Microcircuit tda 7294 connection diagram. Low frequency amplifier (LF) on the TDA7250 chip

Amplifier chip TDA2030 is a fairly popular and cheap microcircuit that allows you to build a high-quality amplifier for domestic needs. Can operate from both bipolar and unipolar power sources.

The TDA2030 is a monolithic integrated circuit in a five-pin Pentawatt package.

The microcircuit is intended for the manufacture of low-frequency audio amplifiers of class AB.

Class "A" amplifier– is linear, amplification occurs in the linear section of the current-voltage characteristic. The advantage is good amplification quality and virtually no transient distortion. The disadvantages include not being economical in terms of energy consumption, hence the low efficiency.

Class B amplifier– amplification occurs by active transistors, each operating in switch mode, amplifying its part of the signal half-wave. This class has a high efficiency, but at the same time the level of nonlinear distortion is higher, due to imperfect joining of both half-waves.

Class AB amplifier- average option. Due to the initial displacement, nonlinear distortions of the audio signal are reduced (“docking” is close to perfect), but there is a deterioration in terms of efficiency.

The chip provides 14 watts of output power (d = 0.5%) at 14 V (bipolar) or 28 V (unipolar) supply voltage and load into 4 ohms. It also provides a guaranteed output power of 12/8 watts into a 4/8 ohm load.

The TDA2030 produces high output current and has very low harmonic and crossover distortion.

Harmonic vibrations arise due to distortion of the voltage waveform from an ideal sinusoid. This leads to the fact that, in addition to vibrations of the primary frequency (first harmonic), vibrations of higher harmonics appear in the form of voltage, which are harmonic distortions.

Crosstalk are the cause of the nonlinear input characteristics of transistors operating in mode “B” amplifiers.

Besides, TDA2030 includes an original and patented short circuit protection system consisting of an automatic power dissipation limiting module to keep the operating point of the output transistors within their safe operating range. There is also a standard overheat shutdown circuit.

Technical characteristics of TDA2030

Overall dimensions and pinout of the TDA2030 microcircuit

Typical TDA2030 connection circuit with output power up to 14 watts

The input signal (approximately 0.8 volts) can be an audio signal from the output of a CD/DVD player, radio, MP3 player. A speaker with a coil resistance of 4 ohms must be connected to the output. Variable resistor P1 is designed to change the value of the input audio signal. If it is necessary to amplify a fairly weak signal, for example, a signal from a microphone or from an electric guitar pickup, then in this case it is necessary to use.

A preamplifier is an amplifier for a weak signal, usually located near the source of this signal to prevent all kinds of distortion due to various interference. Used to amplify low-current signals from devices such as microphones and all kinds of pickups.

It is advisable to assemble the power supply on a separate board from the amplifier itself. The power supply circuit is quite simple.

The rectifier transformer can be any transformer that provides a voltage of about 20...22 volts on the secondary winding. For normal operation of the amplifier, it is advisable to install the TDA2030 chip on a heat sink. A small aluminum plate about 3 mm thick with a total surface area of ​​approximately 15 square meters is quite suitable. see. An amplifier assembled without errors does not require adjustment and starts working immediately.

Bridge connection circuit TDA2030

If you need to get more powerful sound amplification, you can assemble an amplifier using a bridge connection circuit TDA2030

The acoustic signal from the output of the DA1 microcircuit is supplied through a divider on resistors R5, R8 to the inverting input of the DA2 microcircuit. This allows you to work in the opposite phase. In this connection, the voltage at the load increases, and, consequently, the output power increases. With a supply voltage of 16 V and a load resistance of 4 Ohms, the output power can be 32 W.

(1.3 Mb, downloaded: 6,787)

The TDA7294 microcircuit is an integrated low-frequency amplifier, which is very popular among electronics engineers, both beginners and professionals. The network is full of different reviews about this chip. I decided to build an amplifier on it. I took the diagram from the datasheet.

This “micruha” feeds on a bipolar diet. For beginners, I will explain that it is not enough to have a “plus” and a “minus”.

You need a source with a positive terminal, a negative terminal and a common one. For example, relative to the common wire there should be plus 30 Volts, and in the other arm minus 30 Volts.

The amplifier on the TDA7294 is quite powerful. The maximum rated power is 100 W, but this is with nonlinear distortion of 10% and at maximum voltage (depending on load resistance). You can reliably shoot at 70W. Thus, on my birthday, I listened to two parallel-connected “Radio Engineering S30” speakers on one TDA 7294 channel. The entire evening and half of the night, the speakers sounded, sometimes putting them into overdrive. But the amplifier withstood it calmly, although it sometimes overheated (due to poor cooling).

Main characteristicsTDA7294

Supply voltage +-10V…+-40V

Peak output current up to 10A

Operating temperature of the crystal up to 150 degrees Celsius

Output power at d=0.5%:

At +-35V and R=8Ohm 70W

At +-31V and R=6Ohm 70W

At +-27V and R=4Ohm 70W

With d=10% and increased voltage (see), you can achieve 100W, but it will be a dirty 100W.

Amplifier circuit for TDA7294

The diagram shown is taken from the passport, all denominations are preserved. With proper installation and correctly selected element values, the amplifier starts the first time and does not require any settings.

Amplifier elements

The values ​​of all elements are indicated in the diagram. Resistor power 0.25 W.

The “microphone” itself should be installed on the radiator. If the radiator is in contact with other metal elements of the case, or the case itself is the radiator, then it is necessary to install a dielectric gasket between the radiator and the TDA7294 case.

The gasket can be silicone or mica.

The radiator area should be at least 500 sq.cm, the larger the better.

Initially, I assembled two channels of the amplifier, since the power supply allowed, but I didn’t choose the right housing and both channels simply did not fit into the housing in terms of dimensions. I tried to make the PCB smaller, but it didn't work.

After fully assembling the amplifier, I realized that the case was not enough to cool one channel of the amplifier. My case was a radiator. In short, I rolled out the lip into two channels.

When listening to my device at full volume, the crystal began to overheat, but I lowered the volume level and continued testing. As a result, I listened to music at a moderate volume until midnight, periodically causing the amplifier to overheat. The TDA7294 amplifier turned out to be very reliable.

ModeSTAND- BY TDA7294

If 3.5V or more is applied to the 9th leg, the microcircuit exits sleep mode; if less than 1.5V is applied, it will enter sleep mode.

In order to wake the device from sleep mode, you need to connect the 9th leg through a 22 kOhm resistor to the positive terminal (bipolar power source).

And if the 9th leg is connected through the same resistor to the GND terminal (bipolar power source), then the device will enter sleep mode.

The printed circuit board located under the article is routed so that leg 9 is connected via a 22 kOhm resistor to the positive terminal of the power supply. Consequently, when the power source is turned on, the amplifier immediately begins to operate in sleep mode.

ModeMUTE TDA7294

If 3.5V or more is applied to the 10th leg of the TDA7294, the device will exit the muting mode. If you apply less than 1.5V, the device will enter mute mode.

In practice, this is done like this: through a 10 kOhm resistor, connect the 10 leg of the microcircuit to the plus of a bipolar power source. The amplifier will “sing”, that is, it will not be muted. On the printed circuit board attached to the article, this is done using a track. When power is applied to the amplifier, it immediately begins to sing, without any jumpers or toggle switches.

If we connect the TDA7294 leg through a 10 kOhm resistor 10 to the GND pin of the power supply, then our “amplifier” will enter mute mode.

Power supply.

The voltage source for the device was an assembled one, which showed itself very well. When listening to one channel, the keys are warm. Schottky diodes are also warm, although there are no radiators installed on them. IIP without protection and soft start.

The circuit of this SMPS is criticized by many, but it is very easy to assemble. It works reliably without soft start. This circuit is very suitable for novice electronics engineers because of its prostate.

Frame.

The case was purchased.

Full ULF 2x70 Watt on TDA7294.

When assembling an amplifier on microcircuits, the TDA7294 is not a bad choice. Well, however, we will not dwell on the technical characteristics, you can see them in the PDF file TDA7294_datasheet, located in the folder for downloading material for assembling this ULF. As you already understood from the title of the article, this is a complete amplifier circuit that contains a power supply, signal pre-amplification stages with a three-band tone control, implemented on two common 4558 operational amplifiers, two channels of final stages, as well as a protection unit. The circuit diagram is shown below:

With a supply voltage of ±35 Volts into an 8 Ohm load, you get 70 Watts of power.

The PCB sources are as follows:

PCB LAY6 format:

Arrangement of elements on the amplifier board:

Photo view of LAY board format:

The board has a J5 connector for connecting a temperature sensor (Bimetal Thermostat), designated B60-70. In normal mode, its contacts are open; when heated to 60°C, the contacts close and the relay turns off the load. In principle, you can also use thermal sensors with normally closed contacts designed to operate at 60...70°C, but you need to connect it to the gap between the emitter of transistor Q6 and the common wire, while connector J5 is not used. If you are not going to use this function, leave connector J5 empty.

Operational amplifiers are installed in sockets. Relay with an operating voltage of 12 Volts with two groups of switching contacts, the contacts must withstand 5 Amps.

Printed circuit board for LAY6 fuses:

Photo view of the LAY format of the fuse board:

The power connector for the protection unit is located on the board just above connector J5. Just make a jumper with two wires between this connector and the main power connector as shown in the picture below:

External connections:

Additional Information:

4Ohm – 2x18V 50Hz
8Ohm – 2x24V 50Hz

With a power supply of 2x18V 50Hz:

Resistors R1, R2 – 1 kOhm 2W
Resistor RES – 150 Ohm 2W

With a power supply of 2x24V 50Hz:

Resistors R1, R2 – 1.5 kOhm 2W
Resistor RES – 300 Ohm 2W

The JRC4558 operational amplifier can be replaced with NE5532 or TL072.

Please note that on the conductor side of the printed circuit board, an LL4148 diode in SMD version is installed between the contacts of the relay coil; you can solder a regular 1N4148.

There is a GND point on the board near the volume control; it is intended for grounding the housings of all controllers. This piece of bare copper wire is clearly visible in the main picture of the news.

List of elements for repeating the amplifier circuit on the TDA7293 (TDA7294):

Electrolytic capacitors:

10000mF/50V – 2 pcs.
100mF/50-63V – 9 pcs.
22mF – 5 pcs.
10mF – 6 pcs.
47mF – 2 pcs.
2.2mF – 2 pcs.

Film capacitors:

1 mF – 8 pcs.
100n – 8 pcs.
6n8 – 2 pcs.
4n7 – 2 pcs.
22n – 2 pcs.
47n – 2 pcs.
100pF – 2 pcs.
47pF – 4 pcs.

Resistors 0.25W:

220R – 1 pc.
680R – 2 pcs.
1K – 6 pcs.
1K5 – 2 pcs.
3K9 – 4 pcs.
10K – 10 pcs.
20K – 2 pcs.
22K – 8 pcs.
30K – 2 pcs.
47K – 4 pcs.
220K – 3 pcs.

Resistors 0.5W:

2W resistors:

RES - 300R – 2 pcs.
100R – 2 pcs.

Diodes:

Zener diodes 12V 1W – 2 pcs.
1n4148 – 1 pc.
LL4148 – 1 pc.
1n4007 – 3 pcs.
Bridge 8...10A – 1 pc.

Variable resistors:

A50K – 1 pc.
B50K – 3 pcs.

Chips:

NE5532 – 2 pcs.
TDA7293 (TDA7294) – 2 pcs.

Connectors:

3x – 1 pc.
2x – 2 pcs.

Relay – 1 pc.

Transistors:

BC547 – 5 pcs.
LM7812 – 1 pc.

You can download the circuit diagram of the amplifier for TDA7294, TDA7294_datasheet, printed circuit boards in LAY6 format in one file from our website. Archive size – 4 Mb.

I was one of the first to assemble an amplifier based on the TDA7294 according to the circuit proposed by the manufacturer.

At the same time, I was not very happy with the quality of sound reproduction, especially in the high frequencies. On the Internet, my attention was drawn to the LINCOR article posted on the website datagor.ru. The author's rave reviews about the sound of the UMZCH on the TDA7294, assembled using a voltage-controlled current source (VCS) circuit, intrigued me. As a result, I assembled the UMZCH according to the following scheme.

The scheme works as follows. The signal from the IN input is supplied through pass-through capacitor C1 to the low-resistance feedback arm R1 R3, which, together with capacitor C2, forms a low-pass filter that prevents interference and high-frequency noise from penetrating into the audio path. Together with resistor R4, the input circuit creates the first OOS segment, Ku of which is equal to 2.34. Further, if it were not for the current sensor R7, the gain of the second circuit would be set by the ratio R5/R6 and would be equal to 45.5. Final Ku would be about 100. However, there is still a current sensor in the circuit, and its signal, summed with the voltage drop across R6, creates a partial negative feedback on the current. With our circuit ratings Ku=15.5.

Amplifier characteristics when operating at a 4 Ohm load:

– Operating frequency range (Hz) – 20-20000;

– Supply voltage (V) – ±30;

– Nominal input voltage (V) – 0.6;

– Nominal output power (W) – 73;

– Input resistance (kOhm) – 9.4;

– THD at 60W, no more (%) – 0.01.

A 12V parametric stabilizer is installed on the printed circuit board to power service circuits 9 and 10 of the TDA7294, shown in the figure.

In the “Play!” position, the amplifier is in an unlocked state and is ready for use every second. In the “Mute” position, the input and output stages of the microcircuit are blocked, and its consumption is reduced to the minimum standby currents. The capacitances of C11 and C12 are doubled compared to standard ones to provide greater turn-on delay and prevent clicking in the speakers even when charging the power supply capacitors for a long time.

Amplifier parts

All resistors, except R7 and R8, are carbon or metal film 0.125–0.25 W, type C1-4, C2-23 or MLT-0.25. Resistor R7 is a 5W wirewound resistor. White SQP resistors in ceramic housing are recommended. R8 – Zobel circuit resistor, carbon, wire or metal film 2W.

C1 – film, the highest available quality, lavsan or polypropylene. K73-17 at 63V will also give a satisfactory result. C2 – ceramic disk or any other type, for example K10–17B. C3 - electrolyte of the highest available quality for a voltage of at least 35 V, C4 C7, C8, C9 - film type K73-17 for 63 V. C5 C6 - electrolytic for a voltage of at least 50 V. C11 C12 - any electrolytic for a voltage of at least 25 V. D1 – any 12…15 V zener diode with a power of at least 0.5 W. Instead of the TDA7294 chip, you can use TDA7296...7293. In the case of using TDA7296, TDA7295, TDA7293, it is necessary to bite off or bend and not solder the 5th leg of the microcircuit.

Both output terminals of the amplifier are “hot”, neither of them is grounded, because The acoustic system is also a feedback link. The speaker turns on between and .

Below is a board layout with views from the elements and conductors, created using the Sprint-Layout_6.0 program.

Updated: 04/27/2016

An excellent amplifier for home can be assembled using the TDA7294 chip. If you are not strong in electronics, then such an amplifier is an ideal option; it does not require fine tuning and debugging like a transistor amplifier and is easy to build, unlike a tube amplifier.

The TDA7294 microcircuit has been in production for 20 years and has still not lost its relevance and is still in demand among radio amateurs. For a novice radio amateur, this article will be a good help in getting to know integrated audio amplifiers.

In this article I will try to describe in detail the design of the amplifier on the TDA7294. I will focus on a stereo amplifier assembled according to the usual circuit (1 microcircuit per channel) and will briefly talk about the bridge circuit (2 microcircuits per channel).

TDA7294 chip and its features

TDA7294 is the brainchild of SGS-THOMSON Microelectronics, this chip is an AB class low-frequency amplifier, and is built on field-effect transistors.

The advantages of the TDA7294 include the following:

• output power, with distortion 0.3–0.8%:
  • 70 W for 4 ohm load, conventional circuit;
  • 120 W for 8 ohm load, bridge circuit;
• Mute function and Stand-By function;
• low noise level, low distortion, frequency range 20–20000 Hz, wide operating voltage range - ±10–40 V.

Specifications

Pin assignment

Note. The microcircuit body is connected to the power supply negative (pins 8 and 15). Do not forget about insulating the radiator from the amplifier body or insulating the microcircuit from the radiator by installing it through a thermal pad.

I would also like to note that in my circuit (as well as in the datasheet) there is no separation of input and output lands. Therefore, in the description and in the diagram, the definitions of “general”, “ground”, “housing”, GND should be perceived as concepts of the same sense.

The difference is in the cases

The TDA7294 chip is available in two types - V (vertical) and HS (horizontal). The TDA7294V, having a classic vertical body design, was the first to roll off the production line and is still the most common and affordable.

Complex of protections

The TDA7294 chip has a number of protections:

• protection against power surges;
• protection of the output stage from short circuit or overload;
• thermal protection. When the microcircuit heats up to 145 °C, the mute mode is activated, and at 150 °C the standby mode is activated;
• protection of microcircuit pins from electrostatic discharges.

Power amplifier on TDA7294

A minimum of parts in the harness, a simple printed circuit board, patience and known good parts will allow you to easily assemble an inexpensive TDA7294 UMZCH with clear sound and good power for home use.

You can connect this amplifier directly to the line output of your computer sound card, because The nominal input voltage of the amplifier is 700 mV. And the nominal voltage level of the linear output of the sound card is regulated within 0.7–2 V.

Amplifier block diagram

The diagram shows a version of a stereo amplifier. The structure of the amplifier using a bridge circuit is similar - there are also two boards with TDA7294.

• A0. power unit
• A1. Control unit for Mute and Stand-By modes
• A2. UMZCH (left channel)
• A3. UMZCH (right channel)

Pay attention to the connection of the blocks. Improper wiring inside the amplifier may cause additional interference. To minimize noise as much as possible, follow several rules:

1. Power must be supplied to each amplifier board using a separate harness.
2. The power wires must be twisted into a braid (harness). This will compensate for the magnetic fields created by the current flowing through the conductors. We take three wires (“+”, “-”, “Common”) and weave them into a pigtail with a slight tension.
3. Avoid ground loops. This is a situation where a common conductor, connecting blocks, forms a closed circuit (loop). The connection of the common wire must go in series from the input connectors to the volume control, from it to the UMZCH board and then to the output connectors. It is advisable to use connectors isolated from the housing. And for input circuits there are also shielded and insulated wires.

List of parts for TDA7294 power supply:

When purchasing a transformer, please note that the effective voltage value is written on it - U D, and by measuring it with a voltmeter you will also see the effective value. At the output after the rectifier bridge, the capacitors are charged to the amplitude voltage - U A. The amplitude and effective voltages are related by the following relationship:

U A = 1.41 × U D

According to the characteristics of the TDA7294, for a load with a resistance of 4 Ohms, the optimal supply voltage is ±27 volts (U A). The output power at this voltage will be 70 W. This is the optimal power for the TDA7294 - the distortion level will be 0.3–0.8%. There is no point in increasing the power supply to increase power because... the level of distortion increases like an avalanche (see graph).

We calculate the required voltage of each secondary winding of the transformer:

U D = 27 ÷ 1.41 ≈ 19 V

I have a transformer with two secondary windings, with a voltage of 20 volts on each winding. Therefore, in the diagram I designated the power terminals as ± 28 V.

To obtain 70 W per channel, taking into account the efficiency of the microcircuit of 66%, we calculate the power of the transformer:

P = 70 ÷ 0.66 ≈ 106 VA

Accordingly, for two TDA7294 this is 212 VA. The nearest standard transformer, with a margin, will be 250 VA.

It is appropriate to state here that the power of the transformer is calculated for a pure sinusoidal signal; corrections are possible for a real musical sound. So, Igor Rogov claims that for a 50 W amplifier, a 60 VA transformer will be sufficient.

The high-voltage part of the power supply (before the transformer) is assembled on a 35x20 mm printed circuit board; it can also be mounted:

The low-voltage part (A0 according to the structural diagram) is assembled on a 115x45 mm printed circuit board:

All amplifier boards are available in one.

This power supply for the TDA7294 is designed for two chips. For a larger number of microcircuits, you will have to replace the diode bridge and increase the capacitor capacity, which will entail a change in the dimensions of the board.

Control unit for Mute and Stand-By modes

The TDA7294 chip has a Stand-By mode and a Mute mode. These functions are controlled through pins 9 and 10, respectively. The modes will be enabled as long as there is no voltage on these pins or it is less than +1.5 V. To “wake up” the microcircuit, it is enough to apply a voltage greater than +3.5 V to pins 9 and 10.

To simultaneously control all UMZCH boards (especially important for bridge circuits) and save radio components, there is a reason to assemble a separate control unit (A1 according to the block diagram):

Parts list for control box:

• Diode (VD1). 1N4001 or similar.
• Capacitors (C1, C2). Polar electrolytic, domestic K50-35 or imported, 47 uF 25 V.
• Resistors (R1–R4). Ordinary low-power ones.

The printed circuit board of the block has dimensions of 35×32 mm:

The control unit's task is to ensure silent switching on and off of the amplifier using the Stand-By and Mute modes.

The operating principle is as follows. When the amplifier is turned on, along with the capacitors of the power supply, capacitor C2 of the control unit is also charged. Once it is charged, Stand-By mode will turn off. It takes a little longer for capacitor C1 to charge, so Mute mode will turn off second.

When the amplifier is disconnected from the network, capacitor C1 discharges first through diode VD1 and turns on the Mute mode. Then capacitor C2 discharges and sets the Stand-By mode. The microcircuit becomes silent when the power supply capacitors have a charge of about 12 volts, so no clicks or other sounds are heard.

Amplifier based on TDA7294 according to the usual circuit

The microcircuit's connection circuit is non-inverting, the concept corresponds to the original one from the datasheet, only the component values ​​have been changed to improve the sound characteristics.

Parts List:

1. Capacitors:
   • C1. Film, 0.33–1 µF.
   • C2, C3. Electrolytic, 100-470 µF 50 V.
   • C4, C5. Film, 0.68 µF 63 V.
   • C6, C7. Electrolytic, 1000 µF 50 V.
2. Resistors:
   • R1. Variable dual with linear characteristic.
   • R2–R4. Ordinary low-power ones.

Resistor R1 is double because stereo amplifier. Resistance of no more than 50 kOhm with a linear rather than logarithmic characteristic for smooth volume control.

Circuit R2C1 is a high pass filter (HPF) that suppresses frequencies below 7 Hz without passing them to the amplifier input. Resistors R2 and R4 must be equal to ensure stable operation of the amplifier.

Resistors R3 and R4 organize a negative feedback circuit (NFC) and set the gain:

Ku = R4 ÷ R3 = 22 ÷ 0.68 ≈ 32 dB

According to the datasheet, the gain should be in the range of 24–40 dB. If it is less, the microcircuit will self-excite; if it is more, distortion will increase.

Capacitor C2 is involved in the OOS circuit; it is better to take one with a larger capacitance to reduce its effect on low frequencies. Capacitor C3 provides an increase in the supply voltage of the output stages of the microcircuit - “voltage boost”. Capacitors C4, C5 eliminate noise introduced by wires, and C6, C7 supplement the filter capacity of the power supply. All amplifier capacitors, except C1, must have a voltage reserve, so we take 50 V.

The amplifier's printed circuit board is single-sided, quite compact - 55x70 mm. When developing it, the goal was to separate the “ground” with a star, ensure versatility and at the same time maintain minimal dimensions. I think this is one of the smallest boards for TDA7294. This board is designed for installation of one microcircuit. For the stereo option, accordingly, you will need two boards. They can be installed side by side or one above the other like mine. I’ll tell you more about versatility a little later.

The radiator, as you can see, is indicated on one board, and the second, similar one, is attached to it from above. Photos will be a little further.

Amplifier based on TDA7294 using a bridge circuit

A bridge circuit is a pairing of two conventional amplifiers with some adjustments. This circuit solution is designed for connecting acoustics with a resistance of not 4, but 8 ohms! Acoustics are connected between the amplifier outputs.

There are only two differences from the usual scheme:

• the input capacitor C1 of the second amplifier is connected to ground;
• added feedback resistor (R5).

The printed circuit board is also a combination of amplifiers according to the usual circuit. Board size – 110×70 mm.

Universal board for TDA7294

As you have already noticed, the above boards are essentially the same. The following version of the printed circuit board fully confirms the versatility. On this board you can assemble a 2x70 W stereo amplifier (regular circuit) or a 1x120 W mono amplifier (bridged). Board size – 110×70 mm.

Note. To use this board in a bridge version, you need to install resistor R5 and install jumper S1 in a horizontal position. In the figure, these elements are shown as dotted lines.

For a conventional circuit, resistor R5 is not needed, and the jumper must be installed in a vertical position.

Assembly and adjustment

Assembling the amplifier will not pose any particular difficulties. The amplifier does not require any adjustment as such and will work immediately, provided that everything is assembled correctly and the microcircuit is not defective.

Before first use:

1. Make sure the radio components are installed correctly.
2. Check that the power wires are connected correctly, do not forget that on my amplifier board the ground is not centered between plus and minus, but on the edge.
3. Make sure that the microcircuits are isolated from the radiator; if not, then check that the radiator is not in contact with ground.
4. Apply power to each amplifier in turn, so there is a chance you won’t burn out all the TDA7294 at once.

First start:

1. We do not connect the load (acoustics).
2. We connect the amplifier inputs to ground (connect X1 to X2 on the amplifier board).
3. We serve food. If everything is fine with the fuses in the power supply and nothing smokes, then the launch was a success.
4. Using a multimeter, we check the absence of direct and alternating voltage at the output of the amplifier. A slight constant voltage is allowed, no more than ±0.05 volts.
5. Turn off the power and check the chip body for heating. Be careful, the capacitors in the power supply take a long time to discharge.
6. We send a sound signal through a variable resistor (R1 according to the diagram). Turn on the amplifier. The sound should appear with a slight delay, and disappear immediately when turned off; this characterizes the operation of the control unit (A1).

Conclusion

I hope this article will help you build a high-quality amplifier using the TDA7294. Finally, I present a few photos of the assembly process, do not pay attention to the quality of the board, the old PCB is unevenly etched. Based on the assembly results, some edits were made, so the boards in the .lay file are slightly different from the boards in the photographs.

The amplifier was made for a good friend, he came up with and implemented such an original housing. Photos of the assembled stereo amplifier on the TDA7294:

On a note: All printed circuit boards are collected in one file. To switch between “signatures”, click on the tabs as shown in the figure.

list of files