Comparison FiiO X7-II vs Astell&Kern AK70

The operating system under which the player is running.

An operating system is not just any shell programme; this name is applied to the most advanced platforms. The OS has extensive capabilities that go far beyond the traditional functionality of the players, in addition, these capabilities can be further expanded by installing additional applications for various purposes — from online music services and media libraries to games, social network clients, etc. Thus Thus, the presence of an OS usually means that the device is a media player (see "Type"); however, not every media player has a full OS. Hi-Fi players can also have such firmware, however, the OS in them is often heavily modified, and not all such devices allow the installation of third-party applications.

Specific options for the OS can be as follows:

— Android. Operating system developed by Google, widely used by manufacturers of portable electronics; practically ousted other systems from the market, the only alternative is iOS(see below). The original Android is tightly integrated with Google services and uses the Google Play app store; however, there are many branded shells and modifications on the market, including those with rather radical changes. And you can install programs not only from the application store, but also from any other sources — by downloading the installation file to the device. The system h...as an open source code, anyone can write software for this OS, thanks to which the set of applications for Android is extremely extensive, but many of them do not differ in quality.

— iOS. Apple's proprietary operating system is not used by other manufacturers. It is closed: you can install additional applications only from the App Store proprietary storage, and for music and video you need to use the iTunes service. In addition, to create software for iOS, you need to obtain a paid license, which limits the circle of developers. On the other hand, iOS is quite convenient in that the user doesn't have to dig through an extensive set of settings; and apps in the App Store go through fairly strict quality and security controls.

Type of memory cards supported by the player.

Memory cards perform two main functions. First of all, they increase the total amount of the player's memory; at the same time, such memory in terms of gigabytes is much cheaper than built-in drives. Secondly, a memory card allows you to exchange data with another device that has a card reader; for example, it can be used to copy music to the player from a laptop.

Modern players usually use SD or microSD cards of one version or another. SD cards have dimensions of 32x24 mm and are used in relatively large devices, miniature microSD (15x11 mm), respectively, in compact models. Versions can be:

— SD. This marking means that the device is capable of working with at least original SD cards (not related to later versions of SDHC or SDXC). Such cards can have up to 4 GB capacity, their capabilities are quite enough for most tasks related to content playback.

— SD/SDHC. Models compatible with both the original SD (see above) and the newer SDHC format. This format allows you to create removable media up to 32 GB.

— SD/SDHC/SDXC. Support for all major SD formats used today. About SD and SDHC, see above, and SDXC provides card capacity up to 2 TB and increased speed.

— microSD. Players guaranteed to work with original microSD cards. Technically, such cards are similar to the SD cards described above and differ from them only in size. At the s...ame time, it is worth noting that a device with such a marking may actually be compatible with more advanced media (like microSDHC or even microSDXC), just the manufacturer, for one reason or another, did not go into such details. You can clarify this point by evaluating the maximum supported card volume (see below)

— microSD/SDHC Players that support both the original microSD and the later microSDHC standard (see "SD/SDHC").

— microSD/SDHC/SDXC. Players with this marking are compatible with all modern versions of microSD cards — both the newest microSDXC (see "SD / SDHC / SDXC"), and previous standards (see above for them).

Players are produced that have two slots for memory cards at once — usually microSD. Basically, these are Hi-Fi devices (see "Type"), and this feature is provided for an additional increase in available memory volumes: Hi-Fi content has a significant amount and requires appropriate storage.

The maximum size of the memory card that can be used in the player. This parameter is directly related to the card type (see above): each type has its own volume limits. At the same time, the ability to work with capacious media is limited not only by the type of card, but also by the player's hardware. Therefore, many models have a lower capacity limit than the memory card suggests — for example, 128 GB in a model that supports the SDXC format (the theoretical maximum for which is 2 TB).

Note that the reverse situation also occurs — for example, when a device with a maximum capacity of 16 GB only supports microSD cards (theoretical maximum is 4 GB). This usually means that the player can work with newer formats (in our example, at least microSDHC), but for some reason this point is not mentioned in the official specifications (for example, the manufacturer could make a mistake in the documentation).

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

The DAC is one of the key components of any player: it converts the digital data recorded in the audio file into an analogue audio signal, which is fed through an amplifier to the headphones. The quality of the DAC directly affects how accurately the output sound will match the original signal, as well as whether the player can work with advanced digital signal formats: many of them require high computing power, which is not available in every DAC.

Note that the DAC model is indicated only if it is a high-end converter with above-average sound quality. On the modern market, in particular, DACs from such manufacturers are represented: AKM, Cirrus Logic, ESS Saber, Texas Instruments, Wolfson. And players with such equipment usually refer to Hi-Fi devices(see "Type").

It is also worth mentioning that the number of DACs can be different. The simplest option is one module for both sound channels, however, there are players equipped with two converters at once — one per channel. This "division of labor" affects the cost, but reduces the load on each individual DAC, which has a positive effect on the quality and reliability of the sound.

Sampling frequency of the digital-to-analogue converter installed in the player (see "DAC").

Sample rate and bit depth are two key characteristics of a digital audio signal; the higher they are, the better the sound quality, other things being equal. Without going into technical details, the meaning of this parameter can be described as follows: for normal sound reproduction, it is necessary that the sampling rate of the player's DAC is not lower than that of the file being played. Otherwise, playback will not be possible even if the audio format is natively supported by the player. (The exception is DSD, see "Supports audio formats" for more on that).

Note that most popular audio formats use a sampling rate of 44.1 kHz, and all modern portable players are guaranteed to support it. So this parameter is relevant mainly for Hi-Fi models (see "Type") that work with advanced digital sound formats.

The capacity of the digital-to-analogue converter installed in the player (see "DAC").

Bit depth, along with sampling rate, is one of the key characteristics of a digital audio signal; the higher it is, the better the sound quality, other things being equal. Without going into technical details, in this case, the meaning of this parameter can be described as follows: for normal sound reproduction, it is necessary that the bit depth of the player's DAC be no lower than the bit depth of the reproduced digital sound, otherwise playback will be impossible.

It is worth noting that the bit depth used in most popular music formats like MP3 is supported by all modern players. So this parameter is relevant mainly for Hi-Fi players (see "Type") that work with advanced digital sound standards.

The ratio between the level of the useful signal (clear sound) and extraneous noise, given by the player at the output. This parameter directly characterizes the quality of the built-in amplifier: it mainly takes into account the intrinsic noise of electronic circuits, and the higher the signal-to-noise ratio, the less these noises and the clearer the sound.

Note that in the case of players, this characteristic is often not particularly critical: the noise of the amplifier can be lost against the background of ambient sounds, especially in an urban environment, and for such situations even the most modest indicators, at the level of 70 – 80 dB, are enough. At the same time, for Hi-Fi models (see "Type") this moment is one of the most important; in the most advanced devices, the signal-to-noise ratio can exceed 120 dB.

The higher the power, the louder the sound you can get on the headphones, all other things being equal. In addition, higher power allows you to connect "ears" with higher impedance to the device (although there is no hard correlation here, and models with the same output power may have different headphone impedance limits). However, in the case of ordinary (non-Hi-Fi) players, this parameter is more of a reference than practically significant: usually, the power of the amplifier in such models is quite enough to “rock” most consumer-grade headphones. But for Hi-Fi devices (see "Type") models, output power is of key importance: it determines compatibility with high-resistance studio-class "ears". Detailed help on this issue can be found in special sources.

The nominal impedance (impedance) of the headphones that the player can handle normally.

Most consumer-grade headphones are 16 or 32 ohm impedance, which is supported by almost all modern players. Therefore, you should pay attention to this parameter only if you plan to use a device with high-quality "ears" of a studio or audiophile class. A characteristic feature of these headphones is high resistance, already in the hundreds of ohms, and not every player is suitable for them.

Also, it will not hurt to clarify the permissible headphone impedance if you are buying a Hi-Fi class device (see "Type"). Some of these models have a fairly high minimum resistance and are not compatible with standard 16 ohm (and sometimes 32 ohm) "ears".