinates of the sound wave are. It is quite logical that the more points there are and the more precise the coordinates, the more precise the wave will be. But there is still no consensus on how many coordinates and data precision is sufficient to say that the digital representation of the signal is sufficient to accurately reconstruct the analog signal, indistinguishable from the original by our ears.

In terms of data volume, the capacity of a conventional analog audio cassette is only 700-1.1 MB, while a normal CD is 700 MB. This gives an indication of the need for high capacity media. And this results in a separate war of compromises with different requirements for the number of descriptive points and for the precision of the coordinates.

Today, it is considered sufficient to represent a sound wave with a sampling frequency of 44.1 kHz and a bit depth of 16 bits. With a sampling frequency of 44.1 kHz, you can recall up to 22 kHz. As psychoacoustic studies show, a further increase in sample rate is unremarkable, but an increase in bit depth provides a subjective improvement.

How DACs Build the Wave

A DAC is a digital-to-analog converter, an item that converts digital sound to analog. We’ll take a quick look at the basics. If the comments show interest in considering various points in more detail, a separate material will be published.

Multibit DAC

Most often, the wave is presented in the form of steps, which is due to the architecture of the first generation of R-2R multi-bit DACs, which function similar to a relay switch.