Comparison Teac UD-503 vs Fostex HP-A4

The presence of a toroidal transformer in the design of the device.

Such a transformer has a core in the form of a toroid (ring). It is believed that such a design reduces the level of extraneous electromagnetic radiation and minimizes the likelihood of interference from the transformer.

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 bit depth 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. Bit depth is initially one of the characteristics of a digital audio signal. In this case, its meaning is as follows: the bit depth of the DAC must be no lower than the bit depth of the audio signal with which the converter is planned to be used, 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 signal-to-noise ratio provided by the converter.

This parameter describes the ratio of the volume of the pure sound produced by the device to the volume of its own noise (which is inevitably created by any electronic device). Thus, the higher the signal-to-noise ratio, the clearer the sound, the less the DAC's own noise affects the audio signal. Indicators up to 80 dB can be considered acceptable, up to 100 dB — not bad, 100 – 120 dB — good, more than 120 dB — excellent. However, it is worth remembering that the overall sound quality is affected not only by this parameter, but also by many others.

Note that the signal-to-noise ratio is often associated with such a characteristic as the dynamic range (see above). They are similar in general meaning, both describe the difference between an extraneous background and a useful signal. However, the noise level in the calculations is taken differently: for the signal-to-noise ratio, the background of the converter “at idle” is taken into account, and for the dynamic range, the noise that occurs when a low-level signal is output. This is the reason for the difference in numbers.

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.

Adjustments provided directly in the device.

— Bass adjustment. Separate bass level control; usually combined with treble control (see below). This function allows you to change the sound image by adjusting the volume of the bass sound relative to the rest of the frequency range.

— Treble adjustment. Separate treble control. Like the bass adjustment described above, it allows you to adjust the sound picture — in this case, by changing the volume of high frequencies relative to the rest of the range.

— Balance adjustment. Adjusts the sound balance between two stereo channels by increasing the volume for one channel and decreasing the volume for the other. Due to this, in the perception of the listener, the sound "shifts" towards greater volume. This function is mainly used for correction purposes — for example, if the speakers are at different distances from the listener, shifting the balance towards the far speaker allows you to compensate for the difference in audible volume.

— Level adjustment. Adjusting the overall signal level at the output, in other words, adjusting the volume. Adjusting the volume using the DAC's own control is sometimes more convenient than accessing the settings of other components of the audio system.

— Headphone level adjustment.... Headphone sound volume adjustment. This control is provided mainly for user comfort, it allows you to set the sound level in the "ears" to your own preferences. This possibility is especially relevant in light of the fact that headphones are rarely equipped with their own volume controls (and usually these are inexpensive models with relatively low sound quality).

— Sensitivity adjustment. Adjustment of input sensitivity of the converter. This function is found mainly in models with analogue inputs: it allows you to amplify the incoming signal, if necessary, even before it is processed by the converter, if the initial signal level is too low.

— 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").