A simple conceptual amplifier based on tda2050 using the ITUN circuit. Typical connection diagram

The amplifier is built on a single integrated circuit TDA2050V, which is produced by stmicroelectronics. The TDA2050V is designed for use as a Class AB amplifier, with supply voltages ranging from +/-4.5V to +/-25V. With an output power of 25W, the efficiency is about 65%.

It is worth paying attention to the fact that the circuit gain must be at least 24 dB to maintain the stability of the amplifier.

When using 8 ohm speakers with a sensitivity of 92dB, 2.83V/1m, a high sound pressure level is obtained, which makes the TDA2050 amplifier with excellent sound quality. The amplifier can be used to amplify line signal sources such as MP3 player, CD player, tuner, computer and so on.

Before we start looking at building an amplifier, I suggest you take a look at the TDA2050 data, especially if you want to make some changes to fit your stereo setup.

Typical connection diagram for TDA2050 with a bipolar power supply

TDA2050 connection diagram with input regulator and output switch for headphones

The amplifier circuit above is shown for one channel only. Bipolar power supply, the switch is common to both channels and this allows you to switch the output between speakers or the headphone output.

If you don't need a headphone output, you can simplify the circuit and eliminate the switch and post-switch resistors.

The circuit gain is -33 (30 dB), which is enough to work well for most line sources. You can adjust the gain, but note that the minimum gain for stability is at least 16 (24 dB).

Power supply circuit for the amplifier

Description of amplifier manufacturing

The circuit was built on perfboard. ABOUT general layout and PCB design shown in the figure below.

Reverse side of the board with conductors.

General view of the amplifier

I won't make too many comments on sound quality as it is up to the individual listener. In the TDA2050 headphones, the chip produces very good sound, not inferior to expensive various high-quality amplifiers. The amplifier has the ability to produce deep bass, crisp mids with a wide soundstage, and clear highs that aren't too sharp.

You will definitely have fun building this amp! Good luck!

Website materials used: diyaudioprojects.com

P O P U L A R N O E:

This generator for low distortion audio devices generates frequencies from 1 Hz to above 65 kHz.

It can generate four different signals and the output level is adjustable from a few millivolts to 5 volts.

The generator is assembled on an inexpensive ATtiny2313 microprocessor and a 4015 CMOS chip.

The main parameters of the amplifiers are shown in the table below:

To enlarge images click on the picture.

Schematic diagram of the amplifier on TDA2050 (LM1875, TDA2030):

The gain can be adjusted by the value of resistor R5, which is in the feedback circuit, and by the value of capacitance C3 - the lower limit of the range (22...47 mF).

Input capacitor C1 - we put ceramics, or a non-polar electrolyte, capacitance C2 - also ceramics, C4, 5 and 6 - film.

At the output of the amplifier there is a circuit of coil L1 and resistor R7 connected in parallel. This coil can be wound directly onto this two-watt resistor, using PEV-2 wire with a diameter of 0.6 mm, and about 8...10 turns are wound. As you can see in the diagram, resistor R6 is also designed for a power of 2 Watts, the rest can be set to 0.125...0.25 Watts.

Printed circuit board for amplifier on TDA2050:

Please note that there are no installation spots on the board for capacitors C5 and C6; they are soldered directly to the soldering spots for electrolytes C7 and C8 on the track side.

To power the amplifier, the most common rectifier circuit, a step-down transformer, a diode assembly, 3 electrolytic capacitors in parallel in each arm, plus a pair of 0.1 mF capacitors (marked C7 and C8 on the power supply board) are used. In our case, there are 6 electrolytes of 2200 mF each. The PCB is shown in the following image.

On the left, a light vertical rectangle allocates space for installing a diode assembly, for example, you can install KBU601, it holds a current of up to 6 amperes. When choosing a bridge, you can use the following table:

When choosing a transformer for the amplifier power supply, do not forget to determine the voltage of the secondary winding, depending on what kind of microcircuit you are using:

LM1875 - supply voltage ±25V;
TDA2050 - supply voltage ±18V;
TDA2030 - supply voltage ±14V.

On long winter evenings, when TV and the computer are already boring, you really want to do something pleasant and, perhaps, useful. So various crazy, and not so crazy, thoughts and ideas come to mind. One such idea did not appear immediately. The fact is that the acoustics on my Microlab A-6331 computer, although they work properly and beautifully, do not completely satisfy my ears with their sound. In particular, the high frequencies are clearly not enough, the mid frequencies do not impart the characteristic “spatiality” of the sound, and the power is somehow not enough for my Labukhov requirements. In general, it was decided to make an amateur inexpensive multimedia amplifier with a power of 2x25 Watt + 50 Watt sub + rear. After searching the Internet for a couple of days, the TDA2050 microcircuit was taken as a basis; according to reviews, it is a very good alternative for such amplifiers. It was also decided to use the well-proven K157UD2 as pre-amplifiers. It may seem to someone that all this is outdated material, and all this is self-indulgence, then I will answer, I don’t give a damn - I am pursuing the goal PRICE-QUALITY, best solution can not found. So, let’s wipe off the nagging and move on:

1. Bipolar power supply. The transformer is toroidal. The secondary winding is wound with a wire cross-section of 1 mm at 35 V constant with a zero point. It was planned to use 4 microcircuits, so there should be no less capacity in each arm! 20000uF (the more the better), shunted with a film capacitor. Diode bridge using 5A diodes. The scheme is simple:

2. Pre-amplifier. To regulate the frequency response, a 3-band tone control was used for treble, midrange and bass, followed by amplification of the signal on the old and beloved K157UD2 microcircuit.

As can be seen from the diagram, this tone block only increases the frequency response, starting from zero, therefore, at the minimum “volume” value of all bands, complete silence will be clearly audible at its output. To avoid this trouble, the entire tone block is shunted with resistors R* = 150.....470 kOhm, the value of which determines how low the output signal will be at the minimum values ​​of all regulators. The tone control parts R10, R11, R12 are directly soldered by surface mounting to variable resistors. Next, the signals are sent to the input of the left and right ULF and to the low-pass filter for the subwoofer.

After all that was done, we got a multimedia amplifier that can be used with a computer, a DVD player, you can even dig potatoes with it because it turned out to be cheap and cheerful! I carpentered and worked hard for 5 days, 1-1.5 hours of work each, and it cost me $20. The amp started working almost immediately)). There are no errors in the seals! There is no self-excitation.

7.Frame. I did this: I bent 2 sheets of iron so that one “drove” into the other and from below at the corners with 4 bolts, where the legs are attached. The false panel is plexiglass with 4 bolts in the corners, under which there is a paper insert with all the inscriptions, printed on a laser.

P.S.. By the way, here is, in particular, a circuit for the A-6331 amplifier and others like it. They are built on TDA2030, and were taken by me as a sample. The TDA2030, TDA2040 and TDA2050 microcircuits, according to the datasheet, are absolutely identical in pinout (and nothing more!). So, by simple modification, you can “boost” such amps in a couple of hours, in this way:

1. You can take an amplifier made on TDA2030 and go stupid! replace the microcircuits in it with TDA2050. Also pay attention to the electrolyte ratings! - not lower than 25V and change if necessary.

2. You also need to increase the power supply voltage to max. -+25V (if you use a bipolar power supply), and increase the total capacity to min. 40000uF (min. 20000uF on the shoulder).

3. Naturally, Nada will make sure that the power supply of all preamps and active filters does not exceed! acceptable values ​​according to the datasheet, otherwise they will die and won’t ask for fish soup.

4. Remove diodes from the board, they are in the 2050 itself

The amplifier circuit on the TDA2050 integrated circuit presented in this article is built on the operating principle of ITUN. This abbreviation stands for voltage-controlled current source. Most low-frequency amplifiers are built on the principle of a voltage-controlled voltage source (VCS). By the way, the TDA2050 just presents the INUN circuit. The difference in sound between these two modes is obvious, and this design simply needs to be assembled to hear it.

ITUN on the TDA2050 must be listened to on a single-way or two-way speaker system (AS), while a two-way speaker may have a first-order filter (a capacitor is installed in series with the HF head), but there should be no filters in a single-way speaker. For example, if this amplifier is used for the Radiotehnika S-30B speaker system (or another that includes LC filters), then distortion will be heard at the output, or the speaker will not sound at all, since this speaker contains filters in the form of inductors , which is unacceptable for ITUN. For such speakers, you need to use low-frequency amplifiers operating in voltage source mode (INUN), or use ITUN, but install crossover filters before the amplifier.

Even the coil of a dynamic head, when the frequency of the output signal changes, changes its reactance nonlinearly, and can introduce certain distortions in the negative feedback (NFB) in the circuit of which it is included.

In terms of sound, ITUN on the TDA2050 sounds very unique and interesting, having a certain zest, but at the same time it all depends on the speaker on which the audio signal is being listened to. It can also be noted that when listening, the high-frequency and mid-range components stand out clearly (by the way, this is true for an electric guitar), but the low-frequency components are not particularly good (in my opinion).

Amplifier circuitTDA2050 ITUN

Amplifier characteristics and parameters

The supply voltage must be bipolar ±20V. It is not recommended to increase the voltage above this value in this circuit (according to the datasheet, the maximum supplied voltage is ±25V). The output power reaches up to 20W with minimal nonlinear distortion. The output peak current of the microcircuit can increase up to 5A. You will find more detailed information in the datasheet.

Details

Capacitors C1, C3 are film, C2, C5 are ceramic (C5 I have film installed).

It is better to install resistor R4 as a metal wire in ceramic with a power of 2W. I didn’t have one on hand, so I installed a carbon one. R7 should also be 2W. The remaining resistors are 0.25W.

Voltage electrolytic capacitors C4, C6 and C7 must be at least 25V.

Few words…

Elements R7, C5 are a Zobel circuit, and they may not be installed on the board if there are no excitations in the speakers (determined by ear), if excitations are present (crackling, rattling, rustling, etc.), then these elements are necessary install on the printed circuit board.

The TDA2050 chip must be installed on a radiator with an area of ​​at least 300 cm² (it all depends on the supply voltage and output load resistance). The radiator is installed through a mica or silicone gasket, using a dielectric bushing for the mounting screw. Also, do not forget about the heat-conducting paste, which must be applied to the contacting surfaces.

To power two channels of the TDA2050 ITUN amplifier, I used a rectifier consisting of a transformer with two secondary windings of 12V AC 1.5A, two diode bridges and smoothing capacitors.

The AB class amplifier is intended for use as a power amplifier in household appliances.

The TDA2050 chip has thermal protection and protection against short circuit of the output to the case.

A special feature of this amplifier is a very wide range of supply voltages: from ±4.5 to ±20 V, and unipolar power supply is also possible.

Fig.1. TDA2050 chip pinout

The gain in amplifiers with feedback should not be less than 24 dB. Recommended values ​​for hanging elements are given in the table, but other values ​​can be used. The table is intended to guide automotive equipment developers.

Fig.2. Connection diagram for the TDA2050 microcircuit with bipolar power supply

Fig.3. Amplifier circuit board based on TDA2050 with bipolar power supply

Fig.4. Connection diagram of the TDA2050 microcircuit with unipolar power supply

Fig.5. Amplifier circuit board based on TDA2050 with single-pole power supply The protective circuits of the TDA2050 microcircuit limit the output currents of the output transistors in such a way that their operating modes do not go beyond the safe operating zone. This function can be classified as a peak power limiter rather than a current limiter. Thanks to it, the likelihood of damage to the device as a result of an accidental short circuit of the amplifier output to the housing is significantly reduced. As for thermal protection, when the crystal temperature rises above 150°C, the thermal protection system limits current consumption and power dissipation. Therefore, even constant output overload or too heat air will not lead to damage to the TDA2050 chip.

The radiator can be made without a safety margin for overheating, as is done in