A power amplifier is an electronic device designed to convert a low-power electrical signal into a more powerful one. Its action must extend within the audio range audible to humans.

The main requirement for the device is ideal compatibility with various electroacoustic transducers (headphones, loudspeakers), no influence on the input signal in terms of its possible distortion.

By design, it can be an independent device or be part of more complex ones: televisions, radio transmitters, radio receivers, radio broadcast networks, music centers, etc.

A little history

Until the 19th century, the only device that amplified sound was the pipe organ. It was located, as a rule, in churches and was a musical instrument consisting of tubular resonator elements, bellows for creating air flow and control keys.

Alternating pressing of the latter led to the passage of air flows in pipes of different sections and sizes. Each of them caused a certain vibration in the air, which gave rise to its own sound, different from the others. At the same time, it became stronger.

The year 1875 was marked by another invention of the famous American Edison, who proposed the first pneumatic amplifier (or aerophone). In it, a person’s voice, arriving at a membrane (fixed in a valve), controlled the flow of compressed air in the tube.

At first, the idea caused great optimism, but it did not justify itself and was gradually forgotten. On its basis, the Pathé brothers created a phonograph at the beginning of the 20th century, patented under the name “oxetophone”. In them, they directly connected the membrane to the needle.

Intensive development of various amplifier designs became possible after the advent of electronic devices.

The first event was the improvement by American inventor Lee de Forest of D. A. Fleming's vacuum diode. It was expressed in the use of a control electrode in the form of a thin wire mesh to regulate the flow of electrons.

This led to the appearance of the first triode, which is, in fact, an electrical analogue of a mechanical valve.

Having a number of positive qualities, it had a number of significant disadvantages: low power, low reliability, severe overheating. All this made its service life limited.

In the 50s of the last century, the first transistor was created - a semiconductor element in which the movement of electrons occurs not in a vacuum, but in a solid substance. According to some audiophiles, the different properties of this material affect the sound characteristics of transistor power amplifiers.

Amplifier selection

Choosing an amplifier, especially one with above-average performance, is not as simple as it might seem to a user uninitiated in electronics.

First of all, the buyer must decide what the device will be used for and the amount of money he plans to spend on its purchase. Information about the acoustic properties of the room where the acoustic systems are supposed to be installed, and what will be heard with their help, will not be superfluous.

The decisive factors when choosing are always the sound quality, design and technical characteristics of the amplifier. Everything else is secondary and has minimal impact on the decision.

The ideal option would be to be able to borrow all the amplifiers that meet the requirements, connect them one by one to the existing speaker systems and select the appropriate one.

But, given that this is practically unlikely, most buyers have to re-read (more than once) all possible information about the devices and their manufacturers, test results of amplifiers and reviews of people who have already bought them. At the same time, rethink everything critically, go around numerous stores and specialized markets, salons. Listen to their managers, choose and refuse, and listen and choose again.

1. Firstly, the first data that a buyer should be interested in is the frequency response of the device, the signal-to-noise ratio and the output power. The latter has a significant impact on the quality of the amplification and therefore should be of the greatest interest. You should find out what technique was used to measure it, what resistance was used and what power is implied (short-term dynamic, musical or sinusoidal). It is also necessary to find out the amount of distortion that was observed during measurements. As practice shows, to ensure high sound quality, the power for each individual channel must be at least 100 W. Although, in reality, it all depends on the sensitivity of the speaker system, for which the recommended power of the device is given.
2. Secondly, the level of noise emanating from an amplifier connected to the speaker system is affected by the signal-to-noise characteristic. According to the existing rule, you need to choose a device that has more. However, not everything is so simple, because its value strongly depends on the measurement with a short-circuited input, on the position of the volume control (in the minimum or other position), on the state of the amplifier output (loaded or not) and other conditions.
3. Thirdly, the frequency response of the amplifier. Today little attention is paid to it, since the development of electronics easily ensures its balance in the region of 20...20000 Hz. It is important that this be observed over the entire power range possible for the device.
4. Fourthly, you should pay attention to the dynamic qualities of the amplifier, which are expressed by the speed with which the output signal increases. This property affects the quality of music reproduction, especially with frequently and sharply changing musical intonations.
5. Fifthly, it would not be amiss to find out the magnitude of nonlinear, intermodulation and transient distortions. The value of the former is usually very low in modern devices and can be neglected.

Amplifier manufacturers rarely indicate the values ​​of other distortions. Their presence in passports or descriptions indicates a responsible approach by companies to products. Attitudes towards them vary; there are people for whom they help to better understand the music being played.

Let's imagine such a normal amplifier. It doesn’t matter which one - for some it will be Hannibal, for others, for example, Sinfoni. It would seem like a small task to take a signal from a source and amplify it to feed it to the speakers. And what’s interesting is that judging by the numbers on the boxes, both can do this almost perfectly - the distortions are not just tenths, but hundredths or even thousandths of a percent. But come on, they still sound different. I would say, wow, how different. How so?

Here, in fact, there is no need to even dig deep. How are almost all measurements taken? We connect a resistor to the amplifier... Stop! This is one of the ambushes. The resistance of the resistor is the same, no matter what we apply to it - be it direct current, or alternating current, or rap music with mega-bass, or classical music with jazz, or blues with rock, or Kirkorov with Dorn, you never know.

What about life? But in life, we connect to the amplifier not resistors, but acoustic systems. And this is such, you know, capricious disgusting... Judge for yourself, what makes the speaker work? That's right, the coil is in a magnetic field. Doesn't remind you of anything? Yes, this is, his mother, a real electric motor! And everything would be fine, but when the coil begins to move in this very magnetic field, the speaker itself turns into a generator and strives to shoot some of the energy back to the amplifier. Just like a capricious child being spoon-fed, yeah. And if you consider that a speaker is an oscillatory system with its own resonances, then all this begins to look even worse. You see, he eats the applesauce, but the pumpkin porridge goes back into the spoon.

And note this, only one speaker! And in acoustic systems there are several of them, and each with its own character. In good acoustics, of course, the crossover tries to make friends with all this cheerful fraternity. But often, why not, the teacher makes him so-so, and sometimes he himself begins to do this...

The amplifier, as you understand, must ignore all these quirks of acoustics. And he, by the way, is also a contraption, far from an ideal theory, and is nothing more than a real frequency-dependent system with continuous compromises. Each manufacturer solves them in its own way, otherwise there would not be so many circuits - with deep and shallow, local and general feedback, various complex solutions for intermediate stages, or minimalistic ones with one stage at the input, immediately pumping the output transistors... And all this forms what loops, shifts the phase, or even strives to self-excite (hussars, be silent!).

And in this regard, by the way, D-class amplifiers do not even have some of the disadvantages of the traditional AB-class; it all depends on the specific circuit implementation. Now, I hope you understand why statements like “Class D amplifiers suck” seem somewhat... ummm... limited?

In short, it’s far from ideal, at least somehow coping with the audio frequency range and meeting the standards for standard measurements on an active load. And this is exactly what manufacturers have learned to do more or less tolerably, hence the good numbers on the boxes.

If you connect speaker systems to the amplifier, or, to hell with it, hang at least one speaker per channel, then everything that we measured on the resistor will actually turn out to be... Well, you understand. And you also asked why amplifiers sound different with the same parameters...

The numbers that amplifier manufacturers sell to us do not always indicate their real abilities. Uncle Xiao's expensive models and production handicrafts costing three yuan may have the same nonlinear distortion coefficients, the same frequency ranges and the same power ratings. Moreover, formally good technology can have even worse performance. The key word is formal...

Actually, what is distortion? It’s simple – these are differences between the output signal and the input signal in form. This means that “extra” frequency components appear in it, which were not there before. But since the sound signal occupies a large frequency range, it is simply unrealistic to see them on the frequency response. You could say they are “involved” somewhere in the useful signal. Actually, that’s why we perceive them as some “coloring” of the sound, although formally (well, there’s that word again) the frequency response itself remains within reason.

Let's move on. Probably everyone has long understood that distortion is different from distortion. It's all about the peculiarities of our hearing. The sound can have a “soft”, “warm”, “velvety” character or, on the contrary, it can be “hard” and “cold”. And this, by the way, is not always bad. As paradoxical as it may sound, sometimes distortions even help us perceive musical information better. True, this is a topic for a slightly more serious conversation, not all at once.

For now, let’s return to the signal shape and try to understand why some of its changes make the sound “harder” and others “warmer”. It seems that we have found out that we cannot find out anything based on the frequency response of the musical signal. But we can feed the amplifier not music, but a signal with only one frequency. The frequency response of such a signal will be one single “stick” against the background of noise. If anything, it would be more correct to call such graphs spectrograms, and the “sticks” are harmonics. This is true, by the way, who didn’t know.

What is an amplifier for?

When buying a high-quality speaker system, it is logical to expect that there will be several sound sources. Whether you want to listen to music through the player, watch a movie, or plunge into another gaming world on your computer, it doesn’t matter. The main thing is that the sound is at its best, otherwise, why spend money and have trouble sleeping in anticipation of the purchase. The problem is that different devices have different audio output power. In addition, the frequency palette may also vary, which means that your excellent speakers may simply not perform well on some device and produce sound that is little better than the integrated one. To bring everything to the same power and quality, amplifiers are used, which are connected to sound sources through various connectors.

Types of amplifiers

There are few of them, but they exist. Basically, a distinction is made between preliminary, power and integrated (combined) or full.

Pre-amplifier. Its task is precisely to collect all sound sources together and transmit the signal to a power amplifier. Some amplifiers of this type allow you to record sound simultaneously with listening.

The rear panel of the preamplifier is littered with all sorts of connectors. Sometimes an XLR port appears among them, which allows you to connect equipment located at a great distance from the amplifier. This function is used by professionals when connecting stage equipment and is clearly superfluous in everyday life. However, it greatly increases the cost of the amplifier, so be careful: you don't want to pay for something you won't use.

Power amplifier. In appearance, its functionality is quite simple. There is a volume control on the front panel, while on the rear there is only one stereo input and a speaker output. Nothing complicated, but the quality of the original signal depends on this amplifier. Inside the device there are powerful transformers and capacitive capacitors that increase the current. Such an amplifier always weighs a lot and is expensive.

Integrated amplifier. The idea of ​​combining two types of amplifiers into one simply could not help but occur to the developers. As a result, such a device is capable of performing the functions of preliminary and power. However, we remember a simple rule: everything universal is worse than single-tasking. If a combined amplifier is cheap, then think about its quality.

By the way, some developers thought it was not enough to combine two types of amplifiers. They add a radio tuner to the device, karaoke and connect it to the Internet. Further, all this is called a receiver and is sold to happy buyers. In the future, only those who are not too demanding on sound and do not set serious tasks for their acoustic system remain happy. However, having a receiver is still better than not having one, which means that if you are not a sophisticated audiophile, you may be satisfied with such equipment.

A few nuances

If possible, you should choose equipment from one manufacturer, but if this is problematic, then at least one class.

Some music lovers prefer tube amplifiers, placing them one step higher than semiconductor ones. The sound quality of such equipment is better in some aspects, however, not everyone will be able to detect it. On the other hand, such amplifiers are so capricious that you don’t want to bother with them for the sake of an ephemeral advantage. Therefore, we will leave tube technology to connoisseurs and music gurus, and advise ordinary people not to complicate their lives.

The next point when choosing an amplifier is its resistance and the power of the output signal. The amplifier's impedance should match or be lower than that of the speaker system, but never exceed it. Let the output sound power be slightly less than the maximum capabilities of your speakers. This will extend their life and save your nerves.

If possible, you should choose equipment from one manufacturer, but if this is problematic, then at least one class. Otherwise, you simply won't get the most out of your technique.

In general terms, that's all. Now that you know so much, stop torturing yourself in your sleep and make the purchase of your dreams. Good luck!

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An amplifier is one of the main components in a car audio system. With its help you can make your speakers work much more productively. For everyone who is partial to high-quality sound, the selection of amplifiers should be taken very seriously. An equally important system that creates high-quality sound is a car amplifier for a subwoofer. There are different types of these devices. You can also assemble the amplifier yourself. Let's find out how to choose a device so that it really pleases your ears.

Why do you need an amplifier when you have a radio?

Most car radios already have a built-in one, and for many drivers this system is completely suitable. Some people don’t change the standard sound in their car for years at all. But there are also those who like the music in the car to sound high-quality and loud. In this case, there is no way to do without an amplifier. A car subwoofer without an amplifier will not give the desired effect. Such equipment can improve the performance of acoustics regardless of the quality of the head unit.

A distinctive feature of an external amplifier is the absence of strict restrictions on settings. Your favorite music tracks will always sound good - at minimum volume levels and even at the maximum.

A car subwoofer amplifier included provides several serious benefits. With it you can increase not only the sound power, but also its quality.

Very often, car speakers are purchased after installation. If the selected speakers, as well as the subwoofer, are of high quality, then they will need more energy at peak performance. A standard radio cannot provide this. That's why they buy a separate car amplifier for the subwoofer. This solution gives good results.

Types of Acoustic Amplifiers

There are several types of this equipment. Thus, mono amplifiers, or monoblocks, are intended only for low-frequency sounds. Dual-channel solutions can also be distinguished. They are used in the absence of rear acoustics, when only front acoustics are available. Three-channel amplifiers also allow you to connect a subwoofer. Well, the most expensive solutions are four-channel. These models allow you to amplify the sound of the entire acoustic system.

The subwoofer is the most difficult speaker to artificially amplify. Therefore, professionals recommend choosing a monoblock as a car amplifier for a subwoofer. These types of devices can work with a variety of resistances. The design has a tone block for special settings and filters. The latter help loud bass sound at full power.

Multichannel devices are also capable of reproducing low frequencies, but they have difficulty handling low impedances. Amplifiers quickly overheat when the subwoofer is at full power.

Differences between monoblocks and amplifiers

A monoblock is technically the same device as multi-channel devices. However, single-channel models have certain characteristics that their analogues do not have. What does it mean? The monoblock has only one channel and is designed to enhance low-frequency bass. The load for which these devices are designed most often has a resistance of 1 ohm. If this condition is met, high power can be obtained at the output. In this case, the load on the on-board network will be minimal. For resistances of 2 Ohms and 4 Ohms there is no point in purchasing a monoblock.

According to the classification of electric amplifiers, modern monoblocks have class “D”. They are very powerful, but the sound quality is very poor. Quality for a subwoofer is a secondary characteristic. There are also amplifiers of another class - “AB”. These are average level indicators. There are other classes as well.

How to choose an amplifier for a subwoofer in terms of power?

If, to enhance sound, everyone pays attention to sound quality, then in the case of subwoofers, the main characteristic is power. It can be of two different types. This is the maximum possible (or PMPO) and nominal. The inscription "PMPO mono" can be seen on the body. This parameter indicates the total power for all channels inclusive. You should not rely on PMPO - the numbers only serve to ensure that devices are purchased better. In practice, this figure does not matter. Another type of power is nominal. It is recorded in the technical passport. Reviews say that this characteristic should be used as a guide when choosing. This parameter should be indicated at a THD of less than 0.1 percent and a voltage of 14.4 volts.

Some people believe that you need to choose a device so that the amplifier power is less. This is a misconception - weak devices will lead to coil failure. You need to select an amplifier whose power matches the subwoofer. But there is a small catch here - the rated power is calculated at a voltage of 14.4 volts. This voltage will never be maintained at the amplifier output. This may cause the coil to overheat. Reviews say that the right amplifier is the one whose power is higher than that of the subwoofer. This is the best option. The only risk is mechanical damage to the coil.

Other characteristics

Reviews say that, in addition to power, you should also pay attention to the frequency range. The parsing shouldn't be too big. Serious manufacturers make values ​​​​from 15 to 350 hertz. The amplifier class can be “AB” or “D”. The first are analog amplifiers with good sound, but low efficiency and low power. The second ones are powerful, with high performance. But judging by the reviews, such devices have poor sound quality.

Another criterion is the number of channels. Monoblocks are very expensive and rare. They can only be seen in professional audio systems. The class of such monoblocks is “D”. Two-channel models are suitable for a subwoofer designed for a resistance of 4-8 ohms. The connection diagram for a car amplifier and subwoofer in this case is of the “Bridge” type.

Three-channel models are not available. They have been completely replaced by four-channel analogues.

Making a car amplifier with your own hands

To build the system, you will need an output power amplifier, as well as a voltage converter. You can make them yourself, but it takes a very long time. You can simply purchase ready-made items in the store. Then you can proceed directly to making an amplifier for a car subwoofer with your own hands.

The device requires two channels, and the amplifier is single-channel. How is this fixed? This is corrected by connecting two radio channels using an adder. Then the sound signal will be filtered - frequencies that fall outside the range from 16 to 300 hertz will disappear from it. The signal then goes to the filter. The latter removes frequencies from 35 to 150 Hz.

When the engine is idling, according to the car amplifier circuit for the subwoofer, it is supposed to consume 1.5 amperes. To prevent the battery from being discharged, install a relay with a separate REM terminal and a voltage of 12 volts, as well as a current above 20 amperes. This REM connects to the +12 volt output of the radio. The subwoofer will turn on along with the head unit.

Connecting an amplifier at home

It often turns out that there is a subwoofer with an amplifier, but it is impossible to operate them in a car. There is a way out - to put the equipment at home. How to connect a car subwoofer to an amplifier at home? The amplifier has input jacks and output jacks for connecting a speaker system and subwoofer. They are connected by “tulips”. They are shown in the photo below.

The amplifier is powered from a computer power supply. It is better to connect a subwoofer using the “Bridge” principle (the same as a car one).

In conclusion

So, we figured out how to connect a car subwoofer to an amplifier. The type of connection depends on the number of channels of the amplifier. Often installation is carried out using a bridge circuit, which is shown in the photo in the article. In the case of the subwoofer is connected to both channels. Installation of a capacitor is optional.