Comparison FiiO KA17 vs FiiO Q7

DAC model — a digital-to-analogue converter installed in the amplifier.

In accordance with the name, the DAC is responsible for converting a digital signal (for example, coming to the optical input or USB, see "Inputs") into an analogue format, with which the amplifier directly works. The presence of such a converter in an external "amplifier" is important, given the fact that many popular signal sources — such as smartphones or built-in sound cards — are equipped with fairly simple and inexpensive DACs with low sound quality; on external equipment, this quality can be much higher. And the quality of the conversion and, accordingly, the characteristics of the output sound directly depend on the characteristics of the DAC: even the most advanced power amplifier will not “save” a signal converted with significant errors. Accordingly, knowing the converter model, you can find detailed data on it — from official specifications to practical reviews — and evaluate how an amplifier with such a module meets your requirements.

The number of audio channels supported by the amplifier; only specified if the number is greater than one.

Since we are talking about dedicated headphone amplifiers, the term “channel” is used in this case in a slightly different sense than is usual in audio technology. This term most often means a set of two traditional channels (left and right), which allows you to provide full stereo sound in headphones. Simply put, the number of channels is the number of stereo sound sources that can be connected to the amplifier at the same time, and the number of headphones that can simultaneously output the signal from these sources. However, in addition to this, other types of channels can be provided — for example, monophonic. However, anyway, each channel uses its own signal source, its own headphone output (or other playback device) and its own set of adjustments.

Thus, on a multi-channel amplifier, several people can simultaneously listen to different sound sources in headphones; and some models are capable of reproducing individual channels also on external acoustics. At the same time, such functionality complicates the design of the device, increases the likelihood of interference and significantly affects the cost (including due to the need to take measures to compensate for interference). Therefore, there are relatively few multi-channel models nowadays, and these are exclusively stationary solutions (see "Type"), designed mainly for professional use.
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Also note that the number of headphone outputs can be greater than the number of channels; in such cases, several connectors are “attached” to some channels at once, usually of different types (for example, Jack and XLR), which allows the user to choose the option depending on the headphones at hand. Theoretically, the outputs of one channel can be used simultaneously, but it's ok to clarify this possibility separately.

The sampling rate of the digital-to-analogue converter (DAC) installed in the amplifier. Recall that such a converter is responsible for converting digital audio into an analogue audio signal, which is then processed by the main amplifier and fed to the headphones (or other analogue audio device).

The sound in digital form is most often recorded as follows: the original sinusoid of the analogue audio signal is divided into separate sections (samples) — “steps” of a certain length and height, and each of these steps is encoded with its own set of numbers. The sampling rate determines how many such steps there are in a certain section of the original audio signal. Accordingly, the higher this frequency, the more accurately the digital record corresponds to the original signal; on the other hand, an increase in the number of samples per unit of time increases the volume of files and increases the requirements for the hardware power of digital circuits.

Specifically, for a DAC, the native sampling rate of such a module is, in fact, the maximum sampling rate of the incoming digital signal that the converter can effectively handle. With higher input values, the sound quality will at best be limited by the capabilities of the DAC, at worst, the amplifier will not be able to work correctly at all. Anyway, higher numbers in this paragraph (ceteris paribus) mean a more advanced and high-quality converter; on the other hand, this moment significantly affects the...cost, and you can evaluate all the capabilities of a high-end DAC only on audio materials of the appropriate quality.

As for specific numbers, the lowest value that can be found in headphone amplifiers is 44 kHz. According to the laws of physics, it is this sampling frequency that is the minimum necessary for the full transmission of all human-audible sound frequencies (16 — 22,000 Hz), and it is this frequency that is used in the Audio CD format. Many models provide values in 96 kHz and 192 kHz (this is already enough to work with different types of DVD-Audio), and in the most advanced devices this figure can reach 384 kHz and even 768 kHz.

The nominal impedance (impedance) of the headphones for which the amplifier was originally designed.

Modern headphones can have different impedance. In particular, among the most popular options are 16 ohms and 32 ohms, and advanced models have values from 300 ohms and even from 600 ohms. High-resistance is considered to be "ears" with a resistance of 100 ohms. These characteristics improve the purity of the sound, but require increased signal strength — and built-in amplifiers in handheld devices, computer audio cards, etc. usually have difficulty with this. Therefore, external amplifiers are often used for this very purpose — to effectively "shake" high-end headphones with high impedance. For the same reason, some of these amplifiers are not compatible with low-impedance “ears”: there are many devices that require headphones with an impedance of at least 32 ohms, or even higher, and in some models the lower limit of the operating range can reach 100 ohms. As for the maximum resistance, the range of its values is very impressive — from 32 ohms in relatively simple portable "amps" to thousands and even tens of thousands of ohms in high-end stationary models.

Anyway, you should not violate the manufacturer's recommendations for headphone impedance. If the resistance of the “ears” is too low, at best, the sound will be s...ubject to noticeable distortion, at worst, equipment failure and even fire may occur. Too high resistance, in turn, not only reduces the volume, but also worsens the frequency response.

Rated headphone output(s) provided by the amplifier.

Rated is the highest average power that the device is capable of delivering for a long time without overloads; individual “jumps” of the signal may have a higher level, but this indicator is the main one. The sound volume of the headphones connected to the device directly depends on it: with the same characteristics of the “ears” (primarily sensitivity), the high output power of the amplifier allows for a higher sound pressure level.

There are special formulas and tables that allow you to calculate the minimum power level required to achieve a particular volume. For example, to achieve 95 dB (the minimum required level for listening to music in silence at a satisfactory volume), headphones with a sensitivity of 100 dB will need 0.32 mW, for 105 dB (recommended level for powerful sound like rock concerts) — 3, 16 mW, and for 120 dB (the recommended level for watching movies with special effects like thunder, explosions, etc.) — already 100 mW.

At the same time, when choosing by this parameter, note that the actual power of the amplifier at the output will depend on the impedance of the headphones. This paragraph usually indicates the highest power value — with the minimum allowable resistance; for "ears" with numerous ohms, the power will be less, sometimes quite significantly. Therefore, when choosing, it is more convenient to use not a total number, but a specific power value for a parti...cular resistance (see below). The second nuance is that for multichannel amplifiers (see "Number of channels") this parameter can be indicated in different ways: in some models, the power is given for the full channel load mode (that is, we are talking about a guaranteed maximum per channel), in others — for half load or generally for working with one channel; such details should be clarified separately.

Frequency range supported by the output amplifier; in other words, the range that this model is capable of delivering to headphones or another analogue audio device.

Theoretically, the wider the frequency range — the richer the sound of the amplifier, the lower the likelihood that the lower or upper edge of audible frequencies will be “cut off”. However, when evaluating this parameter, several nuances should be taken into account. Firstly, the average person is able to hear frequencies from 16 to 22,000 Hz, and with age, these boundaries gradually narrow. However, headphone amplifiers often have wider operating ranges, and they are very impressive — for example, for some models, a set of frequencies from 1 Hz to 60,000 Hz, or even up to 100,000 Hz, is claimed. Such characteristics are a kind of "side effect" from the use of high-end sound processing circuits; from a practical point of view, these numbers do not make much sense, but they are an indicator of the high class of the amplifier and are often used for advertising purposes.

The second nuance is that any headphones also inevitably have their own frequency limitations — and these limitations can be more significant than in an amplifier. Therefore, when choosing, it's ok to take into account the characteristics of the headphones: for example, you should not specifically look for an amplifier with an upper frequency limit of the full 22 kHz, if in the headphones that you plan to use with it, th...is limit is only 20 kHz.

In conclusion, also note that an extensive frequency range in itself does not guarantee high sound quality — it largely depends on other factors (frequency response, distortion level, etc.).

The ratio between the overall level of the desired signal produced by the amplifier and the level of background noise resulting from the operation of electronic components.

It is impossible to completely avoid background noise, but it is possible to reduce it to the lowest possible level. The higher the signal-to-noise ratio, the clearer the sound produced by the device, the less noticeable its own interference from the amplifier. In the most modest amplifiers from this point of view, this indicator ranges from 70 to 95 dB — not an outstanding, but quite acceptable value even for Hi-Fi equipment. You can often find higher numbers — 95 – 100 dB, 100 – 110 dB and even more than 110 dB. This characteristic is of particular importance when the amplifier operates as a component of a multi-component audio system (for example, "vinyl player — phono stage — preamplifier — headphone amplifier." The fact is that in such systems the final noise of all components at the output is summed up, and for sound purity it is extremely it is desirable that these noises be minimal

Separately, it is worth emphasizing that a high signal-to-noise ratio in itself does not guarantee high sound quality in general.

The coefficient of harmonic distortion that occurs during the operation of the amplifier.

Any electronic circuits are inevitably subject to such distortions, and the quality and reliability of the sound at the output depends on their level. Accordingly, ideally, the harmonic coefficient should be as low as possible. So, as a general rule, a level of 0.09% and below (hundredths of a percent) is considered good, and a level of less than 0.01% (thousandths of a percent) is excellent. The exception is lamp devices: higher values \u200b\u200bare allowed in them (in tenths of a percent), however, this point in many cases is not a drawback, but a feature (for more details, see "Lamp").

It is also worth noting that a low harmonic coefficient is especially important when using the amplifier as part of multicomponent audio systems — for example, when listening to music from a vinyl player with an external phono stage. The fact is that in such systems the sum of distortions from all components affects the final sound — and it, again, should be as low as possible.

The presence of a Bluetooth module in the amplifier for direct wireless communication with other devices - primarily with audio sources that also support this technology (for example, a smartphone, tablet or laptop).

The main convenience of Bluetooth amplifiers is, first of all, the absence of additional wires, which can create various inconveniences. At the same time, the range of wireless communication is usually at least several meters. On the other hand, during normal transmission via Bluetooth, the digital audio signal is heavily compressed, which worsens the sound quality. To correct the situation, Bluetooth models may include aptX technology, which increases the purity of the signal almost to the level of wired Audio CD (or even Hi-Res Audio - in the aptX HD version); however, such functionality significantly affects the cost, and sophisticated music lovers often easily notice the difference between aptX and a wired connection.

In light of all the above, Bluetooth does not make sense to install in stationary equipment, so nowadays such modules are used only in portable amplifiers (see "Type"). At the same time, some of these models are positioned not so much as amplifiers, but as Bluetooth adapters for wired headphones. Nevertheless, such a solution can be a good alternative to classic wireless headphones: decent wired "ears" in combination with a Bluetooth amplifier can provide higher sound quality at a comparable,...or even lower cost, and often such a set turns out to be even more "long-playing" in terms of work without recharging.