Comparison Chord Electronics Mojo vs CEntrance HiFi-M8

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 capacity 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. In this case, the "height" (level) of each step cannot be an arbitrary value — a specific value is selected from a specific list. The bit depth determines how many options this list contains: for example, an indicator of 16 bits means a list of 2 to the power of 16, that is, 2 ^ 16 \u003d 65536 level options. Accordingly, the higher the bit depth — the closer the level of each sample will be to the level of the corresponding section of the sinusoid, the smaller the deviation from the original signal in cases where the original level falls between fixed values. Thus, a high bit depth has a positive effect on the quality and reliability of the sound; on the other hand, it significantly affects the volume of audio materials and the requirements for processing power of the equipment for their processing.

Specifically, for a DAC, the native bit depth of such a module is, in fact, the maximum bit width of the inc...oming digital signal that the converter is able to effectively handle. With higher input values, the sound quality will at best be limited by the capabilities of the DAC, at worst, the device 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 values, the standard options in modern headphone amplifiers are 16 bits, 24 bits and 32 bits. The first value is used, in particular, for the Audio CD format, the second is found in the lossless APE and ALAC formats, and 32 bits may be required to work with FLAC and certain high-end standards.

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 sou...nd will be subject 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.

Rated power delivered by the amplifier when connected to headphones (or other load) with an impedance of 600 ohms.

By itself, the rated power is the highest average power that the device is capable of delivering for a long time without overloading; individual "jumps" of the signal may have a higher level, but in general, the capabilities of the amplifier are determined primarily by this indicator. At the same time, the physical features of the audio equipment are such that the actual power delivered to the load will depend on the resistance of this load. Therefore, in the characteristics of headphone amplifiers, data is often given for different impedance values. Specifically, this value — 600 ohms — is typical for professional "ears", and such resistance is very solid even by the standards of such models; higher performance in headphones is extremely rare.

As for the choice of specific power figures, it depends on the sensitivity of the headphones used, as well as on the sound pressure level (in other words, loudness) that is planned to be achieved by the amplifier. There are special formulas and tables that allow you to calculate the minimum required power for a certain volume at a given sensitivity of the "ears". For example, the minimum for normal listening to music in silence is considered to be a sound pressure of at least 95 dB, and for the most complete experience — at least 105 dB; with a headphone sensitivity of 100 dB, these volume levels wi...ll require at least 0.32 mW and 3.16 mW, respectively.

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 dynamic range provided by the amplifier.

The most simplified dynamic range can be described as follows: this is the range between the highest and lowest signal level at the output, within which normal audibility and the signal-to-noise ratio claimed in the characteristics (see above) are maintained. This parameter is calculated from the logarithmic ratio between the maximum and minimum signal level and is indicated in decibels; the larger the number, the wider the dynamic range.

Note that the overall range of any amplifier is wider than the dynamic range; however, if the output level is too low, the audible sound will be "clogged" by the device's own noise, and if the output level is too high, the level of distortion will increase markedly. Thus, the overall sound quality is usually determined precisely by the dynamic range; in particular, this indicator determines how effectively the amplifier is able to cope with sound that has significant differences in volume (for example, orchestral parts). As for specific numbers, the most modest values in modern headphone amplifiers are about 90 dB, in the most advanced models this figure can reach 130 dB or more.

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.