Introducing a complete subwoofer amplifier module based on the popular TDA7294 ASIC. This is the best microcircuit for UMZCH, in terms of power/price ratio. Therefore, they lose noticeably.
Features and functions of the circuit
- power amplifier on TDA7294 (70-140W)
- bass gain adjustment
- adjustable low pass filter (80-150Hz) switchable
- phase switch (0-180 degrees)
- infra-low pass filter (passive 3rd order 19, 25, 33 Hz to choose from)
- automatic on/off using the switch for this function (ON/AUTO mode)
- mono/stereo input with sensitivity 150 mV
- silent on/off system
- Dimensions of the board with parts are only 10x10 cm
Module diagrams
Power amplifier circuit diagram
The TDA7294 chip is a classic in home audio engineering. Simplicity, reliability and high repeatability: this is what persuades many to choose this particular TDA. It works both in bridged and single connection.
Schematic diagram of a low-pass filter
The input signal processing unit can work as a mono or regular stereo audio signal from the linear output of a DC or PC. The phase shift can be adjusted. The basis is operational amplifiers TL074 and TL062.
Schematic diagram of the subwoofer power supply
In addition to the power supply itself, which generates voltages of 2x12 and 2x33 volts, a speaker turn-on delay unit is shown here (transistor BC546 and 24 V relay).
Transformer selection
For normal operation of the subwoofer PA module, it is necessary to connect a powerful main power transformer and a small 12 V standby transformer. Recommended transformer (to ensure maximum power):
- Version 1 x TDA7294: 100W 2x24V for 4 ohms, 100W 2x30V for 8 ohms
- Version 2 x TDA7294: 200W 2x24V for 8 ohms, 200W 2x30V for 16 ohms
Subwoofer design
Ready-made homemade subwoofer block All elements of a homemade subwoofer are assembled into a single module, which can already be used as a separate device or built into the box of a passive subwoofer, making it active. To do this, you can take a ready-made speaker from the old Soviet AC-90, removing unnecessary speakers and filters from it and moving the controls outside. Download the project files - .
A do-it-yourself amplification device can provide high-quality transmission of low frequencies. There is also a great opportunity to make the device universal, adapting it not only for a car. Any car owner knows about the decent cost of a good audio system. Price for quality speaker system maybe just cosmic. Some music lovers take it upon themselves to build a subwoofer amplifier themselves to save money. Why not do the same? But how to make an amplifier for a subwoofer, what should you pay more attention to? Answering these questions requires understanding many nuances. Before you do the installation itself, you should be well prepared. All this will be discussed in order in this article.
What will you need?
For good sound You need a subwoofer and an amplifier. To start making the latter, you will have to prepare a little and acquire the following components:
- Pulse amplifier block.
- A processing device that will deal with the impulse.
- AC voltage converter from 12 to 40 Volts.
- Rectifier device and switching device.
To create your own car amplifier you will need to build these blocks with my own hands or buy ready-made ones. The second option should be considered by those people who want to save time.
What do you have to work with?
- The low-frequency amplifier unit itself is based on the TDA 7294 board. This option is the most optimal for amplifiers for a 12 V radio. The price for such a component will be absolutely ridiculous, which is an integral advantage. Worth paying attention technical parameters circuits that allow you to output about 100 watts of pure power.
Important! It must be taken into account that all work is done with a single-channel circuit.
- Output transistors are very demanding on cooling, so it is worth bending all the elements towards the board itself in order to achieve an upward contact arrangement.
- You will need to apply thermal paste to the contact surface and install a dielectric film, and only then install the radiators. This approach will help to significantly reduce the size of the device and save a lot of space in the device body.
- The amplifier itself will require a voltage of 12 to 40 Volts. The TL-494 circuit will cope with this task perfectly. But no one forbids you to find more convenient analogues on the Internet.
Important! You need to install a subwoofer taking into account the incoming impulse, so it becomes necessary to highlight only the low frequency range. The circuit itself is a monoblock, so the input pulse must be processed by a channel adder. Such measures will help turn a two-channel impulse into a single-channel one.
Scheme
The circuit itself requires the following individual components:
- A switch that can notify the user that the amplifier element is ready for use.
- A rectifier, which is needed in order to stabilize the pulses transmitted to the base unit of the control system.
Frame
How to make a 12 volt amplifier for a subwoofer at home? You will need to make or purchase a case:
- You can use a trick and mount the amplifier in the housing of a DVD player. Such a device will have small dimensions, interesting design, and the connectors will only help in this whole procedure.
- Also, the best option is to use an aluminum housing. In this case, the case itself will act as a radiator, which will help get rid of excess heat with ease.
- If you are interested in wooden cases, you should think about a high-quality cooling system.
We make the device
If the preparation of all the necessary elements was successful, then you can begin installation. The 12 Volt gadget is very easy to assemble. It is enough to simply connect all the existing components and install them in the housing. The transformer allows you to install a small cooler, since there will be sufficient voltage to power it. Such a cooling system will do an excellent job of protecting against temperature influences, which will help increase the service life of the newly-made device.
Important! When making an amplifier, avoid contact of wires in order to protect yourself from the formation of a short circuit. Install parts so that there is space between them for air circulation.
Also, the circuit will have to be properly fixed, otherwise there is a risk of hearing rattling instead of beautiful music.
Video material
Now you know exactly how to make a subwoofer amplifier with your own hands. Follow the tips and recommendations you've learned today, and don't forget about safety precautions. It's nice to know that the quality will depend only on you, and no “hack work” from the manufacturer can ruin the experience of listening to your favorite music in your car.
Many people are interested in how to use electronic transformer as a power supply for a low-frequency amplifier and the manufacture of such a cheap “amplifier” for a home subwoofer.
The board for such a device was developed in one hour.
It is a combination of a low-frequency power amplifier (approximately 70-100 W), a low-pass filter for the subwoofer to produce only pure bass without other music, a combiner to combine signals from stereo channels into one single one, as well as a switching power supply so that the entire device could work directly from a 220 V network without the use of additional devices.
The result is a small amplifier with great capabilities.
Let's start with the fact that the amplifier is single-channel, operates in class AB and is built on the ultra-legendary TDA7294 chip, providing an output power of 70 pure watts. This is more than enough for a home subwoofer.
The wiring for this microcircuit is quite standard.
The power supply is a very common electronic transformer. A 105 W Taschibra transformer was used.
It was completely disassembled and reassembled on a common board. Secondary winding power transformer was rewound. The original one produced 12 V output voltage, but the new one began to produce bipolar 28 V.
The network winding consists of 85 turns of wire 0.5 mm thick. The secondary winding was wound with a twist, the total diameter of which is 1.2-1.5 mm. It consists of 40 turns with a tap from the middle.
The mains and secondary windings must be isolated from each other. For winding it is possible to use an W-shaped core. This will be even more convenient for isolating windings.
The board turned out to be very compact, despite the fact that it housed 3 separate parts of the system, not counting the passive adder.
Power transistors of the MJE13007 series in the TO220 package are installed on a common heat sink along with a power amplifier microcircuit. All power components, such as microcircuits and transistors, must be isolated from the heat sink. Thermal paste won't hurt either.
The board does not have acoustic protection from “permanent” in case the amplifier burns out. There is no protection on the power supply either. If desired, you can install without problems. The absence of protections does not mean that the scheme is unreliable. If you don't short-circuit anything, everything will work for a very long time. In some car amplifiers industrial production also lacks protection - and nothing!
A fairly standard second-order filter circuit is also used to filter the signal, providing a cutoff of 100 Hz.
The circuit is based on the cheap and popular BA4558 chip. This is a dual operational amplifier that is widely used in audio equipment.
The filter's power supply is unipolar. The supply voltage is around 15 V. A resistor in the power circuit provides current suppression. It should be 2 watt.
It is advisable to install the microcircuit on a DIP-8 socket.
As mentioned earlier, the filter provides a cutoff of about 100 Hz, that is, all frequencies that are higher will be absent. If desired, you can make the cutoff frequency lower.
To combine signals from both channels before the filter, use simple circuit passive adder.
A correctly assembled circuit does not require adjustment. Everything should work right away.
When assembling, pay attention to the presence of two jumpers.
After completing assembly, it is strongly recommended to check the functionality of individual parts. First, the power supply is checked (the filter and amplifier are turned off in advance). If everything is in order with the unit, then the amplifier is connected and its operation is checked. And at the end you can already connect and check the low-pass filter. On the board, the pins of the microcircuits are numbered.
So, main question I finally received an answer about the possibility of using electronic transformers to power amplifiers. Yes it is possible. Even without any modifications, although the use of a surge filter at the input of the electronic transformer, as well as a smoothing electrolyte after the bridge, will only be beneficial. Chokes after the output bridge wouldn't hurt either. But no difference in sound was detected by ear.
Attached files:
Homemade connector for LCD displays
Hi all! Once, sitting in a friend’s car and listening to his music, I promised him to build an amplifier for a subwoofer if he bought the sub himself. Some time passed, a friend called and said he bought a passive subwoofer - make an amplifier, there is nothing to do - I had to assemble it... There was a TDA1562 microcircuit - it fits perfectly in a car subwoofer, he etched one board for the amplifier, another for the adder and low-pass filter.
ULF circuit and board
The diagrams were from the Internet. It worked the first time. There is no need to configure anything - just solder without errors.
UMZCH case - aluminum profile from the door, drilled holes for power terminals, speaker terminal, LEDs, variable resistances.
I screwed it all together, soldered the wires, and put handles on the resistor axis. The top, bottom and side walls, from a Chinese radio - I cut them a little deep and blew them out with paint from a can. It didn't even look bad.
A friend has it in the back of a VAZ-2109 on the shelf, the signal is connected to the rear speakers - the low-pass filter does a good job of dampening the signal if it’s from the radio.
Constant power through a 15 A fuse. And standby mode from the radio.
Despite the apparent simplicity of calculating low-pass filters necessary to form the required amplitude-frequency characteristics, many have difficulty constructing a finished design.
This article presents a description of a simple circuit for amplification audio frequency using a low-frequency loudspeaker, the so-called subwoofer. Despite the fact that the development itself is largely intended for car enthusiasts, it can also be successfully used for a home audio system.
This design is active column with built-in amplifier and with the ability automatic activation(mute) when turning on the sound-reproducing equipment.
Technical data
output power 25 W.Speaker impedance 4 ohms.
Reproducible frequency band 5-300 Hz.
Power supply 12-16 V
Maximum current consumption 3 A.
The graphs clearly show that the higher the order of the filter, the greater the attenuation in the passband. For a 2nd order filter it will already be 20 dB, i.e. the signal is attenuated 10 times. But since the sensitivity of amplifiers for a subwoofer usually lies in the range of 50-250 mV, and the signal taken from the speakers is about 0.5-5 V, an ideal match in signal levels is obtained. From experiments it was found that for high-quality formation of the frequency response, a 2nd order filter is quite sufficient. In all graphs, to assess the attenuation at medium frequencies of 1000 Hz, control point “A” is given. The capacitor values on the filter circuits themselves and on the finished design are somewhat different. This is so that the designer himself can choose the best option for his acoustics. With sufficient accuracy, the filter crossover frequencies can be changed using the above examples as a basis. For example, to reduce the frequency from 100 Hertz to 50 Hertz, it is sufficient to proportionally increase the capacitance of the capacitor(s) from 22 nanofarads to 47 nanofarads. You can also double the resistor values, but do not forget that the amplifier input in this case must be high-resistance. Otherwise, there will be additional signal attenuation in the transparency band.
Actually, the subwoofer itself consists of a low-frequency amplifier assembled on the DA1 TDA7240 chip and an input low-pass filter R1, R2, R3, C1, C2, C3. Resistors R1 and R2 are connected to the signal wires of the right and left speakers of the car radio. Next, the summed signal passes through the low-pass filter and through separating capacitors C3 and C4, arriving at the input of the amplifier. The level is adjusted using potentiometer P1. Activation (mute) of the amplifier is carried out using switches on transistors T1 and T2. The level required for this is +8V. - +12V. removed from the used radio. This allows you to turn off the subwoofer automatically when you turn off the tape recorder. If there is no need for this, then parts T1, T2, R4, R5, R6, R7 should be excluded from the diagram. R8,R9,C9,C10 - anti-excitation chains. The load (loudspeaker) is connected to pins 5 and 7 of the DA1 chip. Since there is potential at these terminals relative to the “common” wire, attention should be paid to careful insulation of both the conductors themselves and the speaker. This should be done if the structural cavities of the car itself will be used as a column.
There are a lot of mute connection options. Select any point where +12 Volts appears when the radio is turned on. This could be a socket for an active antenna and a dial light bulb or power switch contacts.... It is only advisable to install an additional 1 - 10 kOhm resistor in the radio itself and send the activation signal to the subwoofer through it. This will allow, in the event of an accidental short circuit to the housing, to avoid damage to the equipment.
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