Power per channel (8Ω)
The nominal sound power output by the amplifier per channel when operating with a load having a dynamic resistance (impedance) of 8 ohms. In our catalog, this parameter is indicated for the mode when all channels of the amplifier work under load (see "Number of channels"); in the presence of unused channels, the rated power may be slightly higher, but this mode cannot be called standard.
Rated power can be simply described as the highest output signal power at which the amplifier is able to work stably for a long time (at least an hour) without negative consequences. These are average figures, because in fact, the audio signal is by definition unstable, and individual level jumps can significantly exceed the rated power. However, it is she who is the main basis for assessing the overall loudness of the sound.
This indicator also determines which speakers can be connected to the amplifier: their rated power should not be lower than that of the amplifier.
According to the laws of electrodynamics, with different dynamic load resistance, the output power of the amplifier will also be different. In modern speakers, the standard values \u200b\u200bare 8, 6, 4 and 2 Ohms, and power levels are indicated for them.
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.
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.
Main input
The sensitivity and dynamic impedance of the amplifier when a signal is applied to the Main 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.
