A good homemade amplifier. The simplest sound amplifier. Tools for work

This power amplifier is based on the PA100, described in detail in the application from National Semiconductor's AN1192

When I assembled my powerful homemade 4-ohm speakers, the amplifier could not “drive” such a load, so it was decided to assemble more powerful amplifier. I have designed a power amplifier circuit that uses two LM3886s per channel in a parallel circuit. At an 8-ohm load, the output power of the amplifier is about 50 Watts, at a 4-ohm load it is 100 Watts. This amplifier uses four LM3886 ULF chips.

By the way, Jeff Rowland uses LM3886 in some of his Hi-Fi designs and has good reviews. So an inexpensive amplifier can also be of high quality!

The LM3886 chip is connected as a non-inverting amplifier. The input impedance of the ULF depends on resistor R1 (47 kOhm). Resistor R20 (680 Ohm) and capacitor C20 (470 pF) form a high-pass filter on the RCA input connectors. Capacitors C4 and C8 (220 pF) are used to filter RF at the inputs of the LM3886 chip.

When assembling the amplifier, in some places I used high-quality capacitors: C1 (1 µF) "Auricap" for DC filtering, C2 and C6 (100 µF) "Blackgate" and C12, C16 (1000 µF) "Blackgate".

The circuit diagram of the amplifier is shown below.

The development of the printed circuit board was carried out taking into account that the power ground (supply) and signal ground were separated. The signal ground is in the middle and is surrounded by the force ground. Near C5 they are connected by a thin path. The design of the printed circuit board was carried out in the PADS PowerPCB 5.0 program.

I didn’t make the printed circuit board myself, but gave it to a company. When I picked it up, I discovered that some of the holes were smaller in diameter than needed. I drilled it out myself by hand. The photo below is a photo of the board.

Resistors 1kOhm and 20kOhm were manually selected with an accuracy of 0.1%. As output resistors, I used six resistors with a nominal value of 1 Ohm 0.5 Watt 1%, because a 3 Watt 1% resistor is difficult to find.

I used an isolated version of the chip - LM3886 TF, so I directly connected it to the case and heatsink through thermal paste.

Isolation capacitor "Auricap" 1uF 450V. A high quality capacitor was purchased because it is involved in the main signal circuit.

Capacitors in the high-pass filter: "Silver Mica" 47pF and 220pF.

The power filter used a "Blackgate" 1000uF 50V capacitor

Condensers C2 and C6 are also from Blackgate with a nominal value of 100 µF 50 V. For best result It is better to use bipolar capacitors, but I used electrolytes because... bipolar ones would not fit on the board.

The filter chain R20 (680 Ohm) + C20 (470 pF) is placed directly on the RCA connector. This helps filter out RF noise before it reaches the amplifier board.

A 0.1uF power supply decoupling capacitor is soldered to reverse side amplifier boards directly onto the LM3886 leg, this allows for better filtering of RF noise.

The LM3886 chip is mounted on aluminum radiator, and then to the amplifier housing. Outside the case I attached 3 more radiators from CPU fans PC. Thermal paste was used throughout for better heat transfer.

With all these heatsinks, the amplifier heats up quite a bit at medium volume.

In the power supply I used an LT1083 adjustable voltage regulator IC. In front of it I placed capacitors with a capacity of 10,000 μF after - 100 μF. The advantage of using an adjustable voltage stabilizer is that there is virtually no ripple voltage. Without it, a small 50/100 Hz noise is heard.

Powerful MUR860 diodes were used in the diode bridges.

The LT1083 voltage stabilizer can provide current up to 8A.

The transformer was used with a power of 500VA 2x25V. After the stabilizer, the voltage is 30 Volts.

In the future I plan to replace the stabilizer with a more powerful one (see diagram below). The TIP2955 transistor is capable of withstanding currents up to 15A.

After assembling the amplifier I measured constant voltage and got an offset of about 7 mV at the speaker connectors. The voltage difference between the two outputs of the microcircuits is less than 1 mV.

The sound of the amplifier is somewhat similar to the sound of the LM3875 amplifier I assembled earlier - very clean. There is no noise, no hissing, no buzzing. Compared with the LM3875 amplifier, this amplifier develops approximately twice more power on my 4 Ohm speakers and provides deep and punchy bass and good dynamics.

List of radioelements

Designation	Type	Denomination	Quantity	My notepad
	ULF
U1, U2	Audio amplifier	LM3886	2	To notepad
C1	Capacitor	1 µF	1	To notepad
C2, C6		100 µF	2	To notepad
C3, C7	Capacitor	4.7 pF	2	To notepad
C4, C8	Capacitor	220 pF	2	To notepad
C5, C9	Electrolytic capacitor	10 µF	2	To notepad
C10, C11, C13	Capacitor	0.1 µF	3	To notepad
C12, C14	Electrolytic capacitor	1000 µF	2	To notepad
C20	Capacitor	470 pF	1	To notepad
R1	Resistor	47 kOhm	1	To notepad
R2, R3, R7, R8	Resistor	1 kOhm	4	To notepad
R4, R9	Resistor	22 kOhm	2	To notepad
R5, R10	Resistor	10 kOhm	1	To notepad
R6, R11, R13-R16	Resistor	0.5Ohm 1W 1%	6	To notepad
R12	Resistor	2 ohm	1	To notepad
R20	Resistor	680 Ohm	1	To notepad
	power unit
U1, U2	Linear regulator	LT1083	2	To notepad
D1-D8	Rectifier diode	MUR860	8	To notepad
C1, C4	Electrolytic capacitor	10000 µF	2	To notepad
C2, C5	Capacitor	1 µF	2	To notepad
C3, C6	Electrolytic capacitor	100 µF	2	To notepad
R1, R2	Resistor	100 Ohm	2	To notepad
R3, R4	Trimmer resistor	2.5 kOhm	2	To notepad
TX1, TX2	Transformer	220/25V	2	To notepad
	Powerful stabilizer
N1, N2	Linear regulator	LM317	2	To notepad
V1, V2	Bipolar transistor	TIP2955	2	To notepad
V3-V12	Rectifier diode	MUR1560	10	To notepad
V13, V14	Rectifier diode	1N4007	2

Very often, connecting speakers to a device requires a separate amplification device. But what to do if the base amplifier fails? You can try to take the initiative into your own hands and create your own device. How to make a sound amplifier? Possessing basic knowledge in working with printed circuit boards, you can make such a device yourself. And we will tell you about this in this article.

Making an amplification device

Absolutely any assembly must be accompanied by a search for the necessary components and tools:

First you need to get a soldering iron with a heat-resistant support. Special ones are best suited soldering stations, which can be easily found and purchased at any amateur radio store.
If the assembly process at home is carried out only to test the circuit or use it for a short time, then the option with wires is perfect. But this method will require a larger working space to place the parts.
The printed circuit board guarantees the compactness of the device and ease of subsequent operation. A popular budget amplifier for a pair of headphones or speakers is very easy to recreate on the basis of a microcircuit that provides a basic set of components.
To such a circuit you just need to add a couple of resistors and capacitor elements.

The cost of mounting the board is significantly less than the market value of a ready-made amplifier from any hardware store, but the functionality is limited by the capabilities and tools that you have available.

Important! Do not forget about the features of small-sized monoblocks that you will assemble with your own hands. The circuit generates a considerable amount of heat during operation, so it is imperative to exclude any contact of this part with other components of the device. A radiator grill can be used to dissipate heat.

The next feature is the low voltage consumption threshold. This feature allows you to use the amplifier anywhere.

How to assemble an amplifier for a laptop at home?

First you need to understand: is it necessary to create such a device at all? Home assembly may be required for the following cases:

The built-in audio system has failed and you need a new one.
The transmitted sound quality does not meet your needs.

Important! For these cases, you need the simplest amplification element, the operating power of which is about 2 Watts.

Tools for work

First, you will need to acquire the tools that every self-respecting radio amateur has:

Pliers.
Pay.
Soldering iron (soldering station).
Housing and radio components.

Important! You will need polar and non-polar capacitors, as well as a set of resistors. We recommend purchasing several packages with different denominations at once. You also need to purchase a switch and a jack, which you will need to output to the speaker.

After preparation, you can start “creating” the device:

Download the required diagram from the Internet in .lay format.
Find a radiator that is sized to keep the temperature below fifty degrees Celsius.
Open the downloaded diagram, arm yourself with tools and start assembling.

Headphone amplifier

The simplest device must have low power and the necessary energy consumption. Consider the ideal case:

The device is powered by AA batteries or a regular 3V adapter.
It is best to choose a high-quality microcircuit. An excellent candidate is the TDA 2822 circuit or its equivalent.
The following radio components will be needed: four 100 µF capacitors, copper wire with a length of up to 30 centimeters, a jack socket.

Having all these things, you can safely download the necessary diagram from the Internet and get to work.

Important! If you want to fit the whole thing in a small closed case, then you will need to get a heat sink.

If you are a car enthusiast, then it will be useful for you to know how to assemble a sound amplifier for your car yourself.

Subwoofer device

If the previous cases did not raise any questions for you, then everything should go smoothly here too. A low-frequency amplifier at home can be made based on the TDA 7294 microcircuit. Here you will have powerful acoustics with good bass and an excellent car amplifier.

You will need:

Power supply for three tens of volts. The device must be bipolar.
Capacitors and resistors, the values of which will be indicated on the assembly drawing diagram.

Important! Such amplifiers work great at low frequencies and provide an output power of up to 100 watts.

Small amplifier for small speakers

The fact that the device will be motionless is only to your advantage. This will expand the choice of power adapters; any one you have on hand will do. Small size and nice appearance A budget device can be achieved if you follow the following rules:

You need to work with a very high quality printed circuit board.
You need to use a housing made of metal or plastic, which should be quite durable.
You need to skillfully use a soldering iron so as not to cover the device with solder.
It is advisable to use only ready-made nests.
The heatsink should not touch anything other than the chip itself.

Tube amplifier

Such devices are quite expensive if you do not immediately have the necessary “sources” available. Old school hams always keep a small collection of tubes and other useful components in their closet.

In this article we will talk about one of the options for a homemade power amplifier based on Master Kit modules. The project was implemented by a user of our products.

Structurally, the device consists of four main functional blocks:

1) the power amplifier itself (D-class, 2x40W, can be replaced with);
2) digital volume and balance control ();
3) digital signal level indicator;
4) 12V power supply for a current of at least 4A (the author used computer unit food).

The well-known acoustic system Radiotekhnika S-90 (stereo - two speakers) was used as acoustics.

A sketch of the modules connection is shown in the figure:

It should be remembered that the noise level of the entire system depends on the quality of the power supply. You need to be especially careful when using computer power supplies. It is better to use high-quality branded ATX power supplies, since most cheap no-name power supplies have regular jumpers installed instead of filter chokes, which has an extremely negative effect on sound quality.

There are some subtleties of connecting modules that can cause difficulties for insufficiently trained electronics engineers. For example, the MP3106S power amplifier defaults to a balanced connection method, but it is often more convenient to connect the input signal using classic scheme with a common "ground".

To do this, you need to slightly modify the amplifier connection diagram:

In addition to the above basic modules, we additionally had to purchase “small things”: input and output connectors, power switch, fasteners.

The prototype of the future building was an ordinary carton from under the shoes:

The entire system was debugged in such an improvised case. After debugging, all components were transferred to a wooden case.

The system sounds decent: no wheezing, no discernible dips in the frequency range. Of course, music lovers may find some flaws, but for such demanding customers, ready-made HI-FI devices and speaker systems are produced (at the same HI-FI prices). But experience shows that during blind listening, 90% of people cannot distinguish the sound of an expensive tube device from a budget amplifier, and if so, why pay more? Moreover, a DIY design always seems to be the best!

A video of the amplifier layout in operation can be seen here:

The final version of the amplifier can be seen here:

In addition, the assembled amplifier turned out to be very beautiful and original: a real wooden case, a spectacular glowing dial indicator of signal levels - all this is truly mesmerizing!

In the future, so that the amplifier can connect to modern gadgets, the author plans to equip the system with a Bluetooth wireless audio channel (based on the Master Kit module), which will increase the convenience of connecting signal sources.

Connection of this module will not cause any particular difficulties. The line output of the MP3862BT is connected to the line input of the amplifier. And the module power is connected to the system power line:

This audio amplifier circuit was created by everyone's favorite British audio engineer Linsley-Hood. The amplifier itself is assembled with only 4 transistors. It looks like an ordinary low-frequency amplifier circuit, but this is only at first glance. An experienced radio amateur will immediately understand that the output stage of the amplifier operates in class A. The genius thing is that it is simple and this circuit is proof of that. This is a super-linear circuit where the shape of the output signal does not change, that is, at the output we get the same signal shape as at the input, but already amplified. The scheme is better known as JLH - ultra linear class A amplifier, and today I decided to present it to you, although the scheme is far from new. Any ordinary radio amateur can assemble this sound amplifier with his own hands, thanks to the absence of microcircuits in the design, which makes it more accessible.

How to make a speaker amplifier

Audio amplifier circuit

In my case, only domestic transistors were used, since it is not easy to find imported transistors, and even standard circuit transistors. The output stage is built on powerful domestic transistors of the KT803 series - it is with them that the sound seems better. To drive the output stage, a medium power transistor of the KT801 series was used (it was difficult to find). All transistors can be replaced with others (KT805 or 819 can be used in the output stage). Replacements are not critical.

Advice: whoever decides to “taste” this homemade sound amplifier - use germanium transistors, they sound better (IMHO). Several versions of this amplifier have been created, all of them sound... divine, I can't find any other words.

The power of the presented circuit is no more than 15 watts(plus minus), current consumption 2 Amperes (sometimes a little more). The output stage transistors will heat up even without sending a signal to the amplifier input. Strange phenomenon, isn't it? But for class amplifiers. Ah, this is a completely normal phenomenon, a large quiescent current - business card literally all known circuits of this class.

The video shows the operation of the amplifier itself connected to the speakers. Please note that the video was filmed on mobile phone, but the sound quality can be judged this way. To test any amplifier, you only need to listen to just one tune - Beethoven's “Fur Elise”. After turning it on, it becomes clear what kind of amplifier is in front of you.

90% of microcircuit amplifiers will not pass the test, the sound will be “broken,” wheezing and distortion may be observed at high frequencies. But the above does not apply to John Linsley’s circuit; the ultra-linearity of the circuit allows you to completely repeat the shape of the input signal, thereby obtaining only pure gain and a sine wave at the output.

It was a long time ago, I decided to write only now.

S-30B speakers were available.
I wanted to make home speakers for my computer. The amplifier was missing.

Went shopping. The lowest price for low-power amplifiers/receivers (30 watt speakers at peak) is about 6,000 rubles.

I decided to do it myself.

Tube - for audio flows, and there are a lot of problems. Transistor ones take a long time to set up, and the element base must be selected precisely, because errors in parts sold in markets and stores sometimes reach up to 10%.

In the end, the choice fell on microcircuits.

After Googling and reading the forums, I chose the TDA2050 chip.

Connection diagram:

As you can see, the body kit is minimal.

They also need radiators.

I took 500 rubles. and moved towards radio markets and shops.

The entire element base cost a little more than 100 rubles.

A power source was also needed. I won’t go into details about nutrition. Diode bridge + output connectors - about 100 more rubles.

I bought radiators on the market from an old stump, 2 pieces for 20 rubles each.

I bought some other little things, which will be discussed below.

Returned home. We need to make stamps. I decided not to bother for a long time. I took out a piece of PCB from the bins, marked out the paths, and drew them by hand with a marker, as shown in the photo below.

I etched it with ferric chloride (again, I got it from old supplies).

I decided not to drill the signet, but to solder the parts on top of the tracks.

The power supply is a little more responsible. Here, however, I drilled through the PCB, because the condensers are large and if you solder them from above, the mechanical load on the copper foil will be large and may peel off. Well, + stabilizers for +-12 volts, just in case, for the future I attached them to ordinary zener diodes + a transistor with a resistor;)

About the transformer a little later.

I connected everything with a canopy. Connected the sound source and speakers. Stop self-excitement. It beeps and that's it. I soldered 100nan film mikruh conders directly to the power legs. The excitement is gone. I ran it for an hour and it worked.

Now the body.
There was an old Vega 10U-120S lying around (the transformer was made from it)

I threw everything out of him except the trance.
I cleaned off the silver and put a plate on the front panel. I painted everything (the usual spray paint remained matte).
This is what happened. (I made it 2 years ago, so it’s already shabby):

The power supply was plugged into the place of the 2 condensers that were there:

The volume control is a regular 2 kilo-ohm variable:

I screwed the amplifiers onto 1 bolt. They are lightweight, so they hold securely:

I once bought a regulator (variable) knob for 10 rubles:

Wires for audio signal: I bought 2 meters of microphone cable for 30 rubles per meter.

Everything started to look like this:

On the back wall there is a socket for the input signal and output terminals.

Twisted. Connected the computer and speakers. Everything worked immediately and without any complaints.

I'm not a big sound connoisseur. To my ears, it plays no worse than what is sold in the store at a price of 6-10 thousand rubles. But it’s definitely better than it was when this amplifier case had its original guts. The high-rises appeared normal, the bass more or less cut through. It was probably bad because of the dried out old conder in the old offal.

In general, after all this was ready, from 500 rubles there were 30 rubles left. All this taking into account travel from shops to shops.

After some time, I picked up a Magnat Monitor Sub 200 A subwoofer (at that time it cost me 5,000 rubles). But this is already a conversation about acoustics and a different topic.

Since then I have never complained about the sound. Everything works flawlessly. Enough for background music and for movies and for parties so that the neighbors can listen.

p.s. This story happened a long time ago, so some people could have lied a little at some points.