Features
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Concert. Professional amplifiers designed to work at concerts and other similar events. Their main external difference from
home models is rack mounting; for almost all concert models, the mounting size is indicated in the characteristics (see below). In terms of performance, the main difference is the high power, in some models exceeding 1000 watts per channel even at 8 ohm load. You can also note a rather restrained design — where such a technique is used, the appearance is far from being of paramount importance.
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Informational. Amplifiers designed for use in public address systems — at stations, airports, shopping centers, etc. One of the features of this application is that passive loudspeakers can be located at a great distance from the amplifier — tens or even hundreds of metres. The standard way to ensure signal transmission over such a distance is to use transformers at the output of the amplifier and at the inputs of the loudspeakers. Such a "transformer" connection can be carried out according to the standards 100/70 V and 50/25 V; in fact, the presence of at least one type of output is mandatory for power amplifiers and integrated amplifiers (see "Type") for this purpose. However, preamplifiers can also be produced for information. Also note that some data models support only one audio channel; and multi-channel often provide the ability to quickly turn
...on and off individual channels — this allows you to organize broadcasting in separate zones.
— Concert / informational. Devices that combine the capabilities of the two types of amplifiers mentioned in the name (for more details on each, see above). Almost all are rack-mounted (among purely informational models this is less common). They can also be single-channel, and there are quite a few such solutions.Tubes type
The model of tubes installed in a tube or hybrid type amplifier (see "Element base"). The capabilities of the device largely depend on the lamps used in the design, including small details of the sound, not directly spelled out in the characteristics. In addition, this information allows, to some extent, to assess the overall level of the model. On the other hand, in fact, it can only be useful to extremely demanding listeners, attentive to every detail; most users, including audiophiles, will only need information about the type of tubes when they need to be replaced.
Frequency range
The range of audio frequencies that the amplifier is capable of handling. The wider this range, the more complete the overall picture of the sound, the less likely it is that too high or low frequencies will be “cut off” by the output amplifier. However, note that the range of sound audible to a person is on average from 16 Hz to 20 kHz; There are some deviations from this norm, but they are small. At the same time, modern Hi-Fi and Hi-End technology can have a much wider range — most often it is a kind of "side effect" of high-end circuits. Some manufacturers may use this property for promotional purposes, but it does not carry practical value in itself.
Note that even within the audible range it does not always make sense to chase the maximum coverage. It is worth, for example, to take into account that the actually audible sound cannot be better than the speakers are capable of giving out; therefore, for a speaker system with a lower threshold of, say, 70 Hz, there is no need to look for an amplifier with this figure of 16 Hz. Also, do not forget that a wide frequency range in itself does not absolutely guarantee high sound quality — it is associated with a huge number of other factors.
Signal to noise ratio
In itself, the signal-to-noise ratio is the ratio of the level of pure sound produced by the amplifier to the level of extraneous noise that occurs during its operation. This parameter is the main indicator of the overall sound quality — and very clear, because. its measurement takes into account almost all the noise that affects the sound in normal operating conditions. A level of 70 – 80 dB in modern amplifiers can be considered acceptable, 80 – 90 dB is not bad, and for advanced audiophile-class devices, a signal-to-noise ratio of at least 100 dB is considered mandatory.
If the specifications do not specify for which output the signal-to-noise ratio is indicated, it usually means its value for the linear input (see "RCA (par)"). This is quite enough to evaluate the quality of the device for this parameter. However, some manufacturers indicate it for other inputs — Main, Phono; see below for more on this.
Harmonic distortion
This indicator describes the amount of non-linear distortion introduced by the amplifier into the processed signal. Such distortions are not necessarily perceived as extraneous noise, but they degrade the quality of the sound anyway — for example, they can make it more deaf. It is almost impossible to avoid them, but it can be reduced to levels inaudible to the human ear.
As a result, the harmonic distortion factor (harmonics) is one of the main parameters describing the overall sound quality in Hi-Fi and Hi-End amplifiers. The lower it is, the clearer the sound. Hundredths of a percent are considered a good indicator for modern amplifiers, thousandths and below are excellent. The exceptions are tube and hybrid models, for which rather high harmonic coefficients are allowed; see "Element base" for more details.
Line input
The sensitivity and dynamic impedance of the amplifier when a signal is applied to the RCA line input.
Under the sensitivity of any input (except optical) is meant the lowest signal voltage at this input, at which the amplifier is able to provide normal nominal power values (see "Power per channel (8Ω)"). This parameter determines, first of all, the requirements for the signal source. On the one hand, the voltage provided by this source must not be lower than the input sensitivity of the amplifier, otherwise the latter simply will not give the claimed characteristics. However, a significant excess in voltage should not be allowed, otherwise the sound will begin to be distorted. More detailed recommendations on choosing an amplifier by sensitivity are described in special sources.
For any input other than optical, it is believed that the higher this indicator, the less distortion the amplifier introduces into the signal. The minimum level of input impedance in modern models is considered to be 10 kOhm, and in high-end devices it can reach several hundred kOhm.
Preout
Signal level and dynamic impedance provided by the device at the preamplifier output (see "Outputs" for details).
The signal level must not be lower than the sensitivity of the power amplifier (see "Type") to which the signal is received — otherwise the power amplifier will not be able to provide a normal signal level already at its outputs.
Dynamic resistance (impedance) of the preamplifier output. This value is exactly the same as the input impedance of the REC output — see the relevant paragraph above. For more information about the exit itself, see "Exits".
Front panel
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Display. The presence of a display on the front panel of the amplifier. Such displays may have a different design and size, but they are all used to display service information: operating mode, selected signal source, special notifications, overload messages, errors, etc. This provides additional ease of use.
— Indicators. In this case, it means that there are indicators on the front panel that indicate the currently used signal source. Usually they look like a row of light bulbs with the appropriate signatures — "Phono", "CD", "Tuner", "AUX", etc. Such pointers are not as versatile as the display, but they are still very convenient.
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Arrow indicators. Presence on the front panel of indicators in the form of scales with arrows. Usually, such indicators are designed to display the peak level of the output signal. They make it easy to track overloads, and many users find this option more convenient and visual than displays. In addition, the arrow scales give the amplifier a stylish appearance, and, unlike the same displays, do not have complex electronics that can distort the sound. However, this category also includes other types of indicators with scales; some of them may not use an arrow, but other indicators (for example, light ones).
— Regulators behind a hidden panel. The presence of a cover on the front panel that hides the controls of the amplifier. Many models are e
...quipped with additional controls on the front panel; they can be used to adjust both the sound — volume, bass / treble, balance, etc. — and other operation parameters (for example, selecting a signal source or switching between the main and additional speakers). Sometimes these controls (as well as the front panel inputs) are provided with a cover, usually for aesthetic reasons. an abundance of small elements would give the device a sloppy appearance. The cover can also perform protective functions — for example, it reduces the amount of dust that enters the connectors.
— Input audio jack. The presence on the front panel of an input for connecting an audio signal — usually linear, in analogue format. On the one hand, such an input greatly simplifies work with signal sources that need to be connected only occasionally and for a short time — for example, MP3 players: the front panel is always in sight, while getting to the connectors on the back is sometimes very difficult. On the other hand, usually the role of the front audio jack is played by AUX IN with a 3.5 mm mini-Jack jack. This connector is not used among the main inputs, but it is quite popular in portable electronics, in particular, the players already mentioned. Some models may have a pair of RCA jacks on the front panel (see "RCA (pair)"), but this option is less common.
— Headphone output. Headphone output on the front panel of the amplifier. Headphones are portable devices, and on average you have to reconnect them significantly more often than most other components of the audio system; the output located on the front panel greatly simplifies the process.Power consumption
The power consumed by the amplifier during normal operation. Some manufacturers may indicate average power values, some — indicators at maximum load. However, anyway, this parameter allows you to quite adequately assess the power consumption of the device and the requirements for connected power.
In addition, it can be useful if you have doubts about the accuracy of the claimed data on the output power (see "Power per channel (8Ω)"). The basic rule is that the total power rating of all channels cannot exceed the total power consumption of the amplifier. In addition, there are special formulas that allow you to derive the maximum possible rated power depending on the power supply and type of amplifier; they can be found in special sources.