Practical circuits of power amplifiers based on KT 805. Transistor power amplifier. Transformerless transistor power amplifier

Portable speaker for player or phone on tda2822m chip Amplifier test photo:

The following figure shows a list of required parts:

Almost any of the medium and high power bipolar transistors can be used in the circuit n - p - n structures, for example KT 817. It is advisable to install a film capacitor at the input, with a capacity of 0.22 - 1 μF. An example of film capacitors in the following photo:

Here is a drawing of a printed circuit board from the program Sprint-Layout:


The signal is taken from the output of an mp3 player or phone, ground and one of the channels are used. In the following figure you can see the wiring diagram for a Jack 3.5 plug for connecting to a signal source:


If desired, this amplifier, like any other, can be equipped with a volume control by connecting a 50 KOhm potentiometer according to the standard circuit, using 1 channel:


In parallel with the power supply, if there is no high-capacity electrolytic capacitor in the power supply after the diode bridge, you need to install an electrolyte of 1000 - 2200 μF, with an operating voltage greater than the supply voltage of the circuit.
An example of such a capacitor:

You can download the printed circuit board of an amplifier on one transistor for the sprint – layout program in the My files section of the site.

You can evaluate the sound quality of this amplifier by watching a video of its operation on our channel.

Alexey, why not start asking questions more consciously? Then it will be possible to answer more accurately. It’s not because I’m such a guru here all in white, and he’s “beeped” despicable, I’ll drag his face around the table - no, of course. But either “...components can be used or not to increase power...”, or “... there is enough power...” - there’s one thing here, you’ll agree. And if you are interested in why the output transistors heat up, you should ask about it right away.
And, again, in order. “the problem is in the other output they are heating up” - how is this to be understood? The output of the amplifier consists of two wires, signal and common, are they the ones that heat up in your description?
Ok, we are still talking about excessive, in your opinion, heating of the output transistors. You have them “all 4 transistors on the radiator are heating up” - I’ll try to filter this flow. They are heating up - which means “heating up”, within certain limits these transistors should warm up. Do they heat up under a signal at high power or do they heat up without a signal? To what temperature do they heat up - if approximately, then your finger can tolerate it (it’s 50-60 degrees) or can you boil a kettle on a radiator?
Not specified.
“all 4 transistors on the radiator are from the Comet tape recorder” - so what? Alexey, from the 50s until the end of Soviet times, almost enough different models of Comet tape recorders were produced, this again means nothing. What are the dimensions of the heatsink and what is the measured power rating of the amplifier at what size load?
Not specified.
“maybe the radiator is too small” - but who knows, maybe it’s too small. Or maybe just right. Or maybe the quiescent current is too high. What is the quiescent current? What is it like when turned on, that is, on a cold amplifier, and what is it like after running the amplifier without a signal for 20-30 minutes? Why was this value of this current chosen, and not more and not less?
Not specified.
“at the exit kt 819” - again: so what? KT819 in plastic or KT819 in metal - not specified - these varieties have different contact areas with the radiator, plastic ones, all other things being equal, heat up a little more, no big deal.
You see, Alexey, you pose questions in such a way that it is hardly possible to answer your situation, even if you wanted to. Therefore, some reasons for overheating of output transistors are quite abstract:

This is so, I remembered it as I walked. Maybe someone else will remember something. But putting two output transistors in parallel with such an output power makes no sense: at normal load and in normal mode, single ones will pull without any problems. KT819 will definitely pull.
The best thing is not to invent something else to screw somewhere, but to measure the modes of the transistors and see with an oscilloscope what happens in the circuit both without a signal and when operating from sine and pulse generators; what we have at idle, and what we have under load or its equivalent. Such a conversation will be substantive, but for now everything resembles an attempt to describe today’s weather based on the sensations on the slobbery finger stuck out through the window.
And the first thing is to be able to correctly formulate the problem: what is observed, what is not satisfactory, what we are striving for and what costs along this path will be considered acceptable.
And then, Alexey, they will help you more effectively.

High input impedance and shallow feedback are the main secret of warm tube sound. It's no secret that the highest quality and most expensive amplifiers, which belong to the HI-End category, are manufactured using tubes. Let's understand what a quality amplifier is? A low-frequency power amplifier has the right to be called high-quality if it completely repeats the shape of the input signal at the output without distorting it; of course, the output signal is already amplified. On the Internet you can find several circuits of really high-quality amplifiers, which can be classified as HI-End and do not necessarily require tube circuitry. To obtain maximum quality, you need an amplifier whose output stage operates in pure class A. Maximum linearity of the circuit gives a minimum amount of distortion at the output, therefore, in the design of high-quality amplifiers, special attention is paid to this factor. Tube circuits are good, but not always available even for self-assembly, and industrial tube UMZCHs from branded manufacturers cost from several thousand to several tens of thousands of US dollars - this price is certainly not affordable for many.
The question arises - is it possible to achieve similar results from transistor circuits? the answer will be at the end of the article.

There are quite a lot of linear and ultra-linear circuits of low-frequency power amplifiers, but the circuit that will be considered today is a high-quality ultra-linear circuit, which is implemented with only 4 transistors. The circuit was created back in 1969 by British audio engineer John Linsley-Hood. The author is the creator of several other high-quality circuits, in particular class A. Some experts call this amplifier the highest quality among transistor ULFs, and I was convinced of this a year ago.

The first version of such an amplifier was presented at. A successful attempt to implement the circuit forced me to create a two-channel ULF using the same circuit, assemble everything in a housing and use it for personal needs.

Features of the scheme

Despite its simplicity, the scheme has several features. Correct operation may be disrupted due to incorrect board layout, poor placement of components, incorrect power supply, etc.
It is the power supply that is a particularly important factor - I strongly advise against powering this amplifier from all kinds of power supplies; the best option is a battery or a power supply with a battery connected in parallel.
The amplifier power is 10 watts with a 16 Volt power supply into a 4 Ohm load. The circuit itself can be adapted for 4, 8 and 16 Ohm heads.
I created a stereo version of the amplifier, both channels are located on the same board.

The second one is intended for driving the output stage, I installed KT801 (it was quite difficult to get hold of it.
In the output stage itself, I installed powerful bipolar switches of reverse conduction - the KT803 received undoubtedly high-quality sound with them, although I experimented with many transistors - KT805, 819, 808, and even installed powerful composite switches - KT827, with it the power is much higher, but the sound is not compare with KT803, although this is just my subjective opinion.

An input capacitor with a capacity of 0.1-0.33 µF, you need to use film capacitors with minimal leakage, preferably from well-known manufacturers, the same with the output electrolytic capacitor.
If the circuit is designed for a 4 Ohm load, then you should not increase the supply voltage above 16-18 Volts.
I decided not to install a sound regulator; it, in turn, also affects the sound, but it is advisable to install a 47k resistor parallel to the input and minus.
The board itself is a prototype board. I had to tinker with the board for a long time, since the lines of the tracks also had some influence on the sound quality as a whole. This amplifier has a very wide frequency range, from 30 Hz to 1 MHz.

Setup couldn't be easier. To do this, you need to use a variable resistor to achieve half the supply voltage at the output. For more precise settings, you should use a multi-turn variable resistor. We connect one multimeter lead to the minus power supply, put the other one to the output line, i.e. to the plus of the electrolyte at the output, thus slowly rotating the variable we achieve half of the power supply at the output.

They are becoming a thing of the past, and now, in order to assemble any simple amplifier, you no longer have to struggle with calculations and riveting a large printed circuit board.

Now almost all cheap amplification equipment is made on microcircuits. The most widespread are TDA chips for amplifying audio signals. Currently used in car radios, powered subwoofers, home speakers and many other audio amplifiers, they look something like this:

Pros of TDA chips

1. In order to assemble an amplifier on them, it is enough to supply power, connect speakers and several radio elements.
2. The dimensions of these microcircuits are quite small, but they will need to be placed on a radiator, otherwise they will get very hot.
3. They are sold at any radio store. There are some things on Ali that are a little expensive if you buy them at retail.
4. They have built-in various protections and other options, such as muting the sound, etc. But according to my observations, the protections do not work very well, so microcircuits often die either from overheating or from. So it is advisable not to short-circuit the terminals of the microcircuit with each other and not to overheat the microcircuit, squeezing all the juices out of it.
5. Price. I wouldn't say they are very expensive. In terms of price and functions, they have no equal.

Single-channel amplifier on TDA7396

Let's build a simple single-channel amplifier using the TDA7396 chip. At the time of writing, I took it at a price of 240 rubles. The datasheet for the chip said that this chip can output up to 45 Watts into a 2 Ohm load. That is, if you measure the resistance of the speaker coil and it is about 2 ohms, then it is quite possible to get a peak power of 45 watts from the speaker.This power is quite enough to arrange a disco in the room not only for yourself, but also for your neighbors and at the same time get mediocre sound, which, of course, cannot be compared with hi-fi amplifiers.

Here is the pinout of the microcircuit:

We will assemble our amplifier according to a typical diagram, which was attached in the datasheet itself:

We apply +Vs to leg 8, and nothing to leg 4. Therefore, the diagram will look like this:

Vs is the supply voltage. It can be from 8 to 18 Volts. “IN+” and “IN-” – we send a weak sound signal here. We attach a speaker to the 5th and 7th legs. We set the sixth leg to minus.

Here is my wall mounted assembly

I did not use capacitors at the power input of 100nF and 1000uF, since I already have pure voltage coming from the power supply.

I rocked the speaker with the following parameters:

As you can see, the coil resistance is 4 ohms. The frequency band indicates that it is a subwoofer type.

And this is what my sub in a self-made housing looks like:

I tried to take a video, but the sound on the video is very poor. But I can still say that the phone at medium power was already hammering so hard that my ears were turning, although the consumption of the entire circuit in working form was only about 10 watts (multiply 14.3 by 0.73). In this example, I took the voltage as in a car, that is, 14.4 Volts, which is well within our operating range from 8 to 18 Volts.

If you do not have a powerful power source, then you can assemble it according to this diagram.

Don't get hung up on this particular chip. These TDA chips, as I already said, there are many types. Some of them amplify the stereo signal and can output sound to 4 speakers at once, as is done in car radios. So don’t be lazy to scour the Internet and find a suitable TDA. After completing the assembly, let your neighbors check out your amplifier by turning the volume knob all the way up to the balalaika and leaning the powerful speaker against the wall).

But in the article I assembled an amplifier using a TDA2030A chip

It turned out very well, since the TDA2030A has better characteristics than the TDA7396

I’ll also attach, for variety, another diagram from a subscriber whose TDA 1557Q amplifier has been working properly for more than 10 years in a row:

Amplifiers on Aliexpress

On Ali I also found kit kits on TDA. For example, this stereo amplifier is 15 watts per channel and costs $1. This power is quite enough to hang out in your room listening to your favorite tracks.

You can buy it.

But it's ready right away

And in general, there are a lot of these amplifier modules on Aliexpress. Click on this link and choose any amplifier you like.

We bring to your attention another power amplifier. Despite the relatively low power output, it has some undoubted advantages. Firstly, it’s as simple as felt boots and completely accessible to repeat. Secondly, it does not contain scarce or expensive components, so it can be assembled even where access to radio components is difficult or there is a hole in your pocket.

The characteristics of the amplifier are as follows:

The main characteristics are as follows:

The circuit is very simple and if you decide to devote yourself to assembling amplifiers in bulk and studying their activities, then it makes sense to start with this amplifier. The scheme is very stable and non-capricious.

Details:

Settings

Setting up the amplifier comes down to setting the quiescent current of transistor VT9. A milliammeter is connected to the break in the collector wire and the current is set to 50-70 mA by adjusting resistor R11. Then the absence of DC voltage at the amplifier output is checked with an accuracy of 0.1V.

All. We finished the exercise.

All adjustments are made with the load off.

And do not forget to tightly attach transistor VT4 to the heatsink of transistor VT9. The temperature stability of the amplifier depends on this. You can, for example, glue it with hot glue or press it with the flange of the VT9 transistor. Download the printed circuit board in LAY format ( Posted by: Shamrin novel)