Comparison Chord Electronics Mojo vs Chord Electronics Hugo

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 power delivered by the amplifier when connected to headphones (or other load) with an impedance of 300 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, a resistance of 300 ohms indicates the professional level of the “ears”, but this is far from the maximum indicator for such devices.

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". 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 will 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 32 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. A resistance of 32 ohms allows you to achieve quite good sound quality by the standards of low-impedance headphones, while it is not so high as to create problems for the built-in amplifiers of smartphones and other compact equipment. Therefore, most wired general-purpose (non-professional) headphones are made precisely in this resistance, and if the amplifier characteristics generally indicate power for a certain impedance, then most often it is for 32 ohms.

In the most modest modern amplifiers, the output power at this impedance is between 10 and 250 mW ; values of 250 – 500 mW can be called average, 500 – 100 mW are above average, and the most powerful models are capable of delivering ...f="/list/788/pr-19429 /">more than 1000 watts. The choice for specific power indicators depends on the sensitivity of the headphones used, as well as on the sound pressure level (in other words, loudness), which 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". However, in the case of 32-ohm headphones, it does not always make sense to "get into the calculations." For example, the mentioned 10 mW is more than enough to drive headphones with a modest sensitivity of 96 dB to a volume of more than 105 dB — this is already enough to listen to music at quite a decent volume. And in order to achieve the same "ears" level of 120 dB, which provides a full perception of the loudest sounds (like explosions, thunder, etc.), you need to give out a power slightly higher than 251 mW. So in fact, you have to pay attention to this characteristic and resort to calculations / tables mainly in those cases when you have to use 32 Ohm headphones with a relatively low sensitivity — 95 dB or less.

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 way to adjust the level provided in the amplifier, in other words, the way to control the volume.

Most often, a special wheel(rotary control) is responsible for such adjustment, however, there are also models with buttons. Here are the features of each option:

— Wheel. The most common type of volume control nowadays; its popularity is due primarily to two things. The first is ease of use: the control of the wheel is intuitive, and besides, such a knob can be found and turned by touch, blindly, without much difficulty (this is especially important for portable models — see "Type"). The second point is versatility: the wheel can be connected both with the simplest analogue control loop and with a digital circuit. Moreover, analogue control (considered optimal for high-end equipment) in modern headphone amplifiers is carried out only by rotary controls. The disadvantages of this option include perhaps some bulkiness compared to buttons, but even in pocket models this moment is often not critical.

— Buttons. Volume control with buttons; it can be either two separate keys or a rocker like those used in many portable gadgets. Anyway, such controls are more compact than castors. On the other hand, such control is carried out only electronically: the buttons send a signal to the control circuits, which change the volume accordingly. This format is considered less suitable for h...igh-quality audio equipment than analogue control: additional digital circuits not only complicate the design, but are also a potential source of additional noise. Therefore, push-button control can rarely be found nowadays — in certain models of portable amplifiers (see "Type"), where this solution is provided mainly to reduce the size.

Types of additional outputs provided in the design of the amplifier.

We emphasize that in this case we are talking about additional outputs — that is, connectors that are NOT intended for connecting headphones (although these outputs can use the same types of connectors). The presence, type and number of headphone jacks are indicated separately in the specifications (see below — "Mini-Jack outputs (3.5 mm)", "6.35 mm outputs (Jack)", "XLR outputs", "Headphone outputs"). Additional outputs are usually analogue audio interfaces ( mini-Jack 3.5 mm, Jack 6.35 mm, RCA, XLR) or digital format (S/P-DIF in coaxial or optical design). Here is a more detailed description of each of these interfaces:

— Mini-Jack 3.5 mm. Perhaps the most common analogue audio connector nowadays. Among other things, it is widely used as a linear audio output — in particular, for connecting computer speakers and portable acoustics. There are several varieties of mini-jack, but headphone amplifiers usually use a traditional three-pin jack for transmitting stereo sound through a single connector as an additional output. Anyway, the connector itself is small and convenient for use in compact technology; however, in terms of functionality, reliability and connection quality, it is infer...ior to its “big brother” Jack 6.35 mm. Therefore, the presence of additional 3.5 mm mini-jack outputs is typical mainly for portable amplifiers (see "Type"), as well as for individual stationary models designed for compactness.
Separately, we note that other types of inputs can also be built into the 3.5 mm type hardware jack — for example, coaxial and/or optical (see below). However, the presence of a mini-jack is indicated only if this connector is capable of operating in a traditional analogue format.

— Jack (6.35 mm). An analogue of the 3.5 mm mini-Jack described above, which is used mainly in stationary audio equipment — this is due to the large size of this connector (although there are also portable models with additional outputs of this format among headphone amplifiers). However, such dimensions provide a number of advantages: in particular, the connection is more reliable and noise-resistant. In addition, it is quite possible to implement even a balanced connection through a 6.35 mm Jack (for more details, see “XLR” below), although this functionality is relatively rare in headphone amplifiers — the standard format of operation is used much more often, with the transmission of both channels of stereo sound through one 6.35 output mm.

— RCA. RCA is technically a type of connector that can be used for a variety of purposes. However, in this case, a very specific application is implied — in the line-out format (for analogue audio). In this format, one physical connector is responsible for one channel of sound, so this type of output usually consists of a pair of connectors — for the left and right channels. As for use, linear RCA will be convenient primarily for connecting the amplifier to various stationary audio equipment, mainly entry-level and mid-level. This interface itself is not particularly noise-resistant, however, with the proper quality of the connecting wires, it is quite capable of providing more than decent sound quality — quite sufficient not only for everyday use, but also for relatively uncomplicated professional use.

— XLR. The XLR connector has several varieties, differing in the number of contacts; however, all of them have contacts in the form of characteristic pins ("pins") and a round rim, complemented by a separate latch for maximum connection reliability. And as an additional audio output in headphone amplifiers, a three-pin XLR version with balanced connection support is most often used. Such an interface outputs a line-level analogue signal on a "one channel per connector" basis; so an XLR output usually includes at least two hardware jacks, stereo left and right. As for the balanced connection, this is a special format that uses three wires per channel (instead of the standard two) and a special way to process the signal at the receiver input. Due to this, interference arising from third-party interference in the connection cable is mutually canceled when it arrives at the receiver; in fact, the cable itself plays the role of a noise filter. This allows you to work even with fairly long wires without compromising the purity of the sound. On the other hand, the XLR connectors themselves are quite large, and the support for a balanced format affects the cost of the device. Therefore, in general, this interface is considered professional, it is installed in amplifiers of the appropriate level, and only stationary ones — it makes no sense to use additional outputs of this type in portable models for a number of reasons.

— Coaxial S/P-DIF. A variation of the S/P-DIF interface that uses an electrical cable (as opposed to the optical cable described below). The common features of all varieties of S / P-DIF are, firstly, the digital signal format, and secondly, the ability to transmit stereo or multi-channel sound over a single connector. Specifically, the coaxial version uses a shielded electrical cable; it does not have one hundred percent protection against interference, but it is cheaper than fibre optic and does not require special delicacy in handling. As for the application, it makes sense to look for a device with an S / P-DIF output (of any format) if you plan to use it to switch a digital signal — for example, broadcasting sound from a smartphone's microUSB port to the coaxial input of an external audio receiver. Such use in the case of headphone amplifiers is quite exotic, so outputs of this type have not received much distribution.

— Optical S/P-DIF. A variation of the S/P-DIF interface that uses a TOSLINK fibre optic cable. See above for more on S/P-DIF in general and its use in headphone amplifiers. Also note here that an optical cable requires more careful handling than coaxial, but it is practically not subject to electromagnetic interference, since light pulses are responsible for signal transmission in this case.