After mastering the basics of electronics, a novice radio amateur is ready to solder his first electronic designs. Audio power amplifiers tend to be the most repeatable designs. There are a lot of schemes, each differs in its parameters and design. This article will look at some of the simplest and most fully working amplifier circuits that can be successfully repeated by any radio amateur. The article does not use complex terms and calculations, everything is simplified as much as possible so that there are no additional questions.
Let's start with a more powerful scheme.
So, the first circuit is made on the well-known TDA2003 chip. This is a mono amplifier with an output power of up to 7 watts into a 4 ohm load. I want to say that the standard switching circuit of this microcircuit contains a small number of components, but a couple of years ago I came up with a different circuit on this microcircuit. In this scheme, the number of components is minimized, but the amplifier has not lost its sound parameters. After the development of this circuit, I began to make all my amplifiers for low-power speakers on this circuit.
The circuit of the presented amplifier has a wide range of reproducible frequencies, the supply voltage range is from 4.5 to 18 volts (typical 12-14 volts). The microcircuit is installed on a small heat sink, since the maximum power reaches up to 10 watts.
The microcircuit is capable of operating at a load of 2 ohms, which means that 2 heads with a resistance of 4 ohms can be connected to the amplifier output.
The input capacitor can be replaced with any other, with a capacitance from 0.01 to 4.7 uF (preferably from 0.1 to 0.47 uF), both film and ceramic capacitors can be used. All other components should not be replaced.
Volume control from 10 to 47 kOhm.
The output power of the microcircuit allows it to be used in low-power PC speakers. It is very convenient to use a chip for stand-alone speakers for a mobile phone, etc.
The amplifier works immediately after switching on, it does not need additional adjustment. It is advised to additionally connect the minus power supply to the heat sink. All electrolytic capacitors are preferably used at 25 volts.
The second circuit is assembled on low-power transistors, and is more suitable as a headphone amplifier.
This is probably the highest quality circuit of its kind, the sound is clear, the entire frequency spectrum is felt. With good headphones, it feels like you have a full subwoofer.
The amplifier is assembled on only 3 reverse conduction transistors, as the cheapest option, transistors of the KT315 series were used, but their choice is quite wide.
The amplifier can operate on a low-impedance load, up to 4 ohms, which makes it possible to use the circuit to amplify the signal of a player, radio receiver, etc. A 9 volt battery was used as a power source.
KT315 transistors are also used in the final stage. To increase the output power, you can use KT815 transistors, but then you will have to increase the supply voltage to 12 volts. In this case, the power of the amplifier will reach up to 1 watt. The output capacitor can have a capacitance from 220 to 2200 uF.
The transistors in this circuit do not heat up, therefore, no cooling is needed. When using more powerful output transistors, you may need small heatsinks for each transistor.
And finally - the third scheme. A no less simple, but proven version of the amplifier structure is presented. The amplifier is capable of operating from low voltage up to 5 volts, in which case the output power of the PA will be no more than 0.5 W, and the maximum power when powered by 12 volts reaches up to 2 watts.
The output stage of the amplifier is built on a domestic complementary pair. Adjust the amplifier by selecting the resistor R2. To do this, it is desirable to use a 1 kOhm trimmer. Slowly rotate the knob until the quiescent current of the output stage is 2-5 mA.
The amplifier does not have a high input sensitivity, so it is advisable to use a preamplifier before the input.
A diode plays an important role in the circuit; it is here to stabilize the output stage mode.
The output stage transistors can be replaced with any complementary pair of appropriate parameters, for example, KT816/817. The amplifier can power low-power autonomous speakers with a load resistance of 6-8 ohms.
List of radio elements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad | |
|---|---|---|---|---|---|---|---|
| Amplifier on a TDA2003 chip | |||||||
| Audio amplifier | TDA2003 | 1 | To notepad | ||||
| C1 | 47uF x 25V | 1 | To notepad | ||||
| C2 | Capacitor | 100 nF | 1 | Film | To notepad | ||
| C3 | electrolytic capacitor | 1uF x 25V | 1 | To notepad | |||
| C5 | electrolytic capacitor | 470uF x 16V | 1 | To notepad | |||
| R1 | Resistor | 100 ohm | 1 | To notepad | |||
| R2 | Variable resistor | 50 kOhm | 1 | From 10 kΩ to 50 kΩ | To notepad | ||
| Ls1 | dynamic head | 2-4 ohm | 1 | To notepad | |||
| Transistor amplifier circuit number 2 | |||||||
| VT1-VT3 | bipolar transistor | KT315A | 3 | To notepad | |||
| C1 | electrolytic capacitor | 1uF x 16V | 1 | To notepad | |||
| C2, C3 | electrolytic capacitor | 1000uF x 16V | 2 | To notepad | |||
| R1, R2 | Resistor | 100 kOhm | 2 | To notepad | |||
| R3 | Resistor | 47 kOhm | 1 | To notepad | |||
| R4 | Resistor | 1 kOhm | 1 | To notepad | |||
| R5 | Variable resistor | 50 kOhm | 1 | To notepad | |||
| R6 | Resistor | 3 kOhm | 1 | To notepad | |||
| dynamic head | 2-4 ohm | 1 | To notepad | ||||
| Transistor amplifier circuit No. 3 | |||||||
| VT2 | bipolar transistor | KT315A | 1 | To notepad | |||
| VT3 | bipolar transistor | KT361A | 1 | To notepad | |||
| VT4 | bipolar transistor | KT815A | 1 | To notepad | |||
| VT5 | bipolar transistor | KT816A | 1 | To notepad | |||
| VD1 | Diode | D18 | 1 | Or any low power | To notepad | ||
| C1, C2, C5 | electrolytic capacitor | 10uF x 16V | 3 | ||||
Using a desktop computer without sound is very problematic. You can't listen to music or watch a movie. Unless in headphones, because. An audio amplifier for connecting external acoustics is not provided in the computer. Of course, stores in our technological age offer a variety of models of various price categories, but you can try to provide yourself with a good sound environment on your own.
Sound amplifier for computer
Consider one of the simplest amplifiers. Collecting which, perhaps, will be possible for anyone who knows how to hold a soldering iron in their hands and understands at least a little the basics of physics.
The basis of the amplifier will be the TDA 1557 chip, which is widely distributed in radio stores,
Chip TDA 1557Q for computer audio amplifier
which is a bridge stereo amplifier with a simple connection diagram, which can be assembled and surface-mounted by soldering the parts directly on the legs of the microcircuit without etching the printed circuit board.
To assemble the amplifier, in addition to the microcircuit itself, you will need: 2 resistors with a resistance of 10 kOhm, 3 film capacitors, 2 of which are 0.22 - 0.47 uF (220n -470n) and one 0.1 uF (100n), an electrolytic capacitor with a capacity of 2.200 - 10.000 uF with an operating voltage of at least 16 V and a button or toggle switch to turn the amplifier on and off. The cost of all parts for assembly varies from $ 10 to $ 15 or 400 - 600 rubles. You will also need some shielded wire and speakers or speakers with a power of 15 - 30 watts, a resistance of 4 - 8 ohms. A visual installation diagram is shown below.
Amplifier connection diagram on TDA1557Q
Sound must be supplied to the amplifier from the headphone output of the computer sound card with a shielded wire to avoid background and extraneous noise from the speakers. Solder the electrolytic capacitor with the shortest possible wires. The level of voltage drop at power peaks depends on the size of its capacitance, hence the depth and purity of the bass. It is recommended to set at least 2.200 uF. There is no upper capacity limit.
Directly to the legs of this capacitor, you can solder a film 0.1 microfarad. The toggle switch is used to smoothly turn on the amplifier so that there is no click in the speakers when power is applied and the volume is muted, the amplifier sleeps.
The amplifier operates at a voltage of 10 - 18 V, therefore, you can connect it from the computer's power supply from the + 12V output and the COM ground.
I remember somewhere in the comments I promised to post pictures of a homemade amplifier. I am keeping this promise.
In nature, there are a number of integral audio frequency power amplifiers for various types of electronic equipment (radio and television receivers, communication and telephony equipment, stationary, portable and car radios, electronic toys, sound synthesizers, etc.). These devices are not at all difficult to use, and having at least a theoretical skill in owning a soldering iron, you can build a solid amplifier in 40 minutes on your knees that can fit in a perfume box, unless of course you get the idea to put an amplifier there :)
And it all started with the fact that my Odyssey 002 stopped giving sound on one of the channels (And it has 4 of them, more precisely 2 parallel pairs). I found thyristors and capacitors on the market that had failed due to old age, and next to me on the counter I found an interesting TDA-based microcircuit (from Philips).
When I got home and read the info about it on the Internet, I found that this "centipede" the size of a small AAA battery is capable of delivering 35 watts per channel at a voltage of 18 V, and also has a protection device against short circuit, overload and overheating, loudness, auto-shutdown when the signal source is turned off and much more than useful, which I don’t even remember. And if you bridge the channels, you can get a 1-channel amplifier with a power of about 70 watts, which is more than enough to drive the huge S90. (However, as I later realized, the S90 was quite capable of driving a two-channel amplifier with a capacity of 2x35 watts).
Moreover, such microcircuits are used in serious car radios, music centers and other equipment (DO NOT forget that this was in 2003, now microcircuits may be used more seriously).
I will not go into details of soldering and selection of parts. It was not difficult for me to find everything on the market (4 resistors, 4 capacitors, the microcircuit itself, the board, and accessories in order to pickle the board, cut out its shape, + tin, rosin, beer and squid).
Infa and schemes of such amplifiers are in abundance on even more than a hundred sites on the Internet. You can search for "TDA Chip", for example.
I bought a class D chip. I didn’t know (and now I don’t know what classes are and which is better, A or D), but I know that the main advantage of class D amplifiers is high efficiency, reaching 90%, at a low supply voltage . In practice, the scope of class D amplifiers is limited to automotive acoustics and portable devices. Which is exactly what we need.
Also, when choosing, it is worth noting that the power is indicated at a certain voltage. This means that if you apply less voltage, then your power will drop. For example, I connected the assembled amplifier to a computer power supply. There is 12V, which means that at the output I will no longer get 2x35 watts (rated power at 18 V), but about 2x22 watts at a load of 8 ohms.
The second point: I cut out all the "guts" from the S90 speakers. The filters that were there have already rotted over the years, dried up, and rotted again. And it seemed to me that they only spoiled the sound, although their purpose was to separate channels by frequency. I connected everything directly, although this is very wrong, and replaced the regular tweeters with silk ones. The sound has changed for the better. Toli because of the new amplifier, roofing felts due to the replacement of tweeters, roofing felts due to the exclusion of old "micro" circuits from the circuit (the size of a bucket :)).
Here is a description, photo, review and diagram of a slightly simpler microcircuit than mine (I don’t even remember my own marking):
link
Here's what it actually looked like for me:
(The photo was taken in the corridor, a minute before this amplifier, along with the speakers, was bought from me by one of the Hitforum visitors). I hope he was satisfied with the purchase and it has served him faithfully up to the present day.
It was plucked out of the column case because at first I was not going to sell it, but then I thought that I didn’t need it anymore, and I sold it, slightly adding the amount to the price for the speakers.
As you can see from the pictures, the main size here is occupied by a radiator and a cooler. By the way, the heatsink is from the motherboard chipset. Now can you roughly imagine the size of the whole structure? :)
Of course, the assembly has a number of shortcomings, an experienced solderer will say. And yes, she doesn't look good. Nevertheless, everything worked fine, and I assembled a construction of this level for the first (and only) time.
Especially such homemade products, which at first glance may not be easy. In this article I will tell you how to make your own homemade sound amplifier without any difficulties and financial costs.
Many beginners in the radio business know that a sound amplifier, whether it is in a music center or a radio tape recorder, consists of a main element, such as a microcircuit.
Amplifier integrated circuits are widely used in household appliances such as televisions and computer speakers. But the fact is that the amplifier in such cases is weak, and it will cost more, since it has already been assembled.
In order to assemble a sound amplifier, it is powered by the way from a 12 V power supply, you need:
Amplifier chip, bought it in a radio store for 56 rubles
Capacitors, one for 2200 microfarads, the other for 100 microfarads
Fiberglass, a small piece is enough for our microcircuit
Case box.
Tulip plug
A plug for audio input, from broken headphones or from computer speakers, no matter where
switch
five wires
Cooling radiator
four screws
hot glue
Stationery knife
Soldering iron, for convenience, 20-40 watts
Rosin
thermal paste
Varnish, thinner, hydrogen peroxide, citric acid, salt.
All components are ready and they cost no more than 150 rubles in total, so that the microcircuit can be pulled out of a TV, which is even less common on the market, there will not be such an amplifier on an old-style TV.
To begin with, we will arm ourselves with fiberglass, hydrogen peroxide, citric acid and salt. All this solution must be kneaded in a bowl with a wall height of 10 - 20 mm, mix in the proportion of 50 ml of peroxide per 15 grams of citric acid, add a pinch of salt there, 5 grams is enough.
The next step is to paint the future tracks of the board with nail polish. We do this carefully, wipe the excess with a solvent. Our microcircuit requires such an arrangement of tracks.
We wait 5 minutes and lower the board into the solution, on average, the board should be etched in 30-40 minutes. After the time has passed, you need to remove the varnish.
When the varnish is wiped off (you can use any solvent), you need to check in the light for displacement and errors, such as sticking one leg to another, if you make a mistake, this can be corrected with a clerical knife.
Now the board must be covered with a layer of tin, first we coat the tracks with rosin, then we tin all the tracks with a soldering iron. Then we attach the microcircuit and solder it strictly to the legs. It is impossible to overheat the microcircuit, it may not be working.
Next, you can solder the wires, first solder the sound output, take two wires and solder with our plug for connecting the tulip. We have only one sound output.
After the sound is released, we solder the jumper between the 4th leg and 7, this is a minus.
Then we solder a 100 microfarad capacitor to the third track.
Plus, we solder it to the track, and minus it to the other side of the track, as in the photo.
For power, you need a filter, it will be a 2200 microfarad capacitor. Solder it to the plus and minus of the power supply.
We solder two wires to the power tracks.
The next step is soldering the audio input plug.
On this, the amplifier is completely ready; before installing it in the case, it is better to check it by fixing it on the radiator in advance. After checking, you can install everything in the case. First, cut the holes for installing the radiator with a clerical knife.
The photo shows that everything went well. Then you need to fix the radiator with four screws.
When the radiator is firmly seated, you can make holes for connecting to the speaker through a tulip and a power switch. We glue everything with hot glue. Then you can install the amplifier on the radiator through thermal paste.
Many are interested in how to make portable speakers or speakers for smartphones and tablets. However, before you start making the speakers themselves, you need to take care of the amplifier. In this material, we will review the video, which is devoted to the assembly of the simplest amplifier.
So, what do we need to assemble the amplifier:
- crown connector;
- 9 volt crown;
- speaker 0.5-1 W and resistance 8 ohms;
- 3.5 mm mini jack;
- 10 ohm resistor;
- switch;
- LM386 chip;
- 10 volt capacitor.
So that the assembly process does not seem very complicated, we present to your attention the circuit of the future amplifier.
Looking at the chip from a closer distance, you can see that it has four legs on both sides. In total, 8 paws are obtained. In order not to confuse and turn the microcircuit upside down and thereby make a mistake with soldering, a small mark similar to a semicircle is provided on the microcircuit. This label should be at the top.
Let's start by soldering the first wire that will go to the switch and the positive contact of the crown. This wiring must be soldered to the sixth foot of the microcircuit, that is, the second from the bottom on the right side.
The next end of the wiring must be soldered to the switch. It is worth noting here that, according to the author of the idea, the circuit itself does not present any difficulty and even someone who does not have special skills in electronics can handle the assembly.
After successfully soldering the first wire, you need to go to the second contact of the switch, which is currently free. Here you need to solder the positive wire coming from the crown connector. After such a simple soldering, we can say that the first stage of manufacturing the amplifier has been successfully completed.
Let's move on to the next foot, which is marked with the number 5 in the diagram and is located directly under the sixth foot, that is, the one to which we soldered the wire at the previous stage of work. To this foot you need to solder the positive contact of the capacitor.
From the capacitor, we still have a negative contact, which must be soldered to the positive contact of the speaker. If you wish, you can refuse to directly solder the capacitor to the speaker in order to protect it from possible damage, as the author does. In this case, you need to shorten the contact of the capacitor and lengthen it with wiring.
After that, you can solder the wires from the minus of the capacitor to the plus of the speaker.
The negative contact of the speaker must be soldered to the fourth and second paws on the microcircuit. Accordingly, this is the lower and second from the top paws on the left side. To do this, take the wiring and solder to the minus of the speaker.
After that, we connect this wire to the fourth foot of the microcircuit.
To connect the same wire to the second foot, you need to make a jumper. We take a short line. We solder one end to the fourth foot, on which there is already one wire, and the second end to the second foot.
To the third foot on the left side, that is, the one that is between the previous two, we must solder the resistor.
We solder the wiring to the second leg of the resistor, which will go to the positive contact on the mini jack.
We disassemble the mini jack. On the mini jack that the author uses, there are two contacts - for the left and right channels. They need to be connected together and solder the wire coming from the resistor to the contacts.
