Do-it-yourself high-quality sound amplifier. Homemade: a powerful sound amplifier with your own hands How to assemble the simplest sound amplifier

Many owners of smartphones and tablets have a problem with sound, or rather its insufficient volume. Unfortunately, it is very rarely possible to solve it using software. Therefore, you need to use a method that is quite simple and inexpensive to make a simple electronic device that will increase the power of your device. Then you can listen to your favorite music and watch videos at normal or even very high volume.

This video tutorial will show you the simplest sound amplifier that anyone can make, even a school student who has never picked up a soldering iron. Its circuit, suitable for a mobile phone, consists of simple components. When the amplifier is ready, you can improve the sound reproduction quality by using. How to make it is shown in a separate video on the site.

In this article we will talk about an amplifier, to which you can simply connect a speaker, or use the idea as mentioned above.

Audio amplifier circuit based on lm386 chip

What is needed to assemble an amplifier?

First, we need a crown connector, a 9 volt crown, one speaker, 1 watt, and 8 ohms. In addition, you also need one 3.5 mm mini-jack, one 10 ohm resistor, a switch, an LM386 chip and one 10 V and 220 MF capacitor. The diagram was drawn on a piece of paper.

Phone amplifier circuit

As you can see, this IC contains four latches on each side, there are 8 latches in total. To avoid confusion and to avoid turning the chip upside down and soldering it incorrectly, there is a semicircle-shaped notch on it. We need to place the chip so that this icon is located on top and we can solder everything step by step.

You might notice that number 6 is the penultimate tab on the right, we will solder one wire to it. This wire should be tied to the switch, the second contact from the switch should be connected to the plus of the crown connector.

Next stage.

Contact number 5 is the last one on the right side. You need to solder a capacitor to it, which has two poles - plus and minus. How should we identify them? There is a zero with a black stripe - this is a minus, the other side is a plus. According to the diagram, we connect the plus to the last contact on the right.

Let's move forward. The negative from the capacitor must be soldered to the positive of the speaker. We're going to take the wire and extend the capacitor terminal. Now we solder the negative wire of the capacitor to the positive wire from the speaker. Next, we will connect the negative from the speaker to the 4th and 2nd clamps of the microcircuits. We will use a jumper between these legs of the microcircuit.

Now you need to connect the resistor. We solder the wires to its second leg. It is a plus from the mini-jack. If you take it apart, you can see there are two contacts for the left and right channels. Let's connect them together and solder the red wire, which we used to extend the wire from the resistor. The minus, or, in other words, the ground from the mini-jack must be soldered to the minus of the speaker.

Finally, we just have to solder the negative of the crown connector to the negative of the speaker. We take the wire and solder it to the negative of the speaker. That's all. It is very easy. You may have noticed that it took 5-10 minutes.

Now you can check the sound amplifier for mobile phones and smartphones.

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 circuit 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 ones, 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. A strange phenomenon, isn't it? But for class amplifiers. Ah, this is a completely normal phenomenon; a large quiescent current is the hallmark of 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 shot on a mobile phone, but the sound quality can be judged that 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.

In my case, the audio amplifier circuit was implemented on a breadboard; it is not yet possible to assemble the second channel, but in the future I will definitely do it and put everything in the case.

How to achieve high-quality sound of your favorite music? Arm yourself with the necessary knowledge and tools, after which you can assemble a sound amplifier with your own hands.

Which amplifier is better?

There are as many opinions as there are radio amateurs. Basically, the choice depends on the person, so it is very difficult to draw any specific conclusions. Today you can assemble a sound amplifier with your own hands using:

• Transistors. They have low power consumption and compact dimensions. They provide excellent sound quality.
• Lampah. An old fashioned way of assembling radio equipment. Despite its monstrous gluttony, weight and size, it surpasses semiconductor analogues in sound quality.

Where to begin?

Before making a sound amplifier, you need to clearly understand under what conditions and for what purpose it will be used. This directly determines how much power it should have. In order to listen to your favorite songs at home, a small device that will provide high-quality sound with a power of 30 - 50 W is enough. The situation will be completely different if you need to create equipment for large-scale events. In this case, it becomes necessary to assemble a more complex sound amplifier with your own hands. 200W is far from the limit of power that will be needed during operation.

You should also stock up on everything you need:

• Soldering iron.
• Multimeter.
• Screwdriver Set.
• Textolite for the manufacture of microcircuits.
• Material for the housing of a future amplifier.
• Electrical parts that are indicated in the circuit diagram of the product.
• Circuit board diagram of the amplifier selected for assembly.

DIY printed circuit board

Each business has its own subtleties. Making a printed circuit board at home is no exception. It is this that will subsequently become the basis for all further work and will allow you to assemble a sound amplifier with your own hands. First let's look at everything we need:

• Textolite with copper foil.
• Household iron.
• Detergent "Silit".
• Laser printer.
• Chinese self-adhesive film with backing marking 333.
• Drills for making holes in PCB.
• A tampon made of gauze and a piece of cotton fabric.

• We cut out the required piece of PCB so that there is approximately one centimeter of margin left on each side.
• We treat it with detergent until the copper foil turns pink.
• We wash the processed board and send it to dry.
• We take a piece of self-adhesive of the required size, use glue to glue it with a backing to an A4 sheet, remove the film layer, and print the design of the future board on the polished side of the resulting blank. In this case, the toner supply must be set to maximum.
• On the desktop we lay out a sheet of plywood, an old unnecessary book, and on top - a board with the foil facing up.
• Cover the board with regular office paper and heat it with a preheated iron. Approximate warm-up time is one minute.
• Next, remove the iron and sheet of paper, apply the printed design and smooth it with a swab.
• Cover again with a sheet of paper, place the iron on top and wait about 30 seconds. If the surface of the board is larger than the sole of the iron, then you need to iron the entire part evenly.
• Remove the sheet of paper and smooth the pattern with a swab for 30 seconds. Movements should be both along and across. In this case, you need to apply a little pressure on the workpiece.
• After the workpiece has cooled, carefully remove the backing.

How and with what to etch the board

In order to properly assemble a sound amplifier with your own hands, it is not enough to correctly draw the board design or solder the wire. You need to be able to efficiently etch all the tracks on the microcircuit.

Ferric chloride has always been used for these purposes. However, this solution is very expensive and is not always commercially available. For this reason, it can be replaced with a homemade solution of copper sulfate and table salt, which are not in short supply. The proportions for the mixture are as follows:

• A liter of warm water.
• 100 g of copper sulfate.
• 200 g kitchen salt.

When all the components are dissolved, clean and grease-free metal products (for example, a pair of nails), the workpiece itself, a small motor with blades or a compressor from an aquarium are lowered into the container. To enhance the reaction, place the container with the solution in warm water. The approximate time for etching tracks is 25-30 minutes.

Amplifier assembly

The first step that needs to be done in order to assemble a sound amplifier with your own hands is to install all the radio components on the printed circuit board. Particular attention should be paid to polarity here. It would also be worth noting that all work should be carried out with special care and attention. Otherwise, a short circuit may occur, which will lead to inevitable failure of the components of the future amplifier.

After the above procedure, the housing assembly follows. Its dimensions will directly depend on the dimensions of the amplifier board, power supply and the method of implementing volume control and balance between channels. At this stage, you can use a ready-made factory case with some design changes. However, the best way is still to manually manufacture the shell of an electrical appliance. This way you can realize the possibility of creating a unique design. There is also the option of installing a board in the housing of one of the speakers.

Before putting everything together, it is necessary to conduct a test run of the future electrical appliance and, if necessary, eliminate all problems.

The last step is assembling the amplifier, which consists of installing the board, power supply and all other components.

A little off topic

When assembling audio power amplifiers with your own hands, it is not always possible to achieve the desired effect. The secret is that the so-called acoustics are not able to cope with the tasks assigned to them. For this reason, sometimes you have to additionally assemble even the speakers yourself. This approach to the issue will not only guarantee maximum satisfaction of all wishes, but will also help get rid of a separate device by hiding the amplifier in the speaker housing.

– The neighbor stopped knocking on the radiator. I turned the music up so I couldn't hear him.
(From audiophile folklore).

The epigraph is ironic, but the audiophile is not necessarily “sick in the head” with the face of Josh Ernest at a briefing on relations with the Russian Federation, who is “thrilled” because his neighbors are “happy.” Someone wants to listen to serious music at home as in the hall. For this purpose, the quality of the equipment is needed, which among lovers of decibel volume as such simply does not fit where sane people have a mind, but for the latter it goes beyond reason from the prices of suitable amplifiers (UMZCH, audio frequency power amplifier). And someone along the way has a desire to join useful and exciting areas of activity - sound reproduction technology and electronics in general. Which in the age of digital technology are inextricably linked and can become a highly profitable and prestigious profession. The optimal first step in this matter in all respects is to make an amplifier with your own hands: It is UMZCH that allows, with initial training on the basis of school physics on the same table, to go from the simplest designs for half an evening (which, nevertheless, “sing” well) to the most complex units, through which a good rock band will play with pleasure. The purpose of this publication is highlight the first stages of this path for beginners and, perhaps, convey something new to those with experience.

Protozoa

So, first, let's try to make an audio amplifier that just works. In order to thoroughly delve into sound engineering, you will have to gradually master quite a lot of theoretical material and not forget to enrich your knowledge base as you progress. But any “cleverness” is easier to assimilate when you see and feel how it works “in hardware.” In this article further, too, we will not do without theory - about what you need to know at first and what can be explained without formulas and graphs. In the meantime, it will be enough to know how to use a multitester.

Note: If you haven’t soldered electronics yet, keep in mind that its components cannot be overheated! Soldering iron - up to 40 W (preferably 25 W), maximum allowable soldering time without interruption - 10 s. The soldered pin for the heat sink is held 0.5-3 cm from the soldering point on the side of the device body with medical tweezers. Acid and other active fluxes cannot be used! Solder - POS-61.

On the left in Fig.- the simplest UMZCH, “which just works.” It can be assembled using both germanium and silicon transistors.

On this baby it is convenient to learn the basics of setting up an UMZCH with direct connections between cascades that give the clearest sound:

• Before turning on the power for the first time, turn off the load (speaker);
• Instead of R1, we solder a chain of a constant resistor of 33 kOhm and a variable resistor (potentiometer) of 270 kOhm, i.e. first note four times less, and the second approx. twice the denomination compared to the original according to the scheme;
• We supply power and, by rotating the potentiometer, at the point marked with a cross, we set the indicated collector current VT1;
• We remove the power, unsolder the temporary resistors and measure their total resistance;
• As R1 we set a resistor with a value from the standard series closest to the measured one;
• We replace R3 with a constant 470 Ohm chain + 3.3 kOhm potentiometer;
• Same as according to paragraphs. 3-5, V. And we set the voltage equal to half the supply voltage.

Point a, from where the signal is removed to the load, is the so-called. midpoint of the amplifier. In UMZCH with unipolar power supply, it is set to half its value, and in UMZCH with bipolar power supply - zero relative to the common wire. This is called adjusting the amplifier balance. In unipolar UMZCHs with capacitive decoupling of the load, it is not necessary to turn it off during setup, but it is better to get used to doing this reflexively: an unbalanced 2-polar amplifier with a connected load can burn out its own powerful and expensive output transistors, or even a “new, good” and very expensive powerful speaker.

Note: components that require selection when setting up the device in the layout are indicated on the diagrams either with an asterisk (*) or an apostrophe (‘).

In the center of the same fig.- a simple UMZCH on transistors, already developing power up to 4-6 W at a load of 4 ohms. Although it works like the previous one, in the so-called. class AB1, not intended for Hi-Fi sound, but if you replace a pair of these class D amplifiers (see below) in cheap Chinese computer speakers, their sound improves noticeably. Here we learn another trick: powerful output transistors need to be placed on radiators. Components that require additional cooling are outlined in dotted lines in the diagrams; however, not always; sometimes - indicating the required dissipative area of ​​the heat sink. Setting up this UMZCH is balancing using R2.

On the right in Fig.- not yet a 350 W monster (as was shown at the beginning of the article), but already quite a solid beast: a simple amplifier with 100 W transistors. You can listen to music through it, but not Hi-Fi, operating class is AB2. However, it is quite suitable for scoring a picnic area or an outdoor meeting, a school assembly hall or a small shopping hall. An amateur rock band, having such a UMZCH per instrument, can perform successfully.

There are 2 more tricks in this UMZCH: firstly, in very powerful amplifiers, the drive stage of the powerful output also needs to be cooled, so VT3 is placed on a radiator of 100 kW or more. see. For output VT4 and VT5 radiators from 400 sq.m. are needed. see. Secondly, UMZCHs with bipolar power supply are not balanced at all without load. First one or the other output transistor goes into cutoff, and the associated one goes into saturation. Then, at full supply voltage, current surges during balancing can damage the output transistors. Therefore, for balancing (R6, guessed it?), the amplifier is powered from +/–24 V, and instead of a load, a wirewound resistor of 100...200 Ohms is switched on. By the way, the squiggles in some resistors in the diagram are Roman numerals, indicating their required heat dissipation power.

Note: A power source for this UMZCH needs a power of 600 W or more. Anti-aliasing filter capacitors - from 6800 µF at 160 V. In parallel with the electrolytic capacitors of the IP, 0.01 µF ceramic capacitors are included to prevent self-excitation at ultrasonic frequencies, which can instantly burn out the output transistors.

On the field workers

On the trail. rice. - another option for a fairly powerful UMZCH (30 W, and with a supply voltage of 35 V - 60 W) on powerful field-effect transistors:

The sound from it already meets the requirements for entry-level Hi-Fi (if, of course, the UMZCH works on the corresponding acoustic systems, speakers). Powerful field drivers do not require a lot of power to drive, so there is no pre-power cascade. Even more powerful field-effect transistors do not burn out the speakers in the event of any malfunction - they themselves burn out faster. Also unpleasant, but still cheaper than replacing an expensive loudspeaker bass head (GB). This UMZCH does not require balancing or adjustment in general. As a design for beginners, it has only one drawback: powerful field-effect transistors are much more expensive than bipolar transistors for an amplifier with the same parameters. Requirements for individual entrepreneurs are similar to previous ones. case, but its power is needed from 450 W. Radiators – from 200 sq. cm.

Note: there is no need to build powerful UMZCHs on field-effect transistors for switching power supplies, for example. computer When trying to “drive” them into the active mode required for UMZCH, they either simply burn out, or the sound is weak and “no quality at all.” The same applies to powerful high-voltage bipolar transistors, for example. from line scan of old TVs.

Straight up

If you have already taken the first steps, then it is quite natural to want to build Hi-Fi class UMZCH, without going too deep into the theoretical jungle. To do this, you will have to expand your instrumentation - you need an oscilloscope, an audio frequency generator (AFG) and an AC millivoltmeter with the ability to measure the DC component. It is better to take as a prototype for repetition the E. Gumeli UMZCH, described in detail in Radio No. 1, 1989. To build it, you will need a few inexpensive available components, but the quality meets very high requirements: power up to 60 W, band 20-20,000 Hz, frequency response unevenness 2 dB, nonlinear distortion factor (THD) 0.01%, self-noise level –86 dB. However, setting up the Gumeli amplifier is quite difficult; if you can handle it, you can take on any other. However, some of the currently known circumstances greatly simplify the establishment of this UMZCH, see below. Bearing in mind this and the fact that not everyone is able to get into the Radio archives, it would be appropriate to repeat the main points.

Schemes of a simple high-quality UMZCH

The Gumeli UMZCH circuits and specifications for them are shown in the illustration. Radiators of output transistors – from 250 sq. see for UMZCH in Fig. 1 and from 150 sq. see for option according to fig. 3 (original numbering). Transistors of the pre-output stage (KT814/KT815) are installed on radiators bent from 75x35 mm aluminum plates with a thickness of 3 mm. There is no need to replace KT814/KT815 with KT626/KT961; the sound does not noticeably improve, but setup becomes seriously difficult.

This UMZCH is very critical to power supply, installation topology and general, so it needs to be installed in a structurally complete form and only with a standard power source. When trying to power it from a stabilized power supply, the output transistors burn out immediately. Therefore, in Fig. Drawings of original printed circuit boards and setup instructions are provided. We can add to them that, firstly, if “excitement” is noticeable when you first turn it on, they fight it by changing the inductance L1. Secondly, the leads of parts installed on boards should be no longer than 10 mm. Thirdly, it is extremely undesirable to change the installation topology, but if it is really necessary, there must be a frame shield on the side of the conductors (ground loop, highlighted in color in the figure), and the power supply paths must pass outside it.

Note: breaks in the tracks to which the bases of powerful transistors are connected - technological, for adjustment, after which they are sealed with drops of solder.

Setting up this UMZCH is greatly simplified, and the risk of encountering “excitement” during use is reduced to zero if:

• Minimize interconnect installation by placing the boards on radiators of powerful transistors.
• Completely abandon the connectors inside, performing all installation only by soldering. Then there will be no need for R12, R13 in a powerful version or R10 R11 in a less powerful version (they are dotted in the diagrams).
• Use oxygen-free copper audio wires of minimum length for internal installation.

If these conditions are met, there are no problems with excitation, and setting up the UMZCH comes down to the routine procedure described in Fig.

Wires for sound

Audio wires are not an idle invention. The need for their use at present is undeniable. In copper with an admixture of oxygen, a thin oxide film is formed on the faces of metal crystallites. Metal oxides are semiconductors and if the current in the wire is weak without a constant component, its shape is distorted. In theory, distortions on myriads of crystallites should compensate each other, but very little (apparently due to quantum uncertainties) remains. Sufficient to be noticed by discerning listeners against the background of the purest sound of modern UMZCH.

Manufacturers and traders shamelessly substitute ordinary electrical copper instead of oxygen-free copper - it is impossible to distinguish one from the other by eye. However, there is an area of ​​application where counterfeiting is not clear: twisted pair cable for computer networks. If you put a grid with long segments on the left, it will either not start at all or will constantly glitch. Momentum dispersion, you know.

The author, when there was just talk about audio wires, realized that, in principle, this was not idle chatter, especially since oxygen-free wires by that time had long been used in special-purpose equipment, with which he was well acquainted by his line of work. Then I took and replaced the standard cord of my TDS-7 headphones with a homemade one made from “vitukha” with flexible multi-core wires. The sound, aurally, has steadily improved for end-to-end analogue tracks, i.e. on the way from the studio microphone to the disc, never digitized. Vinyl recordings made using DMM (Direct Metal Mastering) technology sounded especially bright. After this, the interconnect installation of all home audio was converted to “vitushka”. Then completely random people, indifferent to the music and not notified in advance, began to notice the improvement in sound.

How to make interconnect wires from twisted pair, see next. video.

Video: do-it-yourself twisted pair interconnect wires

Unfortunately, the flexible “vitha” soon disappeared from sale - it did not hold well in the crimped connectors. However, for the information of readers, flexible “military” wire MGTF and MGTFE (shielded) is made only from oxygen-free copper. Fake is impossible, because On ordinary copper, tape fluoroplastic insulation spreads quite quickly. MGTF is now widely available and costs much less than branded audio cables with a guarantee. It has one drawback: it cannot be done in color, but this can be corrected with tags. There are also oxygen-free winding wires, see below.

Theoretical Interlude

As we can see, already in the early stages of mastering audio technology, we had to deal with the concept of Hi-Fi (High Fidelity), high fidelity sound reproduction. Hi-Fi comes in different levels, which are ranked according to the following. main parameters:

1. Reproducible frequency band.
2. Dynamic range - the ratio in decibels (dB) of the maximum (peak) output power to the noise level.
3. Self-noise level in dB.
4. Nonlinear distortion factor (THD) at rated (long-term) output power. The SOI at peak power is assumed to be 1% or 2% depending on the measurement technique.
5. Unevenness of the amplitude-frequency response (AFC) in the reproducible frequency band. For speakers - separately at low (LF, 20-300 Hz), medium (MF, 300-5000 Hz) and high (HF, 5000-20,000 Hz) sound frequencies.

Note: the ratio of absolute levels of any values ​​of I in (dB) is defined as P(dB) = 20log(I1/I2). If I1

You need to know all the subtleties and nuances of Hi-Fi when designing and building speakers, and as for a homemade Hi-Fi UMZCH for the home, before moving on to these, you need to clearly understand the requirements for their power required to sound a given room, dynamic range (dynamics), noise level and SOI. It is not very difficult to achieve a frequency band of 20-20,000 Hz from the UMZCH with a roll off at the edges of 3 dB and an uneven frequency response in the midrange of 2 dB on a modern element base.

Volume

The power of the UMZCH is not an end in itself; it must provide the optimal volume of sound reproduction in a given room. It can be determined by curves of equal loudness, see fig. There are no natural noises in residential areas quieter than 20 dB; 20 dB is the wilderness in complete calm. A volume level of 20 dB relative to the threshold of audibility is the threshold of intelligibility - a whisper can still be heard, but music is perceived only as the fact of its presence. An experienced musician can tell which instrument is being played, but not what exactly.

40 dB - the normal noise of a well-insulated city apartment in a quiet area or a country house - represents the intelligibility threshold. Music from the threshold of intelligibility to the threshold of intelligibility can be listened to with deep frequency response correction, primarily in the bass. To do this, the MUTE function (mute, mutation, not mutation!) is introduced into modern UMZCHs, including, respectively. correction circuits in UMZCH.

90 dB is the volume level of a symphony orchestra in a very good concert hall. 110 dB can be produced by an extended orchestra in a hall with unique acoustics, of which there are no more than 10 in the world, this is the threshold of perception: louder sounds are still perceived as distinguishable in meaning with an effort of will, but already annoying noise. The volume zone in residential premises of 20-110 dB constitutes the zone of complete audibility, and 40-90 dB is the zone of best audibility, in which untrained and inexperienced listeners fully perceive the meaning of the sound. If, of course, he is in it.

Power

Calculating the power of equipment at a given volume in the listening area is perhaps the main and most difficult task of electroacoustics. For yourself, in conditions it is better to go from acoustic systems (AS): calculate their power using a simplified method, and take the nominal (long-term) power of the UMZCH equal to the peak (musical) speaker. In this case, the UMZCH will not noticeably add its distortions to those of the speakers; they are already the main source of nonlinearity in the audio path. But the UMZCH should not be made too powerful: in this case, the level of its own noise may be higher than the threshold of audibility, because It is calculated based on the voltage level of the output signal at maximum power. If we consider it very simply, then for a room in an ordinary apartment or house and speakers with normal characteristic sensitivity (sound output) we can take the trace. UMZCH optimal power values:

• Up to 8 sq. m – 15-20 W.
• 8-12 sq. m – 20-30 W.
• 12-26 sq. m – 30-50 W.
• 26-50 sq. m – 50-60 W.
• 50-70 sq. m – 60-100 W.
• 70-100 sq. m – 100-150 W.
• 100-120 sq. m – 150-200 W.
• More than 120 sq. m – determined by calculation based on on-site acoustic measurements.

Dynamics

The dynamic range of the UMZCH is determined by curves of equal loudness and threshold values ​​for different degrees of perception:

1. Symphonic music and jazz with symphonic accompaniment - 90 dB (110 dB - 20 dB) ideal, 70 dB (90 dB - 20 dB) acceptable. No expert can distinguish a sound with a dynamics of 80-85 dB in a city apartment from ideal.
2. Other serious music genres – 75 dB excellent, 80 dB “through the roof”.
3. Pop music of any kind and movie soundtracks - 66 dB is enough for the eyes, because... These opuses are already compressed during recording to levels of up to 66 dB and even up to 40 dB, so that you can listen to them on anything.

The dynamic range of the UMZCH, correctly selected for a given room, is considered equal to its own noise level, taken with the + sign, this is the so-called. signal-to-noise ratio.

SOI

Nonlinear distortions (ND) of UMZCH are components of the output signal spectrum that were not present in the input signal. Theoretically, it is best to “push” the NI under the level of its own noise, but technically this is very difficult to implement. In practice, they take into account the so-called. masking effect: at volume levels below approx. At 30 dB, the range of frequencies perceived by the human ear narrows, as does the ability to distinguish sounds by frequency. Musicians hear notes, but find it difficult to assess the timbre of the sound. In people without a hearing for music, the masking effect is observed already at 45-40 dB of volume. Therefore, an UMZCH with a THD of 0.1% (–60 dB from a volume level of 110 dB) will be assessed as Hi-Fi by the average listener, and with a THD of 0.01% (–80 dB) can be considered not distorting the sound.

Lamps

The last statement will probably cause rejection, even fury, among adherents of tube circuitry: they say, real sound is produced only by tubes, and not just some, but certain types of octal ones. Calm down, gentlemen - the special tube sound is not a fiction. The reason is the fundamentally different distortion spectra of electronic tubes and transistors. Which, in turn, are due to the fact that in the lamp the flow of electrons moves in a vacuum and quantum effects do not appear in it. A transistor is a quantum device, where minority charge carriers (electrons and holes) move in the crystal, which is completely impossible without quantum effects. Therefore, the spectrum of tube distortions is short and clean: only harmonics up to the 3rd - 4th are clearly visible in it, and there are very few combinational components (sums and differences in the frequencies of the input signal and their harmonics). Therefore, in the days of vacuum circuitry, SOI was called harmonic distortion (CHD). In transistors, the spectrum of distortions (if they are measurable, the reservation is random, see below) can be traced up to the 15th and higher components, and there are more than enough combination frequencies in it.

At the beginning of solid-state electronics, designers of transistor UMZCHs used the usual “tube” SOI of 1-2% for them; Sound with a tube distortion spectrum of this magnitude is perceived by ordinary listeners as pure. By the way, the very concept of Hi-Fi did not yet exist. It turned out that they sound dull and dull. In the process of developing transistor technology, an understanding of what Hi-Fi is and what is needed for it was developed.

Currently, the growing pains of transistor technology have been successfully overcome and side frequencies at the output of a good UMZCH are difficult to detect using special measurement methods. And lamp circuitry can be considered to have become an art. Its basis can be anything, why can’t electronics go there? An analogy with photography would be appropriate here. No one can deny that a modern digital SLR camera produces an image that is immeasurably clearer, more detailed, and deeper in the range of brightness and color than a plywood box with an accordion. But someone, with the coolest Nikon, “clicks pictures” like “this is my fat cat, he got drunk like a bastard and is sleeping with his paws outstretched,” and someone, using Smena-8M, uses Svemov’s b/w film to take a picture in front of which there is a crowd of people at a prestigious exhibition.

Note: and calm down again - not everything is so bad. Today, low-power lamp UMZCHs have at least one application left, and not the least important, for which they are technically necessary.

Experimental stand

Many audio lovers, having barely learned to solder, immediately “go into tubes.” This in no way deserves censure, on the contrary. Interest in the origins is always justified and useful, and electronics has become so with tubes. The first computers were tube-based, and the on-board electronic equipment of the first spacecraft was also tube-based: there were already transistors then, but they could not withstand extraterrestrial radiation. By the way, at that time lamp microcircuits were also created under the strictest secrecy! On microlamps with a cold cathode. The only known mention of them in open sources is in the rare book by Mitrofanov and Pickersgil “Modern receiving and amplifying tubes”.

But enough of the lyrics, let's get to the point. For those who like to tinker with the lamps in Fig. – diagram of a bench lamp UMZCH, intended specifically for experiments: SA1 switches the operating mode of the output lamp, and SA2 switches the supply voltage. The circuit is well known in the Russian Federation, a minor modification affected only the output transformer: now you can not only “drive” the native 6P7S in different modes, but also select the screen grid switching factor for other lamps in ultra-linear mode; for the vast majority of output pentodes and beam tetrodes it is either 0.22-0.25 or 0.42-0.45. For the manufacture of the output transformer, see below.

Guitarists and rockers

This is the very case when you can’t do without lamps. As you know, the electric guitar became a full-fledged solo instrument after the pre-amplified signal from the pickup began to be passed through a special attachment - a fuser - which deliberately distorted its spectrum. Without this, the sound of the string was too sharp and short, because the electromagnetic pickup reacts only to the modes of its mechanical vibrations in the plane of the instrument soundboard.

An unpleasant circumstance soon emerged: the sound of an electric guitar with a fuser acquires full strength and brightness only at high volumes. This is especially true for guitars with a humbucker-type pickup, which gives the most “angry” sound. But what about a beginner who is forced to rehearse at home? You can’t go to the hall to perform without knowing exactly how the instrument will sound there. And rock fans just want to listen to their favorite things in full juice, and rockers are generally decent and non-conflict people. At least those who are interested in rock music, and not shocking surroundings.

So, it turned out that the fatal sound appears at volume levels acceptable for residential premises, if the UMZCH is tube-based. The reason is the specific interaction of the signal spectrum from the fuser with the pure and short spectrum of tube harmonics. Here again an analogy is appropriate: a b/w photo can be much more expressive than a color one, because leaves only the outline and light for viewing.

Those who need a tube amplifier not for experiments, but due to technical necessity, do not have time to master the intricacies of tube electronics for a long time, they are passionate about something else. In this case, it is better to make the UMZCH transformerless. More precisely, with a single-ended matching output transformer that operates without constant magnetization. This approach greatly simplifies and speeds up the production of the most complex and critical component of a lamp UMZCH.

“Transformerless” tube output stage of the UMZCH and pre-amplifiers for it

On the right in Fig. a diagram of a transformerless output stage of a tube UMZCH is given, and on the left are pre-amplifier options for it. At the top - with a tone control according to the classic Baxandal scheme, which provides fairly deep adjustment, but introduces slight phase distortion into the signal, which can be significant when operating an UMZCH on a 2-way speaker. Below is a preamplifier with simpler tone control that does not distort the signal.

But let's get back to the end. In a number of foreign sources, this scheme is considered a revelation, but an identical one, with the exception of the capacitance of the electrolytic capacitors, is found in the Soviet “Radio Amateur Handbook” of 1966. A thick book of 1060 pages. There was no Internet and disk-based databases back then.

In the same place, on the right in the figure, the disadvantages of this scheme are briefly but clearly described. An improved one, from the same source, is given on the trail. rice. on right. In it, the screen grid L2 is powered from the midpoint of the anode rectifier (the anode winding of the power transformer is symmetrical), and the screen grid L1 is powered through the load. If, instead of high-impedance speakers, you turn on a matching transformer with regular speakers, as in the previous one. circuit, the output power is approx. 12 W, because the active resistance of the primary winding of the transformer is much less than 800 Ohms. SOI of this final stage with transformer output - approx. 0.5%

How to make a transformer?

The main enemies of the quality of a powerful signal low-frequency (sound) transformer are the magnetic leakage field, the lines of force of which are closed, bypassing the magnetic circuit (core), eddy currents in the magnetic circuit (Foucault currents) and, to a lesser extent, magnetostriction in the core. Because of this phenomenon, a carelessly assembled transformer “sings,” hums, or beeps. Foucault currents are combated by reducing the thickness of the magnetic circuit plates and additionally insulating them with varnish during assembly. For output transformers, the optimal plate thickness is 0.15 mm, the maximum allowable is 0.25 mm. You should not take thinner plates for the output transformer: the fill factor of the core (the central rod of the magnetic circuit) with steel will fall, the cross-section of the magnetic circuit will have to be increased to obtain a given power, which will only increase distortions and losses in it.

In the core of an audio transformer operating with constant bias (for example, the anode current of a single-ended output stage) there must be a small (determined by calculation) non-magnetic gap. The presence of a non-magnetic gap, on the one hand, reduces signal distortion from constant magnetization; on the other hand, in a conventional magnetic circuit it increases the stray field and requires a core with a larger cross-section. Therefore, the non-magnetic gap must be calculated at the optimum and performed as accurately as possible.

For transformers operating with magnetization, the optimal type of core is made of Shp (cut) plates, pos. 1 in Fig. In them, a non-magnetic gap is formed during core cutting and is therefore stable; its value is indicated in the passport for the plates or measured with a set of probes. The stray field is minimal, because the side branches through which the magnetic flux is closed are solid. Transformer cores without bias are often assembled from Shp plates, because Shp plates are made from high-quality transformer steel. In this case, the core is assembled across the roof (the plates are laid with a cut in one direction or the other), and its cross-section is increased by 10% compared to the calculated one.

It is better to wind transformers without magnetization on USH cores (reduced height with widened windows), pos. 2. In them, a decrease in the stray field is achieved by reducing the length of the magnetic path. Since USh plates are more accessible than Shp, transformer cores with magnetization are often made from them. Then the core assembly is carried out cut to pieces: a package of W-plates is assembled, a strip of non-conducting non-magnetic material is placed with a thickness equal to the size of the non-magnetic gap, covered with a yoke from a package of jumpers and pulled together with a clip.

Note:“sound” signal magnetic circuits of the ShLM type are of little use for output transformers of high-quality tube amplifiers; they have a large stray field.

At pos. 3 shows a diagram of the core dimensions for calculating the transformer, at pos. 4 design of the winding frame, and at pos. 5 – patterns of its parts. As for the transformer for the “transformerless” output stage, it is better to make it on the ShLMm across the roof, because the bias is negligible (the bias current is equal to the screen grid current). The main task here is to make the windings as compact as possible in order to reduce the stray field; their active resistance will still be much less than 800 Ohms. The more free space left in the windows, the better the transformer turned out. Therefore, the windings are wound turn to turn (if there is no winding machine, this is a terrible task) from the thinnest possible wire; the laying coefficient of the anode winding for the mechanical calculation of the transformer is taken 0.6. The winding wire is PETV or PEMM, they have an oxygen-free core. There is no need to take PETV-2 or PEMM-2; due to double varnishing, they have an increased outer diameter and a larger scattering field. The primary winding is wound first, because it is its scattering field that most affects the sound.

You need to look for iron for this transformer with holes in the corners of the plates and clamping brackets (see figure on the right), because “for complete happiness,” the magnetic circuit is assembled as follows. order (of course, the windings with leads and external insulation should already be on the frame):

1. Prepare acrylic varnish diluted in half or, in the old fashioned way, shellac;
2. Plates with jumpers are quickly coated with varnish on one side and placed into the frame as quickly as possible, without pressing too hard. The first plate is placed with the varnished side inward, the next one with the unvarnished side to the first varnished, etc.;
3. When the frame window is filled, staples are applied and bolted tightly;
4. After 1-3 minutes, when the squeezing of varnish from the gaps apparently stops, add plates again until the window is filled;
5. Repeat paragraphs. 2-4 until the window is tightly packed with steel;
6. The core is pulled tightly again and dried on a battery, etc. 3-5 days.

The core assembled using this technology has very good plate insulation and steel filling. Magnetostriction losses are not detected at all. But keep in mind that this technique is not applicable for permalloy cores, because Under strong mechanical influences, the magnetic properties of permalloy irreversibly deteriorate!

On microcircuits

UMZCHs on integrated circuits (ICs) are most often made by those who are satisfied with the sound quality up to average Hi-Fi, but are more attracted by the low cost, speed, ease of assembly and the complete absence of any setup procedures that require special knowledge. Simply, an amplifier on microcircuits is the best option for dummies. The classic of the genre here is the UMZCH on the TDA2004 IC, which has been on the series, God willing, for about 20 years now, on the left in Fig. Power – up to 12 W per channel, supply voltage – 3-18 V unipolar. Radiator area – from 200 sq. see for maximum power. The advantage is the ability to work with a very low-resistance, up to 1.6 Ohm, load, which allows you to extract full power when powered from a 12 V on-board network, and 7-8 W when supplied with a 6-volt power supply, for example, on a motorcycle. However, the output of the TDA2004 in class B is not complementary (on transistors of the same conductivity), so the sound is definitely not Hi-Fi: THD 1%, dynamics 45 dB.

The more modern TDA7261 does not produce better sound, but is more powerful, up to 25 W, because The upper limit of the supply voltage has been increased to 25 V. The lower limit, 4.5 V, still allows it to be powered from a 6 V on-board network, i.e. The TDA7261 can be started from almost all on-board networks, except for the aircraft 27 V. Using attached components (strapping, on the right in the figure), the TDA7261 can operate in mutation mode and with the St-By (Stand By) function, which switches the UMZCH to the minimum power consumption mode when there is no input signal for a certain time. Convenience costs money, so for a stereo you will need a pair of TDA7261 with radiators from 250 sq. see for each.

Note: If you are somehow attracted to amplifiers with the St-By function, keep in mind that you should not expect speakers wider than 66 dB from them.

“Super economical” in terms of power supply TDA7482, on the left in the figure, operating in the so-called. class D. Such UMZCHs are sometimes called digital amplifiers, which is incorrect. For real digitization, level samples are taken from an analog signal with a quantization frequency that is no less than twice the highest of the reproduced frequencies, the value of each sample is recorded in a noise-resistant code and stored for further use. UMZCH class D – pulse. In them, the analogue is directly converted into a sequence of high-frequency pulse-width modulated (PWM), which is fed to the speaker through a low-pass filter (LPF).

Class D sound has nothing in common with Hi-Fi: SOI of 2% and dynamics of 55 dB for class D UMZCH are considered very good indicators. And TDA7482 here, it must be said, is not the optimal choice: other companies specializing in class D produce UMZCH ICs that are cheaper and require less wiring, for example, D-UMZCH of the Paxx series, on the right in Fig.

Among the TDAs, the 4-channel TDA7385 should be noted, see the figure, on which you can assemble a good amplifier for speakers up to medium Hi-Fi, inclusive, with frequency division into 2 bands or for a system with a subwoofer. In both cases, low-pass and mid-high-frequency filtering is done at the input on a weak signal, which simplifies the design of the filters and allows deeper separation of the bands. And if the acoustics are subwoofer, then 2 channels of the TDA7385 can be allocated for a sub-ULF bridge circuit (see below), and the remaining 2 can be used for MF-HF.

UMZCH for subwoofer

A subwoofer, which can be translated as “subwoofer” or, literally, “boomer,” reproduces frequencies up to 150-200 Hz; in this range, human ears are practically unable to determine the direction of the sound source. In speakers with a subwoofer, the “sub-bass” speaker is placed in a separate acoustic design, this is the subwoofer as such. The subwoofer is placed, in principle, as conveniently as possible, and the stereo effect is provided by separate MF-HF channels with their own small-sized speakers, for the acoustic design of which there are no particularly serious requirements. Experts agree that it is better to listen to stereo with full channel separation, but subwoofer systems significantly save money or labor on the bass path and make it easier to place acoustics in small rooms, which is why they are popular among consumers with normal hearing and not particularly demanding ones.

The “leakage” of mid-high frequencies into the subwoofer, and from it into the air, greatly spoils the stereo, but if you sharply “cut off” the sub-bass, which, by the way, is very difficult and expensive, then a very unpleasant sound jumping effect will occur. Therefore, channels in subwoofer systems are filtered twice. At the input, electric filters highlight midrange-high frequencies with bass “tails” that do not overload the midrange-high frequency path, but provide a smooth transition to sub-bass. Bass with midrange “tails” are combined and fed to a separate UMZCH for the subwoofer. The midrange is additionally filtered so that the stereo does not deteriorate; in the subwoofer it is already acoustic: a sub-bass speaker is placed, for example, in the partition between the resonator chambers of the subwoofer, which do not let the midrange out, see on the right in Fig.

A UMZCH for a subwoofer is subject to a number of specific requirements, of which “dummies” consider the most important to be as high a power as possible. This is completely wrong, if, say, the calculation of the acoustics for the room gave a peak power W for one speaker, then the power of the subwoofer needs 0.8 (2W) or 1.6W. For example, if S-30 speakers are suitable for the room, then a subwoofer needs 1.6x30 = 48 W.

It is much more important to ensure the absence of phase and transient distortions: if they occur, there will definitely be a jump in the sound. As for SOI, it is permissible up to 1%. Intrinsic bass distortion of this level is not audible (see curves of equal volume), and the “tails” of their spectrum in the best audible midrange region will not come out of the subwoofer.

To avoid phase and transient distortions, the amplifier for the subwoofer is built according to the so-called. bridge circuit: the outputs of 2 identical UMZCHs are switched on back-to-back through a speaker; signals to the inputs are supplied in antiphase. The absence of phase and transient distortions in the bridge circuit is due to the complete electrical symmetry of the output signal paths. The identity of the amplifiers forming the arms of the bridge is ensured by the use of paired UMZCHs on ICs, made on the same chip; This is perhaps the only case when an amplifier on microcircuits is better than a discrete one.

Note: The power of a bridge UMZCH does not double, as some people think, it is determined by the supply voltage.

An example of a bridge UMZCH circuit for a subwoofer in a room up to 20 sq. m (without input filters) on the TDA2030 IC is given in Fig. left. Additional midrange filtering is carried out by circuits R5C3 and R’5C’3. Radiator area TDA2030 – from 400 sq. see. Bridged UMZCHs with an open output have an unpleasant feature: when the bridge is unbalanced, a constant component appears in the load current, which can damage the speaker, and the sub-bass protection circuits often fail, turning off the speaker when not needed. Therefore, it is better to protect the expensive oak bass head with non-polar batteries of electrolytic capacitors (highlighted in color, and the diagram of one battery is given in the inset.

A little about acoustics

The acoustic design of a subwoofer is a special topic, but since a drawing is given here, explanations are also needed. Case material – MDF 24 mm. The resonator tubes are made of fairly durable, non-ringing plastic, for example, polyethylene. The internal diameter of the pipes is 60 mm, the protrusions inward are 113 mm in the large chamber and 61 in the small chamber. For a specific loudspeaker head, the subwoofer will have to be reconfigured for the best bass and, at the same time, the least impact on the stereo effect. To tune the pipes, they take a pipe that is obviously longer and, by pushing it in and out, achieve the required sound. The protrusions of the pipes outward do not affect the sound; they are then cut off. The pipe settings are interdependent, so you will have to tinker.

Headphone Amplifier

A headphone amplifier is most often made by hand for two reasons. The first is for listening “on the go”, i.e. outside the home, when the power of the audio output of the player or smartphone is not enough to drive “buttons” or “burdocks”. The second is for high-end home headphones. A Hi-Fi UMZCH for an ordinary living room is needed with dynamics of up to 70-75 dB, but the dynamic range of the best modern stereo headphones exceeds 100 dB. An amplifier with such dynamics costs more than some cars, and its power will be from 200 W per channel, which is too much for an ordinary apartment: listening at a power that is much lower than the rated power spoils the sound, see above. Therefore, it makes sense to make a low-power, but with good dynamics, a separate amplifier specifically for headphones: the prices for household UMZCHs with such an additional weight are clearly absurdly inflated.

The circuit of the simplest headphone amplifier using transistors is given in pos. 1 pic. The sound is only for Chinese “buttons”, it works in class B. It is also no different in terms of efficiency - 13 mm lithium batteries last for 3-4 hours at full volume. At pos. 2 – TDA’s classic for on-the-go headphones. The sound, however, is quite decent, up to average Hi-Fi depending on the track digitization parameters. There are countless amateur improvements to the TDA7050 harness, but no one has yet achieved the transition of sound to the next level of class: the “microphone” itself does not allow it. TDA7057 (item 3) is simply more functional; you can connect the volume control to a regular, not dual, potentiometer.

The UMZCH for headphones on the TDA7350 (item 4) is designed to drive good individual acoustics. It is on this IC that headphone amplifiers in most middle and high-class household UMZCHs are assembled. The UMZCH for headphones on KA2206B (item 5) is already considered professional: its maximum power of 2.3 W is enough to drive such serious isodynamic “mugs” as TDS-7 and TDS-15.

Factory-made devices for amplifying the audio signal are expensive and may not be powerful enough. Looking at the photos of homemade sound amplifiers, it is obvious that they are in no way inferior in appearance to finished products. In addition, their manufacture on their own does not require special skills or large material costs.

Device base

Beginner radio amateurs first of all ask themselves: what can they use to assemble a simple sound amplifier at home? The operation of the device is based on transistors or microcircuits, or a rare option is possible - on lamps. Let's take a closer look at each of them.

Microcircuits

The TDA series microcircuit and a similar one can be purchased in stores or you can use a microcircuit from an unnecessary TV.

Using car amplifier chips with a 12-volt power supply, it is very easy to achieve high-quality sound without the use of special skills and with a minimum of parts.

Transistors

The advantages of transistors are low power consumption. The device produces excellent sound performance, is easily integrated into any equipment and does not require additional configuration. In addition, there is no need to search for and use complex microcircuits.

Lamps

Today, the outdated assembly method based on tubes provides high-quality sound, but has a number of disadvantages:

• increased energy intensity
• dimensions
• cost of components

Recommendations for properly assembling a sound amplifier with your own hands

A device for enhancing sound quality, assembled at home based on TDA series microcircuits and their analogues, generates a lot of heat. For cooling, you need a radiator grille of a suitable size, depending on the model of the microcircuit itself and the power of the amplifier. There must be a place for it in the case.

The advantage of a self-made device is its low energy consumption, which allows it to be used in cars by connecting to a battery, as well as on the road or at home using a battery. Power consumption depends on the required degree of signal amplification. Some manufactured models require a voltage of only 3 Volts.

We take a serious and responsible approach to assembling a sound amplifier in order to avoid short circuits and failure of components.

Necessary materials

During the assembly process you will need the following tools and components:

• chip
• frame
• capacitors
• power unit
• plug
• switch button
• wires
• cooling radiator
• screws
• hot glue and thermal paste
• soldering iron and rosin

Circuits and instructions for making an amplifier at home

Each circuit is unique and depends on the sound source (old or modern digital technology), power supply, and expected final dimensions. It is assembled on a printed circuit board, which will make the device compact and more convenient. During the assembly process, you cannot do without a soldering iron or soldering station.

The British John Linsley-Hood circuit is based on four transistors without microcircuits. It allows you to similarly repeat the shape of the input signal, resulting in only pure gain and a sine wave at the output.

The simplest and most common option for manufacturing a single-channel amplifier is to use a microcircuit based on it, supplemented with resistors and capacitors.

Algorithm of actions for production

• install radio components on the printed circuit board, taking into account the polarity
• assemble the body (providing space for additional parts, for example, a radiator grille)

It is permissible to use a ready-made case or create it yourself, as well as install the board into the speaker case.

• run the device in test mode (identify and eliminate malfunctions if they occur)
• amplifier assembly (connection to the power supply and other components)

Note!

DIY home and car amplifiers

At home, there is often a lack of powerful sound when watching movies on a laptop or listening to music on headphones. Let's look at how to properly make a sound amplifier with your own hands.

For laptop

The sound wave amplifier must take into account the power of external speakers up to 2 watts and the winding resistance up to 4 ohms.

Assembly components:

• 9 volt power supply
• printed circuit board
• chip TDA 7231
• frame
• non-polar capacitor 0.1 µF - 2 pcs.
• polar capacitor 100 µF
• polar capacitor 220 µF
• polar capacitor 470 µF
• constant resistor 10 Kom m 4.7 Ohm
• two-position switch
• input socket

Manufacturing scheme

The assembly algorithm is selected depending on the selected scheme. It is necessary to consider the appropriate size of the cooling radiator so that the operating temperature inside the case does not rise above 50 degrees Celsius. When using a laptop outdoors, you need to provide holes in the case for air access.

For car radio

An amplifier for a car radio can be assembled using the common TDA8569Q microcircuit. Its characteristics:

• supply voltage 6-18 volts
• input power 25 watts per channel into 4 ohms and 40 watts per channel into 2 ohms
• frequency range 20-20000 Hz

Note!

It is imperative to provide, in addition to the circuit, a filter against interference created by the operation of the car.

First, draw a printed circuit board, then drill holes in it. Then the board must be etched with ferric chloride. After tinning and soldering all the parts of the microcircuit. To avoid power additives, a thick layer of solder will need to be applied to the power traces. Provide a cooling system using a cooler or radiator grille.

At the end of the assembly, it is necessary to make a filter against interference from the ignition system and poor noise insulation according to the following scheme: on a ferrite ring with a diameter of 20 mm, wind a choke with a wire with a cross-section of 1-1.5 mm in 5 turns.

Assembling a device to improve sound quality at home is not difficult. The main thing is to decide on the circuit and have on hand all the components from which you can easily assemble a simple sound amplifier.

DIY sound amplifier photo

Note!