Comparison Pioneer GM-D8704 vs Kicx RX 4.120AB

-A. Amplifiers with analogue signal processing. The design of their electronic circuits is such that the current through the amplifying stage is not interrupted during operation (unlike class B). Due to this, the output signal repeats the input signal as accurately as possible, and even at low powers the level of distortion is minimal. This allows the use of such amplifiers even in Hi-Fi systems. On the other hand, class A devices consume full power all the time, whether they are outputting a signal or not, while their power consumption is very significant, and the efficiency (and, accordingly, the output power) is quite low. In addition, this class is characterized by significant heat dissipation — especially at idle, when the power consumed is converted mainly into heat.

— A/B. This class of amplifiers belongs to analogue devices. Without going into technical details, we can say that it combines the principles of operation of classes A (high sound quality with low efficiency) and B (good energy efficiency, but relatively low sound quality). As a result, class A / B devices have a higher efficiency and lower heat dissipation than “pure” class A, and although they lose a little in sound quality, they significantly exceed “pure” class B in this indicator. Among these amplifiers are also found Hi-Fi level models.

— D. Amplifiers using digital signal proc...essing. Their main advantage is high efficiency, which provides good output power (significantly higher than that of the A / B-class). In addition, the dimensions of such devices are very compact. At the same time, the output sound quality is somewhat lower, it is more prone to distortion, and with the same sound quality and other things being equal, a class D model will cost significantly more than A / B. This scheme includes many single-channel (see "Number of channels") amplifiers designed for subwoofers — in this case, power is much more important than signal purity.

— B/D. Despite the name hinting at hybrid operation, these amplifiers are not a hybrid of classes B and D, but digital devices that have some design differences from traditional class D models (see above). According to some manufacturers, these differences allow for higher efficiency than analogue classes (see above), with a lower level of distortion than in the "regular" class D. However, such devices are quite expensive.

— G. A variety of analogue amplifiers designed to increase the efficiency of such devices and, accordingly, provide high power. The design of class G models is based on the fact that the amplifier is rarely used at full capacity. To optimize performance in such models, two voltage options are used to power the output stage, switched depending on the level (in other words, volume) of the input signal. At low volume, low voltage is used, and to provide high power, the device is transferred to high voltage. This not only significantly increases the efficiency, but also provides good sound quality, but the amplifiers themselves are complex in design and expensive.

Rated power output by the amplifier per channel when a load (speakers) with a nominal impedance of 4 ohms is connected to it. For details, see "Nom. channel power (at 1 Ohm)”.

The highest nominal load impedance (speaker) that the amplifier can handle.

Rated impedance (the term “impedance” is also used in acoustics) is one of the most important characteristics for the normal compatibility of acoustics and an amplifier: according to this characteristic, they must match. If the acoustic impedance is higher than the calculated one, the sound volume will be very low even if all other parameters match; if on the contrary, the sound will be distorted, and in the worst case, even the speaker may fail.

For a number of reasons, for car amplifiers, the maximum load resistance is traditionally indicated, that is, the maximum at which the device is still able to provide full sound volume. Standard values in car audio are 1, 2, 4 and 8 ohms. If the amplifier design does not provide resistance adjustment (see above), then the indicated maximum resistance is also the only permissible one. If there is such an adjustment, then the amplifier will be able to provide at least operation with the “neighboring” impedance value: for example, at a maximum resistance of 4 ohms, two-ohm speakers will also be normally supported. The specific “degree of freedom” in the adjustments for different models is different, this point should be clarified according to the official documentation.

The range of audio frequencies that the amplifier is capable of processing. The standard hearing range of the human ear is 16-20,000 Hz, but for some people these limits can be much wider. In addition, low-frequency vibrations, already inaudible to the ear, but extremely close to the lower threshold of audibility, are perceived by the entire surface of the body at high sound power, which creates the impression of the most saturated sound (although care must be taken with this, because infrasound can have a bad effect on well-being).

In general, the wider the frequency range of an amplifier, the richer the sound it can provide. However, this is not an unequivocal guarantee of high sound quality — a lot also depends on the amplitude-frequency characteristic, signal-to-noise ratio (see below) and other features of a particular device. Yes, and the connected speakers must also correspond to this range — otherwise the signal will be "cut off".

Also note that many monoblocks (see "Number of channels") have an upper range limit of only a few hundred Hz — these models are designed for use with subwoofers, and high frequencies for them would be an unnecessary overkill.

One of the main parameters that determine the sound quality of the amplifier as a whole: it describes the ratio of the useful signal (in other words, “clean” sound) and various extraneous noises. This takes into account almost all noise — both due to external causes (for example, electrical "pickup"), and created by the device itself (for example, due to heating during operation). Accordingly, the higher the signal-to-noise ratio, the less audibility of various interferences and the clearer the sound is obtained (of course, under normal operating parameters). The average for car audio is 95-100 dB, but in advanced models this value can be significantly higher.

At the same time, this parameter is not critical for monoblocks designed for subwoofers — most of the interference is high-frequency and will simply not be heard on the low-frequency speaker. The sound quality in this case is highly dependent on the characteristics of the speaker (much more than in multi-channel models), and is weakly related to the “noiselessness” of the amplifier.

Possibility of connection to the amplifier of the remote control. Note that the functionality of remotes for amplifiers is significantly different from other types of electronics. First, the connection is most often carried out by wire. Secondly, the remote itself provides a minimum of adjustments — most often it controls only the Bass Boost function (see "Functions"), allowing you to quickly adjust the bass level depending on the track being played. However, remote control is still significantly more convenient than changing settings from the panel on the amplifier case.

The rating of the fuse installed in the amplifier is the current strength, at which the fuse operates, opening the circuit and de-energizing the device in order to avoid unpleasant consequences (see "Protection — Short circuit protection"). In some models, several fuses can be installed — in this case, this is usually directly indicated in the characteristics, and the current required to operate the protection corresponds to the sum of the ratings. For example, the rating marked "4x25 A" corresponds to four fuses that operate at a current strength of more than 100 A.

This parameter determines, first of all, the features of the power connection: it is desirable that the fuse in the corresponding section of the on-board network of the car be of a higher rating than in the amplifier, otherwise it may burn out at a current that is quite normal for the device. In addition, the fuse rating is related to the power rating of the amplifier and can be useful if you have doubts about the reliability of the data specified by the manufacturer. There are special formulas that allow you to calculate the maximum possible rated power depending on the fuse rating and device class (see above).