Comparison Audinst HUD-DX1 vs Fostex HP-A4

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 dynamic range of a transducer is defined as the ratio between the maximum signal level it is capable of delivering and the level of its own noise when a low amplitude signal is applied. Quite simply, this parameter can be described as the difference between the quietest and loudest sound that the device can produce.

The wider the dynamic range, the more advanced the DAC is considered, the better sound it can produce, all other things being equal. The minimum value for modern devices is about 90 dB, in top models this figure can reach 140 dB.

Also note that this parameter is similar in its meaning to the signal-to-noise ratio, however, these characteristics are measured in different ways; see below for more on this.

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.

The power supply provided in the device.

— From the network. Powered by a normal household outlet. This option is suitable for models with any power and functionality, including the most complex and advanced ones. The mobility of devices with such a power supply is noticeably limited by the power cord, but most of them are initially stationary, so this cannot be called a serious drawback.

— From the USB port. Powered by the port that connects the device to a computer or portable gadget. Most often, we are talking about USB, but other connectors can also be implied: for example, there are devices connected to the iPhone / iPad and powered by a standard “apple” 8-Pin Lightning port, models that are powered by FireWire, etc. The main advantage of this option is the independence of the outlets and the absence of extra wires. On the other hand, connection connectors have limited power supply, so this option is only suitable for the most compact solutions with low power consumption.

— From the network / USB port. Devices that can work both from the network and from the USB connector (or other connection connector). See above for more on these types of food; and their combination in one device provides versatility and allows you to choose the method of nutrition that is most convenient in a given situation.

— From the battery. Power...ed by own battery. The main advantages of such devices are independence from external energy sources and the absence of extra wires. At the same time, battery power has a significant drawback — a limited operating time: after the charge is exhausted, you inevitably have to take a break to charge the battery. And the mentioned advantages in most cases are not critical for DACs and audio interfaces. Therefore, in its pure form, battery power is extremely rare, more often it is combined with a USB or network connection (see below).

— From the network / battery. The ability to work both from the battery and from a conventional outlet. Both types of food are described in more detail above. Here we note that in this case they complement each other, mutually compensating for shortcomings and making the device universal. So, as long as there are sockets nearby, you can use them (many models are even capable of recharging the battery right during operation), and if connecting to the network is impossible or difficult, switch to the battery.

— From the USB port / battery. The ability to work both from the battery and from the USB port (or other connection connector). See above for details on each of these connection types. And their combination is found exclusively in audio interfaces (see "Type"), it makes the device as versatile as possible. Especially such models will be appreciated by those who work with sound on laptops, tablets or other portable equipment: for example, if the laptop works autonomously, without being connected to a power outlet, you can transfer the audio interface to the built-in battery, saving laptop battery power.

The device has an external power supply.

The meaning of this design is to move the power supply outside the case and reduce the amount of interference that affects the hardware of the device and can distort the sound. In addition, due to the external PSU, the device itself is more compact and light.