I'd say it's just a super simple amp that contains all four elements and puts out 40 watts of power into two channels!
4 parts and 40 W x 2 power output Karl! This is a godsend for car enthusiasts, since the amplifier is powered by 12 Volts, the full range is from 8 to 18 Volts. It can be easily integrated into subwoofers or speaker systems.
Everything is accessible today thanks to the use of modern element base. Namely the chip - TDA8560Q.
This is a PHILIPS chip. Previously, the TDA1557Q was in use, on which you can also build a stereo amplifier with an output power of 22 W. But it was later modernized by updating the output stage and the TDA8560Q appeared with an output power of 40 W per channel. Also similar is the TDA8563Q.
Car amplifier circuit on a chip
The diagram shows a microcircuit, two input capacitors and one filter capacitor. The filter capacitor is specified with a minimum capacitance of 2200 µF, but the best solution will take 4 such capacitors and parallel them, this way you will ensure more stable operation of the amplifier on low frequencies. The microcircuit must be installed on a radiator, the larger the better.Building a simple amplifier
It is also possible to increase the number of components in the circuit that increase reliability during operation, but not fundamentally.
Five more details have been added here, I’ll explain why. Two 10K Ohm resistors will remove the hum if there are long wires going to the circuit. A 27 K Ohm resistor and a 47 uF capacitor provide a smooth start of the amplifier without clicks. A 220 pF capacitor will filter out high-frequency noise traveling along the power wires. So I recommend modifying the circuit with these nodes; it won’t be superfluous.
I would also like to add that the amplifier develops full power only at 2 ohm load. At 4 Ohms there will be somewhere around 25 W, which is also very good. So our Soviet acoustics will be rocked.
Low-voltage, unipolar power supply provides additional advantages: use in car speakers, but at home you can power it from an old one. computer unit nutrition.
The minimum number of components allows you to build in an amplifier to replace an old one that has failed on a microcircuit of other brands.
The LM1875 chip is a high-quality monophonic low-frequency power amplifier that delivers 25 watts to the load. The output stage operates in class AB. LM1875 has high sound parameters. Dynamic range– 90 dB. nonlinear distortion – 0.015%, reproduced frequency band 20 – 20000 Hz. The microcircuit is intended for use in household audio systems, to power broadband speakers or low-power subwoofers.
Two standard LM1875 connection schemes are popular. Typical - it is described in the datasheet for the microcircuit and bridge. An amplifier with two LM1875 connected in a bridge circuit is capable of delivering up to 50 watts of output.
This time we suggest you assemble the amplifier using a standard circuit. Small printed circuit board, minimal number of parts, high sound quality - a real Gainclone. Additionally installed on the board diode bridge and two high-capacity electrolytic capacitors. For power, you will only need to connect a transformer with two windings, 18V each.
Specifications
Supply voltage ±8V … ±25V
Output power 25W
Total harmonic distortion at 20W* 0.015%
Signal-to-noise ratio 90dB
*After 20W, the LM1875's rather low harmonic distortion increases sharply, so 20W is the maximum output power for a quality amplifier.
Connection diagram
Appearance
The diagram or project in KiCad can be downloaded in the technical documentation section.
This is an open source project! The license under which it is distributed is Creative Commons - Attribution - Share Alike license. The project was made in KiCad. Any files are available for download.
The LM386 opamp is an excellent basis for building audio amplifiers. However, there are a huge number of circuits using the LM386, but not all of them allow you to create a truly high-quality audio amplifier.
This material will demonstrate how to create a great audio amplifier based on the LM386. At the same time, in such a device it is possible to realize the possibility of enhancing bass.
Before presenting ready-made audio amplifier circuits, you should first take a look at the LM386 component itself. It is a fairly versatile operational amplifier. To create a working amplifier, you only need a couple of resistors and capacitors. The chip has options for gain control and bass boost, and can also be converted into an oscillator capable of generating sine waves or square waves. There are three varieties of LM386, each with different power ratings: LM386N-1 (0.325 W), LM386N-3 (0.700 W), LM386N-4 (1.00 W). Actual output power The amount you get will depend on your supply voltage and speaker impedance. There are graphs in the LM386 documentation that will tell you more about this. In this case, the supply voltage was 9V, but you can power this amplifier with voltage from 4V to 12V. The LM386 pinout is shown in the diagram below.
The LM386 op amp takes the input audio signal and increases its voltage within limits of 20 to 200 times. This number is also referred to as voltage gain. Changing the gain can be achieved by connecting a 10 µF capacitor between pins 1 and 8. If there is no capacitor between pins 1 and 8, the gain will be set to 20. By using a 10 µF capacitor, the gain will be set to 200. The gain can be changed to any value between 20 and 200 by connecting a resistance (or potentiometer) in series with the capacitor.
Now that we've learned a little about the LM386, let's start by building a bare-bones LM386-based amplifier with minimum number elements required for its operation. That way, you can then compare it to a better sounding amp that we'll build later. The schematic and breadboard connection diagrams are shown below.
In the above wiring diagram, the audio input ground is connected to the audio output ground. The output ground is noisy and causes distortion of the input signal when connected this way. The audio input ground is sensitive to any noise, and any noise received by the amplifier is magnified through the amplifier. Aim to keep the input ground separate from other ground paths as much as possible. For example, you can connect the ground for power supply, input and output directly to the ground pin (pin 4) of the LM386 as follows:
This type of connection should sound better than the first circuit, but you will probably still notice some noise. We'll fix this in the next circuit by adding decoupling capacitors and a couple of RC filters.
Several elements in this circuit make it sound better. A 470 pF capacitor between the positive input signal and ground is needed to filter out various noise received from the audio inputs. Capacitors of 100 µF and 0.1 µF between the positive and negative power lines are needed to decouple the power supply. A 100uF capacitor will filter out low frequency noise, and a 0.1uF capacitor will filter out high frequency noise. A 0.1 µF capacitance between pins 4 and 6 is required for additional decoupling of the power supply from the op-amp. A 10 KΩ resistor and a 10 μF capacitor, running in series between line 7 and ground, are needed to isolate the input audio signal. This is how it looks on the layout.
The final step in building a quality audio amplifier with the LM386 is adding bass boost capabilities. Bass boost is basically a simple low-pass filter, and it removes most of the noise not removed by decoupling capacitors. All you need for the bass boost circuit is a 0.033uF capacitor and a 10Kohm potentiometer in series between lines 1 and 5.
You can quickly test the circuit by connecting some audio output device. An easy way to connect the audio input in a circuit like this is to cut the 3.5mm audio jack off an old set of headphones and connect it to the pins on the breadboard. Thus, based on the LM386, you can independently, quickly and inexpensively assemble a high-quality sound amplifier with the ability to enhance bass. LM3886 is definitely one of the best audio amplifiers, but there are amplifiers with more best characteristics. After experimenting with the LM386, you can start creating TDA2003 projects, and then smoothly move on to the TDA2050.
We assemble a 50W ULF on LM3886.
In this article we will look at the amplifier circuit audio frequency, implemented on the LM3886 chip. Despite its simplicity, this ULF has good technical characteristics and does not have a bad sound. The standard connection diagram specified in the datasheet for this microcircuit was taken as a basis, followed by minor changes.
And so, consider the circuit diagram of one amplifier channel, shown in the figure below:
According to the datasheet, this microcircuit is capable of delivering up to 68 watts of power to a 4-ohm load at a supply voltage of 2x28 volts, 38 watts to an 8-ohm load at 2x28 volts, and 50 watts to an 8-ohm load at 2x35 volts. Actually, everything specifications you can find it in the datasheet file, the download link for which is at the very end of the article.
Regarding the output coil, it is wound with PEV-2 wire with a diameter of 0.4...0.5 mm directly onto the body of a one-watt 10 Ohm resistor (R7, according to the above diagram), the number of turns is 15. After winding the wire, the coil can be refined by using a heat-shrinkable tube .
Instead of the polar electrolytic capacitor C2, you can use a non-polar one.
The appearance of the assembled amplifier board is shown in the following photo:
To attach the microcircuit to the radiator, KPT paste, mica, and insulating plastic bushings were used (see the following photo):
In the next photo you see appearance conductor side boards:
The operation of the amplifier boards was tested on a test bench:
The test bench uses a step-down transformer with a power of 105 watts, the voltage of the secondary winding is 2 x 24 volts, but in reality it is necessary to install a more powerful transformer, 180...200 watts. The power supply used is the most simple circuit, an imported diode assembly installed on a small radiator, four capacitors of 10,000 microforads each for an operating voltage of 50 volts, fuses for the plus and minus of the output voltage.
During testing of the amplifier, the following nuances emerged:
When the input signal cable is disconnected, a barely audible background in the form of a hum is heard in the speakers; when a cable from the signal source is connected to the input, this slight background disappears.
If the LM3886 chips are isolated from the heatsink using CPT paste, mica, and insulating bushings, grounding the heatsink eliminates hum when the input signal cable is disconnected.
17.12.2017.
At the request of readers, I drew a printed circuit board for the above project. The watering can is made for one-sided foil fiberglass laminate, size 35 x 58 mm. The difference lies in the used connectors for power supply and amplifier output, and also eliminated the 22k SMD resistor coming from the 8th leg of the microcircuit. And one more nuance, the power supply in the circuit contains 220 mF capacitors, in the template I drew for 1000 mF. If you power the amplifier with a voltage greater than 24-0-24V, install capacitors at 35...50V. The watering can looks like this:
The archive file size for downloading materials on the amplifier on the LM3886 is 0.65 Mb.
Chip LM3886 belongs to the Overture family, developed by National Semiconductor. With its help you can get 100 W of instantaneous peak sinusoidal power, i.e. 180 W sound.
Harmonic distortion - no more than 0.06% in the frequency range 20 Hz...20 kHz. Typical supply voltage ripple rejection is 120 dB, so the design network block also poses no problems.
The signal-to-noise ratio is in the range of 98...120 dB. Thus, with the help of this IC you can achieve good quality sound reproduction.
Chip LM3886
The IC has the following protection systems:
- from overvoltage;
- from overload (short circuit of the output to ground or to power);
- from overheating.
The overvoltage protection operates when the load current exceeds 4 A. By doing this, overloads caused by inductive loads can be eliminated.
Thermal protection turns on when the CHIP temperature rises to 165°C and turns off when it drops below 155°C.
Schematic diagram
Schematic diagram amplifier is shown in Fig. 1. The circuit consists of an IC and a circuit feedback. The loudspeaker is connected to the output via the R7-L1 chain.
Rice. 1. Schematic diagram of a low-frequency power amplifier based on the LM3886 chip (68 W).
To achieve high powers, a high supply voltage is required, and the electrolytic filter capacitors must withstand it.
Pin 8 of the microcircuit is used to enable the "Mute" mode. In normal operation, a negative voltage is supplied to it through R6. The value of resistor R6 can be calculated using the formula:
where I 8 >0.5 mA.
Construction and details
The printed circuit board of the amplifier is shown in Fig. 2, and the layout of the parts on it is shown in Fig. 3. Resistors R7 and R8 with a power of 2 W, accuracy class 1%. To make the output inductance L1, it is necessary to wind 12 turns of wire with a diameter of 0.5...0.6 mm with enamel insulation on a tube or pencil of the same thickness as R7.
Then a resistor is inserted into it - so that it does not touch it anywhere (so as not to damage the insulation). The capacitance of capacitor C2 can be increased for better transmission of low frequencies.
The feedback depth is set by resistor R4. Mute mode is activated when switch S1 is opened. For a network transformer, it is advisable to use a toroid. The secondary winding voltage is 2x25 V.
The rectifier bridge must be designed for a rated current of at least 6 A. Rectified voltage without load ±35÷38V. Capacity electrolytic capacitors C5, C4 4700÷10000 µF, permissible voltage - not less than 50 V. It is advisable to bypass the capacitors with film capacitors Capacitance (0.1 - 1 µF) in the immediate vicinity of the microcircuit terminals.
Rice. 2. Amplifier printed circuit board based on the LM3886 chip.
Rice. 3. Placement of parts on printed circuit board amplifier
Attention! The IC must be installed on the radiator. The internal protection of the chip is only effective when the generated heat is dissipated by an appropriately sized heatsink.
The relatively high voltage on the final transistors (5.2 V) and the quiescent current of about 38 mA significantly increase heat transfer. The dimensions of the radiator can be determined using the graphs in Fig. 4.
The right side of the figure shows graphs of the dependence of the released power on the total voltage (for some speaker impedance values). These powers correspond to the radiator temperatures T c. At a given ambient temperature T A, from the table on the left side you can determine the required thermal resistance of the radiator.
Rice. 4. Thermal resistance of the radiator.
Example. Let the total supply voltage be 80 V and the speaker impedance be 8 Ohms. According to the graphs, these values correspond to the allocated power P D = 40 W, i.e. T C =102°C. Let the maximum temperature of the medium T A be 25°C.
Then for the thermal resistance of the radiator according to the table we get 1.9 °/W. If the amplifier must operate reliably at a maximum temperature of 40°C, this value is reduced to 1.6.
At 50°C, a very large radiator will be needed (a plate approximately 30x30 cm, 5 mm thick). Modern finned or needle-shaped radiators have less thermal resistance than a smooth plate, and you can get by with a much smaller radiator.
The cooling problem can be solved by using a radiator with a length of 150 mm and a bus of 95 mm, which has 16 fins. The radiator must be installed on the board so that air flows can flow freely between the fins. Therefore, it should be located outside the case on the rear wall. Since the case of this IC is also under supply voltage, the radiator must be isolated from the amplifier case (if it is metal).
The question may arise: since the radiator is quite large, wouldn’t it be better to use a small fan for cooling?
However, the noise of a constantly turned on even low-noise fan will interfere with listening to quiet musical passages. Some companies use powerful amplifiers ventilation cooling, but the fan turns on at a certain input signal level.
Since in this case the fan does not interfere with quiet musical melodies (it turns off), this solution has a right to exist. However, when speech is amplified, acoustic interference occurs from the fan turning on and off when the volume changes sharply.
For getting High Quality sound reproduction, the inputs of the microcircuit should receive as little interference as possible. Since power wires inevitably have large ripple currents that can easily be transferred to the amplifier input, the input wires and power wires should be located as far apart as possible.
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