Power per channel (4Ω)
The nominal sound power output by the amplifier per channel when a load with a dynamic resistance (impedance) of 4 ohms is connected to it. See Power per Channel (8Ω) for more information on power rating and its relationship to impedance.
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.
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.
