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Audio pcm what. Digital sound: DSD vs PCM Part 3

Retrieve a “digit” analog signal

But digitizing an analog signal is half the battle. To listen to digital music, you must reverse convert. First, let’s see how to convert a digital DSD broadcast to sound. As we already know, this stream is a high frequency bi-level signal (2.8 MHz or more), the average value of this signal changes with the audio frequency. That is, if the approach to solving the problem is as simple as possible, you need to filter out all the high-frequency components of the DSD stream, leaving only a useful sound signal (frequencies up to 20 … 22 kHz). This is done using an analog low pass filter (LPF). The simplest LPF is an RC chain.

As you can see, the resulting graph only vaguely looks like the original sinusoid. But let’s not forget that we “applied” the simplest filter, improving the filter circuit can achieve an almost total absence of high frequency noise and obtain an analog sound with good quality indicators.

To restore an analog signal from a digital PCM, just an analog low-pass filter is not enough, you must first decrypt the digital data, for this, digital-to-analog converters (DACs) are used. They are of different types, but it is beyond the scope of this article to describe them all. Let’s dwell on the 2 most common types of sound technology. First of all, this is the so called ladder type DAC (also called multibit). As you probably guessed, such a DAC converts a PCM digital data stream into a stream of audio signal values ​​that look like a ladder on the graph (Figure 6). As with DSD, it is imperative to use an analog filter to smooth out the jogging.

Often these converters use intermediate oversampling of the digital PCM signal at higher frequencies (eg 192 kHz): this reduces the “steps”, allowing for simplification of the analog filter circuit.

The second type of DAC, delta-sigma, uses oversampling at even higher frequency values ​​with a simultaneous reduction of the bit depth to one bit. Doesn’t it look like anything? This is a familiar DSD signal! We have already discussed how to further process such a signal and convert it to analog.

PCM and DSD application, advantages / disadvantages
Where can we find each of the encoding methods? PCM format is very common: CDDA discs, DVD audio, MP3 files, FLAC, ALAC, AAC, sound in movies, and so on, it is easier to say when it is not PCM. Super Audio CD, DSD, DSF, DFF files are in DSD format. What is better? What format will we get a better sound from?
The articles dedicated to the DSD format describe many advantages over PCM, but are all the advantages described true, or are they myths invented for laymen who do not understand the technical component to recover the market densely occupied by the PCM format? Let’s briefly review the list.

conclusions
So should you choose DSD or PCM? There is no single answer and it cannot be: PCM 24 bit 92 kHz and DSD128, for example, are very similar in quality characteristics, and these characteristics are better than the equipment on which these formats will be played, which means a further increase in the quality of digital formats for playback at this stage is not practical. When evaluating the quality of sound in different high definition formats, subjective sensations come to the fore, because the human brain is not eaten by the same quality: the design of the equipment, its cost and, most importantly, the well-being and the The listener’s moods have a much greater effect on the sensation of listening to music. Therefore, choose what you like personally and do not impose your opinion on others. Happy listening everyone!
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Audio pcm what. Digital sound: DSD vs PCM Part 2

First, let’s answer the question, what is digital sound? How is it different from analog? In short, in mathematical terms, an analog audio signal is a continuous function, a digital audio signal is a discrete function. What does that mean?

Analog signal
If we draw in our imagination a graph of a sinusoid (this is how a sound wave is most often represented): then, no matter how we magnify it, trying to see all the details, we will always see a smooth and uniform line – this is an analog audio signal

Analog audio (recording) has many parameters that can be used to evaluate its quality. Consider the three most important: frequency range, dynamic range, distortion.

Digital sound. How many myths revolve around this phrase. How many disputes have arisen between lovers of comfort and digital quality and supporters of “live airy” vinyl sound multiplied by “warm tube” sound. In addition, there is a lot of controversy among lovers of “numbers”: is 16×44.1 enough or is 24×192 necessary? Which is better: multibit or delta sigma? CDDA or SACD? PCM or DSD? In this article, I will try to explain the basics of digital sound in simple language and will also expand in more detail on comparing two types of encoding of an analog to digital signal: DSD and PCM.

First, let’s answer the question, what is digital sound? How is it different from analog? In short, in mathematical terms, an analog audio signal is a continuous function, a digital audio signal is a discrete function. What does that mean?

Analog signal
If we draw in our imagination a graph of a sinusoid (this is how a sound wave is most often represented): then, no matter how we magnify it, trying to see all the details, we will always see a smooth and uniform line – this is an analog audio signal

Analog audio (recording) has many parameters that can be used to evaluate its quality. Consider the three most important: frequency range, dynamic range, distortion.

The frequency range is a set of frequencies contained in a sound. It is generally accepted that the frequency range of human hearing is 20 … 20,000 Hz (sometimes 16 to 22,000 Hz is indicated). The frequency range of the music itself is of no interest in terms of quality assessment (for example, the frequency range of the same plane taking off will be very wide and the tenor’s vocal part will be much narrower). A qualitative parameter, say, of an earphone is the potential frequency range, and it is estimated using the amplitude frequency characteristic (AFC). The ideal frequency response, a straight line across the entire range of hearing frequencies, means that the sound source does not amplify or attenuate any individual frequencies, meaning that the extracted sound matches the original.

Dynamic range (DD) is the difference between the quietest and loudest sound. Loudness is measured in decibels (dB). It is generally accepted that the maximum volume that does not cause injury to a person is 130 dB, the sound of an airplane taking off, and the minimum audible volume, 5 … 10 dB, is at the level of the rustling of the leaves in low wind conditions. Naturally, it will be impossible to distinguish the rustle of leaves against the background of a plane taking off, and listening to music at a level of 130 dB is extremely unpleasant. Therefore, it is generally accepted that a comfortable DD for listening to music is 80 … 100 dB.

The distortion is nothing more than a deviation of the signal from the original.

Principles of digital sound presentation
What happens when I digitize analog audio? We will not delve into the technical aspects, we will analyze everything, as they say, on paper: for this we will draw our imaginary “ideal” sinusoid and measure the value of the signal at regular intervals (this process is called sampling or quantization): we will obtain a certain sequential set of values ​​- this will be our digital signal obtained by the pulse code modulation (PCM) method

The two main parameters of PCM signal quality are frequency and bit depth. Frequency is the number of measurements per second, the more, the more accurate the signal is transmitted. Frequency is measured in Hertz: 44100 Hz, 192000 Hz, etc. Bit depth: the number of possible values ​​of the signal value (precision of the value transmission). The more options, the more accurate the signal will be. Bit depth is measured in bits: 16 bits (65,536 possible values, DD 96 dB), 24 bits (16,777,216 values, DD 144 dB), etc.

Audio pcm what. Digital sound: DSD vs PCM Part 1

What is PCM

Let’s start with the fact that PCM (Pulse Code Modulation) is initially older, the first mentions of its successful use date back to the middle of the last century and are associated, like many technological advances, with the defense industry, that is, with the Navy radars. As for home use, first of all, it is a well-known CD with a sampling frequency of 44.1 kHz and a 16-bit quantization level.

What is DSD
DSD (Pulse Density Modulation) is a format developed by Sony and Philips at the end of the last century and intended for the digital archiving of analog phonograms. The physical medium of this format is SACD. In fact, there is only one similarity between these two formats, both are digital, which for the user means the possibility of making unlimited copies without loss. As for the difference, relative to the field of graphic design, it is roughly the same as raster and vector graphics. And if it is even more artistic, like cross stitch and watercolor. In both cases, an image is obtained, but the method of its creation and, as a result of perception, are completely different.

What is the difference?
PCM, even because of its age, is much more studied, it has much better compatibility with a large number of very different devices, it implies the possibility of editing (equalization, division into frequency bands, transformations). DSD is actually a closed format, you can record to it, you can play it, that’s it. However, it is inherently much closer to the original analog signal.

Which is better?
The first and most important conclusion is that from a technical point of view, the formats are far apart in terms of implementation methods, but they are often practically indistinguishable in practical use, that is, in the sound of the final file. We are talking only about minor differences in the nuances of the musical presentation. So, all things being equal, when choosing the next file to download and play, it’s best to focus on the source material. If you are looking to digitize an analog then DSD will probably be preferable and will retain more nuances from the original. If this is a remastering of a digital recording previously made in PCM, then it would make more sense for it to stay in this domain.

Digital sound. How many myths revolve around this phrase. How many disputes have arisen between lovers of comfort and digital quality and supporters of “live air” vinyl sound multiplied by “warm tube” sound. In addition, there is a lot of controversy among lovers of “numbers”: is 16×44.1 enough or is 24×192 necessary? Which is better: multibit or delta sigma? CDDA or SACD? PCM or DSD?

First, let’s answer the question, what is digital sound? How is it different from analog? In short, in mathematical terms, an analog audio signal is a continuous function, a digital audio signal is a discrete function. What does that mean?