Comparison Teac UD-505 vs PS Audio Stellar Gain Cell DAC

- DAC. Actually, digital-to-analog converters in the original sense of the word are devices designed to convert digital audio transmitted via an optical, coaxial or USB interface into an analog line-level audio signal, usually in stereo format. Sometimes switching of a digital signal may also be provided (output unchanged to one or another digital output), rarely also reverse, analog-to-digital conversion and/or sound processing using built-in filters and regulators.

— DAC with amplifier. Digital-to-analog converters (see corresponding paragraph), complemented by a built-in headphone amplifier and headphone output. The use of this feature can vary: some devices use the “ears” to control the sound coming to the DAC outputs, while others are actually high-end compact headphone amplifiers that connect to the digital output of a PC, game console or other similar device.

Model of the digital-to-analogue converter installed in the device.

DAC in this case means the “heart” of the device, the main circuit that directly provides the conversion of digital audio to analogue. The name of the DAC model is given mainly for advertising purposes — as an illustration of the fact that high-quality components are used in the device. In addition, knowing the model, you can find detailed information about a particular DAC; although in fact such a need does not arise often, it may still arise in some specific cases.

Sample rate of the digital-to-analogue converter used in the device.

DAC in this case means the “heart” of the device, the main circuit that directly provides the conversion of digital audio to analogue. And the sampling rate is initially one of the characteristics of digital sound. In this case, its meaning is as follows: the sampling rate of the DAC must not be lower than the corresponding indicator in the incoming audio signal, otherwise the device will not be able to effectively cope with the conversion.

The audio frequency range supported by the device. Most often, we are talking about the frequency range that the device can output in an analogue audio signal at the output.

In general, the wider the frequency range — the fuller the sound, the lower the likelihood that the transducer will “cut off” the upper or lower frequencies. However, note that the human ear is able to hear sounds at frequencies from 16 to 22,000 Hz, and the upper limit decreases with age. So from a practical point of view, it does not make sense to provide a wider range in audio technology. And the impressive numbers found in high-end devices (for example, 1 – 50,000 Hz) are more of a "side effect" of advanced electronic circuits and are given in the characteristics mainly for the purpose of advertising. Also recall that the overall sound quality is affected by many other factors, in addition to the frequency range.

The coefficient of harmonic distortion produced by the converter during operation.

The lower this indicator, the clearer the sound produced by the device is, the less distortion is introduced into the audio signal. It is impossible to completely avoid such distortions, but it is possible to reduce them to a level that is not perceived by a person. It is believed that the human ear does not hear harmonics, the level of which is 0.5% and below. However, in high-end audio applications, distortion rates can be much lower — 0.005%, 0.001% or even less. This makes quite a practical sense: the distortions from the individual components of the system are summed up, and the lower the harmonic coefficient of each component, the less distortion there will be in the audible sound as a result.

Support of the Bluetooth wireless technology by the device. The main application of this technology in the DAC is wireless transmission of sound from an external Bluetooth device (smartphone, laptop, etc.) to the converter. Initially, such transmission was associated with a loss of sound quality, but relatively recently the aptX format appeared, allowing audio to be transmitted via Bluetooth without loss in quality. So when choosing a converter with Bluetooth, it would be a good idea to clarify whether it supports aptX (and, of course, this standard must also be supported by the signal source).
In addition to audio transmission, there are other possible uses for Bluetooth, such as using an external gadget as a remote control. However, they are much less common.

Initially, the transmission of sound via Bluetooth involves quite strong signal compression, which can greatly spoil the impression when listening to music. To eliminate this drawback, various technologies are used (the most popular of which is the aptX codec, for Apple devices it is AAC). Of course, to use any of the technologies, it must be supported not only by the amplifier, but also by the Bluetooth device with which it is used.

— aptX. Bluetooth codec, created to significantly improve the quality of sound transmitted via Bluetooth. According to the creators, it allows you to achieve quality comparable to Audio CD (16-bit/44.1 kHz). The advantages of aptX are most noticeable when listening to high-quality content, but even on regular MP3 it can provide a noticeable improvement in sound.

— aptX HD. This codec is a further development and improvement of the original aptX technology, allowing to transmit sound in even higher quality — Hi-Res (24-bit/48kHz). According to the creators, this standard allows to achieve signal quality superior to AudioCD, and sound purity comparable to wired connection. The latter is often questioned, but it can be said that in general aptX HD provides very high sound quality. On the other hand, all the advantages of this technology become noticeable only on Hi-Res audio — with a quality of 24-bit/48kHz or higher; otherwise, the quality is limited not so much by the connection features as by the properties of the source files....

— aptX Low Latency. A specific variation of the aptX described above, designed not so much to improve sound quality as to reduce delays in signal transmission. Such delays inevitably occur when working via Bluetooth; they are not critical for listening to music, but when watching videos or playing games, a noticeable desynchronization between image and sound may occur. The aptX LL codec eliminates this phenomenon, reducing the delay to 32 ms — such a difference is imperceptible to human perception (although for serious tasks like studio work with sound, it is still too great).

— AAC. A codec used mainly in Apple portable equipment to improve the sound transmitted via Bluetooth. In this sense, it is similar to aptX (see the corresponding points), but is noticeably inferior to it in capabilities: if the sound of aptX is compared with Audio CD, then AAC is at the level of an MP3 file of average quality. However, for listening to the same MP3, this is quite enough, the difference becomes noticeable only on more advanced formats.

— LDAC. Sony's proprietary Bluetooth codec. In terms of bandwidth and potential sound quality, it even surpasses aptX HD, providing indicators at the level of Hi-Res sound 24-bit/96kHz; there is even an opinion that this is the maximum quality that makes sense to provide in wireless headphones — further improvement will simply be imperceptible to the human ear.

— ASIO support. Support for the ASIO audio standard. This feature is relevant when connected to a computer, when the device actually plays the role of an external sound card. ASIO technology is responsible for the interaction between specialized software and audio hardware; at the same time, it provides data transmission with minimal delay, which allows musicians and sound engineers to process sound in real time. This standard is used exclusively in operating systems of the Windows family, interaction with other operating systems is built in other ways (see in particular "MAC support").

— DSD support. The device supports the DSD standard, a specific digital audio signal standard that uses the so-called. pulse density modulation. The bit depth of such a signal is only 1 bit, but the sampling rate reaches 2822.4 kHz (64 times more than in the Audio CD format). Compared to the more common PCM standards, this format provides higher sound quality, better noise and error immunity, and lower noise levels. In general, DSD is considered a professional standard, and its support is found mainly in high-end equipment.

— MQA support. The device supports the MQA (Master Quality Authenticated) standard, designed to preserve and transmit the original quality of sound recordings in high resolution. The technology was invented by the...American company Meridian Audio. In fact, MQA improves standard digital audio by minimizing phase problems and pre-ringing/echo modulation effects. The technology uses special compression algorithms that allow high-quality audio files to be packaged into more compact sizes.

— I2S. Device support I2S standard. This is a digital audio format originally developed for "internal use" — for transmitting a signal between individual modules inside audio devices. However, more recently it has also been used for communication between individual components of audio systems. Note that this format does not have its own connector; various types of connectors can be used to receive the I2S signal, including LAN (RJ-45), BNC and even HDMI. In fact, this connector plays the role of another digital audio input. Specifically, the I2S standard, on the one hand, is distinguished by good communication quality and noise immunity, on the other hand, it is relatively rare.

— Thunderbolt. A universal digital connector, in this case used to connect a device to a computer. Such connectors are most widely used in Apple technology; accordingly, almost all devices equipped with them are compatible with Mac (see the relevant paragraph).

— FireWire. Also known as IEEE 1394 or i-Link. A universal connector that is similar in functionality to USB, and even surpasses it in some characteristics, but is much less common. It is used to connect to computers and some types of specialized audio equipment.

— Bluetooth. The device supports Bluetooth wireless technology. The main application of this technology in DACs is the wireless transmission of audio from an external Bluetooth device (smartphone, laptop, etc.) to the converter. Initially, such a transfer was associated with a loss of sound quality, but relatively recently, the aptX format has appeared, which allows you to transfer audio via Bluetooth without loss in quality. So when choosing a transducer with Bluetooth, it doesn't hurt to check if it supports aptX (and, of course, this standard must also be supported by the signal source).
In addition to broadcasting sound, there are other options for using Bluetooth — for example, using an external gadget as a remote control. However, they are much less common.

— Wi-Fi. Wi-Fi technology supported by the device. Recall that this technology is mainly used as a way to wirelessly connect to the Internet and local networks. Accordingly, most models with this feature are actually network players capable of playing content from local networks and/or the Internet. The specific capabilities of these devices may vary, some of them are even capable of working with Internet radio stations and audio streaming services. Also, Wi-Fi can be used for direct communication with other devices such as smartphones or tablets, but such use is practically not found among DACs.

— Connecting an iPod/iPhone. The presence in the device of special tools for working with portable gadgets from Apple — primarily iPod players and iPhone smartphones. Usually, in such models, the possibility of a wired connection through a standard 8-pin Lightning connector is provided. In addition, the software part may include special functions for integration with the "apple" gadget. But the ways of using such a connection can be different. For example, in a DAC (see "Type"), the iPhone or iPod serves as a source of digital audio, which is converted by the converter and output to the speakers. And audio interfaces with this function are actually adapters for various musical instruments: the sound from the instrument is processed by the interface and digitally transmitted to the gadget for recording and further processing using the built-in software.

— Mac support. Compatibility of the device with computers and laptops from Apple running the proprietary Mac OS X operating system. Such computers have their own specific features and requirements for peripherals, so for guaranteed compatibility, you should choose equipment that originally claims Mac support.

— Phantom power. The presence of phantom power in the device. Such a power supply, with a nominal voltage of 48 V, is necessary for the operation of certain types of microphones — in particular, condenser ones. Accordingly, the presence of this function means compatibility with similar types of microphones — an important feature, given that many high-end studio-level microphones are made specifically with condensers. Phantom power is found only among audio interfaces (see "Type").

Input sensitivity of the RCA and/or XLR inputs provided in the device.

See below for details on the inputs themselves. And input sensitivity is the smallest average (rms) signal level at the input that the device can normally accept and process. Compatibility with external analogue signal sources depends on this indicator: the output voltage of the source must not be lower than the input sensitivity of the converter, otherwise normal sound processing will be impossible. However, you should not allow a significant excess of the input signal level over sensitivity, otherwise overloads are possible. These points are described in more detail in special sources.