It all started with the fact that I had long wanted to build myself an inexpensive, but rather powerful sound amplifier. Not on the simplest 1555
, which play no better than ordinary mini-speakers, but at least fifty watts. Well, that has reached the goal. I assembled an amplifier on a well-known microcircuit TDA7294... You can easily squeeze 100 watts or more from it. I bought a microcircuit for only $ 1.5, and pulled everything else from a Soviet TV, there I found almost everything.
Microcircuit connection diagram
The advantage of this amplifier is that it is so tested and rechecked by thousands of radio amateurs that all beginners can easily assemble this circuit - there are no serious obstacles. All parts can be found at home (except for the microcircuit itself).
Power transformer TS-160 it is permissible to take from the same TV, having disassembled it, left the primary, the secondary wound 172 turns of wire with a diameter of 1.5mm. Low-power transformers will not work here (after all, you need 200 watts only for sound). The minimum power of the transformer must be over 100 watts if the microcircuit is powered by a reduced voltage. It is known that the power supply of the microcircuit 7294
bipolar. The voltage gave - + 55 volts. Current 2-3 Amperes. To be honest, I did not measure the consumption current, that is, I forgot. I remembered when everything was soldered. The power wires should be thicker. At high volume, thin wires heat up and stick to each other, in fact, a short circuit occurs.
The diode bridge was taken from an imported TV, although the diodes heated up significantly during sound reproduction. I got all the other details from Soviet TV.
One more thing, the amplifier is equipped with a cooler, since the heatsink was not very large. I assembled the scheme on a piece of cardboard. I did not find the textolite at all. For many radio amateurs, such luxury as textolite, vitriol, laser printer is not available. I'm on this list too: (But you can see that if you want to do something, you can get by with a little.
The details were connected with copper wires. I did not install LEDs and other indicators at all, since seriousness and performance are important to me in the first place. The speaker is currently 20-30 W, 8 ohms. I haven't bought a 100 watt head yet.
Photo of the finished amplifier above. Yes, neatness is not in the best condition. But surprisingly everything turned out very well - there is no audible distortion. The input signal came from the phone. The amplifier started from the very first turn on and it made me very happy! From SW. best.boy99
Discuss the article POWERFUL AMPLIFIER FOR BEGINNERS
Having bought a good laptop or a cool phone, we are delighted with the purchase, admiring the many functions and the speed of the device. But it is worth connecting 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, "pumped up". Instead of full and clear sound, we hear an unintelligible whisper with background noise.
But do not get upset and scold the manufacturers, the sound problem can be solved on your own. 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 sound amplifier. In our article we will show you how to make a sound amplifier for each type of device.
At the initial stage of work on creating an amplifier, you need to find tools and buy component parts. The amplifier circuit is made on a printed circuit board using a soldering iron. To create microcircuits, use special soldering stations that you can buy in the store. The use of a printed circuit board makes 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 of which is the generation of a large amount of heat. Therefore, try to exclude contact of the microcircuit with other parts with the internal structure of the amplifier. For additional cooling of the amplifier, it is recommended to use a radiator grill for heat dissipation. The size of the grid depends on the chip model and amplifier power. Plan ahead for the heat sink in the amplifier enclosure.
Another feature of the self-made sound amplifier is its low energy consumption. This in turn allows the amplifier to be used in a car by connecting it to a battery or on the road using battery power. Simplified amplifier models require a voltage of only 3 volts.
The main elements of the amplifier 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 schema 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 give diagrams and descriptions of different options for a sound amplifier:
Headphone audio amplifier
The audio amplifier for portable headphones is not very powerful, but consumes very little power. This is an important factor for battery-powered mobile amplifiers. You can also place a connector on the device to power it from the mains through 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 plug socket.
- Connector for adapter.
- Approximately 30 centimeters of copper wire.
- Heat dissipating element (for a closed case).
Headphone audio amplifier circuit The amplifier is manufactured on a printed circuit board or surface-mounted. Do not use a pulse transformer with this type of amplifier as it may cause interference. Once manufactured, this amplifier is capable of delivering powerful and enjoyable sound from your phone, player or tablet.
You can check out 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 built-in speakers is not enough for normal listening, or if the speakers are out of order. The amplifier should be rated for external speakers up to 2 watts and winding resistance up to 4 ohms.
Sound amplifier for laptop To assemble the amplifier you need:
- Printed circuit board.
- Chip TDA 7231.
- 9 volt power supply.
- Component housing.
- Non-polar capacitor 0.1 μF - 2 pieces.
- Polar capacitor 100 μF - 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.
Sound amplifier circuit for laptop The assembly order is determined independently, depending on the scheme. The cooling heatsink must be sized so 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 openings for air circulation. For the case, you can use a plastic container or plastic boxes from under the old radio equipment.
You can see a visual instruction in the video:
Sound amplifier for car radio
This amplifier for a car radio is assembled on a TDA8569Q microcircuit, the circuit is not complicated and very common.
Sound amplifier for car radio The microcircuit has the following declared characteristics:
- Input power 25 watts per channel in 4 ohms and 40 watts per channel in 2 ohms.
- Supply voltage 6-18 volts.
- The range of reproducible frequencies is 20-20000 Hz.
For use in a car, a filter must be added to the circuit against interference that is created by the generator and ignition system. The microcircuit is also protected against output short circuit and overheating.
Sound amplifier circuit for car radio Referring to the diagram provided, purchase the necessary components. Next, draw a PCB and drill holes in it. Then etch the board with ferric chloride. In conclusion, we tinker and begin to solder the components of the microcircuit. Please note that it is better to cover the power tracks with a thicker layer of solder so that there are no power drawdowns.
You need to install a radiator on the microcircuit 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 filter for power supply according to the diagram below:
Anti-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.
Also, this filter can be used if your radio tape recorder catches "pickups".
Attention! Be careful not to mix up the polarity of the power supply, otherwise the microcircuit will burn out instantly.
How to make an amplifier for a stereo signal, you can also learn 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 out transistors in complementary pairs.
- 10 watts of power, with a margin is enough for living rooms.
- Good compatibility with new sound cards and players.
- Great sound quality.
Start assembling the amplifier from the power supply. Separate the two channels for stereo with two secondary windings coming from the same transformer. On the model, make bridges on Schottky diodes for the rectifier. After the bridges, there are CRC filters from two 33000 uF capacitors and a 0.75 Ohm resistor between them. The resistor in the filter needs a powerful cement one, at a quiescent current of up to 2A it will dissipate 3W of heat, so it is better to take it with a margin of 5-10W. For the rest of the resistors in the circuit, 2 W is sufficient.
Transistor amplifier Moving on to the amplifier board. Everything except the Tr1 / Tr2 output transistors is on the board itself. Output transistors are mounted on heat sinks. It is better to first put resistors R1, R2 and R6 with trimmers, after all adjustments, evaporate, measure their resistance and solder the final constant resistors with the same resistance. The setting is reduced 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, with the help of R1 and R2, the quiescent current is set - we put the tester to measure the direct current and measure the current at the input point of the power supply plus. The quiescent current of the amplifier in class A is maximum and, in fact, in the absence of an input signal, all 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 the cooling heatsinks, otherwise they will quickly overheat.
When adjusting and underestimating the resistance of the amplifier, the cutoff frequency of the low frequency can increase, so for the capacitor at the input it is better to use not 0.5 microfarads, but 1 or even 2 microfarads 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 the ground: R 10 Ohm + C 0.1 μF. Fuses must be installed both on the transformer and on the power input of the circuit.
It is a good idea to use thermal paste to maximize contact between the transistor and the heatsink.
Now a few words about the case. The size of the case is set by the 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 the music, you need to properly ground the ground to minimize the background. To do this, connect the SZ to the minus of the input-output, and bring the remaining minuses to the "star" near the filter capacitors.
Transistor audio amplifier housing The approximate cost of consumables for a transistor sound 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 result is an amount of 12,100 rubles.
You can also watch a video on assembling a germanium transistor amplifier:
Vacuum tube 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 stages operate in a triode connection, and the anode current of the lamps is close to the limiting one. Currents are built by cathode resistors - 3mA for the input and 50mA for the output tube.
The parts used for the tube amplifier must be new and of high quality. The permissible deviation of the resistor ratings can be plus or minus 20%, and the capacitances of all capacitors can be increased by 2-3 times.
Filter capacitors must be rated for at least 350 volts. The interstage capacitor must be designed for the same voltage. Transformers for the amplifier can be conventional - TV31-9 or a more modern analogue - TWSE-6.
Vacuum tube amplifier It is better not to install the volume and stereo balance control on the amplifier, since these adjustments can be made in the computer itself or the player. The input lamp is selected from - 6N1P, 6N2P, 6N23P, 6N3P. 6P14P, 6P15P, 6P18P or 6P43P (with increased cathode resistor resistance) are used as an output pentode.
Even if you have a working transformer, it is better to use a conventional transformer with a 40-60 watt rectifier to turn on the foot amplifier for the first time. Only after successful testing and tuning of the amplifier can a pulse transformer be installed.
Use standard sockets for plugs and cables; to connect speakers it is better to install “pedals” on 4 pins.
A case for a claw amplifier is usually made from a shell of old technology or cases of system units.
You can watch another version of the tube amplifier in the video:
Audio amplifier classification
So that you can determine to which class of sound amplifiers the device you have assembled belongs, check out the UMZCH classification below:
Class A amplifier - Class A - amplifiers of this class operate without clipping the signal in the linear section of the current-voltage characteristic of the amplifying elements, which ensures a minimum of nonlinear distortion. But this comes at the price 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 90 degree cutoff. 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 step 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 vehicles that have limited voltage supply to the output stages. The reason for the creation of class H amplifiers is that the real sound signal has a pulsed nature and its average power is much lower than the peak. The circuit for this class of amplifiers is based on a simple circuit for a class AB amplifier, operating in a bridge circuit. Added only a special circuit for doubling the supply voltage. The main element of the doubling circuit is a high-capacity storage capacitor, which is constantly charged from the main power source. At power peaks, this capacitor is connected by a control circuit with the main power supply. The supply voltage of the amplifier's output stage is doubled, allowing it to cope with signal peaks. The efficiency of class H amplifiers reaches 80%, with a signal distortion of only 0.1%.
Class D amplifier - Class D is a separate class of amplifiers called "digital amplifiers". Digital conversion provides additional possibilities for sound processing: from adjusting the volume and tone to the implementation of digital effects such as reverb, noise suppression, suppression of acoustic feedback. Unlike analog amplifiers, the output of class D amplifiers is rectangular. Their amplitude is constant, and 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 doing radio electronics requires a large amount of knowledge and experience that is acquired over a long period of time. Therefore, if something did not work out for you, do not be discouraged, reinforce your knowledge from other sources and try again!
Having bought a good laptop or a cool phone, we are delighted with the purchase, admiring the many functions and the speed of the device. But it is worth connecting 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, "pumped up". Instead of full and clear sound, we hear an unintelligible whisper with background noise.
But do not get upset and scold the manufacturers, the sound problem can be solved on your own. 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 sound amplifier. In our article we will show you how to make a sound amplifier for each type of device.
How to make a sound amplifier?
At the initial stage of work on creating an amplifier, you need to find tools and buy component parts. The amplifier circuit is made on a printed circuit board using a soldering iron. To create microcircuits, use special soldering stations that you can buy in the store. The use of a printed circuit board makes 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 of which is the generation of a large amount of heat. Therefore, try to exclude contact of the microcircuit with other parts with the internal structure of the amplifier. For additional cooling of the amplifier, it is recommended to use a radiator grill for heat dissipation. The size of the grid depends on the chip model and amplifier power. Plan ahead for the heat sink in the amplifier enclosure.
Another feature of the self-made sound amplifier is its low energy consumption. This in turn allows the amplifier to be used in a car by connecting it to a battery or on the road using battery power. Simplified amplifier models require a voltage of only 3 volts.
The main elements of the amplifier
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 schema 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 give diagrams and descriptions of different options for a sound amplifier:
Headphone audio amplifier
The audio amplifier for portable headphones is not very powerful, but consumes very little power. This is an important factor for battery-powered mobile amplifiers. You can also place a connector on the device to power it from the mains through 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 plug socket.
- Connector for adapter.
- Approximately 30 centimeters of copper wire.
- Heat dissipating element (for a closed case).
Headphone audio amplifier circuit
The amplifier is manufactured on a printed circuit board or surface-mounted. Do not use a pulse transformer with this type of amplifier as it may cause interference. Once manufactured, this amplifier is capable of delivering powerful and enjoyable sound from your phone, player or tablet.
You can check out 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 built-in speakers is not enough for normal listening, or if the speakers are out of order. The amplifier should be rated for external speakers up to 2 watts and winding resistance up to 4 ohms.
Sound amplifier for laptop
To assemble the amplifier you need:
- Printed circuit board.
- Chip TDA 7231.
- 9 volt power supply.
- Component housing.
- Non-polar capacitor 0.1 μF - 2 pieces.
- Polar capacitor 100 μF - 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.
Sound amplifier circuit for laptop
The assembly order is determined independently, depending on the scheme. The cooling heatsink must be sized so 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 openings for air circulation. For the case, you can use a plastic container or plastic boxes from under the old radio equipment.
You can see a visual instruction in the video:
This amplifier for a car radio is assembled on a TDA8569Q microcircuit, the circuit is not complicated and very common.
Sound amplifier for car radio
The microcircuit has the following declared characteristics:
- Input power 25 watts per channel in 4 ohms and 40 watts per channel in 2 ohms.
- Supply voltage 6-18 volts.
- The range of reproducible frequencies is 20-20000 Hz.
For use in a car, a filter must be added to the circuit against interference that is created by the generator and ignition system. The microcircuit is also protected against output short circuit and overheating.
Sound amplifier circuit for car radio
Referring to the diagram provided, purchase the necessary components. Next, draw a PCB and drill holes in it. Then etch the board with ferric chloride. In conclusion, we tinker and begin to solder the components of the microcircuit. Please note that it is better to cover the power tracks with a thicker layer of solder so that there are no power drawdowns.
You need to install a radiator on the microcircuit 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 filter for power supply according to the diagram below:
Anti-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.
Also, this filter can be used if your radio tape recorder catches "pickups".
Attention! Be careful not to mix up the polarity of the power supply, otherwise the microcircuit will burn out instantly.
How to make an amplifier for a stereo signal, you can also learn 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 out transistors in complementary pairs.
- 10 watts of power, with a margin is enough for living rooms.
- Good compatibility with new sound cards and players.
- Great sound quality.
Start assembling the amplifier from the power supply. Separate the two channels for stereo with two secondary windings coming from the same transformer. On the model, make bridges on Schottky diodes for the rectifier. After the bridges, there are CRC filters from two 33000 uF capacitors and a 0.75 Ohm resistor between them. The resistor in the filter needs a powerful cement one, at a quiescent current of up to 2A it will dissipate 3W of heat, so it is better to take it with a margin of 5-10W. For the rest of the resistors in the circuit, 2 W is sufficient.
Transistor amplifier
Moving on to the amplifier board. Everything except the Tr1 / Tr2 output transistors is on the board itself. Output transistors are mounted on heat sinks. It is better to first put resistors R1, R2 and R6 with trimmers, after all adjustments, evaporate, measure their resistance and solder the final constant resistors with the same resistance. The setting is reduced 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, with the help of R1 and R2, the quiescent current is set - we put the tester to measure direct current and measure the current at the input point of the power supply plus. The quiescent current of the amplifier in class A is maximum and, in fact, in the absence of an input signal, all goes into thermal energy. For 8 ohm speakers, this 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 the cooling heatsinks, otherwise they will quickly overheat.
When adjusting and underestimating the resistance of the amplifier, the cutoff frequency of the low frequency can increase, so for the capacitor at the input it is better to use not 0.5 microfarads, but 1 or even 2 microfarads 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 the ground: R 10 Ohm + C 0.1 μF. Fuses must be installed both on the transformer and on the power input of the circuit.
It is a good idea to use thermal paste to maximize contact between the transistor and the heatsink.
Now a few words about the case. The size of the case is set by the 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 the music, you need to properly ground the ground to minimize the background. To do this, connect the SZ to the minus of the input-output, and bring the remaining minuses to the "star" near the filter capacitors.
Transistor audio amplifier housing
The approximate cost of consumables for a transistor sound 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 result is an amount of 12,100 rubles.
You can also watch a video on assembling a germanium transistor amplifier:
Vacuum tube 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 stages operate in a triode connection, and the anode current of the lamps is close to the limiting one. Currents are built by cathode resistors - 3mA for the input and 50mA for the output tube.
The parts used for the tube amplifier must be new and of high quality. The permissible deviation of the resistor ratings can be plus or minus 20%, and the capacitances of all capacitors can be increased by 2-3 times.
Filter capacitors must be rated for at least 350 volts. The interstage capacitor must be designed for the same voltage. Transformers for the amplifier can be conventional - TV31-9 or a more modern analogue - TWSE-6.
Vacuum tube amplifier
It is better not to install the volume and stereo balance control on the amplifier, since these adjustments can be made in the computer itself or the player. The input lamp is selected from - 6N1P, 6N2P, 6N23P, 6N3P. 6P14P, 6P15P, 6P18P or 6P43P (with increased cathode resistor resistance) are used as the output pentode.
Even if you have a working transformer, it is better to use a conventional transformer with a 40-60 watt rectifier to turn on the foot amplifier for the first time. Only after successful testing and tuning of the amplifier can a pulse transformer be installed.
Use standard sockets for plugs and cables; to connect speakers it is better to install “pedals” on 4 pins.
A case for a claw amplifier is usually made from a shell of old technology or cases of system units.
You can watch another version of the tube amplifier in the video:
Audio amplifier classification
So that you can determine to which class of sound amplifiers the device you have assembled belongs, check out the UMZCH classification below:
In conclusion, I would like to say that doing radio electronics requires a large amount of knowledge and experience that is acquired over a long period of time. Therefore, if something did not work out for you, do not be discouraged, reinforce your knowledge from other sources and try again!
When a woman comes to the store for shampoo, it is difficult for her to immediately decide on a purchase, and she wanders along the shelves for hours, going through dozens of options. So many radio amateurs, taking on the assembly of a homemade UMZCH, can choose for a long time among a wide variety of circuits and microcircuits. These are the weak TDA2282, and simple TDA1557, and serious TDA7294, and dear STK40... The choice provided by the manufacturers of specialized audio integrated circuits is very large. Which one to stop at? We offer an option that is rightfully considered the golden mean in amplifier construction - the TDA2050 () microcircuit, which, at a price of a couple of tens of rubles, will provide us with honest 30 watts of power. That in the stereo version is already 60 - for an apartment quite.
DIY amplifier circuit
A printed circuit board has been developed for this device, which is suitable for the TDA2050 or LM1875 and has all the necessary components - power, speaker protection, turn-on and quick turn-off delay. This is achieved with the help of a convenient, but not popular in domestic markets, the UPC1237 microcircuit. If it is not possible to buy it, simply remove from the circuit all the elements of its strapping, starting from the resistors R12, R13. Then, in terms of protection, you will rely on the UMZCH microcircuits themselves, which have thermal and short circuit protection. The truth is not very reliable. Yes, and clicks when turning on from the speakers are possible. The parameters of the amplifier itself are described in detail in the documentation.
M / s TDA2050 and LM1875 are completely interchangeable, the differences in their circuits are only in the values \u200b\u200bof a pair of resistors and one capacitor.
All this allows you to make a universal PCB that fits either of these two microcircuits.
Supply voltage source
The UMZCH itself is 2x30 W, but the power depends on the supply voltage and the resistance of the speakers connected to the output. If you have not found a transformer capable of providing the indicated bipolar power supply (2 to 17 V), it does not matter. The circuit can also operate from a reduced voltage, for example, 2 to 12 V. In this case, the power will simply drop proportionally. But such a transformer is easier to find - you can even take two standard ones, 12 V each, and connect their output windings in series.
As for all kinds of timbre blocks, as practice has shown, this is an unnecessary complication of the circuit, which is fraught with unnecessary noise. You can also change the frequency response on a computer (phone). The usual volume control is enough here. And, as an option, channel balance.
DIY amplifier box
The case in our case is plastic, with front and back walls in the form of 1 mm metal plates. You can take absolutely any box that is suitable in size and design, even plastic (easier to process and drill), or metal (anti-interference and strength).
All connectors are standard - 220 V mains, RCA inputs and pedal outputs for speaker systems. Pay particular attention to the resistor for the volume control. Before putting it in the ULF, just plug it in and listen to see if there are any rustles and crackles from the speakers when you turn the knob.
Discuss the article HOW TO MAKE AN AMPLIFIER WITH YOUR OWN HANDS
On Habré there were already publications about DIY-tube amplifiers, which were very interesting to read. No doubt, they sound wonderful, but for everyday use it is easier to use a device with transistors. Transistors are more convenient because they do not require warming up before operation and are more durable. And not everyone dares to start a lamp saga with anode potentials under 400 V, and transformers for transistor ones of a couple of tens of volts are much safer and simply more affordable.
As a circuit for reproduction, I chose a circuit from John Linsley Hood in 1969, taking the author's parameters based on the impedance of my speakers of 8 ohms.
The classic circuit from a British engineer, published almost 50 years ago, is still one of the most reproducible and receives extremely positive reviews about itself. There are many explanations for this:
- the minimum number of elements simplifies installation. It is also believed that the simpler the design, the better the sound;
- despite the fact that there are two output transistors, they do not need to be sorted out into complementary pairs;
- 10 Watt output is enough for ordinary human dwellings, and the input sensitivity of 0.5-1 Volt matches very well with the output of most sound cards or turntables;
- class A - it is also class A in Africa, if we are talking about good sound. Comparison with other classes will be below. 
Interior design
The amplifier starts with power. Separation of two channels for stereo is most correct to carry out already from two different transformers, but I limited myself to one transformer with two secondary windings. After these windings, each channel exists on its own, so we must remember to multiply everything mentioned below by two. On the breadboard we make bridges on Schottky diodes for the rectifier.
It is possible on ordinary diodes or even ready-made bridges, but then they must be shunted with capacitors, and the voltage drop across them is greater. After the bridges, there are CRC filters from two 33000 uF capacitors and a 0.75 Ohm resistor between them. If we take less both the capacitance and the resistor, then the CRC filter will become cheaper and less heated, but the ripple will increase, which is not comme il faut. These parameters, IMHO, are reasonable in terms of price-effect. The resistor in the filter needs a powerful cement one; at a quiescent current of up to 2A, it will dissipate 3 W of heat, so it is better to take with a margin of 5-10 W. For the rest of the resistors in the circuit, 2 W is sufficient.
Next, we move on to the amplifier board itself. A bunch of ready-made whales are sold in online stores, but there are no less complaints about the quality of Chinese components or illiterate layouts on boards. Therefore, it is better to do it yourself, under your own "loose powder". I made both channels on a single breadboard so that later I could attach it to the bottom of the case. Run with test items:
Everything except the Tr1 / Tr2 output transistors is on the board itself. Output transistors are mounted on radiators, more on that below. The following remarks should be made to the author's scheme from the original article:
Not everything needs to be soldered tightly right away. It is better to first put resistors R1, R2 and R6 with trimmers, after all adjustments, evaporate, measure their resistance and solder the final constant resistors with the same resistance. Setting is reduced to the following operations. First, with the help of R6, it is set so that the voltage between X and zero is exactly half of the voltage + V and zero. In one of the channels, 100 kOhm was not enough for me, so it's better to take these trimmers with a margin. Then, with the help of R1 and R2 (keeping their approximate ratio!), The quiescent current is set - we put the tester to measure direct current and measure this very current at the input point of the power supply plus. I had to significantly reduce the resistance of both resistors to obtain the desired quiescent current. The quiescent current of the amplifier in class A is maximum and in fact, in the absence of an input signal, all goes into thermal energy. For 8-ohm speakers, this current, according to the author's recommendation, should be 1.2 A at a voltage of 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 the cooling heatsinks, otherwise they will quickly overheat and die. For they are mainly heated.
It is possible that, as an experiment, you will want to compare the sound of different transistors, so you can also leave the possibility of a convenient replacement for them. I tried 2N3906, KT361 and BC557C inputs, there was a slight difference in favor of the latter. In the pre-weekend we tried KT630, BD139 and KT801, stopped at imported ones. Although all of the above transistors are very good and the difference can be rather subjective. At the exit, I put 2N3055 (ST Microelectronics) right away, since many people like them.
When adjusting and lowering the resistance of the amplifier, the cutoff frequency of the low-frequency can increase, therefore, for a capacitor at the input, it is better to use not 0.5 microfarads, but 1 or even 2 microfarads in a polymer film. A Russian picture-diagram "Ultra-linear class A amplifier" is still walking on the Network, where this capacitor is generally proposed as 0.1 microfarad, which is fraught with a cut of all bass at 90 Hz:
They write that this circuit is not prone to self-excitation, but just in case, a Zobel circuit is placed between point X and the ground: R 10 Ohm + C 0.1 microfarad.
- fuses, they can and should be installed both on the transformer and on the power input of the circuit.
- it would be very appropriate to use thermal paste for maximum contact between the transistor and the radiator.
Locksmith and joinery
Now about the traditionally most difficult part in DIY - the case. The dimensions of the case are set by the radiators, and they should be large in class A, remember about 30 watts of heat on each side. At first, I underestimated this power and made a case with average radiators of 800 cm² per channel. However, with the set quiescent current of 1.2A, they heated up to 100 ° C in 5 minutes, and it became clear that something more powerful was needed. That is, you need to either install larger radiators or use coolers. I did not want to make a quadrocopter, so I bought giant beauties HS 135-250 with an area of \u200b\u200b2500 cm² for each transistor. As practice has shown, such a measure turned out to be a little redundant, but now you can safely touch the amplifier with your hands - the temperature is only 40 ° C even in rest mode. Drilling holes in the radiators for fasteners and transistors became a certain problem - the originally purchased Chinese drills for metal were drilled extremely slowly, each hole would take at least half an hour. Cobalt drills with a sharpening angle of 135 ° from a well-known German manufacturer came to the rescue - each hole is drilled in a few seconds!I made the body itself from plexiglass. We immediately order cut rectangles from the glaziers, make the necessary holes for fasteners in them and paint them on the back with black paint.
Plexiglas painted on the back looks very nice. Now all that remains is to collect everything and enjoy the muses ... oh yes, during the final assembly it is still important to properly dilute the ground to minimize the background. As it was discovered decades before us, C3 needs to be connected to signal ground, i.e. to the minus input-input, and all other minuses can be sent to the "star" near the filter capacitors. If everything is done correctly, then no background can be heard, even if you bring your ear to the speaker at maximum volume. Another "ground" feature that is characteristic of sound cards that are not galvanically isolated from the computer is noise from the motherboard, which can crawl through USB and RCA. Judging by the Internet, the problem is common: in the speakers you can hear the sounds of the HDD, printer, mouse and the background of the system unit's power supply unit. In this case, the easiest way to break the earth loop is to tape the earth on the amplifier plug with electrical tape. There is nothing to fear here, tk. there will be a second ground loop through the computer.
I didn’t do the volume control on the amplifier, because I couldn’t get any high-quality ALPS, and I didn’t like the rustling of Chinese potentiometers. Instead, a conventional 47 kΩ resistor was installed between ground and the input signal. Moreover, the external sound card's regulator is always at hand, and every program also has a slider. Only the turntable has no volume control, so I attached an external potentiometer to the connecting cable to listen to it.
I will guess this container in 5 seconds ...
Finally, you can start listening. Foobar2000 → ASIO → external Asus Xonar U7 is used as a sound source. Columns Microlab Pro3. The main advantage of these speakers is a separate block of their own amplifier on the LM4766 microcircuit, which can be immediately removed somewhere further away. Much more interesting with this acoustics was the amplifier from the Panasonic mini-system with the proud Hi-Fi inscription or the amplifier of the Soviet Vega-109 turntable. Both of the aforementioned devices operate in class AB. The JLH presented in the article outplayed all of the above comrades in one wicket, based on the results of a blind test for 3 people. Although the difference was heard with the naked ear and without any tests - the sound is clearly more detailed and transparent. It is quite easy, for example, to hear the difference between MP3 256kbps and FLAC. I used to think that the lossless effect is more like a placebo, but now the opinion has changed. Likewise, it became much more pleasant to listen to files that were not compressed from loudness war - dynamic range less than 5 dB is not ice at all. Linsley Hood is worth the investment of time and money, as a similar branded amp will cost much more.Material costs
Transformer 2200 r.Output transistors (6 pcs. With a margin) 900 r.
Filter capacitors (4 pcs) 2700 rub.
"Rasspuha" (resistors, small capacitors and transistors, diodes) ~ 2000 r.
Radiators 1800 r.
Plexiglas 650 r.
Paint 250 rub.
Connectors 600 rub.
Boards, wires, silver solder, etc. ~ 1000 r.
TOTAL ~ 12100 p.
