Tag: how digital sound is recorded on compact disc

How to digitize sound quality

Many books and articles have been written on how to use a sound card, including on our website.

However, this time we will not talk about what every regular reader of the Multimedia section already knows, but about what is called the practice of digital sound recording. Surely any owner of a multimedia computer sooner or later starts this exciting activity. Actually, for this (and not only) you buy a computer. However, this process is not that simple and requires some skill to achieve the highest quality. The purpose of this article is to give the readers of the site (and the owners of SB Live! Among them in particular) some useful recommendations in this area, which for one reason or another are not adequately covered by the press or the Web. .

To begin with, at one point I was faced with the question of converting my music library on cassettes to MP3 files, and I had to spend more than one night for the process of transferring audio information to a computer to be the highest quality. and as versatile as possible for most audio recordings. I will say right away that despite my solid experience in recording (both analog and digital), this, at first glance, an innocent occupation required a lot of mobilization of my forces and knowledge.

However, the user of a decent sound card is by no means obliged (as I am) to have a higher education in radio engineering and yet has the right to demand a decent quality of the received recording. I consider it my duty to provide the iXBT audience with that minimum of information which, I hope, will avoid many of the problems associated with digitizing audio (such as interference, interference, etc.). I think some of the information in this material will be useful for advanced users. In order not to go beyond the limits of decency, I will also say that everything that is written below is the result of generalizing the experience of many people, but of course it does not claim to be the ultimate truth. Reasonable reviews from readers are always good! (You can also write your comments on our conference articles About Site Materials.)

General remarks
Most of the time, multimedia users have to digitize the following sources:

Vinyl records . The main thing here is a good turntable and a preamplifier-corrector (the one that is built into expensive amplifiers). Of home turntables, I recommend Phoenix EP 009S (diamond ellipse head, auto arm). And then, we record the record on a computer, clean it from clicks (Click Elimination), filter the infrasound below 16 Hz (to eliminate noise), and cut the recording into songs. It is better not to eliminate the noise, since the noise of 65-70 dB at the output of the player (or the equalizer) is not that great. For example, 65-70 dB is the analog output of most CD-ROMs and nothing. But with the background (an unpleasant low-frequency tone of 50, 100, 150, etc.) it is better to find out before digitizing: the earth is hanging somewhere or the poles inside the player are confused.

Microphone I mean a good mic and mic amp. And about that, and about another, you can find a lot of information in print media, and also on the Web. I will give advice on only one thing.

The point is, in the practice of the study, there is a very clever principle for patch cords. Everyone already knows the twisted pair of signal lines, but here is how to solder the cables at the ends of the cables, only the dedicated ones, and even then not all.

The following image shows how to properly make a cable that will not contribute to the recording quality if it consists of quality cables. A copper braid is used as a screen (copper is desirable everywhere!). The signal wires inside the shield are a twisted pair of copper twisted wires. It is better to buy such a cable from a store that sells professional microphones, guitars, etc. (the cable will cost less than the interference). It is worth noting that only with a microphone it is necessary to be so scrupulous with the cable, otherwise you will switch microphone amplifiers and microphones to the Greek calendars.

How digital sound works. (Part 1)

In this post, I’d like to talk about digital sound and, along the way, expose such a popular form of freestyle as audiophilia.

Unfortunately, lately I see more and more manifestations of this phenomenon, penetrating the minds of even quite reasonable people and causing them to spend money on technological analogues of homeopathic pills. I say “sadly” because everything that I will write in this article should, in principle, be known to all the people who graduated from school. But for some reason that I do not understand, they forget or do not want to apply in practice the knowledge they once acquired. The belief in audiophilia at this point has even penetrated and spread widely among engineers, although that’s really who, and they should understand these things thoroughly.

I originally wanted to write this article in a more aggressive style. But in the end I decided that it would be better for me to do without curses and provocations. On the contrary, I really hope that audiophiles read this article and reflect on what they believe and if they have enough reason to believe. Therefore, I will do so without provocation and will focus solely and exclusively on the facts.

And the most important thing I want to say right now: the audiophile arguments are not arguments related to any technical or engineering aspect. Audifilov’s arguments contradict science, specifically physics and mathematics. They also contradict technical and engineering aspects and audiophiles don’t know how their audio systems work, but this is a small problem compared to how they contradict physical or mathematical laws, showing a complete ignorance of the basics. It is the scientific aspects that I will focus on instead of explaining what the different types of CAD are and other details that are not of fundamental importance.

1. Basics: how sound is reproduced on a computer and any other electronic device

To begin with, an audio file is on a digital medium, such as a hard drive. This audio file has a certain internal format, but they are all a set of zeros and ones (0110010101 …), that is, any file can be represented as a very large number. This number can be easily converted to the usual decimal number system (189208 …).

The direct consequence of this is that the copies of the same file are all exactly the same. It doesn’t matter what medium they are in or how they were transferred or created: if the copies are correct, then they are exactly the same. The difference in playing the same file can only be caused by some other element in this play chain.

And this string is like this:

File -> audio player program -> digital to analog converter (DAC) -> amplifier -> speakers or headphones.

It works like this:

First, the player program loads (or receives from outside) an audio file into memory.

The software then decodes it, if necessary, into an uncompressed digital stream, which is digital audio. We will simply call this uncompressed digital audio .WAV and assume that this is the format in which music is delivered on conventional audio discs (two-channel stereo, 16-bit, 44.1 kilohertz per channel).

After that, this sound enters a digital to analog converter, which takes each number and converts it to an analog value that corresponds to it, most of the time it is a voltage measured in volts (from a certain minimum value that corresponds to a digital number 0 and up to a maximum value that corresponds to the number 65,536 – this is the maximum number that can be written in 16 bits).

After that, the sound, already in the form of electric current, enters the amplifier, the task of which is to raise the voltage to a value that suits the speakers. The amplifier must amplify the signal linearly, that is, each value that reaches it at the input must increase in the same proportion at the output.

In the speakers, the electric current is converted into physical vibrations, which are transmitted to the air and thus the sound we hear is obtained.

This chain, which from now on we will call the audio path, is present in one form or another in any digital audio system. The elements themselves may look very different on different systems (MP3 players, smartphones, computers, etc.), but they are necessarily present. When it comes to a computer, the DAC and amplifier are on the sound card (which is often built into the motherboard). Speakers often have their own built-in amplifier, and some of them may have their own DAC (and connecting to them bypasses the sound card).