The TDA2822 is an integrated audio amplifier that can be used in either mono or stereo mode. The amplifier on this chip is intended for applications where small audio amplification is needed, with low current consumption, for example, it can be used as a headphone amplifier. I have these headphones, they play normally from the computer, but when listening to music from the phone there is clearly not enough power, connecting such an amplifier the volume increases significantly and there is still some reserve left.

Supply voltage: 1.8 – 15 Volts
Maximum output power: 1.4 Watt
Current consumption at load: R=32 Ohm And U=6 V in rest mode 0.1 mA, and during operation it fluctuates within 10-20ma.

Just above you see a circuit of a small amplifier using a TDA2822. The sound volume can be adjusted using a 10 kOhm variable resistor. A 12 volt power source will be ideal for powering the circuit (will have the highest power output, not including speaker impedance), but it will operate on lower voltages. The microcircuit does not heat up at all, so there is no need to use a heat sink. On the first board there are separate large screw fasteners for the input, output and power supply.

The printed circuit board can be downloaded here:

Here is another circuit diagram for connecting this microcircuit, as well as two printed circuit boards, which are more convenient for making a headphone amplifier, on one of them there are lower resistors and capacitors surface mount, and on the second DIP. The tracks for sockets for 3.5 mm jacks are drawn on them; you can easily edit the tracks and spots to suit your connectors. With such a board, you need to connect it to the phone (audio signal source) through a special wire with two jacks, and headphones, respectively, to the connector on the board.

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I decided to make an amplifier using the second circuit using resistors (10k, 4.7) and 100 nF surface mount (smd) ceramic capacitors. The photo shows the tracks drawn with tsaponlak and a parment marker and the finished board after etching in ferric chloride.

Adjusting the sound volume from the audio source itself will upset you, in my case it’s the phone volume rocker, the range is too small. To improve the change in sound strength, add a miniature variable resistor with a resistance of approximately 10-50 kOhm to regulate the strength of the input audio.

The NM5 case with dimensions 57x38x19 and a ridiculous price was ideal for my board. The board fits into it perfectly; we drill holes of the required diameter for the input and output sockets. There is still room in the housing for an energy source. In my opinion, it would be best to put it there lithium polymer battery together with a charging module, for example, from USB. As a result, we get an excellent, convenient, compact amplifier for headphones and small speakers at a meager price.

I used this amplifier for small computer headphones, the sound turned out to be quite good, but at high volumes the sound quality drops noticeably. As you can see, I assembled the circuit using a TDA2822 in a DIP-8 package, and soldered a header onto the board for convenience. The output power will depend on the resistance of the headphones and the supply voltage, we don’t need much, we don’t want to go deaf. It is desirable that the speakers be 2x1W/4 Ohm.

And finally, I’ll say that I recommend assembling such a circuit only to beginners. Unreal high-quality sound You won’t get the same results from industrial and expensive amplifiers, but for the average person this is enough. Here is a video to familiarize yourself with the properties of the output sound from such a circuit.

We all love to listen to music on headphones, since it is not always possible to play it on speakers, especially at late times of the day or on public transport. But the sound quality itself is not always good enough; one of the signs of this is the built-in amplifier in the playback device, be it a phone or a computer or laptop. In this article I will tell you how to make a headphone amplifier with your own hands, a kit kit will help you assemble it; you can order it using the link at the end of the article.

In order to make a headphone amplifier with your own hands, you will need:
* Soldering iron, flux, solder
* Third hand soldering device
* Side cutters
* Solvent 646 or galosh gasoline
* Power supply with 12V output voltage
*Headphones, phone or other playback device

Step one.
This kit comes with a double-sided printed circuit board, its quality is very good and has metallized holes. Also, for ease of assembly, instructions are provided that show the amplifier circuit and component ratings for correct installation on the board.

First of all, we install resistors on the board; their values ​​do not need to be determined, since they are signed on a piece of paper glued to them. Then we insert non-polar ceramic capacitors, and then polar electrolytic capacitors, observing the value and polarity, the plus is the long lead, and the minus is the contact opposite the white stripe on the case; on the board, the minus contact is indicated by a shaded semicircle. To indicate the operation of the amplifier, there is a place on the board for a red LED; we install the long leg in the place indicated by the triangle, and the minus short leg in the hole with a strip next to it.

Step two.
In order to prevent the radio components from falling out during soldering, we bend their terminals to the back of the board. Next, we fix the board in a “third hand” soldering device and apply flux to the contacts, after which we solder the leads using a soldering iron and solder. We remove excess leads using side cutters. When removing pins with side cutters, be careful, as you may accidentally remove a track from the board.

Then we install the remaining components, namely a variable resistor, a power connection socket, two sockets for microcircuits, guided by the key on the case and the board in the form of a recess, as well as sockets for connecting audio input and output.

We solder the components and apply flux for better soldering. We also remove the excess part of the leads using side cutters.

After soldering, the following board is obtained.

We remove flux residues from the board using a brush and solvent 646 or galosh gasoline. This is what a clean board looks like.

Step three.
Now we install microcircuits in special sockets according to the key on the case and board.

Next, we move on to assembling the case, first we try it on the board and remove the protective films from parts of the case. We fasten the posts with threads into four holes to the bottom using a Phillips screwdriver.

Next, install a board with a side panel with holes for connection sockets on the racks.

After that, we assemble the remaining parts and fasten the top cover with screws.

At this point, the headphone amplifier can be considered ready, all that remains is to test it.

Step four.
For full-fledged work The amplifier requires 12 V power. We connect the power supply to the socket via a plug and insert a 3.5 mm Jack plug on both sides, one goes to the phone, the other to the amplifier, insert the headphone plug into the socket labeled OUT and enjoy high-quality sound. The volume is adjusted by turning the variable resistor knob.

I’ve been wanting to make a separate headphone amplifier for a long time - I haven’t had the time, although I’ve already bought headphones for two years. Nothing special, Sennheiser HD 558, but the sound is at an acceptable level for me.
I reviewed a lot of diagrams and read a lot of information and forums. I wanted the circuit to be simple and of high-quality sound. Thinking about what I wanted, I came to the conclusion that the headphones needed relatively little power and some kind of op-amp powered by transistors or just a powerful op-amp with a low THD+N, a “driver” so to speak, should be suitable. And then a microchip from TI turned up, specially designed for these purposes, TPA6120.

At its core, it is a very powerful and very fast op-amp with a monstrously low THD+N (well, according to at least for me). Having surfed a little on Google about various microcircuit inclusions and designs, I found a good option for myself on one website of Czech radio amateur Pavel Ruzicka. The microphone is connected using a non-inverting circuit, with a 50 kOhm potentiometer from the well-known Japanese company ALPS at the input. I decided to implement just this option.

Headphone amplifier circuit based on TPA6120 and power supply

My version of the scheme

power unit

After studying the datasheet on the TPA6120, I still made some changes to the circuit. The so-called blocking capacitors in the original are film, but the datasheet strongly recommends using SMD ceramic capacitors, and even as close as possible to the power terminals - to eliminate possible excitation of the amplifier.
As a matter of fact, I was most excited and afraid, the microcircuit is very fast-acting.

That dreaded PowerPAD has been defeated.

Due to the lack of experience in manufacturing double-sided PCBs, it was decided to make the board single-sided. And then another problem emerged. Due to the fact that the microchip is very powerful for its size, it has a heat sink pad on its “belly” - PowerPAD, which is soldered to the pad under the microcircuit and also serves as a common wire.
I somehow brushed aside the unpleasant thoughts and decided that I would solder it somehow. But first things first.

I started looking for the necessary components, and it immediately became clear that the locals didn’t have the TPA6120, not to mention the ALPS. The great Chinese Brother helps out once again, he ordered a TPA6120 microcircuit and an ALPS potentiometer on Aliexpress.
I bought the housing, transformer and other small items from the locals. After everything was in hand, another 4 months passed before I picked up... an iron.

When designing the amplifier board, I paid special attention to the location of the resistors in accordance with the datasheet, so that there were the shortest distances from the legs of the inputs and outputs to the resistors, so that there was no excitation. And now the boards are etched, drilled and tinned. And here I seriously began to think about how to solder this tricky PowerPAD and what to do with it in general.

Back on the Internet. I found an interesting solution on one of the forums. Without a soldering gun and double-sided PCB with metalized holes, there is only one way out: drill a hole under the microcircuit and through it try to solder a homemade radiator to the PowerPAD of the microcircuit.

I tried this suggested option: a 1.5 mm hole is drilled, a copper wire is taken, tinned and wound into a spiral around a 0.8 mm drill (I wound it around a needle) 2-3 cm long. The microcircuit is positioned and grabbed, the spiral is lowered into the hole and the whole thing is fried with a 40-watt soldering iron , naturally with the addition of solder and flux. The goal is not just to solder the helix, but also to ensure that the edges of the PowerPAD pad are also soldered to the printed circuit board.

Here it is, my cooling system for the TPA6120. Do you see the strange “spring” in the center?

I held the soldering iron for a few seconds and everything worked out! Everything turned out to be simpler than I thought. Thanks to the kind person for the idea!

Sound

The boards are ready, I connect everything with wires, quick check. There is no constant output, I connect my DAC, Senheisers, turn on “The Dark Side Of The Moon” and enjoy... Probably, describing the sound and especially its quality is a thankless task, you just have to hear it for yourself.
In general, I will say that I really liked the sound throughout the entire frequency range. By ear there is a minimum of distortion, for me there is simply none. I used to listen to mine Sennheiser headphones HD 558 with built-in sound card. Now I simply didn’t recognize them! The bass appeared and the sound was very detailed.

Total

Us sings. There is no excitement, and thank God, fortunately, all measures were taken for this. I doubted that the coil would dissipate heat well, so I left it for an hour with music at a decent volume, touched the microcoil - it felt like 30-35 degrees. The coil is warm, the pad on the reverse side is also slightly warm, which means the microcoil is soldered normally, the heat is dissipated well, and that’s where I calmed down.

And the most difficult and painful thing for me began - to collect everything into the case. A couple of evenings with a drill, pliers, screwdrivers, files and a lot of obscene language! Hurray, I stuffed the boards into the case. The case turned out to be too big for the amplifier, but it is convenient to mount and looks more solid in a large box. There is only one task left: to make inscriptions on the front panel. But that's a completely different story.

Due to the large amount of information and photographs, the article will be divided into two parts. In the first part you will learn brief information, which will help orient you to the upcoming work, in the second part I will describe, and also share my impressions after listening to it.

Scheme
The basis was a classic transformerless SRPP circuit using a 6n6p radio tube, the author of which was Oleg Ivanov. The diagram was slightly changed and reworked by me. We selected our own ratings of radioelements and changed part of the power supply circuit. Depending on the choice of the anode voltage rectification method, you can use a rectifier on a kenotron or use a diode bridge.

The choice to use a diode bridge or kenotron in a rectifier is everyone’s business. The diodes have a minimal anode voltage drop, there is no such load on the transformer, and a separate filament winding is also not required. For most tube ULF circuits, 1N4007 diodes are quite suitable.

Kenotron voltage rectification is a classic method in lamp technology; many people prefer it due to aesthetic considerations and some advantages over semiconductor diodes.

Advantages of the kenotronic feeding scheme:
— Smooth supply of anode voltage, which allows you to extend the service life of the amplifier radio tubes (indirect heated kenotron);
— Almost complete absence of through and reverse current;
— Limitation of current surges at the moment of switching on due to smooth heating of the cathode and supplying voltage to the LC filter of the anode power circuit;
— Reducing the magnitude of current pulses for recharging filter capacitors.

The disadvantages of kenotron nutrition include:
— High internal resistance, due to which the anode voltage drops;
— Limited service life of the kenotron;
— To power the kenotron, an additional filament winding and the output of the midpoint of the anode winding of the power transformer are required;
-If the filter elements are incorrectly selected, the kenotron may fail due to an inrush current.

To eliminate anode voltage pulsations, a choke with an inductance of about 5 H is used (in a thorough approach, the inductance is calculated according to the ULF power supply ripples). In this circuit, a D31-5-0.14 inductor was used.

Layout
To check the functionality of the circuit, a prototype is usually made. While working with the layout, you can repeatedly add and change the location of radio components, change the layout, modify the circuit, and also solve issues that may arise during construction tube amplifier. The layout is easy to make. Layout of the circuit can be done by mounted mounting “on wires” or using mounting racks. The plywood base for the model is easy to machine, holes can be drilled well and is pliable to a file. The main thing when desoldering the circuit is to make a good ground (negative) bus.
Mounting on a breadboard differs from final mounting on a chassis. When assembling a finished tube amplifier, long wires and the placement of loose circuit elements on the chassis are not allowed.

Chassis and housing elements of a tube amplifier
The chassis must be made of iron; protective casings for transformers are also made from this material. Iron is a ferromagnetic material; its use will protect against various types of interference and eliminate the possibility of their occurrence.
You can independently cut the chassis from sheet metal, for example, from roofing iron, use old building from system unit computer or choose a metal box of suitable dimensions. You should also not forget about the iron ventilation hoses (ducts).

Protective casings for transformers are made by analogy with the chassis, or they use ready-made solutions (various metal boxes, stainless steel glass jars). Ventilation holes should be made in the protective casings to remove warm air.

At the chassis design stage, you should think about the concept general view finished product. The paint must be applied to the chassis before anything is bolted to it. If various decorative overlays will be used, you should think ahead and make holes for their installation.

Radio components

To prevent failure, overheating and saturation, we select a power transformer with a power reserve. Electrolytic capacitors in the anode power circuit filter are also taken with a 20% voltage margin. To reduce the influence of temperature and external atmospheric factors, we choose Soviet resistors with a small power reserve. Input-output signal sockets and capacitor housings must be isolated from the chassis. Shunt capacitors are preferably film ones.

Before installation, select radio components by measuring with a multimeter close to the nominal value, according to the diagram. It's also a good idea to check the power transformer. Often, to save copper wire, transformers were initially not wound up at factories, which led to a large no-load current primary winding, and this in turn affects the hum of the transformer.

Tools for work
For comfortable work When building a tube amplifier, all plumbing tools will do. The dielectric handles of the tool must be without damage to the insulation. Much, if not almost everything, has to be modified with a file and needle file.

In order to drill holes in the metal chassis, use a cone-shaped step drill. You can also use several methods to make a large hole for the lamp socket. For example, use a compass to draw a circle of the required diameter and drill holes tightly along the line, then use a needle file to grind down the jumpers between the holes. The ideal method for drilling is to use a drill press, but most lamp makers make do with a regular drill or screwdriver.

To solder circuits, use a powerful soldering iron to tin thick wires and wires; radio components are soldered with a soldering iron of lower power so as not to overheat. A sharp utility knife or scalpel is suitable for stripping wire insulation and varnish insulation on wires (when stripping, try not to grind off the copper wire itself). A good pair of tweezers will make installation work much easier and can be used as a heat sink.

A caliper will help with precise definition the dimensions of the parts, and will also help determine the diameters and holes for them. Use a ruler and compass to mark the holes. Having a micrometer in your amateur radio arsenal, you can easily determine the diameter of the wire.

Location of radio components on the chassis
We place the power transformer on top of the chassis - this will protect the output circuits from interference coming from the transformer. Radio tubes and audio signal input/output jacks are placed away from the power transformer. The sockets to which the audio signal will be supplied and removed, as well as the variable resistor of the volume control, are located close to each other, preferably on the front panel closer to the output lamps.
It is better to place the radio panels on the chassis so that the amplifier does not have a three-story installation of radio elements. Moderate free space in the basement of the amplifier will allow you to quickly make adjustments to the circuit and facilitate accessibility to radio elements during repairs.

Circuit wiring
Almost all lamp designs use wall mounting. With this connection method, the use of wires is minimized; all connections of radio components are made with their own terminals. Part of the circuit is soldered onto the petals of the lamp panels.

The circuit is grounded to the chassis body at only one point; the point is chosen experimentally, away from the power transformer. The negative bus is made of thick copper wire and is grounded at the same common grounding point that was chosen for grounding.

Before soldering a wire, carefully inspect the integrity of its insulation. It is not recommended to tighten the wires of the anode supply (anode circuits) and control grids into bundles, lay them parallel or close to each other.

The cross-section of the conductor wires must correspond to the power consumption of the filament current and the anode of the lamps. For example, if your lamp, according to its passport data, consumes a filament current of 600 mA, then the diameter of the wire should be selected in accordance with the maximum permissible current value. For a current of 600mA, according to the table of permissible values ​​for wire, the diameter of the wire will have a diameter of 0.56mm. For several lamps, the total current should be summed up and a suitable wire of the required cross-section should be selected accordingly. In the same way, the permissible current value that the winding of a power transformer or inductor can withstand is determined.

To eliminate background and additional interference, the filament wires are twisted (two filament wires are twisted along their length like a “pigtail”). The background and interference are eliminated due to the fact that the alternating component of the interference currents flows through the filament conductors in antiphase directions and, accordingly, are mutually compensated.

Also, to eliminate background noise, the filament winding is grounded through an artificial midpoint using two resistors of the same resistance value. Resistors of the order of 100 Ohm-200 Ohm are sealed together with the incandescent wires onto the lamp socket. Some ends of the resistor terminals are connected to each other, the other free terminals are soldered to one and to the second filament blade of the lamp socket. The point at which the resistors are connected is grounded to the negative bus. If the transformer has a middle terminal at the filament winding and the voltage on it is equal to half the total voltage, then it is grounded without using resistors (the same middle point).

The filament wires can be made in parallel from socket to socket, rather than running separate wires to each. For the convenience of wiring the circuit, the filament wires are first soldered to the lamp sockets, and the sockets themselves are turned on the side that will ensure the most convenient installation of radio elements. The anode wires from the last electrolyte of the power supply branch with a “fork” to the lamp sockets.

A few words about headphones
The circuit used high-impedance Hungarian headphones FDS-26-600 with a coil resistance of each speaker of 600 Ohms. Headphones with lower impedance have not been tested with this amplifier; to achieve the best sound, you may have to install an output audio transformer (TVZ). Usually the TVZ is rewound under the load resistance; in our case, the load is headphones, whose resistance is ideal for this circuit.

On the Internet, on one of the forums dedicated to tube topics, I came across a table with data from an experiment carried out on an amplifier circuit (please write in the comments whose experiment was carried out and on which forum, so that the author can be indicated in the article). As I understand it, the author did not use TVZ.

Added: Site visitor Andrei pointed to the author of the experiment. The parameters of the radio tubes were taken by Ignatenko Yuri Vasilievich link to

Not all sound cards can provide loud and high-quality sound, and then a headphone amplifier will come to your aid. The reason for assembling a headphone amplifier may be insufficient volume (the main reason), or poor sound quality (large distortions in sound/music). To increase the volume and sound quality, simply connect an additional output stage in series with the sound card, which we see in the diagram below:

The harmonic coefficient for a linear frequency response from 20 Hertz to 20 kHz of such an amplifier is only 0.1% and such an amplifier can be used not only for a computer sound card, but also for low-power devices such as radios, mobile phone, MP3 players, laptops and netbooks.

Let's go through the diagram now. In such a 2-stage ULF, transistors with a lower level of intrinsic noise are used, which affects the quality of the amplifier. Any transistors can be used, the main thing is that p-n-p or n-n-n transitions coincided and the powers of the transistors were the same and transistor T2 must be installed on a radiator with an area of ​​5-8 cm2, because at rest a current of 120 mA passes and will heat up transistor T2, which can lead to overheating or even burn out. (for example, T1 can be put KT361, KT3107, and T2 we can put KT805, KT815). Use any aluminum or copper plate as a radiator to ensure good heat dissipation. For more powerful amplifiers You can use a cooler that will cool the radiator. Chain feedback consists of elements R6, R7, C5. Transistor T2 operates in class A mode. Resistors R1 and R2 must be at least 2 watts, the remaining resistors must be 0.25 watts each.

Now let's look at the power supply to power the amplifier. If you are going to power from the mains, then you will definitely need to assemble a power supply unit (power supply). A transformer with any small secondary current of at least 250 mA and a secondary voltage of 16-24 volts. Next, we assemble a voltage rectifier, which can be assembled from any 4 diodes that are designed for currents of at least 250 mA and a voltage of 25 volts (but is it always better to take it with a reserve?). Or you can purchase a ready-made diode bridge on the radio market. Next, after the diode bridge, we assemble a voltage stabilizer. A voltage stabilizer is needed so that the sound in the headphones does not sag during bass, i.e. so that the voltage does not jump and the sound is not distorted. Transistors can be installed with any medium power, for example: KT805, KT817, KT815, KT803. We must attach the transistor to the radiator. Further, capacitors C4, C5, C6 serve as a filter that removes noise. Resistors R4 and R5 play the role of limiting the current to the base of the transistor, thereby setting a certain gain. We see zener diodes at the base of the transistor. If we need a voltage of 15 volts at the output, then we set the zener diode at 15 volts, if at 20 volts, then we set it at 20 volts, but in this case at 15 volts. We see 2 zener diodes of the D814A brand, which are connected in series and each of which is designed for a voltage of 7.5 volts (i.e. in total we get 15 volts (7.5 + 7.5 = 15)). Also note that the voltage supplied to the zener diodes must exceed 1-1.5 volts for their normal operation. The power supply diagram is below:

If you want even greater sound quality, then I advise you to assemble another small, simple circuit called a tone control. The tone control will help you adjust the music/sound while listening (for example, you can add more bass or, on the contrary, remove it altogether, and this can be done at any frequency). The frequency regulation depth of such a circuit is 20 decibels. This circuit includes an additional cascade on a transistor (transistors KT315, KT342), which compensates for voltage losses for normal operation of the amplifier. This circuit will be powered by the stabilizer that powers the amplifier. You just need to connect the power wires of our circuit in parallel with the power wires of the amplifier. Resistors are 47 kOhm, if for stereo, then double. It will be necessary to install additional resistance at the output, since the output is very sensitive and we must dampen this sensitivity. We select the resistor within the range of 10...150 kOhm for the best sound quality. Schematic diagram tone block:

Now we connect the tone control in the sound card, after the tone control we connect the amplifier and from the amplifier we go to the headphones)) The amplifier does not require any setup - everything works right away! And most importantly, the wire that goes from the sound card to the amplifier/tone control, this wire must be shielded to reduce background sound. The shielding is a wire that is surrounded by a metal mesh. We let the positive wire inside, and shield the plus with the minus, i.e. minutes solder to this grid.