Comparison JBL Stage A9004 vs Pioneer GM-A6704

-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) is connected to it with a nominal impedance of 2 ohms. For details, see "Nom. channel power (at 1 Ohm)”.

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)”.

Rated power delivered by the amplifier to a load connected in a bridge circuit. For more information about the rated power, see "Nom. channel power (at 1 Ohm)”.

With a bridged connection, the speaker is connected not to one channel, but to two at the same time — the “positive” connector of one channel and the “negative” connector of the other are used. If the amplifier has a similar format of operation, then such a pair of channels operates in antiphase, due to which the power is summed up. This allows you to connect speakers to the amplifier, the power of which is twice the nominal power of the device: for example, at 150 watts per channel, 300 watts of acoustics can be bridged. If there are 4 or more channels, it becomes possible to use several speakers according to the "bridge" scheme. This is usually directly indicated in the specifications — for example, the entry "2x300 W" in the "Bridge connection" item means the ability to work with two speakers, each with 300 W.

The requirements for load resistance when connecting with a bridge are the same as for conventional; see "Maximum Resistance" for details.

The highest output power provided by the amplifier. It is worth noting that this indicator is not standardized, and different manufacturers may mean different values \u200b\u200bfor it — for example, the highest power of short-term, in a fraction of a second, peaks (power surges), the highest power that the amplifier can transfer for several seconds, or even the power at which the device will fail. Therefore, it makes no sense to compare different models with each other in terms of maximum power. But when choosing acoustics for an amplifier (or vice versa), this parameter can be very useful: it is desirable that the maximum power of the speaker be at least twice as high as that of the amplifier. This will reduce the risk that a power surge will damage the speakers.

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.

— DSP processor. The digital audio processing processor improves the overall sound quality and provides additional options for its adjustment. One of the most important functions of DSP is time correction: it allows you to adjust the operation of acoustics so that sound from speakers located at different distances from the customer reaches him at the same time. This coordination significantly improves the sound experience.

The presence of a processor significantly affects the price of the amplifier, but in most cases it is a justifiable price to board for the sound quality. But the clear disadvantage of “processor” models is the complexity of installation and configuration; for this it is best to contact a specialist.

— Phase adjustment. The ability to shift signals entering different channels of the amplifier in phase relative to each other; The phase shift in this case is a small, fraction of a second, delay of the signal on one of the channels relative to the other. The need for such a setting is due to the fact that the speakers on different channels (including the subwoofer) may be at different distances from the listener; Because of this, as well as due to the peculiarities of signal processing, the sound from them may arrive with some desynchronization. By adjusting the phases, you can eliminate this phenomenon and achieve the highest quality sound.

— High voltage in...put. This input is useful if the radio does not have a special connector (line output) for the amplifier - it allows you to use the signal going to the speakers when connecting. Such a signal is much more powerful than at the linear output, and outputting it to the standard linear input of the amplifier can damage the device; the high-voltage input will cope with the task without any problems. It must be borne in mind, however, that the high-voltage connection is more of a backup option than a full replacement for the linear input. The fact is that before entering the external amplifier, the signal passes through the radio's own amplifier, which introduces additional distortion.

— Bass Boost function. As the name suggests, this feature is designed to enhance the sound at low frequencies, resulting in a more powerful and rich bass sound. It will be especially useful if the amplifier is planned to be used with a subwoofer. The simplest options involve enhancing the bass without adjustments; more advanced models allow you to adjust the frequency range and degree of gain.

— Infra-low-pass filter (FINCH). This function is relevant primarily when connecting an amplifier to a subwoofer; it allows you to minimize reproduced infrasound - vibrations whose frequency is below the human hearing threshold. There are several purposes for this adjustment. Firstly, high-power infrasound can cause poor health and even health problems. Secondly, some of the power will be spent on its reproduction, which will negatively affect the audible sound. Thirdly, ultra-low frequencies greatly wear out the cone and can even damage the speaker. In some amplifiers, the FINCH has frequency adjustment.

— Low pass filter (LPF). Thanks to this function, the customer can separately change the volume of the bass sound, adjusting the sound to his own preferences and features of the environment. It will be especially useful if the amplifier is used for both the main acoustics and the subwoofer - the low-pass filter will actually work as a volume control for the latter.

— High-pass filter (HPF). The high-pass filter is used to fine-tune the sound - it allows you to separately adjust the volume of high frequencies without affecting the rest, and thus change their share in the overall sound picture.