Do-it-yourself acoustic protection circuit from voltage. Switch-on delay and speaker protection device. Applied parts and setup

When designing the circuit of my low-frequency amplifier, I included in it a speaker protection unit in advance. Why is this needed and what can harm speaker systems? - firstly, I wanted to get rid of the “click” when power is applied to the amplifier.

When the power is turned on, the rectifier capacitors begin to charge, which at this moment affects the ULF - the speaker systems are briefly exposed to constant voltage. To avoid this hit, you need a simple time relay circuit that will delay the connection of speaker systems by 0.5-1 second.

Secondly, anything can happen to the ULF, for example, one of the transistors in the ULF can burn out from an overload and a constant voltage of a sufficiently large value will be supplied to the speakers, which can burn the low-frequency dynamic head or damage part of the filter of your speakers. To eliminate such incidents, you need a circuit that controls the voltage at the ULF output and, in case of problems, disconnects the speaker systems from the ULF.

Schematic diagram

I looked at many circuits for protecting speakers, I wanted to find a universal option with a minimum of electronic components, of all the circuits one clearly stood out - I found it in the magazine RADIO No. 5 for 1998, author of the publication: Yu. Zalisky (Lvov, Ukraine) .

In addition to fulfilling all the points I mentioned above, it is built using only two transistors and provides reliable speaker protection for two channels of the low-frequency amplifier.

Fig.1. Scheme of the device for switching on delay and protection of acoustic systems (AS).

Description of the scheme and log

The schematic diagram of the switch-on delay and AC protection device is shown in the figure above. It consists of an input low-pass filter R1 R2C1, a time relay on transistor VT1 and elements R1-R4, C1 and a switch on transistor VT2.

When the power is turned on, capacitor C1 begins to charge through resistors R1, R2. During its charging time, transistor VT1 will be open, VT2 will be closed and no current will flow through the relay winding.

Resistor R3 eliminates the influence of the base current of transistor VT1 on the charging of the capacitor and increases the positive threshold of the protection device.

When the capacitor is charged, the voltage at the base of transistor VT1 will drop and it will close, and the key transistor VT2 associated with it will open and current will flow through the winding of relay K1.

The relay will operate, and its closed contacts K1.1 and K1.2 will connect the speakers to the amplifier. The switch-on delay is approximately 4 s.

If a constant voltage of positive polarity appears at any of the amplifier outputs, this will lead to partial discharge of capacitor C1, opening transistor VT1 and closing transistor VT2. As a result, the current through the relay coil will stop and its contacts will disconnect the speakers from the amplifiers.

If a constant voltage of negative polarity appears at the outputs of the latter, then it will go directly through the diode VD1 to the base of the transistor VT2, close it and thus de-energize relay K1, the contacts K1.1, K1.2 of which will open and again disconnect the speakers from the amplifier.

Diodes VD1-VD2 limit the maximum negative voltage at the base of the input transistor VT1 to 1.3 V. Although both in the loudspeaker protection mode and in the loudspeaker delay mode, capacitor C1 is charged through the same circuits, the protection response time is an order of magnitude shorter, since to do this the capacitor must change its potential by only a few volts. The protection thresholds are no more than ±4 V.

A correctly manufactured device starts working immediately and does not require any configuration. Any silicon diodes can be used. It is advisable to use the remaining elements as indicated in the diagram. Relay K1—RES-9, passport RS4.524.200 with a winding resistance of approximately 400 Ohms.

Any other relay that operates at the selected supply voltage is also suitable, but in this case you need to select resistor R4, on which the negative threshold of protection operation depends.

The device is operational when the supply voltage changes within 20...30 V. With a different supply voltage, you will need to change the resistance of resistor R4.

The disadvantage of this device is that it needs to be powered from a source with ripples of no more than 1 V, otherwise false alarms are possible.

Notes on the diagram

Now I’ll add on my own behalf: I confirm that the device really needs a well-stabilized power source, otherwise there will be frequent false positives.

For stabilization, I used a stabilizer circuit with voltage regulation based on the KREN5 (7805) microcircuit - I talked about it in the publication about the power supply for my ULF.

Depending on the supply voltage of the circuit (20...30V), you will have to select a relay with a winding designed for a given operating voltage, the main thing here is reliable operation and so that the coil does not overheat from overvoltage. I found a pack of RES-48 with different passports; after looking through the reference book, I chose those that suited me in terms of voltage.

Thus, when the protection is triggered, transistor VT2 will close and the voltage through the relay and resistor will go to the LED - which will signal the triggering.

Also, when the circuit is turned on, while the time relay is operating, the LED lights up, and then when the protection switches to operating mode, it goes out. The result is a simple indication, which is quite enough to track the protection status.

Details and setup

The resistance of the quenching resistor R5* (quenches the current flowing through the LED) is selected experimentally. To do this, you can use a 2-3 kOhm variable resistor switched on instead of R5.

We set the resistor knob to the position with maximum resistance, supply power to the circuit, and a constant voltage from another power supply to its input so that the circuit operates and the relay is de-energized.

By rotating the variable resistor knob, you need to achieve a fairly bright glow of LED VD4 at the moment when transistor VT2 is closed and power to the LED goes through the winding of relay K1.

Then we unsolder this resistor and measure its resistance, installing a constant resistor with the same resistance in the circuit.

Another option is an approximate calculation using a formula based on Ohm’s law:

R_resistor = (U_power - U_LED) / I_LED.

• R - resistance, in Ohms.
• U - voltage, in Volts,
• I - current, in Amperes.

Let us assume that the power supply to the protection circuit is 22V, and the operating voltage of the LED is 2.5V with a current of 15mA:

R = (22V - 2.5V) / 0.015A = 1300 Ohm.

Since the current through the LED in the circuit will also flow through the relay winding, the glow would be less bright if there were just a conductor instead of a relay, but this is enough to indicate the status. It is important that the current through the LED does not exceed the actuation/release current of the relay.

I designed printed circuit boards the old fashioned way:

Rice. 2. Layout of the printed circuit board with a pencil and arrangement of components.

As a result, I made two copies of this device (2+2 channels), this is what happened:

Fig.3. Ready-made switching delay and speaker protection devices.

Be sure to start setting up the circuit with a low-frequency amplifier (LF) and acoustic systems (AS) connected!

Capacitor C1 is charged through a common wire, the current from which goes through the AC and ULF, and then through resistors R1 and R2.

Without AC and ULF, the circuit will not work as it should. If neither the speaker nor the power amplifier is connected to the circuit, then capacitor C1 will charge for a very long time through the chain: R3 + B-E junction of transistor VT1.

You can test the circuit without speakers and without a bass amplifier. This is done like this:

1. Instead of the AC, we temporarily connect a 200-300 Ohm resistor (with a power of 2-5W)
2. We also install the same 200-300 Ohm resistors to the contacts that connect to the amplifier.
3. We turn on the circuit, after a few seconds the relay should click (capacitor C1 was charged through the resistors that we connected to the input instead of the amplifier).
4. By supplying positive and negative DC voltages of 10-20V from an external power supply to the resistors that are connected instead of the amplifier, you can verify that the protection against DC voltage at the output of the amplifier is working; the relay should turn off the resistors that we connected instead of the speakers.

I placed the scarves in the amplifier case as close as possible to the UMZCH boards and the speaker output terminals (on the rear panel), this is necessary to minimize the length of the connecting conductors from the ULF to the protection and to the terminals for connecting the speakers.

Protection of acoustic systems from constant voltage at the output of an amplifier called “Brig” (copied from an amplifier of the same name produced by Soviet industry) has been familiar to many radio amateurs for many years. Over these many years, this scheme has proven itself to be the best, saving hundreds and thousands of speaker systems. The circuit is reliable and simple.

The scheme I presented below is one of the variations on the theme of the “Brig” defense. The skeleton of the scheme remains the same. The changes affected only the circuit ratings and transistor models.

Circuit specifications:
Supply voltage: +27 ... +65V
Speaker connection delay time: 2 seconds
DC input sensitivity: +/- 1.5V

A wide limit of supply voltages is ensured by the use of a voltage stabilizer in the power circuit on VD5, VD6, R13 and transistor VT5. It is necessary to install a small heat sink on the VT5 transistor. If you significantly increase the heat sink area and replace transistor VT5 with BD139, you can increase the maximum supply voltage to +120V.

A composite transistor is used as a relay driver, which made it possible to eliminate the need for an additional low-power transistor and save some space on the board. Other composite transistors, for example: BD875 or KT972, can be used as a relay driver transistor (VT3 VT4). Before replacing transistors with similar ones, you should check their pinout because it does not match for all the listed transistors.

Transistors VT1 and VT2 can be replaced with BC546-BC548 or KT3102. We also do not forget about the pinout, as in the previous case.

VD3 and VD4 are necessary to avoid interference when switching relay contacts. VD1 and VD2 are necessary to protect VT1 and VT2, respectively, from breakdown of the BE junction when there is a negative voltage of less than -15V at the input of the circuit.

The circuit also provides a delay in connecting the speaker system (AS) by 1-2 seconds. This is necessary so that when the amplifier is turned on, no popping or other unpleasant sounds are heard from the speakers that accompany transient processes in the amplifier. Capacitors C3 and C4 are responsible for the delay time for connecting the speakers. The larger their capacity, the longer the delay time for connecting the acoustics. With the values ​​indicated in the diagram, the delay time is about 2 seconds.

The relay must be used with a control winding of 24V, 15mA and a current not less than the output current of the amplifier. I used a relay - Tianbo HJR-3FF-S-Z.

Photo of the finished device

List of radioelements

Designation	Type	Denomination	Quantity	Note	Shop	My notepad
VT1, VT2	Bipolar transistor	2N5551	2	BC546-BC548 or KT3102		To notepad
VT3, VT4	Bipolar transistor	BDX53	2	BD875 or KT972		To notepad
VT5	Bipolar transistor	BD135	1			To notepad
VD1-VD4	Rectifier diode	1N4148	4			To notepad
VD5	Zener diode	1N4742	1			To notepad
VD6	Zener diode	1N4743A	1			To notepad
C1, C2		47 µF	2			To notepad
C3-C5	Electrolytic capacitor	220 µF	3			To notepad
R1, R5	Resistor	1 kOhm	2			To notepad
R2, R6, R13	Resistor	1.5 kOhm	3			To notepad
R3, R7	Resistor	4.3 kOhm	2			To notepad
R4, R8	Resistor

There are many options for protecting speakers from constant voltage, clicks when turned on and off. The most advanced of them are assembled on microcontrollers, control a large number of channels, and have additional functions, for example, a datagor kit

Devices based on specialized microcircuits are also convenient, functional and small-sized. Unfortunately, they are not always available and may take a long time to arrive by mail.

I became interested in which circuit of discrete elements is simple, cheap, functional and requires minimal configuration. I bring to your attention the scheme that best meets these requirements, in my opinion.
Since the article is intended mainly for beginner radio amateurs, I will try to describe in detail even simple things.

AC protection prototype - A. Kotov’s scheme

At first glance, there is a wide selection of circuits, but upon closer examination it turns out that they have disadvantages - many parts, scarce parts, low sensitivity, the need for adjustment, operation in a narrow range of supply voltages, etc.

It turned out to be the most suitable.

However, this scheme is not without its drawbacks:
- there is no quick turn off of the speakers when the amplifier is turned off,
- strictly defined supply voltage,
- all current consumed flows through the LED,
- operating mode with “torn-off base” VT10.
In addition, there is no voltage diagram or tuning recommendations, nor is there a drawing of the printed circuit board.

Improved speaker protection device circuit

These shortcomings can be easily eliminated; here is the version I modified.

The numbering of parts of A. Kotov’s scheme has been preserved and continued.
I would like to note the advantages and features of the scheme:
- the turn-on delay is optimal 4 seconds, determined by the R5C3 chain,
- circuit D5R8R9C4, when disconnected from the network, allows you to quickly de-energize the relay and turn off the speaker,
- after the protection is triggered (the relay is turned off), capacitor C3 discharges quickly and charges through resistor R5 slowly, so there will be no fast chaotic switchings,
- the device operates in a wide range of voltages, from relay response voltage (plus 2 V) to 36 V (limit for TL431),
- practically the only resistor that requires selection - R7 serves to absorb the excess voltage for the relay, the values ​​of the remaining resistors can differ several times and do not require replacement in a wide range of supply voltages,
- all elements, except TL431, operate at very low currents, which ensures high reliability,
- the use of TL431 ensures the key operating mode of the relay,
- the voltages on the capacitors except C4 are very small, no more than 2.5 V, which allows the use of capacitors for low voltages, so I tested the option with single polar capacitors C1 and C2 for low voltage,
- any LED is suitable (preferably bright) since the current through it is set by a resistor,
- the sensitivity is very high (about 1 V), it is better to coarse it; for this purpose, the board has pads for SMD resistors (in gray in the diagram).

Own power supply

If you power the ultrasound from the main power supply of the amplifier (like A. Kotov), ​​when you turn off the network, the relay will not release immediately due to the large capacities of the power supply and a click, crackle, etc. is possible. Here, due to the very small capacity, C4 = 1 -4.7 µF the relay releases immediately.

You can take a variable from the transformer of the main ULF power supply, then you may have to change the divider R8R9 to reduce the voltage.

For the “versatility” of this circuit, you need a power supply with a low-power transformer with a low voltage of the secondary winding. I used a ~230/12 V transformer with a power of 2 VA. The power supply is made on a board of the same width as the protection unit; it is convenient to place them on one board.

The presence of a separate power supply allows you to use the protection unit with any amplifier, including a prototype one, which is especially convenient since the speakers are exposed to increased danger in this case.

Applied parts and setup

A 12VDC relay “OMRON G2R-2” is installed in a transparent case. This was not done by chance - although it has larger dimensions than similar ones in a non-separable opaque case, it can be opened and the contacts can be cleaned. I recommend that when using a non-separable relay, carefully cut its body in advance so that the cover can be removed and replaced. I especially recommend it in the case of a used relay.

Sealed relays are typically smaller in size and can be easily installed with minimal modification to the circuit board. Since I placed the relays and clamps with screw terminals quite tightly, when repeating the board, you need to make sure that the sizes of the clamps are identical, otherwise slightly adjust the printed circuit board. You can do without clamps; it’s even more reliable, but it’s inconvenient, especially when setting up amplifier layouts.

If there are no installation errors and serviceable parts, the circuit starts working immediately, you just need to calculate the current limiting resistor through the relay winding.
For example, +18 V power supply, 12 V relay with a resistance of 280 Ohms. Relay operating current 12 V/280 Ohm = 43 mA.
It is necessary to extinguish 18V - 12V - 2V (voltage drop across an open TL431) = 4 Volts.
4 V / 43 mA = 100 ohms. The resistor power is 43 mA x 4 V = 170 mW, i.e. you need a resistor of 0.25 W and higher. This resistor is “standing” on the board; this is done so that you can install resistors of different sizes and with a power reserve of up to 2 W.

All diodes, except for the relay shunting the winding, are almost any low-power ones, you just need to remember that the stripe marking on the body of the KD522 and other Soviet diodes is the opposite of the imported marking.

If there are problems with operation, first of all you need to check the correct installation of parts, especially diodes, transistors and TL431. Then check the quality of the soldering (my diode leads were poorly soldered), to do this you need to rinse the board thoroughly and inspect the soldering with a magnifying glass (or a good eye).
Then check the DC modes; the voltages at the bases of the transistors must correspond to those indicated in the diagram ± 0.1 V.

Since among novice amateurs there is a passion for gigantomania and amplifiers with a power of hundreds of watts and with a supply voltage of the amplifiers of the order of ± 50 V, we must remember that the greater the power of the amplifier, the greater the currents flow through the relay contacts; at high voltages, the likelihood of an arc between open circuits increases. relay contacts.

In this case, any relay with one group of contacts can be installed on this board; this relay will be intermediate and control another, more powerful relay with contacts designed for a higher current and with an increased distance between open contacts. It will be possible to connect wires of a larger cross-section to this powerful relay.

The versatility of this protection unit with its own power supply lies in the fact that it can be connected to the outputs of a bridge (usually high-power) amplifier. The common wire is connected not to the common wire of the amplifier, but to one output of the amplifier, and one input of the protection unit to the second output of the bridge amplifier.

When installing a protection unit in a finished structure, there is no need for a separate power supply (for a regular, non-bridge amplifier).

Total

I made two copies - with regular resistors and SMD, the board allows you to do this. The impressions from the devices are very good. The length of the board can be reduced by 1...2 cm, especially with SMD resistors, but I prefer wide traces that allow parts to be soldered repeatedly and are forgiving of displacement when drilling holes; sufficient gaps between tracks.

We must not forget that such a device protects only the LF heads from constant voltages and all heads from transient processes in the amplifier, including when the amplifiers fail, and does not protect the HF heads during overloads and excitation of the amplifiers. At the same time, this circuit solution allows you to connect overheating, limitation (clipping), and excitation sensors for the safety of all speaker heads.

In addition (which is used in a number of amplifiers), you can control the connection to the amplifier output of one or more pairs of speakers using a switch on the front panel of the amplifier, without the need to pass high-current signal circuits through this switch.

We checked its performance and assessed the sound quality of the main channel. It's time to add a protection module against accidental short circuits to it so that all the work does not go to waste due to inevitable accidents during its operation. We will also assemble the remaining low-power ULF channels to connect the rear speakers.

UMZCH AS PROTECTION

Initially I thought of using a protection circuit against BRIG , but then reading reviews about triac protection I wanted to try it. The protection blocks were made at the very end, finances were tight then, and triacs and other circuit components turned out to be quite expensive, so we returned to relay protection. I remind you that all diagrams are for review.

As a result, three protection blocks were assembled, one of them for the subwoofer amplifier, and the other two for the OM channels.

You can find a large number of protection block diagrams on the Internet, but I have tried this scheme several times. If there is a constant voltage at the output (above the permissible level), the protection is instantly triggered, saving the dynamic head. After power is applied, the relay closes, and when the circuit is triggered, it should open. The protection turns on the head with a slight delay - this, in turn, is also an additional insurance and the click after turning on is almost inaudible.

The components of the protection unit may deviate from the specified ones, the main transistor can be replaced with ours KT815G, used high voltage transistors MJE13003- I have a lot of them, in addition, they are quite powerful and do not overheat during operation, so they do not need a heat sink. Low-power transistors can be replaced with S9014, 9018, 9012, even on KT315, the best option is 2N5551.

A 7-10 Ampere relay, you can choose any 12 or 24 Volt relay, in my case 12 Volt.

Protection blocks for the OM channels are installed near the transformer of the second inverter, this whole thing works quite clearly, at maximum volume the protection can work (falsely) extremely rarely.

LOW POWER AMPLIFIERS

I spent a long time deciding which amplifier to use for low-power speaker systems. At first I decided to use microcircuits as a cheap option TDA2030, then I thought that 18 watts per channel was not enough and moved on to TDA2050- a more powerful analogue at 32 watts. Then, after comparing the sound of the main options, the choice fell on my favorite microcircuit - LM1875, 24 watts and sound quality is 2-3 orders of magnitude better than the first two microcircuits.

I scoured the net for a long time, but I still couldn’t find a printed circuit board that suited my needs. Sitting at the computer for several hours, we created our own version for a five-channel amplifier on microcircuits LM1875, the board turned out to be quite compact; the board also has a block of rectifiers and filters. This unit was completely assembled in 2 hours - all components were available by that time.

AMPLIFIER VIDEO

The sound quality of these microcircuits is at a very high level, in the end Hi-Fi, the output power is decent - 24 watts sinus, but in my case the power is increased by increasing the supply voltage to 24 volts, in which case you can get about 30 watts of output power. On the main amplifier board I had space for a 4-channel amplifier on TDA2030, but for some reason I didn’t like it...

The board for LM is attached to the main ULF board through racks in the form of tubes and bolts. The power for this unit is taken from the second inverter; a separate winding is provided. The rectifier and filter capacitors are located directly on the amplifier board. Already traditional rectifier diodes KD213A.

I did not use chokes to smooth out RF interference, and there is no need to use them, since even fairly branded car amplifiers often do not install them. As a heat sink I used a set of duralumin blanks 200x40x10 mm.

A cooler is also attached to the board, which simultaneously removes warm air from this unit and blows away the heat sinks of the inverters. We've completely figured out the electronics of the audio complex - let's move on to Yours sincerely - AKA KASYAN.

Discuss the article HOME AMPLIFIER - ULF AND PROTECTION UNIT

Don't dream, act!

Direct coupled audio power amplifiers pose a hazard to loudspeaker systems. Almost all failures of internal amplifier components result in a significant (according to Murphy's laws, up to the supply voltage) offset at the output. As a result, expensive speaker systems can fail, and it would be reckless not to equip the amplifier with a protection circuit that turns off the load when a constant potential appears at the amplifier output. The protection should be triggered when the constant potential at the amplifier output is exceeded ±1.5 V, or low-frequency oscillations with a frequency below 2...3 Hz appear.
Practice shows that it is necessary to use simple and reliable protection circuits for acoustic systems based on electromagnetic relays.

Scheme for protecting the acoustic systems of the amplifier "Brig-001"

In Fig. Figure 1 shows a time-tested scheme for protecting speaker systems from constant bias of the Brig-001 amplifier. The input of the protection circuit is connected to the output of the power amplifier, and the output of the amplifier is connected to the normally open contacts of relay K1. After supplying power to the protection circuit, after some time determined by the time constant R6, C2, the composite pair of transistors VT2, VT3 open, relay K1 is activated, and with its contacts connects the amplifier output to the speaker systems. The turn-on delay allows you to eliminate transient processes in the amplifier at the moment of switching on, perceived as unpleasant pops that are destructive to speaker systems.

Rice. 1. Protection circuit for the acoustic systems of the “Brig-001” amplifier

When any of the channels of direct voltage of positive polarity appears at the output of the amplifier, transistor VT1 opens, which shunts the base circuit of the composite transistor to a common wire. In this case, the current through relay K1 decreases so much that it releases the contacts and disconnects the speakers from the amplifier. Capacitor C1 prevents relay K1 from operating from the alternating voltage of the output signal.
If a voltage of negative polarity appears at the output of the amplifier, it will flow through the divider R6, R7 to the base of the composite transistor, as a result of which relay K1 will release and disconnect the load from the amplifier.

The case where bipolar voltages of equal magnitude appear at the amplifier outputs is taken into account by choosing different values ​​for resistors R1 and R2.
Thus, the speaker system is protected from direct voltage of any polarity at the amplifier output.

A similar speaker protection scheme worked in one of my amplifiers for more than two decades, and never failed, although the amplifier worked at entertainment events for about half of that period.

The proposed device can be used both for this project and for independent construction of audio frequency amplifiers.

Advantages:
simplicity and reliability;
almost complete absence of false positives;
versatility of application.

Flaws:
There is no circuit to turn off the speakers when the power goes out.
This drawback was introduced for the sake of the simplicity and reliability of the device.

The protection circuit contains second-order passive infrasound low-pass filters (C3, C5, R10, R12 and C4, C6, R11, R13, respectively) and emergency DC voltage sensors at the amplifier output (VT2, VT4, VT6 and VT3, VT5, VT7) . When a voltage of any polarity is more than 1.5 V, the corresponding key opens (VT2 or VT3 for the positive polarity of the direct voltage and VT4, VT6 or VT5, VT7 for the negative). In the event of an accident, the base of the composite transistor VT8, which controls the series-connected electromagnetic relays K1 and K2, is reliably connected to the common wire through a low-resistance anti-ringing resistor R5, opening the connection of the speaker outputs through the relay contacts.

The integrating circuit R1, C2 in the base circuit of transistor VT1 provides a delay in connecting the speakers when the power is turned on (for a time of 1.8 s), thereby preventing interference caused by transient processes in the amplifier from entering the speaker system.
The protection circuit is universal and can be used with other UMZCH. In the table located in the upper right corner of the diagram in Fig. 5 shows the ratings of R6, R7, which must be changed in accordance with the supply voltage Up of the amplifier.

Specifications:
Supply voltage, V= +25...45
Turn-on delay time, s= 1,8
Protection threshold, V= more than ±1.5
Output current for powering the relay, mA= up to 100
PCB dimensions, mm= 75x75

Details of the modernized speaker protection device circuit.

VT1…VT3, VT6, VT7 – Transistor BC546B (TO-92) – 5 pcs.,
VT4, VT5 – Transistor BC556B – 2 pcs.,
VT8 – Transistor KT972A – 1 pc.,
VD1 - Zener diode KS212Zh (BZX55C12, 12V/0.5W, DO-35 housing) – 1 pc.,
VD2 - Diode 1N4004 – 1 pc.,
K1, K2 - Electromechanical relay (1C, 12VDC, 30mA, 400R) BS-115C-12A-12VDC – 2 pcs.,
R1 - Res.-0.25-220 kOhm (red, red, yellow, golden) – 1 pc.,
R2 - Res.-0.25-1 m (brown, black, green, golden) – 1 pc.,
R3, R4 - Res.-0.25-11 kOhm (brown, brown, orange, golden) – 2 pcs.,
R5 - Res.-0.25-10 Ohm (brown, black, black, gold) – 1 pc.,
R6 - Res.-0.25-2.2 kOhm (red, red, red, golden) – 1 pc.,
R7 – Jumper,
R8…R11 - Res.-0.25-22 kOhm (red, red, orange, golden) – 4 pcs.,
R12, R13 - Res.-1-22 kOhm (red, red, orange, golden) – 2 pcs.,
C1, C2 - Cond. 47/25V 0511 +105 °C – 2 pcs.,
C3 – C6 - Cond.47/50V 1021 NPL (47/25V 1012 NPL) – 4 pcs.,
Terminal block 2k pitch 5mm per board TB-01A – 5 pcs.

After completing the assembly, do not rush to turn on the device, but check the installation in accordance with the diagram (Fig. 6). In this case, pay special attention to the absence of jumpers between current-carrying tracks, cold soldering (insufficient soldering of the contact of the element with the printed circuit board). If there are any, remove them with a soldering iron. Check the correct installation of polar electrolytic capacitors, transistors, diode and zener diode.
The appearance of the speaker protection device assembled by nephew Alexey is shown in the abstract of the article. I have an intermediate version of the protection device with the RES22 relay working.
To cut and remove insulation from wires (cables), it is better to use a special tool (Fig. 9).

Rice. 9. Pliers for stripping wires and crimping lugs - an assistant when installing an amplifier

Let's turn it on!

The first turn on is always indicative. I turn on the amplifier, I hear the click of the triggered relays of the protection device, then silence. Although I “drove” all the nodes separately, I once again measure the supply voltages and zeros at the outputs: everything is in order.
I get distracted by business and only half an hour later I start listening. The amplifier sounds good, delivering about 20 W to a 6 Ohm load.
It operates cleanly and transparently, delivering a listening pleasure. However, we should not forget that the amplifier is not an entry-level system (the best of the simple) and there is room for growth and development.

Let me remind you once again that you can use and instead; in this case, the supply voltage of the bipolar source should be ±22 V for, ±16 V for, and ±12 V for TDA2006.

I strongly advise everyone to repeat this project in order to gain experience and build a good amplifier for a radio complex. It is no coincidence that I chose the slogan “Don’t dream, act!” as the motto of the project. .