Economy class low frequency amplifier. How to separate the grounds and connect the housing when building a low-frequency amplifier

Prologue

Often, during the first test of a homemade ULF, it turns out that it is phoning (amplifying an interference signal with a frequency of 50 or 100 Hertz) or reproducing some other unnecessary sounds. All these artifacts are especially clearly visible in the absence of a useful signal at the input.

The cause of interference can be either ULF excitation at ultrasonic frequencies, or the penetration of supply voltage ripples into the useful signal, or interference caused by external electromagnetic fields.

Excitation of the amplifier usually occurs due to a malfunction of the Negative Feedback (NFB) for direct current, for example, loss of capacitance of the NFC filter, or incorrect calculation of the VLF frequency response correction circuits. Excitation is easy to identify by the current consumption of the ULF and the distortion of the useful signal. In most cases, it is possible to disrupt the excitation of the ULF without any significant modifications to the design.

But it can be much more difficult to eliminate various kinds of interference associated with power supply or external interference that penetrates the amplification path due to design flaws.

Therefore, it is advisable, even during the design of the amplifier, to know about possible “clamps” and methods for eliminating them.

Let's look at the main reasons that cause hum and other interference in a speaker system and try to understand them using simplified equivalent circuits.

We will consider the symbol position 1 to be a connection to a common bus or, more simply, to a wire to which the common power wire and the common wire of the useful ULF signal are connected. In most low-frequency amplifiers, these two conductors are galvanically connected.

Conditional image of poses. 2 we designate the point of connection of the shielding elements with each other or with the ULF housing, if it is metal.

How to properly connect the input signal and power grounds?

Even at the ULF design stage, all circuits should be analyzed for the flow of currents from different sources through the same wires, screens or printed circuit board tracks. The most convenient way to do this is with the help of so-called equivalent circuits. It is not necessary to draw this diagram; it is quite enough to keep it in mind during design.

In this picture you see a diagram of connecting two independent alternating current generators to the corresponding loads. These two circuits have complete galvanic isolation and penetration of the signal from one generator into the load of the other is possible only through electromagnetic waves. But this is a shielding issue and we will look at it in the next paragraph.

This diagram shows the connection of two AC sources to loads using a common bus. The need to use a common bus arises due to the fact that the input circuits of the amplifiers and their power supply circuits are galvanically connected.

In addition, common buses can be used to save wire or to simplify the layout of printed circuit boards. Although, in some cases, for example, when designing printed circuit boards for pulsed or RF devices, there are other reasons.

Let's assume that only generator G1 is running and is generating some current into load R1. This current, flowing through a common bus that has some, even insignificant, resistance, which we will conventionally designate R3, will create a voltage drop on this very bus. This voltage will be applied through the internal resistance of the generator G2 to the load R2 and some interference current will flow through the latter. Thus, interference from generator G1 can enter load R2.

What does this threaten us with?

The noise voltage at the linear input of the amplifier can be fractions of a microvolt, while the magnitude of the ripple in the circuits of an unstabilized power supply can reach tenths of a volt. If we keep in mind that the input impedance of the ULF linear input is tens of kilo-ohms, then it becomes clear how these ripples can penetrate into the input circuits of the amplifier if the common buses are routed without regard to such an equivalent circuit.

Suppose we are assembling a signal amplifier according to the given circuit.

If we connect the connecting wires as shown in the diagram above, we will get a picture like this.

As you can see, with this connection, a section has appeared on the common bus through which not only the input signal current will flow, but also the current from the power source.

To correct this mess, we move the connection point of the common wires of the power supply and the input signal, position 1, as close as possible to the amplifier circuit in order to reduce the influence of interference. Of course, these same principles will have to be followed when designing a printed circuit board.

Even if all the conductors of the amplifier's common bus are routed correctly, it is still not protected from the effects of interference that can be induced on the amplifier elements by external or internal electromagnetic fields.

The picture shows a familiar diagram of connecting two alternating current generators. But, in this case, we will try to trace how an external or internal electromagnetic field can cause interference to penetrate into the input circuits of the amplifier.

Let us conventionally designate the capacitance between the “hot” conductors of the generators as C1.

To minimize interference penetration, shielding is used.

This could significantly reduce the influence of external fields on the input signal if we did not run the G1 generator current through the cable shielding in the same way as was the case with the common bus described above.

Therefore, we will modify our circuit so as to prevent the flow of generator G1 current through the shielding braid. To do this, it is enough to connect the cable braid to the common bus at only one point.

Now we will use shielding of the signal wire in the ULF to protect it from interference.

When the level of the amplified signal is very low, the effects of interference from all kinds of electromagnetic radiation become noticeable. Electromagnetic waves easily penetrate the shielding braid of the wire, which is usually made of non-magnetic materials.

In order to minimize the level of interference in highly sensitive amplifier circuits, shielded twisted pair cable is used, which is popularly called a microphone cable.

The currents generated by electromagnetic fields in twisted pair wires flow in one direction and are almost equal, due to the identical shape of each twisted pair conductor. At the same time, the useful signal currents flow in different directions along the twisted pair conductors. Thus, in one wire the interference current is added to the useful signal, and in the other it is subtracted, which leads to complete compensation of the interference.

But, in amateur practice, twisted pair may not be needed so often, and is used only to connect a dynamic microphone or electromagnetic pickup to a pre-amplifier.

Typically, the linear input of a low-frequency amplifier is connected approximately according to this diagram. As you can see, the common line input wire is not connected to the socket body. At the same time, the socket body is connected to the metal body of the amplifier. In the same way, other shielding elements are connected to the metal amplifier housing, for example, the interwinding shield of the power transformer and the metal shield of the pre-amplifier.

But, in all cases, the common bus of the amplifier is connected to the metal case (screen) only at one point, position 1. If there are more than one such points, then the currents “traveling” through the metal body of the amplifier will begin to “look” into the common bus, which can cause interference.

If a 3.5mm jack type socket is used for the linear input, and the amplifier case is metal, then you will have to isolate the socket mount from the case, since the common terminal pos. 1 and the fastening elements pos. 2 in such sockets are galvanically connected.

So, let's summarize.

The metal housing of the amplifier must be connected to the common bus of the amplifier at only one point. Although other shielding elements, with the exception of those through which the useful signal flows, can be connected to the housing arbitrarily.

To connect weak signal sources, such as a dynamic microphone head or an electromagnetic pickup, use shielded twisted pair cable.

Having bought a good laptop or a cool phone, we rejoice at the purchase, admiring the many functions and speed of the device. But as soon as we connect the gadget to the speakers to listen to music or watch a movie, we understand that the sound produced by the device, as they say, “let us down.” Instead of full and clear sound, we hear an unintelligible whisper with background noise.

But don’t get upset and scold the manufacturers; you can solve the sound problem yourself. If you know a little about microcircuits and know how to solder well, then it will not be difficult for you to make your own audio amplifier. In our article we will tell you how to make a sound amplifier for each type of device.

At the initial stage of creating an amplifier, you need to find tools and buy components. The amplifier circuit is made on a printed circuit board using a soldering iron. To create microcircuits, use special soldering stations that can be bought in the store. The use of a printed circuit board allows you to make the device compact and easy to use.

Audio amplifier

Do not forget about the features of compact single-channel amplifiers based on TDA series microcircuits, the main one of which is the release of a large amount of heat. Therefore, when designing the internal structure of the amplifier, try to prevent the microcircuit from coming into contact with other parts. For additional cooling of the amplifier, it is recommended to use a radiator grille to dissipate heat. The size of the grid depends on the model of the microcircuit and the power of the amplifier. Plan in advance a place for the heat sink in the amplifier case.
Another feature of making your own sound amplifier is low energy consumption. This in turn allows you to use the amplifier in a car by connecting it to a battery or on the road using battery power. Simplified amplifier models require a current voltage of only 3 volts.

Basic amplifier elements

If you are a beginner radio amateur, then for more convenient work, we recommend that you use a special computer program - Sprint Layout. With this program you can independently create and view diagrams on your computer. Please note that creating your own scheme only makes sense if you have sufficient experience and knowledge. If you are an inexperienced radio amateur, then use ready-made and proven circuits.

Below we provide diagrams and descriptions of different sound amplifier options:

Headphone amplifier

The sound amplifier for portable headphones is not very powerful, but consumes very little energy. This is an important factor for mobile amplifiers that are powered by batteries. You can also place a connector on the device for power supply via a 3 volt adapter.

Homemade headphone amplifier

To make a headphone amplifier you will need:

Chip TDA2822 or analogue KA2209.
Amplifier assembly diagram.
Capacitors 100 uF 4 pieces.
Headphone jack.
Adapter connector.
Approximately 30 centimeters of copper wire.
Heat sink element (for a closed case).

Headphone amplifier circuit

The amplifier is manufactured on a printed circuit board or mounted. Do not use a pulse transformer with this type of amplifier as it may cause interference. After manufacturing, this amplifier is capable of providing powerful and pleasant sound from a phone, player or tablet.
You can see another version of a homemade headphone amplifier in the video:

Sound amplifier for laptop

An amplifier for a laptop is assembled in cases where the power of the speakers built into it is not enough for normal listening, or if the speakers are out of order. The amplifier must be designed for external speakers up to 2 watts and winding resistance up to 4 ohms.

Sound amplifier for laptop

To assemble the amplifier you will need:

Printed circuit board.
Chip TDA 7231.
9 volt power supply.
Housing for housing components.
Non-polar capacitor 0.1 µF - 2 pieces.
Polar capacitor 100 uF - 1 piece.
Polar capacitor 220 uF - 1 piece.
Polar capacitor 470 uF - 1 piece.
Constant resistor 10 Kom - 1 piece.
Constant resistor 4.7 Ohm - 1 piece.
Two-position switch - 1 piece.
Loudspeaker input jack - 1 piece.

Audio amplifier circuit for laptop

The assembly order is determined independently depending on the diagram. The cooling radiator must be of such a size that the operating temperature inside the amplifier case does not exceed 50 degrees Celsius. If you plan to use the device outdoors, then you need to make a case for it with holes for air circulation. For the housing, you can use a plastic container or plastic boxes from old radio equipment.
You can watch the visual instructions in the video:

Sound amplifier for car radio

This amplifier for a car radio is assembled on a TDA8569Q chip; the circuit is not complicated and very common.

Sound amplifier for car radio

The microcircuit has the following declared characteristics:

Input power is 25 watts per channel into 4 ohms and 40 watts per channel into 2 ohms.
Supply voltage 6-18 volts.
Reproducible frequency range 20-20000 Hz.

For use in a car, a filter must be added to the circuit to prevent interference generated by the generator and ignition system. The microcircuit also has protection against output short circuit and overheating.

Audio amplifier circuit for car radio

Referring to the diagram presented, purchase the necessary components. Next, draw the circuit board and drill holes in it. After this, etch the board with ferric chloride. Finally, we tinker and begin to solder the components of the microcircuit. Please note that it is better to cover the power paths with a thicker layer of solder so that there are no power drawdowns.
You need to install a radiator on the chip or organize active cooling using a cooler, otherwise the amplifier will overheat at increased volume.
After assembling the microcircuit, it is necessary to make a power filter according to the diagram below:

Interference filter circuit

The choke in the filter is wound in 5 turns, with a wire with a cross-section of 1-1.5 mm, on a ferite ring with a diameter of 20 mm.
This filter can also be used if your radio picks up interference.
Attention! Be careful not to reverse the polarity of the power supply, otherwise the microcircuit will burn out instantly.
You can also learn how to make an amplifier for a stereo signal from the video:

Transistor sound amplifier

As a circuit for a transistor amplifier, use the circuit below:

Transistor audio amplifier circuit

The scheme, although old, has a lot of fans, for the following reasons:

Simplified installation due to the small number of elements.
There is no need to sort transistors into complementary pairs.
10 watts of power, sufficient for living rooms.
Good compatibility with new sound cards and players.
Excellent sound quality.

Start assembling the amplifier with the power supply. Separate the two channels for stereo with two secondary windings coming from the same transformer. On the breadboard, make bridges using Schottky diodes for the rectifier. After the bridges there are CRC filters consisting of two 33,000 uF capacitors and a 0.75 Ohm resistor between them. A powerful cement resistor is needed for the filter; at a quiescent current of up to 2A, it will dissipate 3 W of heat, so it is better to take it with a margin of 5-10 W. For the remaining resistors in the circuit, a power of 2 W will be enough.

Transistor amplifier

Let's move on to the amplifier board. Everything except the output transistors Tr1/Tr2 is on the board itself. The output transistors are mounted on radiators. It is better to first set up resistors R1, R2 and R6 as trimmers, unsolder them after all adjustments, measure their resistance and solder the final constant resistors with the same resistance. The setting comes down to the following operations - using R6, it is set so that the voltage between X and zero is exactly half of the voltage +V and zero. Then, using R1 and R2, the quiescent current is set - we set the tester to measure direct current and measure the current at the positive input point of the power supply. The quiescent current of an amplifier in class A is maximum and, in fact, in the absence of an input signal, all of it goes into thermal energy. For 8 ohm speakers, this current should be 1.2 A at 27 volts, which means 32.4 watts of heat per channel. Since setting the current can take several minutes, the output transistors must already be on cooling radiators, otherwise they will quickly overheat.
When adjusting and lowering the resistance of the amplifier, the low-frequency cutoff frequency may increase, so for the input capacitor it is better to use not 0.5 µF, but 1 or even 2 µF in a polymer film. It is believed that this circuit is not prone to self-excitation, but just in case, a Zobel circuit is placed between point X and ground: R 10 Ohm + C 0.1 μF. Fuses must be placed both on the transformer and on the power input of the circuit.
It is a good idea to use thermal paste to ensure maximum contact between the transistor and the heatsink.
Now a few words about the case. The size of the case is determined by radiators - NS135-250, 2500 square centimeters for each transistor. The body itself is made of plexiglass or plastic. Having assembled the amplifier, before you start enjoying music, you need to properly distribute the ground to minimize background noise. To do this, connect the SZ to the minus of the input-output, and connect the remaining minuses to the “star” near the filter capacitors.

Transistor audio amplifier housing

Approximate cost of consumables for a transistor audio amplifier:

Filter capacitors 4 pieces - 2700 rubles.
Transformer - 2200 rubles.
Radiators - 1800 rubles.
Output transistors - 6-8 pieces, 900 rubles.
Small elements (resistors, capacitors, transistors, diodes) about 2000 rubles.
Connectors - 600 rubles.
Plexiglas - 650 rubles.
Paint - 250 rubles.
Board, wires, solder about - 1000 rubles

The resulting amount is 12,100 rubles.
You can also watch a video on assembling an amplifier using germanium transistors:

Tube sound amplifier

The circuit of a simple tube amplifier consists of two stages - a 6N23P pre-amplifier and a 6P14P power amplifier.

Tube amplifier circuit

As can be seen from the diagram, both cascades operate in triode connection, and the anode current of the lamps is close to the limit. The currents are adjusted by cathode resistors - 3mA for the input and 50mA for the output lamp.
Parts used for a tube amplifier must be new and of high quality. The permissible deviation of resistor values can be plus or minus 20%, and the capacitances of all capacitors can be increased by 2-3 times.
Filter capacitors must be designed for a voltage of at least 350 volts. The interstage capacitor must also be designed for the same voltage. Transformers for the amplifier can be ordinary - TV31-9 or a more modern analogue - TWSE-6.

Tube sound amplifier

It is better not to install a stereo volume and balance control on the amplifier, since these adjustments can be made in the computer or player itself. The input lamp is selected from - 6N1P, 6N2P, 6N23P, 6N3P. The output pentode is 6P14P, 6P15P, 6P18P or 6P43P (with increased cathode resistor resistance).
Even if you have a working transformer, it is better to use a regular transformer with a 40-60 watt rectifier to turn on the claw amplifier for the first time. Only after successful testing and tuning of the amplifier can the pulse transformer be installed.
Use standard sockets for plugs and cables; to connect speakers, it is better to install 4-pin “pedals”.
The housing for the claw amplifier is usually made from the shell of old equipment or system unit cases.
You can watch another version of a tube amplifier in the video:

Classification of sound amplifiers

So that you can determine which class of sound amplifiers the device you assembled belongs to, read the UMZCH classification below:

Class A amplifier

- Class A- amplifiers of this class operate without signal cutoff in the linear section of the current-voltage characteristic of the amplifying elements, which ensures a minimum of nonlinear distortions. But this comes at the cost of a large amplifier and huge power consumption. The efficiency of a Class A amplifier is only 15-30%. This class includes tube and transistor amplifiers.

Class B amplifier

- Class B- Class B amplifiers operate with a signal cutoff of 90 degrees. For this mode of operation, a push-pull circuit is used, in which each part amplifies its half of the signal. The main disadvantage of class B amplifiers is signal distortion due to a stepwise transition from one half-wave to another. The advantage of this class of amplifiers is considered to be high efficiency, sometimes reaching 70%. But despite the high performance, you will not find modern class B amplifier models on the shelves.

Class AB amplifier

- Class AB is an attempt to combine amplifiers of the classes described above in order to achieve the absence of signal distortion and high efficiency.

Class H amplifier

- Class H- designed specifically for cars that have a limitation of the voltage supplying the output stages. The reason for the creation of Class H amplifiers is that the real audio signal is pulsed in nature and its average power is much lower than the peak power. The circuit of this class of amplifiers is based on a simple circuit for a class AB amplifier operating in a bridge circuit. Only a special circuit for doubling the supply voltage has been added. The main element of the doubling circuit is a large-capacity storage capacitor, which is constantly charged from the main power source. At power peaks, this capacitor is connected by the control circuit to the main power supply. The supply voltage to the amplifier's output stage is doubled, allowing it to handle signal peaks. The efficiency of class H amplifiers reaches 80%, with signal distortion of only 0.1%.

Class D amplifier

Class D is a separate class of amplifiers called “digital amplifiers”. Digital conversion provides additional sound processing capabilities: from adjusting volume and timbre to implementing digital effects such as reverberation, noise reduction, and acoustic feedback suppression. Unlike analog amplifiers, the output of Class D amplifiers is a square wave. Their amplitude is constant, but their duration varies depending on the amplitude of the analog signal entering the amplifier input. The efficiency of amplifiers of this type can reach 90%-95%.

In conclusion, I would like to say that working in radio electronics requires a large amount of knowledge and experience, which is acquired over a long time. Therefore, if something doesn’t work out for you, don’t be discouraged, reinforce your knowledge from other sources and try again!

Presented here two-channel amplifier circuit 1000 W, which is intended for scoring musical events held on large stages, as well as in modern recording studios, various clubs or restaurants.

In general, this short article is provided to those who intend to assemble a high-quality 1000 W power amplifier on their own at home. For normal and stable operation of the amplifier at a 4 ohm load, the optimal supply voltage will be ±95v relative to the midpoint; I would not recommend raising the voltage higher in order to avoid negative consequences when the mains voltage surges, for example, up to 240 volts. The fact is that such jumps in alternation negatively affect the electrolytic capacitors in the rectifier circuit when the rectified voltage rises above 100 V.

Therefore, ±95 volts per arm is quite enough to produce 1 kW output. To remove such power from an amplifier, you also need a corresponding transformer in the power supply, the overall power of which must be at least 1400 W. It is from this moment, that is, choosing an effective power source, that some problems begin. If, for example, we calculate how much a ready-made custom-made armor transformer costs, then the cost of the amplifier will double compared to a switching power supply. If you have the skills and capabilities, then the most suitable option would be to make your own transformer on a toroidal core.

Schematic diagram of the amplifier in its original version

Here is a modified 1000W amplifier circuit

In this version, there were minor changes both in the path of the input differential stage and in the output line circuits. As for the topology of this particular circuit variant, during testing of the device, many experts who took part in the test came to the conclusion that the 1N4007 rectifier diode is not necessary in the circuit and can be omitted. But still, there are other opinions, so it would be better to check this through an experiment. In the output stage, aluminum cooling radiators are equipped with IRFP240 field-effect transistors with a power of 150 W and an operating drain current of 20 A, and a maximum of up to 80 A. The operating voltage of these transistors at the drain-source junction is 200 V. To create normal, comfortable conditions for the operation of the final stage, it is necessary to install a forced cooling system in the device body to dissipate the large amount of heat generated by MOSFET transistors.

There are several options for the design of printed circuit boards two-channel amplifier circuits 1000 W. One is rectangular in shape and the other is somewhat elongated. The output stage circuits are laid in the central part of the printed circuit board. You can use any board, that is, the one that is most suitable in design for installation in the case.

Sketches of printed circuit boards with markings on them for installation of electronic components can be downloaded from this link

Photo of the printed circuit board from the back side:

The amplifier circuit on the TDA2030 is the simplest and highest quality amplifier that even a schoolchild can replicate.

Description of the TDA2030A chip

In the role of an amplifier microcircuit in this article, we will take the TDA2030A microcircuit, which can be bought in absolutely any radio store at a price no more expensive than a loaf of black bread.

TDA2030A is a chip that is executed by Pentawatt (a package with five pins for power linear integrated circuits). Used mainly as a low frequency amplifier (LF) in the AB amplification class. The maximum single-polar supply is 44 Volts. It is unlikely that you will find this voltage in your home laboratory. Therefore, using this chip is quite suitable for your electronic trinkets without the harm of burning the chip.

The TDA2030A also has high output current up to 3.5 Amps peak and has low harmonic and crossover distortion. This means that an amplifier assembled on this chip will have a very good sound. In addition, the chip includes protection against and automatically limits power dissipation. Overheat protection is also included, in which the chip automatically turns off when the case heats up too much.

P.S. Since the market is mostly flooded with Chinese TDAs, it is possible that these protections may not work as expected, or may not work at all. Therefore, I do not recommend checking them for short circuits and overheating.

The simplest amplifier circuit on TDA2030A

As you can see, there is nothing complicated here. When assembling the circuit, do not forget about electrolytic ones, which have polarity and maximum voltage. As you remember, it should not exceed +Upit. +Up in this circuit you can take from 12 to 44 Volts.

Powerful amplifier circuit on TDA2030A

If you wish, you can assemble a circuit with a pair of complementary transistors, thereby increasing the output power. In other words, your speaker will scream even louder, if it is, of course, designed for such power. The scheme is no more complicated than the previous one:

If you do not find foreign transistors BD907 and BD908, then they can be replaced with domestic analogues KT819 and KT818, respectively.

All of the above proposed schemes amplify only one channel. To amplify the stereo signal, we will need to make another similar amplifier. Also, do not forget about radiators, since at high power the microcircuit gets very hot.

Conclusion

I have been collecting these circuits for a long time and have become convinced of their functionality. Although the bear stepped on my ear, I can say for sure that the sound quality of such amplifiers is in no way inferior to some fancy Hi-Fi amplifiers. It’s perfect for a small room or a medium-sized garage to dance to your favorite songs.

You can also find all these circuits in the datasheet for the chip. You can download the datasheet from the link, or easily find it on the Internet.

Where to buy an amplifier

Aliexpress even has a ready-made simplified amplifier circuit

You can watch it at this link.

If you don’t want to bother with soldering amplifiers at all, then you can purchase ready-made modules, which will be several times cheaper than ready-made amplifiers in a housing

Evgenia Smirnova

To send light into the depths of the human heart - this is the purpose of the artist

Content

Connecting speakers to a laptop, TV, or other music source sometimes requires amplification of the signal using a separate device. The idea of building your own amplifier is a good one if you are inclined to work with printed circuit boards at home and have some technical skills.

How to make a sound amplifier

The beginning of work on assembling an amplification device for speakers of one type or another consists of searching for tools and components. The amplifier circuit is assembled on a printed circuit board using a soldering iron on a heat-resistant support. It is recommended to use special soldering stations. If you assemble it yourself for the purpose of testing the circuit or for use for a short period of time, the “on wires” option is suitable, but you will need more space to place the components. The printed circuit board guarantees the compactness of the device and ease of further use.

A cheap and widespread amplifier for headphones or small speakers is created on the basis of a microcircuit - a miniature control unit with a pre-wired set of commands for controlling an electrical signal. All that remains to be added to the circuit with the microcircuit is a few resistors and capacitors. The total cost of an amateur-grade amplifier is ultimately significantly lower than the price of ready-made professional equipment from the nearest store, but the functionality is limited to changing the output volume of the audio signal.

Remember the features of compact single-channel amplifiers that you assemble yourself based on TDA series microcircuits and their analogues. The microcircuit generates a large amount of heat during operation, so you should eliminate or minimize its contact with other parts of the device. A radiator grille for heat removal is recommended for use. Depending on the model of the microcircuit and the power of the amplifier, the size of the required heatsink increases. If the amplifier is assembled in a housing, you should first plan a place for the heat sink.

Another feature of assembling a sound amplifier with your own hands is the low voltage consumption. This allows you to use a simple amplifier in cars (powered by a car battery), on the road or at home (powered by a special unit or batteries). Some simplified audio amplifiers require a voltage of only 3 Volts. Power consumption depends on the degree of audio signal amplification required. The sound amplifier from the player for standard headphones consumes about 3 Watts.

It is recommended that a novice radio amateur use a computer program to create and view circuit diagrams. Files for such programs can have a *.lay extension - they are created and edited in the popular virtual tool Sprint Layout. Creating a circuit with your own hands from scratch makes sense if you have already gained experience and want to experiment with the knowledge you have gained. Otherwise, look for and download ready-made files that can be used to quickly assemble a replacement for a low-frequency amplifier for a car radio or a digital combo amplifier for a guitar.

For laptop

A do-it-yourself sound amplifier for a laptop is assembled in one of two cases: the built-in speakers are out of order, or their volume and sound quality are not enough for your needs. You will need a simple amplifier designed for a power of external speakers up to 2 Watts, and a winding resistance of up to 4 Ohms. To assemble it yourself, in addition to standard amateur radio tools (pliers, soldering station), you will need a printed circuit board, a TDA 7231 microcircuit, and a 9-volt power supply. Select your own housing to house the amplifier components.

Add the following items to the list of purchased components:

non-polar capacitor 0.1 µF – 2 pcs.;
polar capacitor 100 µF – 1 pc.;
polar capacitor 220 µF – 1 pc.;
polar capacitor 470 µF – 1 pc.;
constant resistor 10 KOhm – 1 pc.;
constant resistor 4.7 Ohm – 1 pc.;
two-position switch – 1 pc.;
jack for loudspeaker output – 1 pc.

Determine the assembly order yourself depending on which *.lay electrical diagram you downloaded. Select a radiator of such a size that its thermal conductivity allows you to maintain the operating temperature of the microcircuit below 50 degrees Celsius. If the device is constantly used outdoors with a laptop, it will need a homemade case with slots or holes for air circulation. You can assemble such a case with your own hands from a plastic container or the remains of old radio equipment, securing the board with long screws.

For DIY headphones

The simplest stereo amplifier for portable headphones should have low power, but the most important parameter will be power consumption. In an ideal example, the design is powered by AA batteries or, in extreme cases, by a simple 3-volt adapter. You will need a high-quality TDA 2822 microcircuit or its analogue (for example, KA 2209), an electronic circuit for assembling an amplifier with your own hands using a TDA 2822. Additionally, take the following components:

capacitors 100 µF (4 pcs.);
up to 30 cm of copper wire;
socket for headphone cable.

A heat sink element will be needed if you want to make the amplifier compact and with a closed housing. The amplifier can be assembled on a ready-made or home-made printed circuit board or by surface mounting. The pulse transformer in the power supply may cause interference, so do not use it in this amplifier. The finished amplifier will provide pleasant and powerful sound from the player (record or radio signal), tablet or phone.

Subwoofer amplifier circuit

The low-frequency amplifier is assembled with your own hands on the TDA 7294 microcircuit. It is used both to create powerful acoustics with bass in the apartment, and as a car amplifier - in this case, however, you need to purchase a bipolar power supply of 30-35 Volts. The figures below describe the location of components, as well as the values of resistors and capacitors. This subwoofer amplifier will provide an output power of up to 100 watts with outstanding low frequencies.

Mini sound amplifier for speakers

The design described above for laptops is suitable as a sound amplification device for domestic or foreign home speakers. Stationary placement of the device will allow you to choose any power adapter from those available. You can ensure the miniature size and acceptable appearance of an inexpensive amplifier by following several rules:

Ready-made high-quality printed circuit board.
Durable plastic or metal case (order from a specialist).
The placement of components is pre-planned.
The amplifier is soldered neatly, without unnecessary drops of solder.
The heatsink only touches the chip.
Ready-made sockets are used for signal output and power input.

DIY tube sound amplifier

Tube sound amplifiers are expensive devices, provided that you purchase all the components at your own expense. Old radio amateurs sometimes keep collections of tubes and other parts. Assembling a tube amplifier at home with your own hands is relatively easy if you are willing to spend a few days searching for detailed circuit diagrams on the Internet. The sound amplifier circuit in each case is unique and depends on the sound source (old tape recorder, modern digital equipment), power source, expected dimensions and other parameters.

Transistor sound amplifier

Assembling a sound preamplifier with your own hands without using complex microcircuits is possible using transistors. An amplifier based on germanium transistors can be easily integrated into modern audio systems; it does not require additional configuration. The disadvantage of transistor circuits is the larger size of the board assembly. The dependence on the “purity” of the background is also unpleasant - you will need a shielded cable, or an additional circuit for suppressing noise and ripple from the network.

Video: DIY audio power amplifier

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