Not every computer user is aware of what a DAC actually is. Everyone hears a sound, but how it is processed, as it turns out, is imagined by a few. In considering this topic, you will have to go a little deeper into the understanding of the nature of sound and its reproducing devices.
What is a DAC? Sound: the basics of understanding
Some people mistakenly believe that the DAC is the central audio processor. Partly the way it is. But in fact, the DAC is a frequency-to-analog converter, which changes the audio signal to the form that is perceived by the human ear.
Here you need to make the difference between digital and analog signal. The technology used in the “digit” or in digitizing audio involves software processing methods, which is why many fans of vinyl records cannot listen to similar recordings on CD / DVDs only because of the lack of a specific rattle issued by the player’s diamond head when touching the record .
Analog processing was first used in tube amplifiers and reel tape recorders. Such devices are still very popular among professional musicians who are trying to add some warmth to the sound of their composition.
Frequency response
Sound, the DAC convertible and reproducible, directly depends on the signal output device, that is, the sound card. But that is not all. Far from the last role is played by acoustic systems in the form of the same speakers (speakers) and amplifiers.
Here you need to understand that no system can play sound with parameters below the capabilities of the sound card. Today, if you do not go into details of the operation of such devices, the following characteristics are considered optimal:
- sampling rate at 48 kHz (although the standard is 44.1 kHz);
- depth 24 or 32 bits (although the standard is 16 bits);
- bitrate of 320 kbps and higher (although the standard is 128 kbps).
Extra options
As frequency parameters, it should also be taken into account that the DAC sound can be converted using the sound parameters perceived by the human ear. Here it is worthwhile to dwell on what exactly we can hear.
Our hearing impairment ranges from 16 Hz to 20 kHz (sometimes 22 or even 24, but this is rare). And all the main DAC sound are processed precisely in this range. Next, we dwell on the testing methodology offered by one of the popular Internet resources.
Proposed DAC Testing Methodology
As a rule, testing of external devices rather than integrated soundcards is taken, since they are believed to have characteristics that are an order of magnitude lower compared to external equipment.
In terms of the DAC software used, high-quality sound is tested on the basis of AudioDoctor FSQ 2006 technology, which, however, was originally developed to test car audio systems, and only then adapted to home conditions. Devices called DACs were connected directly via the USB interface and through S / PDIF using unbalanced RCA outputs (balanced XLR outputs may show completely different characteristics).
A separate role was assigned to the M2Tech HiFace Evo converter, through which the files were converted to the most readable format. Mandatory testing was performed using the ASIO drivers.
DAC chip rating by sound
What did the result show? The rating of DACs in sound is approximately as follows:
- ASUS Essence III;
- Burson Audio Conductor Virtuoso 9018;
- Cary Audio DAC100;
- Chord 2Qute;
- Densen DenDAC 50;
- Fostex HP-A8;
- North Star Design Supremo;
- OPPO HA-1.
The priority is very arbitrary, since often much depends not even on sound characteristics, but on price.
However, Cary Audio in this list shows the highest performance in terms of sound and stereo expansion. In addition, do not forget that the rating of DACs in sound includes some undocumented features of devices of this type.
Using sound cards
The transducers are designed for use in sound cards. How does the DAC work? Sound (the principle of operation confirms this) is reproduced on the basis of the conversion of a digital signal at the input in the form of a binary code, each value of which corresponds to a certain voltage, current and charge.
ADC devices operate on the opposite principle. But if you look specifically at the DAC, the sound, the conversion description of which will be discussed below, is reproduced solely on the basis of the input code. For its perception, the system uses standard PCM technology. Many probably noticed that standard WAV files are marked exactly as PCM.
But it’s not enough just to have a DAC. Sound, signal processing and reproduction is impossible without the use of appropriate software tools called codecs. They are just designed so that the sound card can recognize incoming data and play sound through the speakers. Codecs and converters in this case act as a kind of bridge between the digital code and the "iron" device (similar to how DirectX works).
Sound cards, which are based on the use of DACs, are mainly external devices, not removable ones installed in slots on the motherboard, not to mention integrated sound chips like Intel Audio or Realtek.
DAC (external sound module is meant) is able to process by its own means (for this it was created). But in order to transmit the processed signal to the playback device, it is necessary for it to work correctly. But here you can not do without the use of initialization control programs called drivers.
Device drivers
Most sound cards are automatically detected by operating systems of any type. Drivers are installed from their own database. But for some devices, manual installation may be required, not only drivers, but also related codecs (for example, the K-Lite Codec Pack).
In order not to engage in such procedures, for any DAC with good sound, it is advisable to install or update drivers (keeping them up to date) using special automatic update programs. One of these is the Driver Booster utility, which initially makes an appeal to the Internet resource of the equipment manufacturer, and then downloads the latest device driver that is automatically detected and integrates it into the system.
Software
Sound processing through the DAC is not possible without the appropriate software. Codecs and drivers have already been said. But tuning the optimal sound quality or even processing audio information, as many sound engineers believe, cannot be done without the use of a software package.
Apart from installing drivers, it is advisable to have programs like SoundMax on your computer. Such utilities, unlike the same operating system tools, allow for more fine-tuning.
For audio processing, it is better to use specialized editors, in which, by the way, you can even change the standard settings, including sampling frequency and depth. And if ASIO4ALL drivers are installed in parallel, in the sound settings panel itself you can change such characteristics as the number of samples (for example, 512, which corresponds to a delay speed of 10 ms), not to mention the sound quality (for example, set the value not to 44100 Hz, but say 48 or 96 kHz).
Mobile technology
The best sound from a smartphone with a DAC can be estimated very conditionally. Judge for yourselves, because to reproduce the same low frequencies you need an appropriate speaker with a diameter of 32 inches. And where does it come from in the phone or tablet?
But preference can be given to manufacturers who are initially positioned as the first-born in the field of sound processing and the founders of this type of technology. Sony Corporation - a vivid confirmation of this.
When choosing a device, models with a plastic case should be preferred, since the reflection of sound in them is much higher in its characteristics and level. Metal housings, even when the most powerful converter is installed, look much weaker. This is due only to the fact that metal absorbs sound. In addition, the larger the space between the main speaker and the back cover, the better the reflection. But you should not overdo it, because too much clearance can cause the appearance of side effects of reverb or chorus, or more simply, distortion of sound in its original version.
additional characteristics
As already clear, the DAC processes sound based on a digital binary code, using a change in voltage and current frequency for this. But here you also need to understand that only these characteristics of this type of device are not limited. Among all the parameters that are used in the description of any DAC, many incomprehensible values ​​can be found, like parameters of the PCM frequency-wave modulation. This is precisely the basic principle of operation of absolutely all converters.
In the simplest case, the analysis of the input signal and its conversion is based on the principle of summing the values ​​of voltage, current and charge, which in digital terms can take either zero or one (based on the conditions for using the binary code).
Separately, it is worth paying attention to such parameters as bit depth, sometimes also called resolution or quantization step, transfer characteristic, Nyquist frequency (sampling), range of input signal parameters, monotonicity, output surge when changing data in a certain period of time, bias error between real the signal and the parameter accepted as "ideal", the integral and differential nonlinearity of the deviation of the characteristics with the observed difference in the increments of the output dnyh signals.
For the DAC, each value of the binary code can correspond to one transistor to which the signal is sent. Converters for connection are divided into parallel and serial. But still, they turn to the nodes of the electric network, interacting with the output.
Most devices are based on the R - 2R matrix, which is one of the most common and currently used structures that use only two resistance values, each other in a 2: 1 ratio. Thus, DAC testing is reduced to two methods: determination of voltage and current strength in normal and inverse modes. In this case, a constant impedance parameter and the absence of capacitive currents are achieved. But the disadvantage is that for the reference source, the main condition is the presence of a very low impedance. In addition, it is impossible to send a signal to use a resistor connected in series with the reference source. But in this connection scheme, as a rule, it is not required to make grounding.
Separately, it is worth noting the so-called sigma-delta modulation, which is responsible for the level of sampling frequency. The transformation (quantization) is carried out by a single charge, which can be tens or even hundreds of times higher than the fundamental Nyquist frequency. An interpolation filter used at one of the stages of signal conversion changes the sequence of the binary code by adding zeros for low-frequency data streams and units for high-frequency ones.
Since most conductors are both active and reactive, the maximum accuracy during testing is achieved only if the smallest circuits of return currents are used, which helps to reduce cable inductance and, as a result, reduce noise. An example is even guitar effect pedals. Guitarists know that the longer the cord from the guitar to the “lotion”, the stronger the background. It is this situation that best illustrates the understanding of the essence of the issue.
DAC can be directly connected to the load. But for this, an additional device such as a voltage follower or an inverting op-amp, acting as a buffer or matching device, should be used. In this case, it is worthwhile to dwell on the issue of grounding of any circuit. It is recommended to use the creation of separate polygons for the digital and analog parts, since noise from digital components can affect the analog part of the network. This is achieved by using a thin conductor or using two inner layers through a double hole.
Instead of a total
Of course, some scientific principles and even technical issues were considered here, which, in general, are completely useless to the average user. But, if you think about it, sometimes knowledge of the theory can be very useful. The same choice of a sound card cannot do without knowing the basic aspects regarding the principles of its operation and correct functioning in a computer system.
Perhaps some users have not yet realized that the low quality of sound reproduced through the speakers is directly related to the equipment used. In this case, the sound card used to play the converted digital signal in its analog form should only be of the external type. It is such devices that allow you to hear everything that integrated or removable devices cannot be played. It is believed that in 80 percent of cases the problem is precisely this. By the way, many services like iTunes, Spotify or something else are “ground” just for using DACs. There are even special docking stations in the form of external devices that connect to iPods, not to mention the rest of the mobile gadgets.
It goes without saying that not the last role is played by both the speaker system and the headphones, because it will be impossible to extract normal sound from the speaker, whose capabilities are limited by sound characteristics at the level of 20-10,000 Hz. Therefore, most of the proposed devices in the form of headphones for mobile systems should not be used. For that matter, why not listen to music on the K99 headphones manufactured by AKG, or use similar devices from Sennheiser? However, the choice today is quite large.
As for the testing technology, which was discussed above, its understanding is impossible even without basic knowledge of physics explaining the nature of sound waves, and even electrical engineering, since this discipline provides the basis for understanding any electrical circuit. And, of course, only basic brief information regarding signal converters was given here . To understand this issue most fully, it is advisable to read additional literature.