Comparison Chord Electronics Mojo vs iFi micro iDSD

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 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 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 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.

Rated power delivered by the amplifier when connected to headphones (or other load) with an impedance of 16 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. And 16 ohms is a rather low resistance indicator even for low-resistance "ears"; such characteristics are provided mainly in general-purpose headphones designed for pocket gadgets with low-power amplifiers.

As for the choice for specific power values, 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". At the same time, it is worth noting that at 16 ohms, even the most low-power modern “amps” are capable of delivering about 20 mW — this is enough to drive headphones with a sensitivity of 88 dB (far from the highest figure) to a vo...lume of 105 dB (the minimum value recommended for a complete listening experience). And in most amplifiers, when operated with a given impedance, they provide much more power. So paying attention to this point and going into the calculations makes sense mainly either with low sensitivity of the "ears" (less than the mentioned 88 dB), or if you want to end up with a level above 105 dB.

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.

The presence of the Gain Control function in the amplifier — that is, adjusting the input sensitivity, or, in other words, adjusting the degree of gain. The higher the "gain" — the higher the final volume of the sound (with the same characteristics of the headphones and the input signal).

Most often, modern headphone amplifiers provide the simplest two-stage (High / Low) or three-stage (High / Mid / Low) sensitivity adjustment. However, even such a setting provides additional features for coordinating the signal source, amplifier and headphones. For example, the ability to increase Gain may come in handy when changing headphones to higher-impedance or less sensitive ones: a weak gain sometimes does not allow you to achieve the desired volume on such “ears”. Conversely, for sensitive headphones, a high degree of gain may be excessive.