Professional power amplifiers. Transistor ULF with low dynamic distortion (20 watts) ULF 20 watts and above

Comments (19):

Thank you very much, but I would suffer again for a long time) very good site! +5

Why might there be a strong background?

#3 root April 01 2011

Maybe due to a bad power filter, try replacing and increasing the capacity of the electrolytic capacitor, which is located after the diode bridge in the rectifier. C5 is used as a power supply filter in the above circuit, try changing it. Also, the background may be due to interference in the input circuits. The wires carrying the signal to the amplifier input must be shielded, and the shield must be connected to the common one (minus).

with C5 everything was fine, I installed a rectifier at the output of 2 4000mk 50V condensers and shielded everything possible, the background was blown away) now another problem is the bass is wheezing, what could it be? Everything is fine with the column.

#5 root April 02 2011

In this case, there are more options, I’ll give you the ones I came across:

1. It is most likely that the power supply cannot withstand the load; when driving this amplifier, it consumes considerable current. Try connecting the circuit to a more powerful power supply or to a high-capacity 12V battery.
2. It is possible that at high volumes the signal source itself is distorted (it is faulty or the equalizer is poorly configured), try connecting a player to an amplifier or taking a signal from a computer sound card.
3. You came across a defective microcircuit, try to replace it with one purchased from another store (it often happens that you come across a batch of defective ones).
4. Adjust the feedback circuit further - R1, C1, C2. Instead of R1, we turn on a variable resistor; it is advisable to check C1, C2. We supply power and signal to the amplifier, achieving normal gain without distortion or overload.

#6 Alexander December 24 2014

What's the problem people? I assembled the amplifier according to the second circuit, after turning it on, after about 5 minutes the electrolyte capacitor C5 heats up, and noise and hissing begin, maybe the reason for this is in the resistors R2, R3 I set to 0.8 ohms, or in the ceramics C4, C6,..C9?

#7 root December 24 2014

The publication was updated and put in order; the old information and diagram from Bashirov’s brochure were removed because the diagram and printed circuit board there did not match and there were other errors.

Alexander, it’s very strange that capacitor C5 is heating up, from what source are you powering the circuit? - you need to power it with rectified constant voltage - a step-down transformer + diode bridge, at the output we get a constant voltage.

#8 Alexander December 24 2014

In general, I found and fixed the error, it turns out I mixed up the polarity of the capacitor, I am powered by a Soviet power supply unit 6-9 volts 0.1 ampere, constant. I am very grateful to the site for the diagram and help in setting up. For updating the site 5+

#9 Nazar February 24 2015

Why does the finished amplifier play quietly?

#10 root February 24 2015

• Check for shorts between tracks and other debris on the printed circuit board;
• The signal level at the amplifier input is low; for the experiment, apply a signal to the amplifier from another source;
• Weak power supply, there is not enough current to drive the ULF, try powering it from a battery or a powerful power supply;
• One or more electrolytic capacitors are faulty - check the charge/discharge tester and try to replace them;
• Resistor R1 is soldered to a different value;
• The microcircuit is scorched, check whether it gets too hot in idle mode, try replacing the microcircuit.

#11 Evgeniy March 16 2015

A good amplifier put together such a mono. I'm pleased with the gain factor, the S90 rocks. Collected according to the production seal. Can be downloaded from lay at http://ampexpert.ru/usilitel-20-vt-na-tda2005-mono/

#12 Alexander March 27 2015

good afternoon. I have this situation, the amplifier perceives interference from the signal source, a whistling sound from the computer from the DVD player, clicks from the computer, small whistling sounds from the phone, barely perceptible but there. I sinned on the power supply, connected it to the computer unit and the same thing, then I wandered around various sites and found that there are circuits where a high-frequency transistor SS9014 is placed at the input of the microcircuit, I think you just need to raise the frequency at the input a little so that it does not coincide with the network, but I don’t know how much this will help, since the sound goes from 20 to 20 000 Hz, which means raising the frequency to at least 100 Hz, allowing it to be connected to the mains, raised it, but what about the sound if the sub is at 20-40 Hz, but in fact it can help or can you not experiment with it?

#13 root March 27 2015

Here's what to try:

• connect a 47-100 kOhm variable resistor to the amplifier input to adjust the volume. The middle leg of the resistor goes to C6, one of the outer ones goes to the ground, after which we send a signal to the remaining outer leg and the ground.
• Between pin 1 of the microcircuit and ground, connect a 100 pF capacitor and a 30 kOhm resistor connected in parallel. Set capacitor C6 to 0.47 - 1 µF, not electrolytic.
• To connect the player and other signal sources to the amplifier, use a shielded cable, connect the screen itself to ground (common) in the diagram, it will also serve as a minus.

#14 Alexander March 27 2015

Using this circuit, I put together a simple experiment about the speakers, but as it shows, it works normally, only the only noise is at the input, while I’m working on your advice, I’m trying to determine which capacitors are coming from which leg.

#15 root March 27 2015

According to the diagram that you provided, there is no point in turning on the speaker like this - the power delivered will be equal to the power of one channel, or even less. Look at the wiring diagram for the microcircuit in this article and compare it with the one you provided: legs 4, 2 (feedback) and 5, 1 (inputs). Bridged ULF is not just about connecting a speaker to the output of each channel.

#16 Alexander March 27 2015

eureka there is no noise, for some reason it was noisy with the power supply from the computer, then I connected it to a trance with a block of capacitors and a diode bridge, it was the same thing, then I connected 2 small 10 uF capacitors from the ground to the radiators, then I connected the volume control 1 to 33 com 0.25 watt and another in series at 100 kom 0.25 watt and surprisingly, the noise disappeared, the background remained in the case from the power supply, you will probably need to go through all the capacitors in the power supply, maybe you need to replace it, and I realized that you need to put trimmers at the input to reduce the input power at 47-100 com and variable volume at 47-100 com, and then the noise goes away.

#17 Evgeniy January 09 2017

Hello, dear radio amateurs, I would like to ask you for help... This is the first time a problem has arisen with this amplifier! Before this, I assembled an amplifier exactly according to your mono circuit and everything worked perfectly without any problems, but now the problem is the following: after assembling the amplifier, two resistors, R2 and R3, get wildly hot, the output sound is dirty and with wild interference. I checked everything carefully, there is no short circuit anywhere, the amplifier is assembled according to the same circuit and works great, I connect this one, and it... In general, I would really like to know, maybe the reason is that this amplifier is a TDA2005R, and the old one is just TDA2005? Please help me figure it out...(

#18 root January 10, 2017

Evgeniy, in your case you need to make sure that the power supply is powerful enough and the voltage drop under load is not very large. It is possible that one of the channels of the microcircuit is scorched or there is a manufacturing defect.
Heating of resistors R2 and R3 may indicate that the amplifier is overexcited and operates as a generator. The reason may be a poor layout of the printed circuit board, a malfunction of one of the capacitors or one of the channels of the microcircuit.
TDA2005R is a newer version of the chip, the inclusion is the same as for TDA2005. For this microcircuit, it is better to use a switching circuit with a voltage boost (boostrap), as in Figure 5, this will slightly increase the ULF output power.

#19 Alexander April 23 2017

In general, it is better and more reliable to always take diagrams from the datasheet itself. Then there will be fewer problems...

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  Good afternoon Now we will assemble a low frequency amplifier. The TDA2004 microcircuit is taken as the basis.
  
  It has two outputs, but the power of each individually is 8 watts, which is not so much. Therefore, we will use bridging. This inclusion will allow you to more than double the power.

  Amplifier Specifications

  So, the main characteristics of our amplifier:
  • Supply voltage: 8-18 volts;
  • Rated output power: 20 Watt;
  • Maximum output power: 25 Watt.
  The diagram looks like this:
  

  

  Required Parts

  • DD.1 – TDA2004;
  • C1, C2, C3, C7, C8 – 0.1 µF;
  • C4 – 470 uF, 25 Volts;
  • C5 – 10 µF;
  • C6 – 1 nF;
  • R1 – 470 Ohm;
  • R2, R3 – 22 Ohm.

  

  Printed circuit board

  For the printed circuit board we will need a piece of PCB measuring 3x2 cm, as well as a drawing of the board:
  

  (downloads: 133)

  
  

  

  Making a low frequency amplifier

  We cut and transfer using the laser-iron method. We finish painting everything that has not completely transferred with varnish.
  

  

  
  We will etch in a solution of hydrogen peroxide and citric acid. Pour three tablespoons of peroxide into a large disposable glass, add a tablespoon of citric acid and add a pinch of ordinary salt, it is a catalyst and is not consumed during the reaction. Stir the solution until the substances are completely dissolved and throw the board into it. Hydrogen bubbles begin to be released, and the solution turns blue.
  

  

  
  The board is etched for about half an hour. You can speed up the process a little by placing the solution in the sun.
  When the excess copper has dissolved, take out the board and rinse it with water.
  

  

  
  The used solution should be poured into the public sewer.
  Next, we clean the board from toner with acetone and tin the tracks.
  

  

  
  First, we solder the microcircuit into place, then the remaining components.
  Carry out installation based on the picture:
  
  At this stage the amplifier is ready. Before turning on, the microcircuit should be installed on a heat sink.
  

  

  
  

  

  
  This is a compact but quite powerful amplifier. I connected a 25 Watt 4 Ohm low-frequency head to it - it did an excellent job, at full volume there were no wheezes, clicks or other sound distortions. After an hour of operation, the radiator heated up to 60 degrees.
  And with this my article has come to an end, good luck to everyone in the repetition!

  category Amplifier circuits materials in category * Subcategory Transistor amplifier circuits

  So-called dynamic intermodulation distortion occurs in transistor amplifiers when there are sharp changes in signal level. These distortions are especially noticeable when playing music programs. In order to reduce these distortions, this amplifier widely uses local current feedback, uses a so-called “current mirror” that improves the symmetry of the amplified signal at the input of the final stage, and uses leading frequency response correction.

  Basic amplifier parameters

  Nominal frequency range, Hz .... 16... 100 000;

  Rated output power into an 8 ohm load (at 0.35% harmonic distortion at frequencies
  1,000 and 10,000 Hz), W .... 20;

  Rated input voltage, V .... 1;

  Relative noise and background level, dB .... -60.
  

  Amplifier circuit diagram

  The amplifier contains an input differential stage on transistors V1, V2, a balancing stage on transistors VЗ, V5 with a “current mirror” on transistors V4, V6, an output stage on transistors V14-V17 and a short-circuit protection device on the load on transistors V9, V10 .

  Resistors R3, R4 in the emitter circuits of the transistors of the first stage create local current feedback, which increases the linearity and input resistance of the stage, as well as improving its symmetry. Resistors R11, R14 create local feedback in the second stage. Correction of the frequency response in advance is carried out by capacitors C2 and C6.

  The output stage is made according to a traditional circuit with a phase inverter using transistors of different structures V14, V15. The quiescent current of transistors V16, V17 is set by trimming resistor R15 and is stabilized when the temperature changes by transistor V7, which has a thermal connection with one of them. Diodes V18, V19 protect the transistors of the output stage from overvoltages due to the inductive nature of the load.

  The amplifier is covered by an OOS, the voltage of which is removed from the load and, through circuit R10C4C5R9, supplied to the input of the first stage (to the base circuit of transistor V2). Circuit R28C10 increases the amplifier's stability against self-excitation.

  The output stage protection device against short circuit in the load is made according to a bridge circuit. For the negative half-wave of the amplified signal, the bridge is formed by the load resistance and resistors R26, R20 and R17. The emitter junction of transistor V9 is included in the diagonal of the bridge.

  With a sharp decrease in load resistance, the balance of the bridge is disrupted, transistor V9 opens and, with its low resistance of the emitter-collector section, shunts (via diode V8) the input of the pre-terminal stage on transistor V14. As a result, the output stage current is instantly limited. For a positive half-wave of the signal, the bridge is formed by the load resistance and resistors R27, R21 and R19; the emitter junction of transistor V10 is included in the diagonal of the bridge.

  For good linearity of the amplifier, pairs of transistors V1 and V2, VЗ and V5 V4 and V6, V16 and V17 must be selected according to the static current transfer coefficient h21e.

  Amplifier parts and setup

  Transistors V14, V15 are installed on U-shaped heat sinks, bent from a strip of sheet (24 mm thick, 20 mm wide) aluminum alloy (heat sink dimensions - 20 X 25 X 15 mm). The heat sinks of each of the transistors V16, V17 must have a cooling surface with an area of ​​about 250 cm2. Transistor V7 is glued to one of these heat sinks with 88-N glue.

  Setting up the amplifier comes down to eliminating (with trimming resistor R7) the constant voltage at the output and setting (with trimming resistor R15) the quiescent current of the output stage within 80... 100 mA.

  ULF for 20 watts (like a question for filling...) I needed a more powerful ULF for my EMR. I decided to assemble it myself. I reviewed a bunch of diagrams. I chose the one most suitable for me, with the necessary parameters, not very complicated, with protection for the output transistors and for my existing parts. Designed a signet. Well, along the way, the power supply with the stabilizer was also “bungled”. BP launched. Soldered the ULF (see photo). Turned it on and... the power transistors (KT819) immediately heated up and failed. It seems that I checked all the circuits on the short circuit beforehand, and the power supply also has protection (and the ULF itself also has one). Replaced the transistors. I checked all the circuits again for short circuit - everything is fine. I set the device to measure current consumption and turned it on for a second (the resistor that regulates the quiescent current was previously set to minimum). The current... is wild (it goes off scale... but there is no "short circuit"). In short, I've been fiddling with this amp for a long time, and I have experience - I've run similar ones more than once, but here - well, as a first-grader - I can't! By the way, I installed Soviet transistors (not soldered), but recommended ones. I won’t torment you for long - of course, I started this amp and it worked fine. But I decided not to reveal my setup progress yet. But I’ll give you a diagram and description of this amp (from the book). Let's organize a brainstorming session and try to collectively (even if in absentia) figure out this amplifier - why it didn't work immediately after assembly and what needs to be done to get it to work. Agree, radio components are now expensive - it’s a pity for power transistors... Well, then, if people can’t solve this riddle problem, I’ll tell you what’s wrong with this circuit... why it doesn’t start, what are the reasons for the failure of power transistors and, in general, how it should be launched. I tried to set the quiescent current - nothing worked. But half the supply voltage at the connection point R17, R21 was set normally (+15 volts). I looked at the output with an oscilloscope - boom, two frequencies of enormous amplitude at once: 1...2 Hz and 15 kHz. And what’s interesting is that none of these frequencies can be heard at the output (previously I heard up to 17 kHz - in Moscow in a medical center in a room completely isolated from sounds, they checked it, but now, apparently, age has taken its toll...). The ULF excitation at a frequency of 15 kHz was removed by introducing a capacitor with a capacity of 36 pF between the base and collector T5 (negative feedback on alternating current). But with excitation at a frequency of 1...2 hertz, it’s more complicated. Assuming that this was the work of the protection circuit, I turned it off and removed T3, T6 and T7. Alas, the excitement remains. Then I reviewed (and compared) the circuit of this ULF with similar ones, and at the same time reread the theory of operation of this amplifier in a new way (refreshed my memory - maybe I’ve already forgotten something...). I came to the conclusion that it is necessary to install a resistor with a nominal value of 1.2 kOhm in the circuit between the nodes of the connection points C7, Gr and R4, R5, C5. I installed it and the excitation at a frequency of 1...2 hertz immediately stopped. I set the quiescent current of output transistors T9 and T11 to 50 mA. Gave a signal to the input. The signal at the ULF output is very weak, although up to 1 volt was supplied to the input. I looked where it disappeared - on the T1 collector its amplitude is much less than on the base. I removed the modes of this transistor relative to the positive power bus (!!!). At the base there is 10 volts, at the emitter 14 volts, that is, the transistor is “wildly” locked. And only after that it dawned on me that I was reading the constant modes with a tester, and its resistance was 20 kOhm (the base circuit is very high-resistance - the device bypasses this circuit) - this means that the problem here is not in the constant modes, but in something else. I measured it with an oscilloscope - the modes turned out to be normal (the oscilloscope input is high-impedance). But the cascade still doesn’t work. Okay, then I tried to eliminate the negative AC feedback arising from the presence of resistor R8 (12 kOhm) - I bypassed it with a 0.47 μF capacitor (!). The amplifier started working immediately (but similar amplifiers work fine without this...). Once again I carefully compared the circuit of this amplifier with similar others. I removed this additional capacitor, but at the same time replaced capacitor C4 with a capacity of 4.7 microfarads with 47 microfarads (50 volts). That's it... the amplifier worked as it should - the power is sufficient (both audible and visible from the current), and the output sine wave is symmetrical. And when I was putting away all the used literature, I came across an old Radio magazine (1973 No. 8), where I discovered the same circuit (I accidentally flipped through it...), but with my own “modifications” (except for the capacitor at 36 pF), which I reached... through “one place”. It was a shame - when I was looking through magazines to look for similar ULF circuits, I simply ignored the old magazines (you’re unlikely to find what you need in the old ones). I thought that he was smart and cunning - the diagram of this ULF was taken from a book published in 1982, and the magazine was published in 1973 (I am posting an article from it - see the scan) ... there is almost a ten year difference. And that’s how it turned out... It was in vain that he ignored the old times... oh, in vain! So I’m thinking, maybe someone will find my “games” of “starting up vintage amplifiers” useful? Or, maybe, for you, dear colleagues, everything starts immediately after assembly? Unfortunately, I… don’t! 04/29/2017 Rubtsov V.P. UN7BV. Astana, Kazakhstan.

  
  
  
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