To assemble, you need to have a desire and a certain amount of free time, and you also need to always strive to ensure that you get a high-quality power amplifier that you can assemble with your own hands. In addition, you need to have certain knowledge and skills, and there are also financial costs.

However, the end result will be pleasing, and the amplifier will delight your ears with clean, transparent sound with plenty of power output. In the process of designing a car amplifier, you may encounter some difficulties in finding the necessary electronic components; in such cases, you can use their analogues. Creating a block design for sound amplification in a vehicle audio system, although the process is not fast, in the end it turns out to assemble five compact amplifiers, the total power of which will be 690 W. If desired, it is possible to increase this value to 760 W. p>

Necessary device requirements

First you need to decide on the technical characteristics that you expect to get in the final result. As a rule, this is high sound quality, high output power, a technologically simple design that creates ease of use, low cost, the ability to work with twelve dynamic drivers and a subwoofer. Such requirements can be obtained by making DIY car amplifier in the amount of five pieces, of which one should work for the subwoofer. The optimal solution to this problem is to manufacture a separate power amplifier according to the Lanzar circuit diagram.

To assemble such a device, you will need four microcircuits, namely two TDA 7384 - 4x40W and two TDA 2005 - 1x20W. These microcircuits are intended to power the front speaker system. This schematic solution is the most economical in terms of monetary costs.

Efficient voltage converter

IN car sound amplifier The most important and at the same time time-consuming part is the voltage converter. Therefore, it is from this block that you should begin assembling the entire sound amplifier complex. The well-known push-pull pulse-width modulation controller of special precision - TL494 - is used as the converter's pulse generator. If such a microcircuit is not available, you can use its analogue - 1114EU3/4. The microcircuit does not have a separate output amplifier. In each arm of the converter cascade, a pair of powerful IRF3205 field-effect transistors are installed on heat sinks, which are secured through an insulating gasket using heat-conducting paste. Radiators for this purpose can be used from computer power supplies.

The rectifier circuit uses KD 213A diodes with a maximum current of 10 A, but they do not require additional cooling. In addition, you will need a pair of electromagnetic relays designed for an operating current of 20 A, but to be sure, it is better to set it to 50-60 A. The voltage converter has a remote control function, which is undoubtedly an effective device, since when controlling the power and turning on the subwoofer, no additional installation of powerful switches. When a positive voltage appears on the remote control, the relay is instantly turned on and power is supplied to the converter.

Collect DIY car sound amplifier in principle, not very difficult, but some difficulties may arise during the manufacture of the transformer, that is, if there are no ferrite rings available, then you will have to look for old, suitable power sources. Power supplies from a computer are excellent for these purposes. There, too, you will have to do a little magic, since the two halves of the ferrite rings are securely glued together, to separate them you need to slightly heat the joints with a lighter, and then carefully remove them from the frame and remove the standard windings. Before we start winding the winding we need, we need to remove the side walls of the frames and then connect them to each other so that we get one long frame on which all the necessary turns of the windings can easily fit.

The primary winding is wound at the rate of ten turns with a midpoint (2 x 5 V) with five strands of enamel wire with a diameter of 0.8 mm. It’s easier to do this: I wound 5 turns along the entire length of the frame, made a tap, and insulated the winding with varnished cloth, then wound another five turns on top. Next, you need to perform phasing, that is, connect the beginning of the first winding to the end of the second. The junction of the ends is the tap to which positive voltage from the general power supply will be supplied. After the phasing has been done, you can begin winding a test secondary winding with any number of turns, with the help of which we will determine the correct phasing.

When the converter is connected to the network, the transformer should not overheat at idle and not emit extraneous sounds such as buzzing; the transistors should remain cold. Next, we connect an incandescent lamp to the secondary winding circuit, and it should glow at full heat, and the transistor should not heat up, only over time it warms up a little. If after this test there are no problems, then remove the test winding and wind the normal one.

Assembly of the structure

Before I start my article, I want to say that if you have strong nerves, a lot of free time, certain skills in electronics, like to listen to very loud music in the car, powerful bass and are willing to spend a lot of money on such a project, then this article is just for you !

The idea of ​​​​creating a high-power amplifier has been around for a long time, but due to lack of time and finances, the project was postponed. And then summer... vacation... It was decided to turn the idea into reality and exactly 3 months were spent for this, since there were big problems with the parts, but despite this, the amplification complex was successfully assembled and tested.

To begin with, I would like to clarify the meaning of the expression “enhancing complex”. The fact is that it was decided to assemble a high-quality amplifier that could power the entire car audio system. The entire power section (power amplifiers) had to be combined “under one roof”, the result was 5 separate amplifiers with a total power of 680 watts, do not confuse with Chinese watts, there is a pure 680 watts of rated power, the maximum power of the system reaches 750 watts.
The requirements for the complex were as follows.
1) High sound quality
2) High output power
3) Relatively simple design
4) Low costs compared to the prices of factory systems of this kind
5) Ability to power 10 -12 speakers + subwoofer
To implement this idea, 5 separate power amplifiers were used, including a high-quality Lanzar amplifier to power the subwoofer channel.

Below are the parameters and series of microcircuits that were used in this amplifier.
TDA 7384 - 4x40W (2 pieces, total power of microcircuits 320 watts or 8 channels, 40 watts per channel)
TDA 2005 - 1x20W (2x10W) (2 pieces, total power 40 watts or 2 channels 20 watts each)

The above microcircuits are designed to power front speakers. This solution is the most economical; to create an amplifier of this kind, you can find out about the monetary costs at the end of the article.
The most difficult part in any amplifier of this kind is the voltage converter, it is designed to power the subwoofer amplifier, perhaps we’ll start with it.
Voltage transformer

It took me exactly two weeks to create.

The voltage converter pulse generator (from now on PN) is built on a traditional TL494 microcircuit. This is a high-precision push-pull PWM controller, a domestic analogue of 1114EU3/4.
The microcircuit does not contain an additional output amplifier. The additional stage is built on low-power transistors, the signal from them is fed to the gates of the field switches.

The circuit is known as a push-pull or push-pull converter. The circuit is not new, but I had to change some of the circuit values ​​to suit my needs. On each shoulder there are two powerful field workers of the IRF3205 series. Through heat-conducting gaskets they are mounted on heat sinks that were removed from computer power supplies

In the rectifier part, KD213A diodes are used, they are just for such purposes, since they can operate at frequencies of 70-100 kHz, and the maximum current reaches 10 amperes; in this circuit, the diodes do not need additional heat sinks, I did not notice any overheating.

I used 2 relays for power supply, 20 amperes each, but it is advisable to install a relay for 50-60 amperes, since the converter draws a considerable current. The remote control system (REM) is implemented in the PN, i.e. No powerful switches are needed to turn on the subwoofer. By applying plus to the remote control, the relays are instantly activated and power is supplied to the converter.

I especially struggled with winding the transformer, since the transformer was of my own design. Unfortunately, I could not find ferrite rings, so I had to go for an alternative solution.
We got several computer power supplies for free, and large transformers were soldered out of them.

The ferrite halves are tightly glued to each other, so they need to be heated with a lighter for 30 seconds, then carefully removed from the frame. As a result, the standard windings were unwound from the transformers, and the terminals were cleaned.

At the end the frames are attached to each other. The result is one elongated frame onto which we can freely wind the windings we need

Through experiments, the required number of turns in the primary winding was found. As a result, the primary winding contains 10 turns (2x5vit) with a tap from the middle.

Winding was done immediately with 5 strands of 0.8 mm wire. First, 5 turns are wound along the entire length of the frame, then we insulate the winding and wind another 5 turns on top identical to the first. We wind the windings IN THE SAME DIRECTION, for example clockwise.

After winding the wires, we twist them into a pigtail, not forgetting to remove the varnish in advance, then we tin them and cover them with a layer of tin.
Now you need to phase the windings. In fact, there is nothing difficult here, you just need to find the “beginning” and “end” of the windings and connect, for example, the beginning of the first winding with the end of the second or the beginning of the second with the end of the first, the connection point is a tap to which the plus from the general power supply is supplied ( see diagram).
After phasing the windings, we wind a test secondary winding; it is needed so that if the phasing is incorrect, we do not wind the entire secondary winding. The test winding can contain any number of turns, for example 3 turns with 0.8 mm wire, then we assemble the transformer by inserting the core halves.

When turning on the circuit, the transformer should not emit a “buzz”; the transistors should not overheat if the converter is idle. We connect a 12-volt incandescent lamp of a couple of watts to the secondary winding, which should light up with almost full heat, while the transistors should be cold and only after a few minutes of operation you can feel a slight heat release. If everything is normal, then remove the test winding and wind in its place a normal one, which is wound according to the same principle as the primary.

This time the winding is wound with two strands of 0.8-1mm wire and contains 30 turns (2x15 volts). Two identical windings are wound, each with 15 turns and stretched along the length of the entire frame. After winding the first half, we insulate the winding and wind the second one on top. The windings are phased according to the same principle as the primary.

After winding the secondary winding, the wires at the ends are twisted and tinned. At the final stage, the core halves are strengthened. The transformer is ready!

IMPORTANT! In converters of this kind (push-pull) there should be no gap between the halves of the core! Even the slightest gap of a fraction of a millimeter will lead to a sharp increase in the quiescent current and overheating of the field-effect transistors! It was because of my clumsiness that I burned several field-effect transistors. Make sure that the ferrite halves are pressed against each other as tightly as possible. Such a transformer is capable of providing the required voltage and current to power the subwoofer amplifier.
We solder the transformer onto the board and begin winding the chokes.

Throttle
The circuit uses 3 chokes. They are designed to filter out RF noise and interference that can form on the power lines. The main choke is used on the positive power line of the converter. It is wound with 4 strands of 0.8 mm wire. The ring used those in computer power supplies. The number of throttle turns is 13.

The remaining two chokes are located after the diode rectifier in the PN, they are also wound on rings from computer power supplies and contain 8 turns of 3 cores of 0.8 mm wire.

To be honest, I didn’t expect that such a high-quality voltage supply would be obtained, the quiescent current of the circuit does not exceed 200 mA, this is normal for such a monster, the output voltage is +/-63 volts, the slope is insignificant, only half a volt. The maximum power of the converter would allow powering two of these amplifier, but here it works with a large margin.

Amplifiers based on TDA2005, for low-power heads

Assembling this block took only 2 hours. During this time, two identical power amplifiers were assembled. The amplifiers were chosen as the cheapest option for low-power speakers; they can be used to power speakers located on the front panel of the car. Each microcircuit develops 20-24 watts of power and has very good sound quality.

Each microcircuit is connected via a bridge circuit; with a stereo connection, one microcircuit is capable of delivering up to 12 watts into a 4 ohm load

The microcircuits are installed on the heat sink through an insulating gasket. The volume is adjusted in advance using a regulator. At first, another board was planned, amplifiers were assembled from this one, then a general board was invented, which was entered into the project archive.

TDA 7384 for front speakers

For more powerful speakers, TDA 7384 quadraphonic microcircuits are used. Each microcircuit is capable of delivering up to 40 watts of power per channel into a 4 Ohm load. The result is 8 channels of 40 watts, sounds very good.

Such microcircuits are used in car radios; if you are too lazy to buy them, you can get them from non-working radios.

Microcircuits have different filters independent of each other; if you use a common filter, then noise and excitation are possible.
Both amplifiers start working when +12 volts are supplied from the battery to the REM pin. The amplifiers were assembled on one board, but later the blocks had to be rearranged, so each amplifier was implemented on a separate board.

Subwoofer amplifier

The famous Lanzar circuit, full description, assembly, circuit and configuration are described here, so there is no need to talk about this amplifier. The amplifier is completely assembled using transistors, has very good sound quality and increased output power. I made some changes in the diagram and below is the diagram I used to assemble it, the original diagram in the same forum thread.

Since I could not find some of the circuit ratings, I had to make some changes, in particular the emitter resistors were replaced with 0.39 Ohm 5 watts. The BD139 transistor was replaced with a domestic analog KT815G, in addition, the low-power transistors of the differential stages and pre-output stages of the circuit were replaced.

Electrolytic capacitors can be removed at the input if the input is replaced with 2.2 µF or more.

It is advisable to do the first start-up of the amplifier with one pair of output transistors with the input shorted to ground, so that in case of breakdowns the transistors of the final stage do not burn out; they are the most expensive thing in this amplifier.

Pay special attention to the installation of the circuit, monitor the pinouts of the transistors and the correct connection of the zener diodes, the latter, if connected incorrectly, work like a diode. I installed a regular quiescent current regulator, I do not advise anyone to repeat my mistake, it is better to install a multi-turn one, it can be used to accurately adjust the quiescent current of the circuit, also convenient for setup.

The output stage of the amplifier operates in AB mode, this is essentially a fully symmetrical circuit, the level of nonlinear distortion is reduced to a minimum. Due to its high performance, this amplifier belongs to the Hi-Fi category; getting 300 watts from this amplifier is not a problem. It is also possible to connect a 2 Ohm load at the output, i.e. you can power as many as two subwoofer heads by connecting them in parallel. In this case, you cannot raise the amplifier voltage above 45-50 volts.

You can increase the power of the amplifier by adding one or two more pairs of output transistors, but do not forget about increasing the power supply, since the output power of the amplifier directly depends on the power supply.

AC protection

Despite the fact that the power amplifier is quite reliable, sometimes problems can occur. The output stage is the most vulnerable part of any amplifier; due to the failure of the output transistors, a constant voltage is formed at the output. The constant disables the expensive dynamic head. Any amplifier of this kind has protection that will protect the speakers from constant voltage.
When the amplifier is turned on, the relay closes, including the head; with a constant voltage at the output of the PA, the relay opens, maintaining the head

The protection has a relatively simple circuit, contains 3 active components (transistors), a 10-20 ampere relay, and the rest is little things. When the PA is turned on, the relay closes with a slight delay. Power for protection is supplied from one arm of the converter, through a limiting resistor of 1 kiloohm, select a resistor with a power of 1-2 watts.

Low-power transistors can be replaced with any others whose parameters are similar to those used. The relay is connected to the collector of a more powerful transistor, therefore, the final transistor needs a more powerful one. From the domestic interior, you can use transistors KT 815.817 or more powerful - KT805.819. I noticed heat generation on this transistor, so I mounted it on a small heat sink. Protection and output signal indicator are mounted on one board.

Stabilization block

Bipolar voltage stabilizer provides the necessary voltage to power the filter unit and audio signal indicator. Zener diodes stabilize voltage up to 15 volts.

This unit is assembled on a separate board; it is advisable to use zener diodes with a power of 0.5 watts

Audio level indicator

I won’t go too deep into the operation of the circuit, since the circuit of such an indicator is described in one of my

The indicator uses LM324 microcircuits. It is advisable to use an operational amplifier for these purposes, since the microcircuits cost only $0.7 (each). The indicator uses 8 LEDs; you can install any LEDs that are at hand. The indicator operates in the "column" mode. The indicator is powered by a voltage converter, then the voltage is stabilized to the desired value and supplied to the level indicator. The indicator is connected to the output of the power amplifier, using a trimmer we adjust the indicator to the desired level of LED response.

Adder and low-pass filter block

The adder is designed to sum the signal of both channels, since we have only one subwoofer. After this, the signal is filtered, frequencies lower than 16Hz and higher than 300Hz are cut off. The regulation filter cuts off the signal from 35Hz - 150Hz.

Assembly

After a thorough check of all blocks, you can begin installation.

Unfortunately, I couldn’t find a case from a DVD player or anything else convenient. I attached indicator LEDs to the front panel, where the display used to be located. All boards are attached to the bottom of the amplifier through insulating washers, which in turn were removed from domestic equipment

All microcircuits and transistors are screwed to the heat sinks through insulating gaskets. It is advisable to use thermal paste; unfortunately, we do not sell it, but even without it everything is not so bad.
The input connectors of the amplifiers were soldered out of the DVD, and a connector from the car radio was used as output terminals.

My design uses only one cooler, it is designed to cool the heat sinks of the PN and TDA7384 power switches; the subwoofer amplifier does not need forced cooling, since for it I selected a huge heat sink that practically does not heat up.
The power wires of each amplifier are connected to common power terminals. REM control allows you to turn off any of the amplifiers (for example, a pair of TDA 2005) at the right time. Each amplifier is powered through relays, which are activated when positive is applied to the REM pin.

Each of the amplifiers has a separate remote control system, which is located on the contact platform on the side of the housing.

Subwoofer box

A couple of months after the start of assembly, I managed to buy a SONY XPLOD XS-GTX120L subwoofer head, the head parameters are below.
Rated power - 300 W
Peak power - 1000 W
Frequency range 30 - 1000 Hz
Sensitivity - 86 dB
Output impedance - 4 Ohm
Frequency range - 30 - 1000 Hz
Diffuser material – polypropylene

Since stores only sold laminated chipboards, and we don’t have MDF at all, we had to choose from what was available. Fortunately, we were lucky with the material. Chipboard from USSR times was perfectly preserved in the attic, thickness 22 mm.

The diameter of the FI port is 14 cm, the length of the pipe is 7 cm.
A hole with a diameter of 28 cm was cut for the head. After making all the parts of the box, it was time to assemble it. It is convenient to start assembly by joining the bottom and front of the box. First, holes for the screws were made with a drill (with a small diameter drill), and only then the screws were screwed on. Before this, the fastening points were covered with PVA glue.
There is no need to spare glue, so as not to complain about whistling later. I got a pretty good box, I worked as neatly as possible. Finally, the seams were coated with silicone on the inside of the box (silicone has an unpleasant odor, so this work should be done in a garage or outdoors). After assembling the box, I couldn’t resist, put the head where it was supposed to be and turned it on

I cannot convey this in words or even in a video, because it needs to be felt, not heard. You can feel the full volume of the box, the scope of the head, the power and quality of Lanzar, and all this is embodied in the pressure on your chest.... It’s impossible to describe in words and only then you begin to understand that everything around you is collapsing and falling apart, the glass is moving on the table by itself, the glass is starting to "swell" from pressure. In a word, everything in the house was under a “dose” of vibration.

We sold special glue for carpet, but a can of aerosol costs $25, so we had to use PVA glue. To begin with, I sanded the box; this process took me 4 hours. Apply PVA glue to the already cut carpet. After this, the box needs to be “rolled” over a pre-cut carpet. We wrapped the box, now in order for the glue to dry properly, we hammer small nails along the edges, then after drying they can be removed or left.

Then we cut out the holes for the head and the bass reflex. The head is attached to the box with ten self-tapping screws, this ensures tight contact, no additional gaskets are needed.

This alternative solution is again caused by a shortage of factory connectors.

It turned out well. A separate hole was cut for it.
On the inside, after sealing the wire, the connector hole was sealed with silicone sealant to avoid whistles and unwanted noise.

Total construction costs

Voltage transformer:
BC557 3pcs - $2.5
TL494 1pc - 1$
IRF3205 4pcs - 10$
Diodes KD213A 4pcs - $4
Polar capacitors - $10

Resistors - $2
Chokes and transformers - from old PC power supplies
Relay - from voltage stabilizer

Lanzar amplifier:
Transistors
2SA1943 2pcs - 6$
2SC5200 2pcs - 6$
2SB649 2pcs - 2$
2SD669 2pcs - 2$
2N5401 2pcs - 1$
2N5551 2pcs - 1$
Resistors 5 watt - 4 pcs - $3
Other resistors - $4
Non-polar capacitors - $3
Polar capacitors - $5
Zener diodes - 2 pcs - 1$

Other amplifiers:
TDA7388 2pcs - 15$
TDA2005 2pcs - $2.5
Resistors - $2
Non-polar capacitors - $4
Non-polar capacitors - $6

Filter block:
TL072 1pc -1$
TL084 1pc - 1$
Non-polar capacitors - $3
Resistors - $2
Regulators 3pcs - 4$

Indicator block:
LM324 2pcs - 2$
LEDs and everything else - $2

Stabilizer block:
Transistors 2$
Zener diodes 13 volt 6pcs - $1.5
Stabilizers 7815 2 pcs - $1.5
Zener diodes 7915 1 piece - $0.7
The rest is $2

AC protection:
Transistors - $2
Relay - for free
everything else is 1$
Fortunately, plugs, sockets and connectors were in stock

Subwoofer Box:
Self-tapping screws 50 pcs - $0.5
Sealant 2 bottles - $2

Chipboard - for free
PVA glue - for free
Head - $65
Carpet - $15

Results

That's all. I'm pleased with the results, very pleased! It is not possible to buy such an amplifier; amplifiers of similar power cost from $400! Although Chinese manufacturers offer it for significantly little money, quality and reliability.... In general, the amplifier turned out to be a thrice-bang success! Everything works great, all you have to do is buy a car and enjoy your hand-made amplifier, while the amplifier will work at home for now, from a powerful 12-volt power supply.

Housing for low frequency amplifier. And a little about the amplifier itself

Making a decent case for an electronic device is often more difficult and time-consuming than assembling the device itself. I will describe how I solved the housing issue for a small power amplifier, assembled on my knee during a period of idleness and itching in my hands.

The ULF was based on a ready-made construction kit for self-assembly on the TA8210 chip; a simple power supply was selected and assembled independently. 2008, first test launches:

For 4 years the ULF was operated in a semi-disassembled state with connectors and volume control dangling on the wires; there was only a power supply in the case to avoid electrical injuries. This year, it was decided to start finalizing the design into a more suitable case, especially since I found an aluminum box that was suitable in my opinion:

I don’t see the point in describing in detail the intricacies of marking the mounting holes for various connectors and toggle switches. I’ll show you the labor-intensive moments:
Installing the power connector:

In the absence of a milling machine, there was no way to make a smooth window and embed a finished grille, so I decided to try to drill the grille directly into the body using an ancient drilling machine.
Stencil:

Marked centers:

When drilling, the drill still wandered, there was no normal movable table, so as a result, everything turned out not as beautiful as we would like.
During the assembly process, it turned out that the tea toggle switch (blue in the picture above) did not survive tinning and soldering with my hands and was falling apart; scoop toggle switches were found:

Arrangement of blocks in the housing. The radiator had to be sawed to fit into the body in height. To exchange heat with the case, I put it on thermal paste; the heat exchanger on top needs to be modified to make contact with the lid:

More details on the connectors:

“Input selector” and volume control:

View from below. Self-adhesive legs from some network equipment:

Test run after assembly. In the frame you can see handmade audiophile wires. It immediately turned out that I forgot to connect the amplifier case to electrical ground (terribly foul!):

The last improvements and all that remains is to put a knob on the volume control, which, by the way, I inherited from my father (I once sharpened it for my homemade reel-to-reel tape recorder, which was never finished):

The final photo can be seen in the header.

This project probably let me go for a while, but over time it is planned to improve the internal shielding of the power supply (you can still hear a little trance when there is no signal) and install a fan between the transformer and the radiator. Next, you can experiment with other ULF circuits.

Advice on choosing this very circuit (power 2x30-50 W) and recommendations on inexpensive passive bookshelf acoustics (within 5-7 thousand rubles) are accepted.

Tags: electronics for beginners, sound, hobby

The part about circuitry was mercilessly cut out - we can do that ourselves.

Making an amplifier is not as difficult as it seems. All work can be done at home in the kitchen, with a minimum set of tools and materials. But nevertheless, you can get impressive results. In this article I will tell you how to do this. I will also not use machines and will do all the work by hand.

For the case you will need an aluminum square 15X15 millimeters, more is possible, but not less, otherwise the case will not have sufficient rigidity. First you need to cut the workpiece.

I recommend that you first draw the body on paper and calculate all the dimensions, so that later it will not be excruciatingly painful. When I make cases, I proceed from the fact that all standard Hi-Fi class devices have cases 430 or 460 millimeters long, and their height and depth are not limited. The size 460 millimeters seems too big to me, so I took the size 430 millimeters. I plan to trim the body itself with glass 4 millimeters thick. It follows that the frame must be smaller in size than the final size of the amplifier. If there is a glass lid of 4 millimeters and a bottom of aluminum 1.5 millimeters thick, then the height of the frame should be 5.5 millimeters less than the planned size. And if you make the sides glass, then you need to subtract two glass thicknesses from the total length.

Well, the blanks are cut, you can start processing. Let's start with the vertical posts of the frame. Here, too, we must not forget that from their height we must subtract two thicknesses of the shelf of the square used. In my case, with a total amplifier thickness of 60 millimeters, a glass cover thickness of 4 mm, a bottom of 1.5 mm, and a thickness of the angle shelf, the height of the stand was 51.5 millimeters.

I processed all the racks with a package, this will allow them to be the same height.

When the racks are ready, we begin processing the horizontal frame elements. Each end of the square must be cut at an angle of 45 degrees for convenient joining. You can draw it using a school square (I promised not to use a professional tool).

Pay attention to the next two photographs; they show how to cut off the end of the square.

The bevel should go to the shelf, forming an acute angle. You can first saw off most of the metal with a hacksaw, and finally finish it with a file. Make sure that all similar parts are the same length. To assemble a case with dimensions 430X250X60, you will need four squares 422 millimeters long, and four squares 250 millimeters long. An hour later I had all the blanks done, and I started assembling the frame.

I will assemble it using M3 screws, it was possible to rivet it, but rivets have now become scarce, and rivets are not suitable for this purpose - their heads will stick out. The screws must be purchased with a countersunk head and the drill must be sharpened at an angle of 90 degrees to drill recesses for the screw head.

Two squares are assembled on one vertical stand, as shown in the picture.

And this is the view from the back.

For greater accuracy, you can drill by holding the parts in a vice.

It should look like an aquarium.

Now we need to make the bottom and back wall. I made them from aluminum sheet 1.5 millimeters thick. But you can use roofing iron or plexiglass - it won’t be worse. You just have to recalculate the height of the racks. I used a jigsaw to cut out the blanks, but you can cut them in any available way.

When cutting, do not try to get it to size right away; it is better to make it a millimeter larger and finally adjust the protruding edge into place. Here, the bottom is ready. It must be screwed to the frame with screws with a pitch of no more than one hundred millimeters, this will prevent it from deflecting.

Now you can cut the protruding part of the bottom to size.

The back of the body is done in the same way. The power connector, input and output jacks will be installed on it. They must be purchased in advance.

Mark and drill holes in the back wall.

Well, everything is simple here - the holes are round, but you will have to tinker with the power connector.

We mark the place for the future window and use a thin drill to drill holes as close to each other as possible. Then we cut the jumpers with side cutters...

Five minutes of file work and the window is ready!

Now he’ll think about the legs of our future amplifier. They can be used ready-made from an old computer case, but I found legs from a suitcase that are made of soft plastic. They fit perfectly.

You can start making the front panel. I made it from an aluminum strip 5 millimeters thick, but this is not critical, it can be thinner, just a thick panel looks somehow more beautiful.

In the picture you can see some markings, this is what I forgot to mention. Specifically in this amplifier, I wanted to make a dial level indicator. There must be some kind of zest. But you can do without indicators; those who do not do them can safely skip the entire description about indicators.
Indicators... For them I purchased two voltmeters.

And took them apart...

Of these, we only need the mechanism itself. It must be handled with the utmost care.

To give the indicator a professional look, we will combine them in one housing and provide backlighting. We transfer the markings from the original nameplate onto the aluminum plate and cut it out with a needle file.

And we also need to make a bar that will cover the mechanism from prying eyes.

It should look something like what is seen in the photo.

It is worth paying attention to the side covers - they are needed to complete the structure. And three more holes in the center - LEDs indicating the enabled input will be located there. This is what it looks like from the back.

The entire structure is supported by a square, which is located in the middle. The illumination will be provided by a strip of blue LEDs. They are located in the upper part of the case, above the indicator.

Three red LEDs must be glued into the holes located in the center of the indicator.

Well, we solder a board with resistors to the terminals. The LEDs themselves are connected in parallel to the relay windings on the switching board.

We need to cut a window under the indicator; we will use the same technology as when cutting a window under the power connector. Only here you need to show maximum accuracy and patience - the appearance of the amplifier will depend on this.

Here I couldn’t resist and milled out a recess for the glass on the back side, but this is not necessary. You can use a thin transparent film for laser printers; this film is very thin and will not affect the dimensions, which cannot be said about glass.

The holes for the buttons are drilled with an 8.4 mm drill. This is because I have an eight millimeter diameter aluminum rod that will make great buttons.

It is best to make a chamfer in a hole using a countersink; it is difficult to achieve a flat surface with a drill.

The button itself is sawn off from a rod of the required length and polished by hand using a hand drill. On the reverse side you need to drill a 4 mm hole. It is advisable to polish the end.

The power switch is attached to two long screws, this will allow you to accurately set its height so that the button does not rub in the hole.

You can use a ready-made volume knob; this will not worsen the appearance. There are such beautiful pens on sale.

But I don’t like it, I used a homemade one. If you have a turner friend, I advise you to ask him for help and make a handle like this.

And for complete completion, you need to make a decorative ring.

In combination with the handle, this will take on a completely finished look.

But I’ll say it again - this is not necessary, it will look great with a different handle. Work remains on finishing the body. The front panel must be sanded thoroughly. To do this, let's assemble a small device.

The panel is fixed on a chipboard base, a square is screwed to the side - it serves as a guide. A strip of medium-grit sandpaper is attached to a section of the same chipboard. The sandpaper is moved along the panel and at the same time pressed against the guide. This will allow you to get parallel risks on the panel.

When processing, the panel must be watered generously with kerosene. It can be poured into a spray bottle, it will be very convenient. The panel must always be damp. Don't rub it dry! Hard-to-remove defects may remain.

In an hour you will be able to admire the results.

The volume knob can be polished using a drill.

All that's left to do is cut out the glass to finish the case. I used a gray mirror for this. The simplest thing is to order all this from a mirror workshop, but you can do it yourself. Cutting glass is not a problem, but processing the edges requires effort. Treatment is carried out with sandpaper and water. By gradually decreasing the numbers, you can achieve almost perfect polishing. But you can also stop at a flat matte surface.

The side strips of glass are glued to the body using aquarium silicone.

The glass is glued into the recess using epoxy glue. After curing, excess glue is removed with a sharp blade.

Assembling the indicator. The picture for the nameplate is drawn in any graphics editor and printed on self-adhesive white film.

It would also be a good idea to order decorative supports for the screws from a turner; they will give the amplifier a professional look.

The body itself is covered with black spray paint, but this is also not necessary - the frame is almost invisible. If the case cover is made of glass, by the way, an ordinary mirror gives good results, you need to drill holes in it. I made them using a tubular drill. First, up to half the thickness on the back side of the mirror...

And then from the front. If you do it the other way around, you won’t be able to see where to drill, and I don’t recommend drilling all the way through - in this case, chips are inevitable.

Now we take a red LED with a diameter of three millimeters. A hole with a diameter of three millimeters is drilled in the volume knob on the front side, and on the back, almost to the end, it must be drilled with a four millimeter drill. A resistor is soldered to the LED, and the wires are insulated with tubes. It is advisable to use MGTF brand wire.

The resulting structure is inserted into the hole and secured with a drop of glue.

The handle is put in place, and the wires are passed through the gap between the panel and the axle. The wires from the LED are connected to the supply voltage.

That's it now! All that remains is to secure the top cover. It is also advisable to place decorative pads under the screws. But you can use black screws.

The final step is to make the inscriptions on the front panel. The easiest option is to print them on transparent self-adhesive film. That's exactly what I did.

This is what you should end up with.

Without bragging, I will say that this work took me sixteen hours. So this amplifier is quite possible to build in a weekend. Good luck!