Setting up a Lanzar power amplifier - circuit diagram of a power amplifier, description of the circuit diagram, recommendations for assembly and adjustment. Amplifier "Green Lanzar" on N-channel MOSFETs. Balanced amplifier with quasi-complementary output In
Frankly speaking, we never expected that this scheme would cause so many difficulties when repeating it, and that the thread on the Soldering Iron forum would cross the 100-page threshold. So we decided to put an end to this topic. Of course, when preparing materials, material from this thread will be used, since it is simply not realistic to foresee some things - they are too paradoxical.
The Lanzar power amplifier has two basic circuits - the first is entirely based on bipolar transistors (Fig. 1), the second using field ones in the penultimate stage (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.
INCREASE
Figure 2 Circuit of the LANZAR power amplifier using field-effect transistors in the penultimate stage.
INCREASE
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 R13 = 1 x 470 VD3,VD4 = 2 x 1N4007 |
FOR THE OPTION WITH FIELDS C3,C2 = 2 x 22µ0 C4 = 1 x 470p C6,C7 = 2 x 470µ0 x 25V VT11,VT13 = 2 x 2SA1943 C11,C9 = 2 x 47µ0 C11,C10 = 2 x 47µ0 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 R13 = 1 x 470 R29,R28 = 2 x 3R9 |
The printed circuit board drawing in LAY format has two types - one developed by us and used for assembling and selling power amplifier boards, as well as an alternative version developed by one of the SOLDERING IRON forum participants. The boards differ quite a lot. Figure 4 shows a sketch of our power amplifier board, and Figure 5 shows an alternative option.
Figure 5 Sketch of the printed circuit board of the LANZAR power amplifier.
DOWNLOAD
Figure 6 Sketch of an alternative printed circuit board for the LANZAR power amplifier. DOWNLOAD
ATTENTION! THERE IS AN ERROR ON THE BOARD - CHECK IT AGAIN!
The power amplifier parameters are summarized in the table: |
PARAMETER | |||||||||||||||||||||||||||||||||||||||||||||||||
power amplifier circuit diagram of the Lanzar power amplifier operation description recommendations for assembly and adjustment |
||||||||||||||||||||||||||||||||||||||||||||||||||
PER LOAD |
||||||||||||||||||||||||||||||||||||||||||||||||||
(4 ohm bridge) | ||||||||||||||||||||||||||||||||||||||||||||||||||
Maximum supply voltage, ± V Maximum output power, W |
|
|
|
|||||||||||||||||||||||||||||||||||||||||||||||
at distortion up to 1% and supply voltage: | ||||||||||||||||||||||||||||||||||||||||||||||||||
±30 V | ||||||||||||||||||||||||||||||||||||||||||||||||||
±35 V | ||||||||||||||||||||||||||||||||||||||||||||||||||
±40 V | ||||||||||||||||||||||||||||||||||||||||||||||||||
±45 V | ||||||||||||||||||||||||||||||||||||||||||||||||||
±55 V |
240 |
±65 V 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).
Figure 9. Amplifier power dissipation map ENLARGE
The places where installation errors most often occur are shown.
Figure 12 One of the options for attaching power amplifier transistors to a radiator.
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). 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.
Figure 14 Transistors of different structures, but from the same batch.
Figure 15 Rejection of powerful transistors based on gain.
Figure 17 Shape of supply voltages on the final transistors and voltage amplifier
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.
Figure 19 Change in the amplitude of the output signal when using different elements in the amplifier. 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.
, 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.
Figure 20 Voltage map of a power amplifier with improperly soldered zener diodes. The next popular mistake is mounting transistors upside down
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.
Figure 24 The transistors of the last stage of the voltage amplifier are soldered upside down.
Figure 25 Incorrect installation of transistors in the last stage of the voltage amplifier.
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.
Figure 27 Power amplifier voltage map in the event of a short circuit burnout of the final transistors (2SC5200)
Figure 28 Voltage amplifier transistor VT5 has broken.
Figure 29 Voltage amplifier transistor VT5 has “shorted”.
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. 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: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 was made by one of the visitors to the forum of the site "SOLDERING IRON" in the SPRINT-LAYOUT-5 program (DOWNLOAD BOARD). Details about this program can be found.
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 on each 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
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 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. The entire operation of the structure depends on the accurate operation of 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 starts.
To amplify the output signal, a driver is assembled using low-power bipolar transistors of the BC556 (557) series.
The pre-amplified signal is fed through limiting resistors 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. The primary winding 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 with, 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, with a current of up to 10A. These diodes can operate at frequencies up to 100kHz - an excellent option for our case. You can also use other powerful pulse diodes with a reverse voltage of at least 180 Volts.
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.
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.
An input capacitor with a capacity of 1 μF can be selected to suit your taste, but since lanzar is mostly used to power the subwoofer channel, it is advisable to take a larger capacitor capacity.
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 | PER LOAD (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 resistance, 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.
- FOR THE OPTION WITH FIELDS
- 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
- C14,C16 = 2 x 220µ0 x 100V
- 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
- R13 = 1 x 470
- VD3,VD4 = 2 x 1N4007
- VD3,VD4 = 2 x 1N4007
- VT3,VT1 = 2 x 2N5551
- VT5 = 1 x KSE350
- VT6 = 1 x KSE340
- VT7 = 1 x BD135
- VT7 = 1 x BD135
- 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 low-power signals are supplied to the input (for example, from a PC, player or mobile phone), the amplifier will not sound particularly loud, since the nominal value of the input signal 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.
Turn on the amplifier for 10-20 minutes at medium volume and adjust the quiescent current of the amplifier. It is advisable to set the TP in the region of 100-130mA. Setting the quiescent current and measuring the power of the amplifier are shown in the diagrams.
HOW TO ADJUST THE LANZAR AMPLIFIER
The Lanzar power amplifier has two basic circuits - the first is entirely based on bipolar transistors, the second using field ones in the penultimate stage.
The circuit diagram of the LANZAR amplifier will not be given here - it is in the SPLAN 6 archive, where you can also find a list of parts necessary for self-assembly of this power amplifier. By the way, there are two circuits in the archive - one is traditional, and the second is with one pair of final stage transistors.
Figure 1: Retrieving a list of elements from a SPLAN drawing
Figure 2 shows the circuit of the Lanzar amplifier, but executed in the MS-8 simulator. The position numbers of the elements do not match, so this page will talk about the circuit made in MICROCAP to avoid confusion.
Figure 2 Circuit of the LANZAR power amplifier from the MS-8 simulator
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 will get the voltage map shown in Figure 3.
Figure 3.
The currents flowing through the power amplifier elements are shown in Figure 4.
Figure 4.
The power dissipation of each element is shown in Figure 5 (about 990 mW is dissipated on transistors Q5, Q6, therefore both the TO-126 and TO-220 packages will require a heat sink).
Figure 5
For other popular supply voltages, pictures with voltage maps are shown below in the right column.
The cards start with a supply voltage of ±30V, since at a lower voltage it is too expensive to use the LANZAR amplifier - well, it is not designed for a power of less than 100 W. In the figure, the elements that adjust the operating modes of the amplifier to a given supply voltage are highlighted in green. The number next to resistor X3 indicates the percentage position of the trimmer resistor slider
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.
Figure 12 One of the options for attaching power amplifier transistors to a radiator.
Figure 13 Checking the amplifier's final transistors before installation and in case of suspected breakdown of the transistors after critical situations. 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 a spread of parameters between transistors of the same batch of no more than 2%, which in itself indicates the good quality of the 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.
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).
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, but 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.
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.
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.
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. Well, now a few words about the most popular mistakes when assembling a LANZAR amplifier yourself.
, i.e. 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 20 Voltage map of a power amplifier with improperly soldered zener diodes. 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.
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.
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.
The penultimate stage and the final transistors in the amplifier are confused in places too rarely, so this option will not be considered.
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.
Figure 27 Power amplifier voltage map in the event of a short circuit burnout of the final transistors (2SC5200)
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).
Finally, all that remains is to offer a few oscillograms at the most coordinate points of the amplifier:
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 supply for power amplifiers. 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. Although no... Not all of it... For those who want to understand the circuitry of this amplifier, there is a thread on this topic. For those who don’t like the proposed printed circuit boards, you can assemble this amplifier in a two-story version and then LANZAR will look like this: This version of the printed circuit board (DOWNLOAD) differs from the basic one in the presence of a buffer amplifier on an op-amp and overload protection. 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%. |