Amplifier lanzar about coil l1. Powerful amplifier according to the Lanzar circuit. Some possible replacements
It is wound on a 10mm drill and consists of 10 turns of 0.8mm wire; to firmly fix the turns, you can spread superglue on the finished coil.
The emitter resistors of the output transistors are selected with a power of 5 watts; during operation they overheat. The value of these resistors is not critical and can be from 0.22 to 0.39 Ohms.
After completing the amplifier assembly, we proceed to the testing stage. We carefully ring the terminals of the transistors and check for short circuits; there should not be any. Then we look at the installation again, check the board by eye - we pay special attention to the correct connection of transistors and zener diodes, if some transistors have been replaced with similar ones, then look at the reference books, since the conclusions of the transistors and analogues used in the circuit may differ.
The zener diodes themselves, if connected incorrectly, act as a diode and there is a possibility of ruining the entire circuit due to an incorrectly connected zener diode.
Variable resistor for adjusting the quiescent current of the output stages - it is advisable (very desirable) to use multi-turn resistors with a resistance of 1 kOhm, while the resistance during installation should be maximum - 1 kOhm. A multi-turn resistor will allow you to adjust the quiescent current of the output stage with very high accuracy.
It is advisable to take all electrolytic capacitors with an operating voltage of 63, or even better, 100 Volts.
Before assembling the amplifier, we carefully check all components for serviceability, regardless of whether they are new or used.
Figure 1 Circuit of the LANZAR power amplifier 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
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LIST OF ELEMENTS INSTALLED IN THE LANZAR AMPLIFIER |
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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 VD1,VD2 = 2 x 15V VT2,VT4 = 2 x 2N5401 |
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 VD1,VD2 = 2 x 15V VT8 = 1 x IRF640 |
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. Regulation of the quiescent current (current flowing through the terminal transistors when the input is closed to a common wire and compensating the current-voltage characteristic of the transistors) is carried out 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:
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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. | |||||
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REST CURRENT OF ONE PAIR OF TERMINAL TRANSISTORS, mA |
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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 good quality 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.
However, this amplifier is also assembled using domestic components. This is quite realistic, but let’s make allowance for the fact that the parameters of the KT817 purchased and those found on the shelves in your workshop, purchased back in the 90s, will differ quite significantly. Therefore, here it is better to use the h21 meter available in almost all digital test rooms. True, this gadget in the tester shows the truth only for low-power transistors. Using it to select transistors for the final stage will not be entirely correct, since h21 also depends on the current flowing. This is why separate testing stands are already being made to reject power transistors. from the adjustable collector current of the transistor being tested (Figure 15). The calibration of a permanent device for rejecting transistors is carried out in such a way that the microammeter at a collector current of 1 A deviates by half the scale, and at a current of 2 A - completely. When assembling an amplifier, you don’t have to make a stand for yourself; two multimeters with a current measurement limit of at least 5 A are enough.
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 are not entirely typical inclusion, compared to factory analogue amplifiers. This is due to the fact that with this connection the result is a rather non-polar capacitor. large capacity, and the use of a 1 µF film capacitor compensates for the not entirely correct operation of electrolytes at 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 The gain coefficient depends on the values of resistors R25 and R13
(at the nominal values used, the gain is almost 27 dB). Calculate Gain coefficient in dB can be obtained using the formula Ku =20 lg R25 / (R13 +1), 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 is sometimes necessary when making a pre-amplifier and calculating the amplitude of the output signal in volts in order to prevent the power amplifier from operating in hard clipping mode.
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. More detailed map voltage for this power amplifier installation 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. If the assembled amplifier is planned to operate only at powers above average (cafes, bars, etc.), then the cooler can be turned on for continuous operation, since it will still not be heard. If the amplifier is assembled for home use and will be used at low powers, then the operation of the cooler will already be audible, and there will be no need for cooling - the radiator will hardly heat up. For such operating modes, it is better to use controlled coolers. There are several options for controlling the cooler. The proposed cooler control options are based on monitoring the temperature of the radiator and are turned on only when the radiator reaches a certain, adjustable temperature. The problem of failure of window transistors can be solved either by installing additional overload protection, or by carefully installing the wires going to the speaker system (for example, using oxygen-free wires to connect speakers to an amplifier of automobiles, which, in addition to reduced active resistance, have increased insulation strength, resistant to shock and temperature ).
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 greater 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.
Figure 27 Power amplifier voltage map in case of burnout of the final transistors (2SC5200) on short circuit
The amplifier will behave in exactly the same way in the event of a breakdown of the penultimate stage - when the terminals are cut off, only one half-wave of the sine wave will be reproduced, and if the transitions are short-circuited, huge consumption and heating will occur.
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 by 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 unavailable 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:
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.
Having a powerful, high-quality subwoofer is the desire of every car enthusiast who values high-quality, loud sound and deep low frequencies(bass). The project was implemented in the summer of 2012 and took as much as 3 months; this delay was due to the shortage of many components that were used in the project. The device is a complex of amplifiers with a total power of about 750-800 watts. In several articles I will try to explain in detail the design of a subwoofer amplifier using the Lanzar circuit.
A voltage converter, a filter-adder, a stabilizer block and dynamic head protection are the component parts for the operation of such an amplifier. The voltage converter produces 500 watts of power, and all of these 500 watts are used to power the main amplifier. The lanzar's power can reach up to 360-390 watts, although the maximum power is obtained with increased power and is quite dangerous for individual parts of the amplifier.
Such an amplifier powers a powerful homemade subwoofer based on a SONY XPLOD dynamic head with a rated power of 300-350 watts, maximum (short-term power) up to 1000 watts. In a separate article we will look at the process of making a subwoofer box and all the subtleties associated with it. The case was used from a DVD player and fit perfectly. To cool the main amplifier, a huge heat sink from a Soviet radio amplifier was used. There is also a high-speed laptop cooler to remove warm air from the case.
Let's start looking at the design with a voltage converter, since this is what will need to be done first. From precise work The entire operation of the structure depends on the converter. It provides a bipolar output voltage of 60 volts per arm - this is exactly what is needed to provide the specified output power of the amplifier.
The voltage converter, despite its simple design, develops a power of 500 watts, and in force majeure situations up to 650 watts. TL494 is a two-channel PWM controller, a rectangular pulse generator tuned to a frequency of 45-50 kHz is the engine of this converter, and this is where it all begins.
To amplify the output signal, a driver is assembled using low-power bipolar transistors of the BC556 (557) series.
Previously amplified signal through limiting resistors it is supplied to the gates of powerful power switches. This circuit uses powerful N-channel field-effect transistors of the IRF3205 series, there are 4 of them in the circuit.
The converter transformer was initially wound on two cores (W-shaped) from the ATX power supply, but then the design changed and a new transformer was wound. Ring from an electronic transformer for powering halogen lamps (power 150-230 watts). The transformer contains two windings. Primary winding it is wound with 10 strands of 0.5-0.7 mm wire at once and contains 2X5 turns. Winding is done like this. To begin, we take a test wire and wind 5 turns, stretching the turns around the entire ring. We unwind the wire and measure its length. We take measurements with a margin of 5 cm. Next, we take 10 cores of the same wire - we twist the ends of the wires. We make two such blanks - 2 buses of 10 cores each. Then we try to wind it as evenly as possible around the entire ring, you get 5 turns. Then you need to separate the tires, in the end we get two equal halves of the winding.
We connect the beginning of one winding with the end of the second winding, or vice versa - the end of the first with the beginning of the second. Thus, we have phased the windings and the circuit can be checked. To do this, we connect the transformer to the circuit, and wind a test winding (secondary) on the ring. The winding can contain any number of turns; it is better to wind 2-6 turns of 0.5-1mm wire.
The first start of the converter is best done through a 20-60 watt lamp (halogen).
After winding the test secondary winding, we start the converter. We connect an incandescent lamp with a power of a couple of watts to the test winding. The lamp should glow, while the transistors (if without heat sinks) should heat up slightly during operation.
If everything is normal, then you can wind a real winding; if the circuit does not work properly or does not work at all, then you need to turn off the gates of the transistors and use an oscilloscope to check for the presence of rectangular pulses on pins 9 and 10. If there is generation, then the problem is most likely in the transistors, if they are also normal, then the transformer is incorrectly phased, you need to change the beginning and end of the windings (phasing was discussed in part 2).
The secondary winding is wound according to the same principle as the primary winding and is phased in the same way. The winding contains 2X18 turns and is wound with 8 strands of 0.5 mm wire at once. The winding needs to be stretched across the entire ring. The midpoint tap will be the body, since we are required to obtain bipolar voltage. The output voltage is obtained at an increased frequency, so the multimeter is not capable of measuring it.
The diode rectifier in my case was assembled from powerful domestic diodes of the KD213A series. The reverse voltage of the diode is 200V, at a current of up to 10A. These diodes can operate at frequencies up to 100kHz - great option for our case. You can also use other high-power pulse diodes with reverse voltage not less than 180 Volts.
In this article I will show my Lanzar amplifier.The amplifier was assembled half a year ago to order, but in the end the customer changed his mind and I abandoned work on it.
I remembered about him only now, when the competition began. The amplifier is almost complete, all that is missing is a couple of field switches in the converter and we need to achieve adequate protection, but everything is ready. Unfortunately, I will not conduct tests of the amplifier in the video, the two main reasons are the lack of a powerful 12 volt power source and the second - the 100 watt test speaker gave up life during the previous tests, the diffuser simply jumped out along with the coil, now I am without a speaker :) for Then I measured the power, at 5 - almost 6 ohms it was 300-310 watts.
One thing that surprises me about this amplifier is that with an output power of almost 300 watts, the output transistors do not burn out, although they were bought on eBay for 100 rubles/pair.
Below is the amplifier circuit
The circuit was taken from the Internet, as was the printed circuit board.
Now let's look at the converter circuit
I drew the circuit myself, here we see a voltage converter on IR2153, the frequency of the converter is 70 kHz, IRF3205 are used as power transistors, 2 pieces per arm.
And – the converter’s power can be supplied (through a fuse, of course) directly to the battery, because the converter will turn on only when 12 volts are supplied from the radio to the REM contact, namely to the power leg of the microcircuit. Here's a clever launch scheme. By the way, the cooler is powered not directly from the battery, but from a separate output of the converter specifically so that it turns on only when the amplifier itself is turned on, and does not spin endlessly, which would greatly reduce its lifespan.
The transformer is wound on two folded rings with a permeability of 2000
The primary winding contains 5 turns per arm with 0.8 mm wire in 10 cores. The main secondary winding has 26+26 turns with the same wire of 4 cores. The low-pass filter power winding contains 8+8 turns of the same wire. The winding for powering the cooler is 8 turns.
At the output we have a bipolar voltage of +- 60 volts to power the amplifier itself and the protection unit, a bipolar stabilized +-15 volt to power the low-pass filter, and a unipolar stabilized 12 volt to power the cooler. All voltages are rectified by diode bridges. The main output is 4 FCF10A40 10 Ampere 400 Volt diodes, they are placed on the radiator. The remaining bridges are built from ultra-fast 1 Amp UF4007 diodes.
There is no low-pass filter or protection circuit, but there are printed circuit boards with all component ratings.
This is what I ended up with
REVIEW OF LANZAR POWER AMPLIFIER
Frankly speaking, I was very surprised that the expression SOUND AMPLIFIER was gaining so much popularity. As far as my worldview allows me, only one object can act under the sound amplifier - a horn. It has really been amplifying sound for decades now. Moreover, the horn can amplify sound in both directions.
As can be seen from the photo, the horn has nothing in common with electronics, however, search queries for POWER AMPLIFIER are increasingly being replaced by SOUND AMPLIFIER, and the full name of this device, AUDITORY FREQUENCY POWER AMPLIFIER, is entered only 29 times a month versus 67,000 searches for SOUND AMPLIFIER.
I’m just curious what this is connected with... But that was a prologue, and now the fairy tale itself:
Schematic diagram The LANZAR power amplifier is shown in Figure 1. This is an almost standard symmetrical circuit, which has made it possible to seriously reduce nonlinear distortions to a very low level.
This circuit has been known for quite a long time; back in the eighties, Bolotnikov and Ataev presented a similar circuit on a domestic element base in the book " Practical schemes high-quality sound reproduction." However, work with this circuitry did not begin with this amplifier.
It all started with the PPI 4240 car amplifier circuit, which was successfully repeated:
Schematic diagram of the PPI 4240 car amplifier
Next was the article “Opening Amplifier -2” from Iron Shikhman (the article has unfortunately been removed from the author’s website). It dealt with the circuitry of the Lanzar RK1200C car amplifier, where the same symmetrical circuitry was used as an amplifier.
It is clear that it is better to see once than to hear a hundred times, so delving into my hundred-year-old recorded discs, I found the original article and present it as a quote:
OPENING THE AMPLIFIER - 2
A.I. Shikhatov 2002
A new approach to the design of amplifiers involves the creation of a line of devices using similar circuit solutions, common components and style. This allows, on the one hand, to reduce design and manufacturing costs, and on the other hand, it expands the choice of equipment when creating an audio system.
The new line of Lanzar RACK amplifiers is designed in the spirit of rack-mounted studio equipment. The front panel, measuring 12.2 x 2.3 inches (310 x 60 mm), contains controls, and the rear panel contains all connectors. With this arrangement, not only does it improve appearance system, but also simplifies the work - cables do not interfere. On the front panel you can mount the included mounting strips and carrying handles, then the device takes on a studio look. The ring illumination of the sensitivity control only enhances the similarity.
The radiators are located on the side surface of the amplifier, which allows you to stack several devices in a rack without interfering with their cooling. This is an undoubted convenience when creating extensive audio systems. However, when installing in a closed rack, you need to worry about air circulation - install supply and exhaust fans, temperature sensors. In short, professional equipment requires a professional approach in everything.
The line includes six two-channel and two four-channel amplifiers, differing only in output power and cabinet length.
The block diagram of the crossover of the Lanzar RK series amplifiers is shown in Figure 1. A detailed diagram is not given, since there is nothing original in it, and it is not this unit that determines the main characteristics of the amplifier. The same or similar structure is used in most modern mid-priced amplifiers. The range of functions and characteristics are optimized taking into account many factors:
On the one hand, the crossover capabilities should allow the construction of standard audio system options (front plus subwoofer) without additional components. On the other hand, there is little point in introducing a full set of functions into a built-in crossover: This will significantly increase the cost, but in many cases it will remain unclaimed. It is more convenient to delegate complex tasks to external crossovers and equalizers, and to disable the built-in ones.
The design uses double operational amplifiers KIA4558S. These are low-noise, low-distortion amplifiers designed with "audio" applications in mind. As a result, they are widely used in preamp stages and crossovers.
The first stage is a linear amplifier with variable gain. He will agree output voltage signal source with the sensitivity of the power amplifier, since the transmission coefficient of all other stages is equal to unity.
The next stage is the bass boost control. In amplifiers of this series, it allows you to increase the signal level at a frequency of 50 Hz by 18 dB. In products from other companies, the rise is usually less (6-12 dB), and the tuning frequency can be in the region of 35-60 Hz. By the way, such a regulator requires a good power reserve of the amplifier: an increase in gain by 3 dB corresponds to doubling the power, by 6 dB - quadrupling, and so on.
This is reminiscent of the legend about the inventor of chess, who asked the Raja for one grain for the first square of the board, and for each subsequent one - twice as many grains as for the previous one. The frivolous Raja could not fulfill his promise: there were no such quantity of grains on the entire Earth... We are in a more advantageous position: an increase in the level by 18 dB will increase the signal power “only” 64 times. In our case, 300 W are available, but not every amplifier can boast such a reserve.
The signal can then be fed directly to a power amplifier, or the required frequency band can be selected using filters. The crossover part consists of two independent filters. The low-pass filter is tunable in the range of 40-120 Hz and is designed to work exclusively with a subwoofer. The tuning range of the high-pass filter is noticeably wider: from 150 Hz to 1.5 kHz. In this form, it can be used to work with a broadband front or for the MF-HF band in a system with channel amplification. The tuning limits, by the way, were chosen for a reason: in the range from 120 to 150 Hz there is a “hole” in which the acoustic resonance of the cabin can be hidden. It is also noteworthy that the bass booster is not turned off in any of the modes. Using this cascade simultaneously with a high-pass filter allows you to adjust the frequency response in the interior resonance region no worse than using an equalizer.
The last cascade has a secret. Its task is to invert the signal in one of the channels. This will allow without additional devices use the amplifier in bridge connection.
Structurally, the crossover is made on a separate printed circuit board, which is connected to the amplifier board using a connector. This solution allows the entire line of amplifiers to use only two crossover options: two-channel and four-channel. The latter, by the way, is simply a “double” version of the two-channel one and its sections are completely independent. The main difference is the changed layout of the printed circuit board.
Amplifier
The Lanzar power amplifier is made according to a typical scheme for modern designs, shown in Figure 2. With minor variations, it can be found in most amplifiers of the middle and lower price category. The only difference is in the types of parts used, the number of output transistors and supply voltage. The diagram of the right channel of the amplifier is shown. The left channel circuit is exactly the same, only the part numbers start with a one instead of a two.
A filter R242-R243-C241 is installed at the amplifier input, eliminating radio frequency interference from the power supply. Capacitor C240 does not allow the DC component of the signal to enter the power amplifier input. These circuits do not affect the frequency response of the amplifier in the audio frequency range.
To avoid clicks when turning on and off, the amplifier input is connected to a common wire with a transistor switch (this unit is discussed below, together with the power supply). Resistor R11A eliminates the possibility of self-excitation of the amplifier when the input is closed.
The amplifier circuit is completely symmetrical from input to output. A double differential stage (Q201-Q204) at the input and a stage on transistors Q205, Q206 provide voltage amplification, the remaining stages provide current amplification. The cascade on transistor Q207 stabilizes the quiescent current of the amplifier. To eliminate its "unbalance" at high frequencies, it is bypassed with a mylar capacitor C253.
The driver stage on transistors Q208, Q209, as befits a preliminary stage, operates in class A. A “floating” load is connected to its output - resistor R263, 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 300 W of rated power and up to 600 W of peak power. Resistors in the base and emitter circuits eliminate the consequences of technological variation in the characteristics of transistors. In addition, resistors in the emitter circuit serve as current sensors for the overload protection system. It is made on transistor Q230 and controls the current of each of the four transistors in the output stage. When the current through an individual transistor increases to 6 A or the current of the entire output stage to 20 A, the transistor opens, issuing a command to the blocking circuit of the supply voltage converter.
The gain is set by the negative circuit feedback R280-R258-C250 and is equal to 16. Correction capacitors C251, C252, C280 ensure the stability of the amplifier covered by OOS. The circuit R249, C249 connected at the output compensates for the increase in load impedance at ultrasonic frequencies and also prevents self-excitation. In the audio circuits of the amplifier, only two electrolytic non-polar capacitors are used: C240 at the input and C250 in the OOS circuit. Due to their large capacity, it is extremely difficult to replace them with other types of capacitors.
Power supply The high-power power supply is made of field-effect transistors. A special feature of the power supply is the separate output stages of the converter for powering the power amplifiers of the left and right channels. This structure is typical for high-power amplifiers and makes it possible to reduce transient interference between channels. For each converter there is a separate LC filter in the power supply circuit (Figure 3). Diodes D501, D501A protect the amplifier from erroneous switching on in the wrong polarity.
Each converter uses three pairs of field-effect transistors and a transformer wound on a ferrite ring. The output voltage of the converters is rectified by diode assemblies D511, D512, D514, D515 and smoothed by filter capacitors with a capacity of 3300 μF. The output voltage of the converter is not stabilized, so the power of the amplifier depends on the voltage of the on-board network. From the negative voltage of the right and positive voltage of the left channel, parametric stabilizers generate voltages of +15 and -15 volts to power the crossover and differential stages of power amplifiers.
The master oscillator uses the KIA494 (TL494) microcircuit. Transistors Q503, Q504 increase the output of the microcircuit and speed up the closing of the key transistors of the output stage. The supply voltage is supplied to the master oscillator constantly, the switching is controlled directly from the Remote circuit of the signal source. This solution simplifies the design, but when turned off, the amplifier consumes insignificant quiescent current (several milliamps).
The protection device is made on a KIA358S chip containing two comparators. The supply voltage is supplied to it directly from the Remote circuit of the signal source. Resistors R518-R519-R520 and a temperature sensor form a bridge, the signal from which is fed to one of the comparators. A signal from the overload sensor is supplied to another comparator through a driver on transistor Q501.
When the amplifier overheats, a high voltage level appears at pin 2 of the microcircuit, and the same level appears at pin 8 when the amplifier is overloaded. In any emergency case, signals from the output of the comparators through the OR diode circuit (D505, D506, R603) block the operation of the master oscillator at pin 16. Operation is restored after eliminating the causes of the overload or cooling the amplifier below the temperature sensor response threshold.
The overload indicator is designed in an original way: the LED is connected between the +15 V voltage source and the on-board network voltage. During normal operation, voltage is applied to the LED in reverse polarity and it does not light. When the converter is blocked, the +15 V voltage disappears, the overload indicator LED turns on between the on-board voltage source and the common wire in the forward direction and begins to glow.
Transistors Q504, Q93, Q94 are used to block the input of the power amplifier during transient processes when turning on and off. When the amplifier is turned on, capacitor C514 is slowly charged, transistor Q504 is in the open state at this time. The signal from the collector of this transistor opens the keys Q94,Q95. After charging the capacitor, transistor Q504 closes, and the -15 V voltage from the output of the power supply reliably blocks the keys. When the amplifier is turned off, transistor Q504 instantly opens through diode D509, the capacitor quickly discharges and the process is repeated in the reverse order.
Design
The amplifier is mounted on two printed circuit boards. On one of them there is an amplifier and a voltage converter, on the other there are crossover elements and turn-on and overload indicators (not shown in the diagrams). The boards are made of high-quality fiberglass with a protective coating for the tracks and are mounted in a housing made of an aluminum U-shaped profile. Powerful transistors The amplifier and power supply are pressed with pads to the side shelves of the case. Profiled radiators are attached to the outside of the sides. Front and back panels The amplifiers are made of anodized aluminum profile. The entire structure is secured with self-tapping screws with hexagon heads. That's all, actually - the rest can be seen in the photographs.
As you can see from the article, the original LANZAR amplifier itself is not bad at all, but I wanted it to be better...
I searched the forums, of course, Vegalab, but didn’t find much support - only one person responded. Perhaps it’s for the better - there aren’t a ton of co-authors. Well, in general, this particular appeal can be considered Lanzar’s birthday - at the time of writing the comment, the board was already etched and soldered almost completely.
So Lanzar is already ten years old...
After several months of experiments, the first version of this amplifier, called "LANZAR", was born, although of course it would be fairer to call it "PIPIAY" - it all started with him. However, the word LANZAR sounds much more pleasant to the ear.
If someone SUDDENLY considers the name an attempt to play on a brand name, then I dare to assure him that there was nothing like that in mind and the amplifier could have received absolutely any name. However, it became LANAZR in honor of the LANZAR company, since this particular automotive equipment is included in that small list of those who are personally respected by the team that worked on fine-tuning this amplifier.
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.
The figure shows the appearance of the 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. However, if the amplifier is being made for a loved one, then it will not be useless to assemble the test stand given at the end of THIS ARTICLE.
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 LANZAR amplifier. INCREASE .
Figure 2 - appearance of the LANZAR V1 amplifier.
Figure 3 - appearance of the LANZAR MINI amplifier
Schematic diagram of a powerful stage power amplifier 200 W 300 W 400 W UMZCH on high quality transistors Hi-Fi UMZCH
Power amplifier specifications:
390
As can be seen from the characteristics, the Lanzar amplifier is very versatile and can be successfully used in any power amplifiers that require good characteristics UMZCH and high output power.
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... Amplifier audio frequency UM LANZAR based on powerful bipolar transistors will allow you to assemble a very high-quality audio amplifier in a short period of time. Power supply ±70 V - 3.3 kOhm...3.9 kOhm Of course, ALL resistors are 1 W, zener diodes at 15V are preferably 1.3 W Regarding heating VT5, V6 - in this case you can increase the radiators on them or increase their emitter resistors from 10 to 20 Ohms. About LANZAR amplifier power filter capacitors: |
Since this amplifier is quite popular and questions about making it yourself quite often come up, the following articles were written:
Transistor amplifiers. Basics of circuit design
Transistor amplifiers. Building a balanced amplifier
Lanzar tuning and circuit design changes
Setting up the LANZAR power amplifier
Increasing the reliability of power amplifiers using the example of the LANZAR amplifier
The penultimate article quite intensively uses the results of parameter measurements using the MICROCAP-8 simulator. How to use this program is described in detail in a trilogy of articles:
AMPovichok. CHILDREN'S
AMPovichok. YOUTHFUL
AMPovichok. ADULT
BUY TRANSISTORS FOR LANZAR AMPLIFIER |
|
And finally, I would like to give the impressions of one of the fans of this circuit, who assembled this amplifier on his own:
The amplifier sounds very good, the high damping factor represents a completely different level of bass reproduction, and high speed The signal build-up does an excellent job of reproducing even the smallest sounds in the high-frequency and mid-range.
You can talk a lot about the delights of the sound, but the main advantage of this amplifier is that it does not add any color to the sound - it is neutral in this regard, and only repeats and amplifies the signal from the sound source.
Many who heard the sound of this amplifier (assembled according to this circuit) gave the highest rating to its sound, as a home amplifier for high-quality speakers, and its endurance in *close to military action* conditions gives the chance to use it professionally for scoring various events at outdoors, as well as in the halls.
For simple comparison I’ll give an example that will be most relevant among radio amateurs, as well as among those already *sophisticated good sound*
in the soundtrack of Gregorian-Moment of Peace, the choir of monks sounds so realistic that the sound seems to pass right through, and the female vocals sound as if the singer is standing right in front of the listener.
When using time-tested speakers such as 35ac012 and others like them, the speakers get a new lease of life and sound just as clearly even at maximum volume.
For example, for fans of loud music, when listening to the music track Korn ft. Skrillex - Get Up
The speakers were able to play all the difficult moments with confidence and without noticeable distortion.
As a contrast to this amplifier, we took an amplifier based on the TDA7294, which, already at a power of less than 70 W per 1 channel, was able to overload the 35ac012 so that it was clearly audible how the woofer coil hit the core, which was fraught with damage to the speaker and, as a result, losses.
The same cannot be said about the *LANZAR* amplifier - even with about 150W of power supplied to these speakers, the speakers continued to work perfectly, and the woofer was so well controlled that no extraneous sounds it just wasn't there.
In the musical composition Evanescence - What You Want
The scene is so elaborate that you can even hear the drumsticks hitting each other. And in the composition Evanescence - Lithium Official Music Video
The skipping part is replaced by an electric guitar, so that the hairs on your head just begin to move, because there is simply no *longness* to the sound, and the quick transitions are perceived as if a painful form of 1 is flashing in front of you, one moment and YOU are immersed in new world. Not forgetting about the vocals, which throughout the entire composition bring generalization to these transitions, giving harmony.
In the composition Nightwish - Nemo
The drums sound like gunshots, clearly and without boom, and the rumble of thunder at the beginning of the composition simply makes you look around.
In the composition Armin van Buuren ft. Sharon den Adel - In and Out of Love
We are again immersed in the world of sounds that penetrate us through and through, giving us a feeling of presence (and this is without any equalizers or additional stereo expansions)
In the song Johnny Cash Hurt
We are again immersed in the world of harmonious sound, and the vocals and guitar sound so clearly that even the increasing tempo of the performance is perceived as if we are sitting behind the wheel of a powerful car and pressing the gas pedal to the floor, while not letting go but pressing harder and harder.
With a good source sound signal and good acoustics, the amplifier *doesn’t bother you at all* even at the highest volume.
Once a friend was visiting me and he wanted to listen to what this amplifier was capable of, putting on a track in AAC format Eagles - Hotel California, he turned it up to full volume, while instruments began to fall from the table, his chest felt like well-placed punches of a boxer , the glass tinkled in the wall, and we were quite comfortable listening to music, while the room was 14.5 m2 with a ceiling of 2.4 m.
We installed ed_solo-age_of_dub, the glass in two doors cracked, the sound was felt by the whole body, but the head did not hurt.
The board on the basis of which video was made in LAY-5 format.
If you assemble two LANZAR amplifiers, can they be bridged?
You can, of course, but first, a little poetry:
For a typical amplifier, the output power depends on the supply voltage and load resistance. Since we know the load resistance and we already have power supplies, it remains to be seen how many pairs of output transistors to use.
Theoretically, the total output power of alternating voltage is the sum of the power delivered output stage, which consists of two transistors - one n-p-n, the second p-n-p, therefore each transistor is loaded with half the total power. For the sweet couple 2SA1943 and 2SC5200, the thermal power is 150 W, therefore, based on the above conclusion, 300 W can be removed from one pair of outputs.
But practice shows that in this mode the crystal simply does not have time to transfer heat to the radiator and thermal breakdown is guaranteed, because the transistors must be insulated, and the insulating spacers, no matter how thin they are, still increase the thermal resistance, and the surface of the radiator is unlikely to who polishes to micron precision...
So for normal operation, for normal reliability, quite a lot of people have adopted slightly different formulas for calculating the required number of output transistors - the output power of the amplifier should not exceed the thermal power of one transistor, and not the total power of the pair. In other words, if each transistor of the output stage can dissipate 150 W, then the output power of the amplifier should not exceed 150 W, if there are two pairs of output transistors, then the output power should not exceed 300 W, if three - 450, if four - 600.
Well, now the question is - if a typical amplifier can output 300W and we connect two such amplifiers in a bridge, then what will happen?
That's right, the output power will increase approximately twofold, but the thermal power dissipated by the transistors will increase by 4 times...
So it turns out that to build a bridge circuit you will no longer need 2 pairs of outputs, but 4 on each half of the bridge amplifier.
And then we ask ourselves the question - is it necessary to drive 8 pairs of expensive transistors to get 600 W, if you can get by with four pairs simply by increasing the supply voltage?
Well, of course, it’s the owner’s business....
Well, several options of PRINTED BOARDS for this amplifier will not be superfluous. There are also original versions, and some taken from the Internet, so it’s better to double-check the board - it will give you mental training and fewer problems when adjusting the assembled version. Some options have been corrected, so there may not be any errors, or maybe something has slipped through the cracks...
One more question remains unanswered - assembly of the LANZAR amplifier on a domestic element base.
Of course, I understand that crab sticks are made not from crabs, but from fish. So is Lanzar. The fact is that in all attempts to assemble on domestic transistors, the most popular ones are used - KT815, KT814, KT816, KT817, KT818, KT819. These transistors have a lower gain and a unity gain frequency, so you won’t hear Lanzarov’s sound. But there is always an alternative. At one time, Bolotnikov and Ataev proposed something similar in circuit design, which also sounded pretty good:
You can see more details about how much power a power supply is needed for a power amplifier in the video below. The STONECOLD amplifier is taken as an example, but this measurement makes it clear that the power of the network transformer may be less than the power of the amplifier by about 30%.
At the end of the article, I would like to note that this amplifier requires a BIPOLARY power supply, since the output voltage is formed from the positive side of the power supply and the negative one. The diagram of such a power supply is shown below:
You can draw conclusions about the overall power of the transformer by watching the video above, but I’ll give a short explanation about the other details.
The secondary winding must be wound with a wire whose cross-section is designed for the overall power of the transformer plus an adjustment for the shape of the core.
For example, we have two channels of 150 W each, therefore the overall power of the transformer must be at least 2/3 of the power of the amplifier, i.e. with an amplifier power of 300 W, the transformer power must be at least 200 W. With a power supply of ±40 V into a 4 Ohm load, the amplifier develops about 160 W per channel, therefore the current flowing through the wire is 200 W / 40 V = 5 A.
If the transformer has an W-shaped core, then the voltage in the wire should not exceed 2.5 A per square mm of cross-section - this way there is less heating of the wire, and the voltage drop is less. If the core is toroidal, then the voltage can be increased to 3...3.5 A per 1 square mm of wire cross-section.
Based on the above, for our example, the secondary must be wound with two wires and the beginning of one winding is connected to the ends of the second winding (the connection point is marked in red). The diameter of the wire is D = 2 x √S/π.
At a voltage of 2.5 A we get a diameter of 1.6 mm, at a voltage of 3.5 A we get a diameter of 1.3 mm.
The diode bridge VD1-VD4 not only must calmly withstand the resulting current of 5 A, it must withstand the current that occurs at the moment of switching on, when it is necessary to charge the power filter capacitors C3 and C4, and the higher the voltage, the greater the capacitance, the higher the value of this starting current. Therefore, the diodes must be at least 15 Amperes for our example, and in the case of increasing the supply voltage and using amplifiers with two pairs of transistors in the final stage, 30-40 Ampere diodes or a soft start system are needed.
The capacity of capacitors C3 and C4, based on Soviet circuit design, is 1000 μF for every 50 W of amplifier power. For our example, the total output power is 300 W, which is 6 times 50 W, therefore the capacitance of the power filter capacitors should be 6000 uF per arm. But 6000 is not a typical value, so we round up to the typical value and get 6800 µF.
Frankly speaking, such capacitors do not come across often, so we put 3 capacitors of 2200 μF in each arm and get 6600 μF, which is quite acceptable. The issue can be solved somewhat simpler - use one 10,000 µF capacitor
