Electrical circuit diagram of the Lanzar amplifier. Setting up a Lanzar power amplifier - circuit diagram of a power amplifier, description of the circuit diagram, recommendations for assembly and adjustment. Some possible replacements

Amplifier Lanzar. The repetition of the same questions on every page of discussion about this amplifier prompted me to write this short sketch. Everything written below is my idea of ​​what a novice radio amateur needs to know who decides to make this amplifier, and does not claim to be the absolute truth.

Let's say you are looking for a good transistor amplifier circuit. Schemes such as “UM Zueva”, “VP”, “Natalie”, and others seem complicated to you, or you have little experience to assemble them, but good sound I want to. Then you have found what you were looking for! Amplifier Lanzar It is an amplifier built according to a classic symmetrical circuit, with an output stage operating in class AB, and has a pretty good sound, without complicated settings and scarce components.

Amplifier circuit:

I found it necessary to make some minor changes to the original circuit: the gain was slightly increased - up to 28 times (R14 was changed), the values ​​of the input filter R1, R2 were changed, and also, on the advice of MayBe I'm a Leo, the resistor values ​​of the base divider of the thermal stabilization transistor (R15 , R15') for smoother adjustment of the quiescent current. The changes are not critical. The numbering of elements has been preserved.

Amplifier power

Amplifier power supply- the most expensive link in it, so you should start with it. Below are a few words about IP.

Based on the load resistance and the desired output power, the desired supply voltage is selected (Table 1). This table was taken from the original source site, however, I personally would strongly not recommend operating this amplifier at powers of more than 200-220 Watts.

REMEMBER! This is not a computer, no super-cooling is needed, the design should not work at the limit of its capabilities, then you will get a reliable amplifier that will work for many years and delight you with sound. We decided to make a high-quality device, and not a bouquet of New Year’s fireworks, so let all sorts of “squeezers” go through the forest.

For supply voltages below ±45 V/8 Ohm and ±35 V/4 Ohm, the second pair of output transistors (VT12, VT13) can be omitted! At such supply voltages, the Lanzar amplifier receives an output power of about 100 W, which is more than enough for a home. I note that if you install 2 pairs at such voltages, the output power will increase by a very insignificant amount, on the order of 3-5 W. But if “the toad is not strangling,” then in order to increase reliability, you can install 2 pairs.

Transformer power can be calculated using the PowerSup program. A calculation based on the fact that the approximate efficiency of the amplifier is 50-55%, which means that the power of the transformer is equal to: Ptrans = (Pout * N channels * 100%) / efficiency is applicable only if you want to listen to a sine wave for a long time. In a real music signal, unlike a sine wave, the ratio of peak to average values ​​is much smaller, so there is no point in spending money on extra transformer power that will never be used anyway.

In the calculation, I recommend choosing the “heaviest” peak factor (8 dB), so that your power supply does not bend if you suddenly decide to listen to music with such a p-f. By the way, I also recommend calculating the output power and supply voltage using this program. For the Lanzar dU amplifier, you can choose about 4-7 V.

More details about the “PowerSup” program and the calculation method are written on the author’s website (AudioKiller).

All this is especially true if you decide to buy a new transformer. If you already have it in your bins, and suddenly it turns out to have more power than the calculated one, then you can safely use it, a reserve is a good thing, but there is no need for fanaticism. If you decide to make a transformer yourself, then on this page of Sergei Komarov there is a normal calculation method.

The circuit itself of the simplest bipolar power supply looks like this:

The circuit itself and the details for its construction are well described by Mikhail (D-Evil) in TDA7294.
I will not repeat myself, I will only note an amendment about the power of the transformer, described above, and about the diode bridge: since the Lanzar amplifier can have a supply voltage higher than the TDA729x, the bridge must “hold” a correspondingly higher reverse voltage, no less:

Urev_min = 1.2*(1.4*2*Uhalf-winding_of the transformer) ,

where 1.2 is the safety factor (20%)

And with large transformer powers and capacitances in the filter, in order to protect the transformer and bridge from colossal inrush currents, the so-called. “soft start” or “soft start” scheme.

Amplifier parts

A list of parts for one channel is attached in the archive in the file

Some denominations require special explanation:

C1– separation capacitor, Lanzar amplifier must be of good quality. There are different opinions on the types of capacitors used as isolation capacitors, so those experienced will be able to choose the best one for themselves. the best option thereof. For the rest, I recommend using polypropylene film capacitors from well-known brands such as Rifa PHE426, etc., but in the absence of such, widely available lavsan K73-17 are quite suitable.

The lower limit frequency, which will be amplified, also depends on the capacitance of this capacitor.

In the printed circuit board, as C1, there is a seat for a non-polar capacitor, composed of two electrolytes, connected with “minuses” to each other and “pluses” in the circuit and shunted by a 1 μF film capacitor:

Personally, I would throw out the electrolytes and leave one film capacitor of the above types, with a capacity of 1.5-3.3 μF - this capacity is enough to operate the amplifier at “wideband”. In the case of working with a subwoofer, a larger capacity is required. Here it would be possible to add electrolytes with capacities of 22-50 μF x 25 V. However, the printed circuit board imposes its own limitations, and a 2.2-3.3 μF film capacitor is unlikely to fit there. Therefore, we set 2x22 uF 25 V + 1 uF.

R3, R6– ballast. Although initially these resistors were chosen to be 2.7 kOhm, I would recalculate them to the required supply voltage of the amplifier using the formula:

R=(Ushoulder – 15V)/Ist (kOhm) ,

where Ist – stabilization current, mA (about 8-10 mA)

L1– 10 turns of 0.8 mm wire on a 12 mm mandrel, everything is lubricated with superglue, and after drying, resistor R31 is placed inside.

Electrolytic capacitors C8, C11, C16, C17 must be designed for a voltage no lower than the supply voltage with a margin of 15-20%, for example, at ±35 V capacitors of 50 V are suitable, and at ±50 V you need to choose 63 Volts . The voltages of other electrolytic capacitors are indicated in the diagram.

Film capacitors (non-polar) are usually not made rated for less than 63 V, so this should not be a problem.

Trimmer resistor R15 – multi-turn, type 3296.

For emitter resistors R26, R27, R29 and R30 – the board provides seats for wire-wound ceramic SQP resistors with a power of 5 W. The range of acceptable values ​​is 0.22-0.33 Ohm. Although SQP is far from the best option, it is affordable.

The Lanzar amplifier also requires the installation of domestic resistors C5-16. I haven't tried it, but they might even be better than SQP.

The remaining resistors are C1-4 (carbon) or C2-23 (MLT) (metal film). All except those indicated separately - at 0.25 W.

Some possible replacements:

Paired transistors are replaced with other pairs. Composing a pair of transistors from two different pairs is unacceptable.

VT5/VT6 can be replaced with 2SB649/2SD669. It should be noted that the pinout of these transistors is mirrored relative to the 2SA1837/2SC4793, and when using them, they must be rotated 180 degrees relative to those drawn on the board.

VT8/VT9– on 2SC5171/2SA1930

VT7– on BD135, BD137

Transistors of differential stages (VT1 and VT3), (VT2 and VT4) It is advisable to select pairs with the smallest beta spread (hFE) using a tester. An accuracy of 10-15% is quite enough. With a strong scatter, a slightly increased level of direct voltage at the output is possible. The process is described by Mikhail (D-Evil) in the FAK on the VP amplifier

Another illustration of the beta measurement process:

Transistors 2SC5200/2SA1943 are the most expensive components in this circuit and are often counterfeited. Similar to the real 2SC5200/2SA1943 from Toshiba, they have two break marks on top and look like this:

It is advisable to take identical output transistors from the same batch (in Figure 512 is the batch number, i.e., say both 2SC5200 with number 512), then the quiescent current when installing two pairs will be distributed more evenly across each pair.

Printed circuit board

The corrections on my part were mainly of a cosmetic nature; some errors in the signed values ​​were also corrected, such as mixed up resistors for the thermal stabilization transistor and other little things. The board is drawn from the parts side. There is no need to mirror to make LUTs!

IMPORTANT! Before soldering, each part must be checked for serviceability, the resistance of the resistors is measured to avoid errors in the nominal value, the transistors are checked with a continuity tester, and so on. Look for similar errors later on assembled board much more complicated, so it’s better to take your time and check everything. Save a LOT of time and nerves.

IMPORTANT! Before soldering in the tuning resistor R15, it must be “unscrewed” so that its full resistance is soldered into the gap in the track, i.e., if you look at the picture above, between the right and middle terminals. all the resistance of the trimmer.

Jumpers to avoid accidental short circuit. It is better to do it with insulated wires.

Transistors VT7-VT13 are installed on a common radiator through insulating gaskets - mica with thermal paste (for example, KPT-8) or Nomakon. Mica is more preferable. VT8, VT9 indicated in the diagram are in an insulated housing, so their flanges can simply be lubricated with thermal paste. After installation on the radiator, the tester checks the transistor collectors (middle legs) for the absence of short circuits. with radiator.

Transistors VT5, VT6 also need to be installed on small radiators - for example, 2 flat plates measuring about 7x3 cm, in general, install whatever you find in the bins, just don’t forget to coat it with thermal paste.

For better thermal contact, the transistors of the differential stages (VT1 and VT3), (VT2 and VT4) can also be lubricated with thermal paste and pressed against each other with heat shrink.

First launch and setup

Once again, we carefully check everything, if everything looks normal, there are no errors, “snot”, short circuits to the radiator, etc., then you can proceed to the first start.

IMPORTANT! The first startup and setup of any amplifier must be carried out with input shorted to ground, power supply current limited and no load . Then the chance of burning something is greatly reduced. The simplest solution that I use is incandescent lamp 60-150 W connected in series with the primary winding of the transformer:

We run the amplifier through the lamp, measure the DC voltage at the output: normal values ​​are no more than ±(50-70) mV. “Walking” constant within ±10 mV is considered normal. We control the presence of voltages of 15 V on both zener diodes. If everything is normal, nothing exploded or burned, then we proceed to the setup.

When starting a working amplifier with a quiescent current = 0, the lamp should flash briefly (due to the current when charging the capacitors in the power supply), and then go out. If the lamp is bright, it means something is faulty, turn it off and look for the error.

As already mentioned, the amplifier is easy to configure: you only need to set the quiescent current (TC) of the output transistors.

It should be set on a “warm up” amplifier, i.e. Before installation, let it play for a while, 15-20 minutes. During installation of the TP, the input must be short-circuited to ground and the output suspended in the air.

The quiescent current can be found by measuring the voltage drop across a pair of emitter resistors, for example on R26 and R27 (set the multimeter to the limit of 200 mV, probes on the emitters VT10 and VT11):

Respectively, Ipok = Uv/(R26+R26) .

Next, SMOOTHLY, without jerking, turn the trimmer and look at the multimeter readings. It is required to set 70-100 mA. For the resistor values ​​shown in the figure, this is equivalent to a multimeter reading (30-44) mV.

The light bulb may begin to glow a little. Let's check the DC voltage level at the output again, if everything is normal, you can connect the speakers and listen.

Other useful information and possible troubleshooting options

Self-excitation of the amplifier: Indirectly determined by the heating of the resistor in the Zobel circuit - R28. Reliably determined using an oscilloscope. To eliminate this, try increasing the ratings of correction capacitors C9 and C10.

High level of DC component at the output: select transistors of the differential stages (VT1 and VT3), (VT2 and VT4) according to “Betta”. If it doesn’t help, or there is no way to choose more precisely, then you can try changing the value of one of the resistors R4 and R5. But this solution is not the best; it is still better to choose transistors.

Option to slightly increase sensitivity: You can increase the sensitivity of the amplifier (gain) by increasing the value of resistor R14. Coef. gain can be calculated by the formula:

Ku = 1+R14/R11, (once)

But you shouldn’t get too carried away, since with an increase in R14, the depth of the feedback decreases and the unevenness of the frequency response and SOI increases. It is better to measure the output voltage level of the source at full volume (amplitude) and calculate what Ku is needed to operate the amplifier with the full output voltage swing, taking it with a margin of 3 dB (before clipping).

For specifics, let the maximum to which it is tolerable to raise Ku is 40-50. If you need more, then make a preamplifier.

Download: Printed circuit board
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Assembly of the LANZAR power amplifier

Another summer project. This time I wanted to create a super-powerful amplification system for a car. I had a few hundred dollars at my disposal, so I could buy new components rather than rummaging through the trash for every resistor like I did last time.

So, the new amplifier had to operate from 12 Volts, I decided to assemble a complex of Hi-Fi amplifiers. The first to be completed was the Laznar subwoofer amplifier, which we will talk about today.

The lanzar layout is completely linear - from input to output. The maximum power of the circuit according to the application is 390 watts and the circuit can easily develop the specified power.

Like any powerful amplifier, Lanzar is also powered from a bipolar source. The upper peak of the supply voltage is ±70 V, the lower ±30 V, although it may be less, but if you are going to power the amplifier from ±30 V, I advise you not to do this, since the Lanzar itself is a powerful and high-quality amplifier and with such power supply the operation of individual circuit nodes.

The limiting resistors of the differential stages are selected based on the nominal supply voltage, the selection of the nominal is given below (the power of the resistors is 1 watt, thanks to det for the plate).	Power supply ±70 V
3.3 kOhm…3.9 kOhm	Power supply ±60 V
2.7 kOhm…3.3 kOhm	Power supply ±50 V
2.2 kOhm…2.7 kOhm	Power supply ±40 V
1.5 kOhm…2.2 kOhm	Power supply ±30 V

1.0 kOhm…1.5 kOhm

Amplifier lanzar printed circuit board.lay

Zener diodes are designed to stabilize the supply voltage of differential cascades. You should use 15 Volt zener diodes with a power of 1-1.3 watts.

It is advisable to use transistors that are used in the circuit, although I had to use analogues.

Coil - wound with 0.8 mm wire on a drill with a diameter of 10 mm. The coil turns are glued together with superglue for reliability.

The emitter resistors of the output transistors are selected with a power of 5 watts; during operation they can overheat. The value of these resistors can be selected in the region of 0.22-0.30 Ohms.

3.9 Ohm resistors are selected with a power of 2 watts.

The amplifier operates in class AB, therefore, to cool the transistors of the output stage, a serious heat sink is needed; in my case, a radiator from the domestic radio engineering amplifier U-101 was used.

It is better to take a multi-turn tuning resistor 1 kOhm; it is used to adjust the quiescent current of the output stage; a multi-turn resistor allows you to make very precise adjustments.

All output stage transistors are secured to the heat sink through insulating plates and washers. Before starting, carefully check for short circuits of the transistor terminals to the heat sink.

All film capacitors are 63 volts or more; there should be no problems with them, since almost all film capacitors are made for the specified voltage. Capacitors can be replaced with ceramic ones, but this may affect the sound quality of the amplifier.

The power table and main parameters of the amplifier are presented below.

PARAMETER	PER LOAD
	8 ohm	4 Ohm	2 Ohm (4 ohm bridge)
Maximum supply voltage, ± V	65	60	40
Maximum output power, W at distortion up to 1% and supply voltage:
±30 V	40	85	170
±35 V	60	120	240
±40 V	80	160	320
±45 V	105	210	DO NOT TURN ON!!!
±50 V	135	270	DO NOT TURN ON!!!
±55 V	160	320	DO NOT TURN ON!!!
±60 V	200	390	DO NOT TURN ON!!!
±65 V	240	DO NOT TURN ON!!!	DO NOT TURN ON!!!
Gain coefficient, dB		24
Non-linear distortion at 2/3 of maximum power, %		0,04
Output signal slew rate, not less than V/µS		50
Input impedance, kOhm		22
Signal-to-noise ratio, not less, dB		90

It is not recommended to increase the supply voltage rating more than ±60 V, but since I am a fan of force majeure situations, I applied ±75 Volt to the circuit, removing about 400 watts, although everything on the board began to heat up, I don’t think it’s worth repeating my experience, perhaps I was just lucky (I replaced the diff cascade resistors with 4kOhm ones).

Below is a list of components for assembling a Lanzar amplifier with your own hands.

• C3,C2 = 2 x 22µ0
• C4 = 1 x 470p
• C6,C7 = 2 x 470µ0 x 25V
• C5,C8 = 2 x 0µ33C11,C9 = 2 x 47µ0
• C12,C13,C18 = 3 x 47p
• C15,C17,C1,C10 = 4 x 1µ0
• C21 = 1 x 0µ15
• C19,C20 = 2 x 470µ0 x 100V
• C14,C16 = 2 x 220µ0 x 100V

• L1 = 1 x

• R1 = 1 x 27k
• R2,R16 = 2 x 100
• R8,R11,R9,R12 = 4 x 33
• R7,R10 = 2 x 820
• R5,R6 = 2 x 6k8
• R3,R4 = 2 x 2k2
• R14,R17 = 2 x 10
• R15 = 1 x 3k3
• R26,R23 = 2 x 0R33
• R25 = 1 x 10k
• R28,R29 = 2 x 3R9
• R27,R24 = 2 x 0.33
• R18 = 1 x 47
• R19,R20,R22
• R21 = 4 x 2R2
• R13 = 1 x 470

• VD1,VD2 = 2 x 15V
• VD3,VD4 = 2 x 1N4007

• VT2,VT4 = 2 x 2N5401
• VT3,VT1 = 2 x 2N5551
• VT5 = 1 x KSE350
• VT6 = 1 x KSE340
• VT7 = 1 x BD135
• VT8 = 1 x 2SC5171
• VT9 = 1 x 2SA1930
• VT10,VT12 = 2 x 2SC5200
• VT11,VT13 = 2 x 2SA1943

• X1 = 1 x 3k3

First startup and setup

The first start-up of the amplifier should be done with the INPUT SHORTED TO GROUND, this is less likely to burn something if the amplifier is assembled incorrectly or there is a problem with the operation of the components. CHECK INSTALLATION CAREFULLY before starting. Observe the polarity of the power supply, the pinout of the transistors and the correct connection of the zener diodes; if they are turned on incorrectly, the latter will act as a semiconductor diode.

power unit- to begin with, you can use a low-power power supply of 1000 watts. It is advisable to supply power in the region of bipolar 40 Volts. When using network transformers, it is recommended to use a capacitor bank with a capacity of 15,000 µF per arm, or better yet, up to 30,000 µF. When using switching power supplies, 5000uF will be sufficient.

In my case, the amplifier must be powered by a pulse voltage converter, so I used a block of 5 capacitors with a capacity of 1000 μF (each), i.e. There is a working capacitance of 5000 μF in the shoulder.

When using a mains transformer, the secondary winding is connected to the mains through a series-connected incandescent lamp; this is also an additional precaution.

We start the amplifier, if there are no explosions or smoke effects, then we leave the amplifier on for 10-15 seconds, then turn it off and check the heat dissipation on the output stage transistors by touch; if no heat is felt, then everything is OK. Next, disconnect the output wire from the ground and turn on the amplifier (we connect acoustics to the amplifier output in advance). We touch the input of the amplifier with our finger, the acoustics should roar, if everything is so, then the amplifier is working.

Next, you can attach a heat sink to the outputs and turn on the amplifier while listening to music. In general, amplifiers of this type require a preamplifier when applying low-power signals to the input (for example, from a PC, player or mobile phone) the amplifier will not sound particularly loud, since the input signal rating is clearly not enough for maximum power. During the experiments, I gave a signal from the music center, and I advise you to do the same.

The Lanzar power amplifier has two basic schemes- the first is entirely based on bipolar transistors (Fig. 1), the second using field ones in the penultimate cascade (Fig. 2). Figure 3 shows a circuit of the same amplifier, but executed in the MS-8 simulator. The position numbers of the elements are almost the same, so you can look at any of the diagrams.

Figure 1 LANZAR power amplifier circuit entirely based on bipolar transistors.
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Figure 2 Circuit of the LANZAR power amplifier using field-effect transistors in the penultimate stage.
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Figure 3 Circuit of the LANZAR power amplifier from the MS-8 simulator. INCREASE

LIST OF ELEMENTS INSTALLED IN THE LANZAR AMPLIFIER
FOR BIPOLAR OPTION	FOR THE OPTION WITH FIELDS
C3,C2 = 2 x 22µ0 C4 = 1 x 470p C6,C7 = 2 x 470µ0 x 25V C5,C8 = 2 x 0µ33 C11,C9 = 2 x 47µ0 C12,C13,C18 = 3 x 47p C15,C17,C1,C10 = 4 x 1µ0 C21 = 1 x 0µ15 C19,C20 = 2 x 470µ0 x 100V C14,C16 = 2 x 220µ0 x 100V R1 = 1 x 27k R2,R16 = 2 x 100 R8,R11,R9,R12 = 4 x 33 R7,R10 = 2 x 820 R5,R6 = 2 x 6k8 R3,R4 = 2 x 2k2 R14,R17 = 2 x 10 R15 = 1 x 3k3 R26,R23 = 2 x 0R33 R25 = 1 x 10k R28,R29 = 2 x 3R9 R27,R24 = 2 x 0.33 R18 = 1 x 47 R19,R20,R22 R21 = 4 x 2R2 R13 = 1 x 470 VD1,VD2 = 2 x 15V VD3,VD4 = 2 x 1N4007 VT2,VT4 = 2 x 2N5401 VT3,VT1 = 2 x 2N5551 VT5 = 1 x KSE350 VT6 = 1 x KSE340 VT7 = 1 x BD135 VT8 = 1 x 2SC5171 VT9 = 1 x 2SA1930 VT10,VT12 = 2 x 2SC5200 VT11,VT13 = 2 x 2SA1943	C3,C2 = 2 x 22µ0 C4 = 1 x 470p C6,C7 = 2 x 470µ0 x 25V C5,C8 = 2 x 0µ33 C11,C10 = 2 x 47µ0 C12,C13,C18 = 3 x 47p C15,C17,C1,C9 = 4 x 1µ0 C21 = 1 x 0µ15 C19,C20 = 2 x 470µ0 x 100V C14,C16 = 2 x 220µ0 x 100V R1 = 1 x 27k R2,R16 = 2 x 100 R8,R11,R9,R12 = 4 x 33 R7,R10 = 2 x 820 R5,R6 = 2 x 6k8 R4,R3 = 2 x 2k2 R14,R17 = 2 x 10 R15 = 1 x 3k3 R26,R23 = 2 x 0R33 R25 = 1 x 10k R29,R28 = 2 x 3R9 R27,R24 = 2 x 0.33 R18 = 1 x 47 R19,R20,R22 R21 = 4 x 2R2 R13 = 1 x 470 VD1,VD2 = 2 x 15V VD3,VD4 = 2 x 1N4007 VT8 = 1 x IRF640 VT9 = 1 x IRF9640 VT2,VT3 = 2 x 2N5401 VT4,VT1 = 2 x 2N5551 VT5 = 1 x KSE350 VT6 = 1 x KSE340 VT7 = 1 x BD135 VT10,VT12 = 2 x 2SC5200 VT11,VT13 = 2 x 2SA1943

For example, let's take the supply voltage equal to ±60 V. If the installation is done correctly and there are no faulty parts, then we get the voltage map shown in Figure 7. The currents flowing through the elements of the power amplifier are shown in Figure 8. The power dissipation of each element is shown in Figure 9 (about 990 mW is dissipated on transistors VT5, VT6, therefore the TO-126 case requires a heat sink).

Figure 7. LANZAR power amplifier voltage map ENLARGE

Figure 8. Power amplifier current map ENLARGE

Figure 9. Amplifier power dissipation map ENLARGE

A few words about details and installation:
First of all, you should pay attention to the correct installation of parts, since the circuit is symmetrical, errors are quite common. Figure 10 shows the arrangement of parts. Adjustment of the quiescent current (current flowing through the terminal transistors when the input is closed to the common wire and the compensating current-voltage characteristic transistors) is produced by resistor X1. When turned on for the first time, the resistor slider should be in the highest position according to the diagram, i.e. have maximum resistance. The quiescent current should be 30...60 mA. There is no thought to setting it higher - there are no noticeable changes in either instruments or audibly. To set the quiescent current, the voltage is measured on any of the emitter resistors of the final stage and set in accordance with the table:

VOLTAGE AT THE TERMINALS OF THE EMITTER RESISTOR, V	TOO SMALL STOP CURRENT, POSSIBLE "STEP" DISTORTION NORMAL REST CURRENT, THE STILL CURRENT IS HIGH - EXCESSIVE HEATING, IF THIS IS NOT AN ATTEMPT TO CREATE CLASS "A", THEN THIS IS AN EMERGENCY CURRENT.
	REST CURRENT OF ONE PAIR OF TERMINAL TRANSISTORS, mA

Figure 10 Location of parts on the power amplifier board. The places where installation errors most often occur are shown.

The question was raised about the advisability of using ceramic resistors in the emitter circuits of terminal transistors. You can also use MLT-2, two of each, connected in parallel with a nominal value of 0.47...0.68 Ohm. However, the distortion introduced by ceramic resistors is too small, but the fact that they are breakable - when overloaded they break, i.e. their resistance becomes infinite, which quite often leads to the salvation of the final transistors in critical situations.
The radiator area depends on the cooling conditions; Figure 11 shows one of the options, it is necessary to attach power transistors to the heat sink through insulating gaskets .

It is better to use mica, since it has a fairly low thermal resistance. One of the options for mounting transistors is shown in Figure 12.

Figure 11 One of the radiator options for a power of 300 W, subject to good ventilation
Figure 12 One of the options for attaching power amplifier transistors to a radiator.

Insulating gaskets must be used.

Before installing power transistors, as well as in case of suspected breakdown, the power transistors are checked with a tester. The limit on the tester is set to test diodes (Figure 13).

Figure 13 Checking the amplifier's final transistors before installation and in case of suspected breakdown of the transistors after critical situations. Is it worth selecting transistors according to the code? gain? There are quite a lot of disputes on this topic and the idea of ​​​​selecting elements dates back to the late seventies, when the quality of the element base left much to be desired. Today, the manufacturer guarantees the spread of parameters between transistors of the same batch of no more than 2%, which in itself indicates elements.

In addition, given that the terminal transistors 2SA1943 - 2SC5200 are firmly established in audio engineering, the manufacturer began producing paired transistors, i.e. transistors of both direct and reverse conduction already have the same parameters, i.e. the difference is no more than 2% (Figure 14). Unfortunately, such pairs are not always found on sale, however, we have had the opportunity to buy “twins” several times. However, even having sorted out the coffee code. gain between forward and reverse transistors, you just need to make sure that transistors of the same structure are of the same batch, since they are connected in parallel and the spread in h21 can cause an overload of one of the transistors (which has this parameter higher) and, as a result, overheating and failure building. Well, the spread between the transistors for the positive and negative half-waves is fully compensated by the negative feedback.

Figure 14 Transistors of different structures, but from the same batch.
The same applies to differential stage transistors - if they are of the same batch, i.e. purchased at the same time in one place, then the chance that the difference in parameters will be more than 5% is VERY small. Personally, we prefer the 2N5551 - 2N5401 transistors from FAIRCHALD, however, the ST also sounds quite decent.
To carry out rejection, you should take any transistor from the rejected batch and set the collector current with a variable resistor to 0.4...0.6 A for transistors of the penultimate stage and 1...1.3 A for transistors of the final stage. Well, then everything is simple - transistors are connected to the terminals and, according to the readings of the ammeter connected to the collector, transistors with the same readings are selected, not forgetting to look at the readings of the ammeter in the base circuit - they should also be similar. A spread of 5% is quite acceptable; for dial indicators, “green corridor” marks can be made on the scale during calibration. It should be noted that such currents do not cause poor heating of the transistor crystal, and given the fact that it is without a heat sink, the duration of measurements should not be extended over time - the SB1 button should not be held pressed for more than 1...1.5 seconds. Such screening will first of all allow you to select transistors with a really similar gain factor, and checking powerful transistors with a digital multimeter is only a check to ease the conscience - in microcurrent mode, powerful transistors have a gain factor of more than 500, and even a small spread when checking with a multimeter in real current modes can turn out to be huge . In other words, when checking the gain coefficient of a powerful transistor, the multimeter reading is nothing more than an abstract value that has nothing in common with the gain coefficient of the transistor, at least 0.5 A flows through the collector-emitter junction.

Figure 15 Rejection of powerful transistors based on gain.

Feed-through capacitors C1-C3, C9-C11 have a non-typical connection compared to factory analogue amplifiers. This is due to the fact that with this connection, the result is not a polar capacitor of a rather large capacity, and the use of a 1 µF film capacitor compensates for the not entirely correct operation of the electrolytes on high frequencies. In other words, this implementation made it possible to obtain a more pleasant amplifier sound, compared to one electrolyte or one film capacitor.
In older versions of Lanzar, instead of diodes VD3, VD4, 10 Ohm resistors were used. Changing the element base allowed for slightly improved performance at signal peaks. For a more detailed look at this issue, let's look at Figure 3.
The circuit does not model an ideal power source, but one closer to a real one, which has its own resistance (R30, R31). When playing a sinusoidal signal, the voltage on the power rails will have the form shown in Figure 16. In this case, the capacitance of the power filter capacitors is 4700 μF, which is somewhat low. For normal operation of the amplifier, the capacitance of the power capacitors must be at least 10,000 µF per channel, more is possible, but a significant difference is no longer noticeable. But let's return to Figure 16. The blue line shows the voltage directly at the collectors of the final stage transistors, and the red line shows the supply voltage of the voltage amplifier in the case of using resistors instead of VD3, VD4. As can be seen from the figure, the supply voltage of the final stage has dropped from 60 V and is located between 58.3 V in the pause and 55.7 V at the peak of the sinusoidal signal. Due to the fact that capacitor C14 is not only charged through the decoupling diode, but also discharged at signal peaks, the amplifier supply voltage takes the form of a red line in Figure 16 and ranges from 56 V to 57.5 V, i.e. has a swing of about 1.5 IN.

Figure 16 voltage waveform when using decoupling resistors.

Figure 17 Shape of supply voltages on the final transistors and voltage amplifier

By replacing the resistors with diodes VD3 and VD4, we obtain the voltages shown in Figure 17. As can be seen from the figure, the ripple amplitude on the collectors of the terminal transistors has remained almost unchanged, but the supply voltage of the voltage amplifier has taken on a completely different form. First of all, the amplitude decreased from 1.5 V to 1 V, and also at the moment when the peak of the signal passes, the supply voltage of the UA sags only to half the amplitude, i.e. by about 0.5 V, while when using a resistor, the voltage at the peak of the signal sags by 1.2 V. In other words, by simply replacing resistors with diodes, it was possible to reduce the power ripple in the voltage amplifier by more than 2 times.
However, these are theoretical calculations. In practice, this replacement allows you to get a “free” 4-5 watts, since the amplifier operates at a higher output voltage and reduces distortion at signal peaks.
After assembling the amplifier and adjusting the quiescent current, you should make sure that there is no constant voltage at the output of the power amplifier. If it is higher than 0.1 V, then this clearly requires adjustment of the operating modes of the amplifier. In this case, the most in a simple way is the selection of the “supporting” resistor R1. For clarity, we present several options for this rating and show the DC voltage measurements at the output of the amplifier in Figure 18.

Figure 18 Change in DC voltage at the amplifier output depending on the value of R1

Despite the fact that on the simulator the optimal constant voltage was obtained only with R1 equal to 8.2 kOhm, in real amplifiers this rating is 15 kOhm...27 kOhm, depending on which manufacturer the differential stage transistors VT1-VT4 are used.
Perhaps it’s worth saying a few words about the differences between power amplifiers using bipolar transistors and those using field devices in the penultimate stage. First of all, when using field-effect transistors, the output stage of the voltage amplifier is VERY heavily unloaded, since the gates of field-effect transistors have practically no active resistance - only the gate capacitance is a load.

In this embodiment, the amplifier circuitry begins to step on the heels of class A amplifiers, since over the entire range of output powers the current flowing through the output stage of the voltage amplifier remains almost unchanged.

The increase in the quiescent current of the penultimate stage operating on the floating load R18 and the base of the emitter followers of powerful transistors also varies within small limits, which ultimately led to a rather noticeable decrease in THD. However, there is also a fly in the ointment in this barrel of honey - the efficiency of the amplifier has decreased and the output power of the amplifier has decreased, due to the need to apply a voltage of more than 4 V to the field gates to open them (for a bipolar transistor this parameter is 0.6...0.7 V ). Figure 19 shows the peak of the sinusoidal signal of an amplifier made on bipolar transistors (blue line) and field-field switches (red line) at the maximum amplitude of the output signal.
Figure 19 Change in the amplitude of the output signal when using different elements in the amplifier. In other words, reducing THD by replacing field-effect transistors leads to a “shortage” of about 30 W, and a decrease in the THD level by about 2 times, so it’s up to each individual to decide what to set. It should also be remembered that the THD level also depends on the amplifier’s own gain. In this amplifier, where R13 and R25 are the resistance in Ohms, 20 is the multiplier, lg is the decimal logarithm. If it is necessary to calculate the gain coefficient in times, then the formula takes the form Ku = R25 / (R13 + 1). This calculation may be necessary in the manufacture preamp and calculating the amplitude of the output signal in volts to eliminate the operation of the power amplifier in hard mode clipping.
Reducing your own coffee rate. gain up to 21 dB (R13 = 910 Ohm) leads to a decrease in the THD level by approximately 1.7 times at the same output signal amplitude (the input voltage amplitude is increased).

Well, now a few words about the most popular mistakes when assembling an amplifier yourself.
One of the most popular mistakes is installation of 15 V zener diodes with incorrect polarity, i.e. These elements do not operate in voltage stabilization mode, but like ordinary diodes. As a rule, such an error causes a constant voltage to appear at the output, and the polarity can be either positive or negative (usually negative). The voltage value is based between 15 and 30 V. In this case, not a single element heats up. Figure 20 shows the voltage map for incorrect installation of zener diodes, which was produced by the simulator. Invalid elements are highlighted in green.

Figure 20 Voltage map of a power amplifier with improperly soldered zener diodes.

The next popular mistake is mounting transistors upside down, i.e. when the collector and emitter are confused. In this case, there is also constant tension and the absence of any signs of life. True, switching the transistors of the differential cascade back on can lead to their failure, but then depending on your luck. The voltage map for an “inverted” connection is shown in Figure 21.

Figure 21 Voltage map when the differential cascade transistors are turned on “inverted”.

Often transistors 2N5551 and 2N5401 are confused, and the emitter and collector can also be confused. Figure 22 shows the voltage map of the amplifier with the “correct” installation of interchanged transistors, and Figure 23 shows the transistors not only interchanged, but also upside down.

Figure 22 The differential cascade transistors are reversed.

Figure 23 The transistors of the differential stage are reversed, and the collector and emitter are reversed.

If the transistors are swapped, and the emitter-collector is soldered correctly, then a small constant voltage is observed at the output of the amplifier, the quiescent current of the window transistors is regulated, but the sound is either completely absent or at the level “it seems to be playing.” Before installing transistors sealed in this way on the board, they should be checked for functionality. If the transistors are swapped, and even the emitter-collector places are swapped, then the situation is already quite critical, since in this embodiment, for the transistors of the differential stage, the polarity of the applied voltage is correct, but the operating modes are violated. In this option, there is strong heating of the terminal transistors (the current flowing through them is 2-4 A), a small constant voltage at the output and a barely audible sound.
Confusing the pinout of the transistors of the last stage of the voltage amplifier is quite problematic when using transistors in the TO-220 housing, but transistors in the TO-126 package are often soldered upside down, swapping the collector and emitter. In this option, there is a highly distorted output signal, poor regulation of the quiescent current, and lack of heating of the transistors of the last stage of the voltage amplifier. A more detailed voltage map for this power amplifier mounting option is shown in Figure 24.

Figure 24 The transistors of the last stage of the voltage amplifier are soldered upside down.

Sometimes the transistors of the last stage of the voltage amplifier are confused. In this case, there is a small constant voltage at the output of the amplifier; if there is any sound, it is very weak and with huge distortions; the quiescent current is regulated only in the direction of increase. The voltage map of an amplifier with such an error is shown in Figure 25.

Figure 25 Incorrect installation of transistors of the last stage of the voltage amplifier.

The penultimate stage and the final transistors in the amplifier are confused in places too rarely, so this option will not be considered.
Sometimes an amplifier fails; the most common reasons for this are overheating of the terminal transistors or overload. Insufficient heat sink area or poor thermal contact of the transistor flanges can lead to heating of the terminal transistor crystal to the temperature of mechanical destruction. Therefore, before the power amplifier is fully put into operation, it is necessary to make sure that the screws or self-tapping screws securing the ends to the radiator are fully tightened, the insulating gaskets between the flanges of the transistors and the heat sink are well lubricated with thermal paste (we recommend the good old KPT-8), as well as the size of the gaskets larger than the transistor size by at least 3 mm on each side. If the heat sink area is insufficient, and there is simply no other option, then you can use 12 V fans, which are used in computer equipment.
For example, let's look at several options for failure of terminal transistors. Figure 26 shows the voltage map if the reverse end-of-line transistors (2SC5200) go to open, i.e.

The transitions are burnt out and have the maximum possible resistance. In this case, the amplifier maintains operating modes, the output voltage remains close to zero, but the sound quality is definitely better, since only one half-wave of the sine wave is reproduced - negative (Fig. 27). The same thing will happen if the direct terminal transistors (2SA1943) break, only a positive half-wave will be reproduced.

Figure 26 The reverse end-of-line transistors burned out to the point of breaking.

Figure 27 Signal at the amplifier output in the case when the 2SC5200 transistors are completely burned out

Figure 27 shows a voltage map in a situation where the terminals have failed and have the lowest possible resistance, i.e. shorted. This type of malfunction drives the amplifier into VERY harsh conditions and further burning of the amplifier is limited only by the power supply, since the current consumed at this moment can exceed 40 A. The surviving parts instantly gain temperature, in the arm where the transistors are still working, the voltage is slightly higher than where the short circuit to the power bus actually occurred.

However, this particular situation is the easiest to diagnose - just before turning on the amplifier, check the resistance of the transitions with a multimeter, without even removing them from the amplifier. The measurement limit set on the multimeter is DIODE TEST or AUDIO TEST. As a rule, burnt-out transistors show a resistance between junctions in the range from 3 to 10 ohms.
If there is overheating, when it is believed that the radiator for the transistors of the last stage of the voltage amplifier is not needed (transistors VT5, VT6), they can also fail, both due to an open circuit and a short circuit. In the case of burnout of the VT5 transitions and an infinitely high resistance of the transitions, a situation arises when there is nothing to maintain zero at the output of the amplifier, and slightly open 2SA1943 end-of-line transistors will pull the voltage at the amplifier output to minus the supply voltage. If the load is connected, then the value of the constant voltage will depend on the set quiescent current - the higher it is, the greater the value of the negative voltage at the output of the amplifier. If the load is not connected, then the output voltage will be very close in value to the negative power bus (Figure 28).

Figure 28 Voltage amplifier transistor VT5 has broken.

If the transistor in the last stage of the voltage amplifier VT5 fails and its transitions are short-circuited, then with a connected load at the output there will be a fairly large constant voltage flowing through the load D.C., about 2-4 A. If the load is disconnected, then the voltage at the amplifier output will be almost equal to the positive power bus (Fig. 29).

Figure 29 Voltage amplifier transistor VT5 has “shorted”.

Finally, all that remains is to offer a few oscillograms at the most coordinate points of the amplifier:

Voltage at the bases of the differential cascade transistors at an input voltage of 2.2 V. Blue line - bases VT1-VT2, red line - bases VT3-VT4. As can be seen from the figure, both the amplitude and phase of the signal practically coincide.

Voltage at the connection point of resistors R8 and R11 (blue line) and at the connection point of resistors R9 and R12 (red line). Input voltage 2.2 V.

Voltage at the collectors VT1 (red line), VT2 (green), as well as at the top terminal R7 (blue) and the bottom terminal R10 (lilac). The voltage dip is caused by load operation and a slight decrease in the supply voltage.

The voltage on the collectors VT5 (blue) and VT6 (red. The input voltage is reduced to 0.2 V, so that it can be more clearly seen, in terms of constant voltage there is a difference of approximately 2.5 V

All that remains is to explain about the power supply. First of all, the power of the network transformer for a 300 W power amplifier should be at least 220-250 W and this will be enough to play even very hard compositions. You can learn more about the power of the power amplifier power supply. In other words, if you have a transformer from a tube color TV, then this is an IDEAL TRANSFORMER for one amplifier channel that allows you to easily reproduce musical compositions with a power of up to 300-320 W.
The capacitance of the power supply filter capacitors must be at least 10,000 μF per arm, optimally 15,000 μF. When using capacities higher than the specified rating, you simply increase the cost of the design without any noticeable improvement in sound quality. It should not be forgotten that when using such large capacitances and supply voltages above 50 V per arm, the instantaneous currents are already critically enormous, so it is strongly recommended to use soft start systems.
First of all, it is strongly recommended that before assembling any amplifier, you download manufacturers’ plant descriptions (datasheets) for ALL semiconductor elements. This will give you the opportunity to take a closer look at the element base and, if any element is not available for sale, find a replacement for it. In addition, you will have the correct pinout of transistors at hand, which will significantly increase the chances of correct installation. Those who are especially lazy are encouraged to VERY carefully at least familiarize themselves with the location of the terminals of the transistors used in the amplifier:

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Finally, it remains to add that not everyone requires a power of 200-300 W, so the printed circuit board was redesigned for one pair of terminal transistors. This file made by one of the visitors to the forum of the site "SOLDERING IRON" in the SPRINT-LAYOUT-5 program (DOWNLOAD THE BOARD). Details about this program can be found.

The schematic diagram of the amplifier is shown in Figure 1. This is an almost standard symmetrical circuit, which has made it possible to seriously reduce nonlinear distortion to a very low level.
To enlarge small drawings, click on it - the drawing will open in a new window and in VERY good quality.
A wide range of supply voltages makes it possible to build an amplifier with a power from 50 to 350 W, and at powers up to 300 W for UMZCH coffee. nonlinear distortion does not exceed 0.08% throughout the entire audio range, which allows the amplifier to be classified as Hi-Fi.
Figure 2 shows appearance amplifier
The amplifier circuit is completely symmetrical from input to output. A double differential stage (VT1-VT4) at the input and a stage on transistors VT5, VT6 provide voltage amplification, the remaining stages provide current amplification. The cascade on transistor VT7 stabilizes the quiescent current of the amplifier. To eliminate its “asymmetry” at high frequencies, it is bypassed with capacitor C12.
The driver stage on transistors VT8, VT9, as befits a preliminary stage, operates in class A. A “floating” load is connected to its output - resistor R21, from which the signal is removed to excite the transistors of the output stage. The output stage uses two pairs of transistors, which made it possible to extract up to 300 W of rated power from it. Resistors in the base and emitter circuits eliminate the consequences of technological variation in the characteristics of transistors, which made it possible to abandon the selection of transistors by parameters.
We remind you that when using transistors from the same batch, the spread in parameters between transistors does not exceed 2% - this is the manufacturer’s data. In reality, it is extremely rare that parameters go beyond the three percent zone. The amplifier uses only “one-party” terminal transistors, which, together with balance resistors, made it possible to maximally align the operating modes of the transistors with each other.
Regarding the circuitry, it only remains to add that such a circuitry solution provides one more advantage - complete symmetry eliminates transient processes in the final stage (!), i.e. at the moment of switching on, there are no surges at the output of the amplifier, which are characteristic of most discrete amplifiers.

Figure 1 - schematic diagram of the amplifier.

Figure 2 - appearance of the amplifier.

Schematic diagram of a powerful stage power amplifier 200 W 300 W 400 W UMZCH on transistors High Quality Hi-Fi UMZCH

PARAMETER	PER LOAD
			2 Ohm (4 ohm bridge)
Maximum supply voltage, ± V
			DO NOT TURN ON!!!
			DO NOT TURN ON!!!
			DO NOT TURN ON!!!
		390	DO NOT TURN ON!!!
	240	DO NOT TURN ON!!!	DO NOT TURN ON!!!
Gain coefficient, dB
Non-linear distortion at 2/3 of maximum power, %
Output signal slew rate, not less than V/µS
Input impedance, kOhm
Signal-to-noise ratio, not less, dB

As can be seen from the characteristics, this amplifier is very versatile and can be successfully used in any power amplifiers that require good UMZCH characteristics and high output power.

The operating modes were slightly adjusted, which required installing a radiator on transistors VT 5-VT 6. How to do this is shown in Figure 3, perhaps no explanation is required. This change significantly reduced the level of distortion compared to the original circuit and made the amplifier less capricious of the supply voltage.

Figure 4 shows a drawing of the location of parts on the printed circuit board and a connection diagram.

Figure 4

You can, of course, praise this amplifier for quite a long time, but it is somehow not modest to engage in self-praise. Therefore, we decided to look at the reviews of those who heard how it works. I didn’t have to search for long - this amplifier has been discussed on the Soldering Iron forum for a long time, so take a look for yourself:

There were, of course, negative ones, but the first was from an incorrectly assembled amplifier, the second from an unfinished version with a domestic configuration...

For those who want to assemble an amplifier themselves, we recommend visiting this page - it contains several recommendations and a drawing. printed circuit board in jpg and lay. It will also be useful to read the theory from A to Z and a few words about tuning this amplifier - usually a huge number of questions disappear...

Quite often people ask how an amplifier sounds. We hope that there is no need to remind you that there are no comrades according to taste and color. Therefore, in order not to impose our opinion on you, we will not answer this question. Let's note one thing - the amplifier really sounds. The sound is pleasant, not intrusive, good detail, with a good signal source.

The audio frequency power amplifier UM LANZAR based on powerful bipolar transistors will allow you to assemble a very high-quality audio frequency amplifier in a short period of time.

Structurally, the amplifier board is made in a monophonic version. However, nothing prevents you from purchasing 2 amplifier boards for assembling a stereo UMZCH, or 5 for assembling a 5.1 amplifier, although of course the high output power appeals more to a subwoofer, but it plays too well for a subwoofer...

Considering that the board is already soldered and tested, all you have to do is attach the transistors to the heat sink, apply power and adjust the quiescent current in accordance with your supply voltage.

Relatively low price already finished board 350 W power amplifier will pleasantly surprise you.

The power amplifier UM LANZAR has proven itself well in both automotive and stationary equipment. It is especially popular among small amateur musical groups not burdened with large finances and allows you to increase power gradually - a pair of amplifiers + a pair acoustic systems. A little later, once again a pair of amplifiers + a pair of speaker systems and already a gain not only in power, but also in sound pressure, which also creates the effect of additional power. Even later, UM HOLTON 800 for a subwoofer and transfer of amplifiers to the mid-HF link and as a result, a total of 2 kW of VERY pleasant sound, which is quite enough for any assembly hall...

www.interlavka.narod.ru

If you are interested in this article, then you have already read a lot of positive reviews on websites and various forums. Quite a few radio amateurs have already repeated this scheme, and, as we understand, they did not regret their choice. It is clear that transistor amplifiers are superior in sound quality to amplifiers implemented on microcircuits. LANZAR has an amazingly low coefficient of nonlinear distortion, and with a fairly wide range of supply voltage it allows you to develop 50...300 Watts of power at a load. And even at three hundred watts, these distortions do not exceed 0.08% over the entire audio range. Briefly about the amplifier parameters:

Gain coefficient – ​​24 dB;
Coef. nelin. distortion at 60% power - % 0.04%;
The slew rate of the output signal is at least 50 V/µS;
Input impedance – 22 kOhm;
Signal-to-noise ratio, no less than 90 dB;
Supply voltage, ± 30…65 V;
Output power - from 40 to 300 Watts (depending on U power supply)

Schematic diagram of the Lanzar V3.1 amplifier:

Pay attention to resistors R3 and R6 - these are current-limiting resistors of parametric stabilizers formed by these resistors and zener diodes VD1 and VD2. The lower the supply voltage, the lower the values ​​of these resistors.

● Supply voltage ±70 Volts – 3.3…3.9 kOhm;
● Supply voltage ±60 Volts – 2.7…3.3 kOhm;
● Supply voltage ±50 Volts – 3.2…2.7 kOhm;
● Supply voltage ±40 Volts – 1.5…2.2 kOhm;
● Supply voltage ±30 Volts – 1…1.5 kOhm;
● Supply voltage ±20 Volts - it is better to choose a different amplifier circuit for assembly.

The value of the constant voltage at the output of the amplifier depends on the rating of R1. In the diagram, the nominal value of R1 is 27 kOhm, you can put 22 kOhm. Often it has to be selected in the range from 15 to 47 kOhm.

2 resistors installed in the emitters of the differential stage (R7, R12 and R9, R13) - the values ​​of these resistors directly depend on how accurately you can select the gains of transistors VT1, VT3 and VT2, VT4. The more accurately the gain factors of these transistors are selected, the lower the value can be used in emitter circuits, and the lower the value of these resistors, the less nonlinear distortion introduced by the differential stage. Resistor values ​​without selecting transistors should be about 82...100 Ohms. If the transistors are selected, the resistor values ​​can be reduced to 10 Ohms.

The value of resistor R14 determines the gain of the amplifier.
The resistor located between the emitters of transistors VT8 and VT9 is rated at 47 Ohms. It is not recommended to change.
Resistors located in the base circuits of the output transistors, their value can be in the range of 1...2.4 Ohms.
Resistors in the emitter circuits of the output transistors - power of at least 5 Watts, nominal value 0.1...0.3 Ohm. Of course, the values ​​of these resistors must be the same.

Diodes VD3 and VD4 are designed for a current of 1...1.5 Amperes (the brand does not matter), the main thing is that they are the same.
At the input, two electrolytic capacitors are connected in series with their positive leads outward; they form a non-polar capacitance. And a film capacitor connected in parallel with them creates minimal distortion sound signal over the entire frequency range. Similar chain in the chain feedback amplifier

Capacitor C4 is noise suppressing. The rating can be from 330 to 680 pF.
Capacitors C12 and C13 - nominal 33 pF. They serve to reduce the speed of the amplifier, since without them the rise in the output signal is too large, and the amplifier becomes prone to self-excitation. Exactly the same capacitor is connected in parallel to resistor R25, which determines the gain.

Resistor R13 can also be used to adjust the gain.
Resistors in the base circuit of transistor VT7 - setting the quiescent current of the final stage. VT7 is installed on a radiator with output transistors for thermal stabilization of the quiescent current of the latter. Trimmer resistor – multi-turn type 3296.

Coil - 10 turns of wire with a diameter of 0.8 mm on a mandrel with a diameter of 12 mm.

The amplifier is turned on for the first time after checking the installation for the presence of “snot”. The resistor slider of the quiescent current regulator is in the upper extreme position according to the circuit, this means that the quiescent current of the output stage transistors should be minimal. It is also worth limiting the current developed by the power source, for this purpose it is in series with power transformer an incandescent lamp of 40…60 Watts turns on. We apply supply voltage to the circuit, and if after a short flash the light goes out, or glows so that the filament is barely visible, then there are no serious errors in the installation. We check the presence of zero at the output of the amplifier and the voltage at the zener diodes VD1 and VD2. Next, turn off the power and remove the incandescent lamp from the circuit. Turn on the power again. We adjust the quiescent current of the output stage with a variable resistor; it should be in the range of 70...100 mA.

Lanzar amplifier circuit board:

Is there some more alternative version printed circuit board of this amplifier, its appearance is shown in the figures below (this version of the board has not been tested, so check its correctness before proceeding with its manufacture, errors are possible):

You can download the diagram and both versions of the printed circuit board in LAY format using a direct link from our website. Also in the archive you will find a file in PDF format, from which you will also learn a lot useful information. The download file size is 0.65 Mb.