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Schematic diagram, PCB drawing of the NATALY preamplifier. high quality umzch nataly amplifier nataly home version final

Amplifier Specifications:
Power supply up to +\- 75V
Rated output power, W - 300 W \ 4 Ohm
Kg (THD) at rated output power at 1 kHz, 0.0008% or less (0.0006% or less typical)
Intermodulation distortion factor, not more than 0.002% (typical value is less than 0.0015%)

The UMZCH scheme has:
balanced input
cliplimiter on AOP124 optocoupler
protection system against current overloads and short circuit in the load

Circled in red are nodes that are not needed for the truncated version. In parentheses are the ratings for +\- 45V power supply.

Implemented in defense:
speaker connection delay
protection against constant output, against short circuit
airflow control and shutdown of the speakers when the radiators overheat
Protection scheme

Recommendations for assembling and configuring UMZCH:
Before assembly printed circuit board you should perform relatively simple operations with the board, namely, look through the light to see if there are short circuits between the tracks that are hardly noticeable under normal lighting. Factory production does not exclude manufacturing defects, unfortunately. Soldering is recommended to be carried out with solder POS-61 or similar with a melting point not higher than 200 * C.

First you need to decide on the applied OS. The use of op amps from Analog Devices is highly discouraged - in this UMZCH, their sound character is somewhat different from that intended by the author, but unnecessarily high speed can lead to irreparable self-excitation of the amplifier. The replacement of ORA134 with ORA132, ORA627 is welcomed. they have less distortion at high frequencies. The same applies to the op amp DA1 - it is recommended to use OPA2132, OPA2134 (in order of preference). It is acceptable to use OPA604, OPA2604, but there will be slightly more distortion. Of course, you can experiment with the type of op-amp, but at your own peril and risk. UMZCH will also work with KR544UD1, KR574UD1, but the zero offset level at the output will increase and the harmonics will grow. The sound is ... I think no comments are needed.
From the very beginning of the installation, it is recommended to select transistors in pairs. This is not a necessary measure as the amplifier will work with a spread of 20-30%, but if you set a goal to get the maximum quality, then pay attention to this. Of particular note is the selection of T5, T6 - they are best used with maximum H21e - this will reduce the load on the op-amp and improve its output spectrum. T9, T10 should also have as close gain as possible. For latch transistors selection is optional. Output transistors - if they are from the same batch, you can not select them, because. the culture of production in the West is somewhat higher than we are used to, and the spread is within 5-10%.
Further, instead of the terminals of the resistors R30, R31, it is recommended to solder pieces of wire a couple of centimeters long, since it will be necessary to select their resistances. An initial value of 82 ohms will give a UN quiescent current of about 20..25 mA, but statistically it turned out from 75 to 100 ohms, this strongly depends on the specific transistors.
As already noted in the topic on the amplifier, you should not use transistor optocouplers. Therefore, it is worth focusing on AOD101A-G. Imported diode optocouplers were not tested due to unavailability, this is temporary. The best results are obtained on AOD101A of one batch for both channels.
In addition to transistors, it is worth picking up UNA complementary resistors in pairs. The spread should not exceed 1%. You need to carefully select R36=R39, R34=R35, R40=R41. For reference, I note that with a spread of more than 0.5%, it is better not to switch to the option without environmental protection, because. there will be an increase in even harmonics. It was the impossibility to get the exact details that stopped the author's experiments in the non-OOS direction at the time. The introduction of balancing into the current feedback circuit does not completely solve the problem.
Resistors R46, R47 can be soldered at 1 kOhm, but if there is a desire to more accurately adjust the current shunt, then it is better to do the same as with R30, R31 - solder the wires for soldering.
As it turned out in the course of repeating the circuit, under some set of circumstances, excitation in the EA tracking circuit is possible. This manifested itself in the form of an uncontrolled drift of the quiescent current, and especially in the form of oscillations with a frequency of about 500 kHz on collectors T15, T18.
The necessary adjustments were originally included in this version, but it's still worth checking with an oscilloscope.
Diodes VD14, VD15 are placed on the radiator for temperature compensation of the quiescent current. This can be done by soldering the wires to the leads of the diodes and gluing them to the heatsink with Moment glue or similar.
Before turning it on for the first time, it is necessary to thoroughly wash the board from traces of flux, look for the absence of short circuits with solder, make sure that the common wires are connected to the midpoint of the power supply capacitors. It is also strongly recommended to use the Zobel circuit and the coil at the output of the UMZCH, they are not shown in the diagram, because. the author considers their application as a rule of good form. The ratings of this circuit are common - these are a 10 Ohm 2 W resistor connected in series and a K73-17 capacitor or similar with a capacity of 0.1 μF. The coil is wound with a varnished wire with a diameter of 1 mm on an MLT-2 resistor, the number of turns is 12 ... 15 (before filling). On the protection board, this circuit is completely wired.
All transistors VK and T9, T10 in UN are mounted on a radiator. Power transistors VK are installed through mica gaskets and KPT-8 type paste is used to improve thermal contact. It is not recommended to use near-computer pastes - there is a high probability of a fake, and tests confirm that KPT-8 is often the best choice, and also very inexpensive. In order not to fly into a fake, use KPT-8 in metal tubes, like toothpaste. We haven't gotten there yet, fortunately.
For transistors in an insulated package, the use of a mica gasket is optional and even undesirable, because. worsens the conditions of thermal contact.
Be sure to turn on a 100-150W light bulb in series with the primary winding of the network transformer - this will save you from many troubles.
Short the D2 optocoupler LED pins (1 and 2) and turn on. If everything is assembled correctly, then the current consumed by the amplifier should not exceed 40 mA (the output stage will operate in mode B). The DC bias voltage at the UMZCH output should not exceed 10 mV. Turn on the LED. The current consumed by the amplifier should increase to 140 ... 180 mA. If it increases more, then check (it is recommended to do this pointer voltmeter) collectors T15, T18. If everything works correctly, there should be voltages that differ from the supply voltages by about 10-20 V. In the case when this deviation is less than 5 V, and the quiescent current is too large, try changing the diodes VD14, VD15 to others, it is very desirable that they were from the same party. The UMZCH quiescent current, if it does not fit in the range from 70 to 150 mA, can also be set by selecting resistors R57, R58. Possible replacement for diodes VD14, VD15: 1N4148, 1N4001-1N4007, KD522. Or, reduce the current flowing through them by simultaneously increasing R57, R58. In my thoughts there was the possibility of implementing a bias of such a plan: instead of VD14, VD15, use transitions of BE transistors from the same batches as T15, T18, but then you will have to significantly increase R57, R58 - up to full customization the resulting current mirrors. In this case, the newly introduced transistors must be in thermal contact with the radiator, as well as the diodes, instead of which they are placed.
Next, you need to set the quiescent current UNA. Leave the amplifier on and after 20-30 minutes check the voltage drop across resistors R42, R43. 200 ... 250 mV should fall there, which means a quiescent current of 20-25 mA. If it is greater, then it is necessary to reduce the resistances R30, R31, if less, then increase accordingly. It may happen that the quiescent current of the UNA will be asymmetrical - in one arm 5-6mA, in the other 50mA. In this case, unsolder the transistors from the latch and continue without them for now. The effect did not find a logical explanation, but disappeared when the transistors were replaced. In general, it makes no sense to use transistors with a large H21e in a latch. A gain of 50 is enough.
After setting the UNA, we again check the quiescent current of the VC. It should be measured by the voltage drop across resistors R79, R82. A current of 100 mA corresponds to a voltage drop of 33 mV. Of these 100 mA, about 20 mA is consumed by the pre-terminal stage and up to 10 mA can go to control the optocoupler, therefore, in the case when, for example, 33 mV drops across these resistors, the quiescent current will be 70 ... 75 mA. You can refine it by measuring the voltage drop across the resistors in the emitters of the output transistors and subsequent summation. The quiescent current of the output transistors from 80 to 130 mA can be considered normal, while the declared parameters are fully preserved.
Based on the results of measuring the voltages on the collectors T15, T18, we can conclude that the control current through the optocoupler is sufficient. If T15, T18 are almost saturated (the voltages on their collectors differ from the supply voltages by less than 10 V), then you need to reduce the values ​​\u200b\u200bof R51, R56 by about one and a half times and re-measure. The voltage situation should change, and the quiescent current should remain the same. The optimal case is when the voltages on the collectors T15, T18 are equal to about half of the supply voltages, but a deviation from the supply by 10-15V is quite enough, this is the reserve that is needed to control the optocoupler on a music signal and a real load. Resistors R51, R56 can heat up to 40-50 * C, this is normal.
Instantaneous power in the most difficult case - with an output voltage close to zero - does not exceed 125-130 W per transistor (according to technical conditions, up to 150 W is allowed) and it acts almost instantly, which should not lead to any consequences.
Latch actuation can be determined subjectively by a sharp decrease in output power and a characteristic “dirty” sound, in other words, there will be a highly distorted sound in the speakers.

The background of the project is this, around 2008, then the little-known waso (Vadim Mogilny) posted on the amateur radio forums Vegolab and Soldering for discussion his project - an amplifier circuit own design. The author's name of the project was ULF Natalie. The amplifier circuit was developed long before it was posted on the forums, back in 1996. The first models of ULF Natalie were going to domestic details, due to the fact that in Novokuznetsk in the mid-90s, imports were tight. Even on the domestic configuration, the ULF sounded quite good, the noises were barely distinguishable only in the immediate vicinity of the speakers. Now, of course, ULF Natalie and the entire subsequent line of modifications have been transferred to import. The first ULF models were tested in a merciless mode at discos and voice acting for various events.

In the discussion of the project, incl. expressing critical remarks participated many members of the forum. But the greatest and most direct assistance to the author in the development of the project was provided by tsf54 (Sergey) and Shurika (Vadim). A lot of work has been done: modes were adjusted on the layouts, measurements were made, the selection of the element base, then wiretapping, rejection ... and all over again.

The result of this work was ULF Natalie EA. The operating mode of the output stage is SuperA (economical A) at a quiescent current of 80 to 120 mA.

Technical parameters of UMZCH:
Rated output power, W (pro_version - four pairs of output transistors) - 300 W \ 4 Ohm
Stripped-down version, W (home_version - two pairs of output transistors) - 150 W \ 4 Ohm.
Kg (THD) at rated output power at 1 kHz, 0.0008% or less (0.0006% or less typical)
Intermodulation distortion factor, not more than 0.002% (typical value is less than 0.0015%)

For the home version, a one-sided PP was divorced; for compact installation, the VD18, 19 diodes are attached from the soldering side.

ULF Nataly EA mounting on a radiator

Mounting the output stage in one row on the radiator was not widely used, but it was tested in the layout:

We assembled ULF Natalie EA home and pro_versions at least a hundred times, but I especially want to highlight the assembly from this stream dimon(Dmitry, St. Petersburg). In the ULF, everything should be perfect: sound, details, case... Try to make a similar case at home.

What do I have on this moment:

1. Amplifier itself:

2. Naturally, the power supply of the final amplifier:

When setting up the PA, I use a device that provides a safe connection of the PA transformer to the network (through a lamp). It is made in a separate box with its own cord and socket and, if necessary, connects to any device. The diagram is shown below in the figure. This device requires a relay with a 220 AC winding and two groups of make contacts, one momentary pushbutton (S2), one latching pushbutton or switch (S1). When S1 is closed, the transformer is connected to the network through the lamp, if all PA modes are normal, when the S2 button is pressed, the relay closes the lamp through one group of contacts and connects the transformer directly to the network, and the second group of contacts, duplicating the S2 button, constantly connects the relay to the network. The device is in this state until S1 opens, or the voltage decreases below the holding voltage of the relay contacts (including short circuit). The next time S1 is turned on, the transformer is again connected to the network through the lamp, and so on ...

Noise immunity various ways shielding of signal wires

3. We also have assembled AC protection against DC voltage:

Implemented in defense:
speaker connection delay
protection against constant output, against short circuit
airflow control and shutdown of the speakers when the radiators overheat

Adjustment:
Suppose everything is assembled from serviceable and tested transistors and diodes by the tester. Initially, put the trimmers in the following positions: R6 - in the middle, R12, R13 - in the top according to the diagram.
Do not solder the VD7 zener diode at first. On the protection PCB, the Zobel circuits necessary for the stability of the amplifier are separated, if they are already on the UMZCH boards, then they do not need to be soldered, and the coils can be replaced with jumpers. Otherwise, the coils are wound on a mandrel with a diameter of 10 mm, for example, the tail of a drill with a wire with a diameter of 1 mm. The length of the resulting winding should be such that the coil fits into the holes allotted for it on the board. After winding, I recommend impregnating the wire with varnish or glue, for example, epoxy or BF - for rigidity.
The wires going from the protection to the outputs of the amplifier, while connected to the common wire, disconnecting from its outputs, of course. It is necessary to connect the ground protection polygon marked on the PCB with the mark “Main GND” with the “Mecca” of the UMZCH, otherwise the protection will not work correctly. And, of course, the GND pads next to the coils.
Having turned on the protection with the speakers connected, we begin to reduce the resistance R6 until the relay clicks. Having unscrewed one or two more turns of the trimmer, we turn off the protection from the network, turn on two speakers in parallel on any of the channels and check whether the relays will work. If they don’t work, then everything works as intended, with a load of 2 Ohms, the amplifiers will not connect to it, in order to avoid damage.
Next, we disconnect the wires “From UMZCH LC” and “From UMZCH PC” from the ground, turn everything on again and check whether the protection will work if a constant voltage of about two or three volts is applied to these wires. The relays should turn off the speakers - there will be a click.
You can enter the indication "Protection" if you connect a chain of a red LED and a 10 kΩ resistor between ground and VT6 collector. This LED will indicate a fault.
Next, set up the temperature control. We put the thermistors in a waterproof tube (attention! They should not get wet during the test!).
It often happens that a radio amateur does not have thermistors indicated in the diagram. Two of the same ones available, with a resistance of 4.7 kOhm, will do, but in this case, the resistance R15 should be equal to twice the resistance of the series-connected thermistors. Thermistors must have a negative resistance coefficient (reduce it with heating), the thermistors work the other way around and they have no place here. Boil a glass of water. We give it 10-15 minutes to cool in calm air and lower the thermistors into it. We twist R13 until the LED goes out "Overheat" - Overheat, which should have been lit initially.
When the water cools down to 50 degrees (this can be accelerated, how exactly is a big secret) - turn R12 so that the “Blow” LED or FAN On goes out.
We solder the VD7 zener diode in place.
If there are no glitches from the sealing of this zener diode, then everything is fine, but it was such that without it the transistor part works flawlessly, but with it it does not want to connect the relay to any. In this case, we change it to any one with a stabilization voltage from 3.3 V to 10V. The reason is the leakage of the zener diode.
When the thermistors are heated to 90 * C, the “Overheat” LED should light up - Overheating and the relay will disconnect the speakers from the amplifier. With some cooling of the radiators, everything will be connected back, but this mode of operation of the device should at least alert the owner. With a working fan and a tunnel not clogged with dust, thermal operation should not be observed at all.
If everything is fine, solder the wires to the output of the amplifier and enjoy.
Airflow (its intensity) is adjusted by selecting resistors R24 and R25. The first determines the performance of the cooler with the airflow turned on (maximum), the second determines the performance of the cooler when the radiators are only slightly warm. R25 can be excluded altogether, but then the fan will operate in ON-OFF mode.
If the relays have windings for 24V, then they must be connected in parallel, if for 12, then in series.
Parts replacement. As an op amp, you can use almost any dual cheap op amp in SOIK8 (from 4558 to ORA2132, although I hope it will not reach the latter), for example, TL072, NE5532, NJM4580, etc.
Transistors - 2n5551 are changed to BC546-BC548, or to our KT3102. We will replace BD139 with 2SC4793, 2SC2383, or with a similar current and voltage, it is possible to put at least KT815.
The field worker changes to a similar one used, the choice is huge. A field radiator is not required.
Diodes 1N4148 are changed to 1N4004 - 1N4007 or to KD522. In the rectifier, you can put 1N4004 - 1N4007 or use a diode bridge with a current of 1 A.
If the blower control and overheating protection of the UMZCH are not needed, then the right side of the circuit is not soldered - the op-amp, thermistors, field, etc., except for the diode bridge and the filter capacitor. If you already have a 22..25V power supply in the amplifier, then you can use it, not forgetting about the protection current consumption of about 0.35A when the blower is turned on.

Recommendations for assembling and configuring UMZCH:
Before assembling the printed circuit board, you should perform relatively simple operations with the board, namely, look through the light to see if there are short circuits between the tracks that are hardly noticeable under normal lighting. Factory production does not exclude manufacturing defects, unfortunately. Soldering is recommended to be carried out with solder POS-61 or similar with a melting point not higher than 200 * C.

First you need to decide on the applied OS. The use of op-amps from Analog Devices is highly not recommended - in this UMZCH their sound character is somewhat different from what the author intended, and an excessively high speed can lead to irremovable self-excitation of the amplifier. The replacement of ORA134 with ORA132, ORA627 is welcomed. they have less distortion at high frequencies. The same applies to the op amp DA1 - it is recommended to use OPA2132, OPA2134 (in order of preference). It is acceptable to use OPA604, OPA2604, but there will be slightly more distortion. Of course, you can experiment with the type of op-amp, but at your own peril and risk. UMZCH will also work with KR544UD1, KR574UD1, but the zero offset level at the output will increase and the harmonics will grow. The sound is ... I think no comments are needed.

From the very beginning of the installation, it is recommended to select transistors in pairs. This is not a necessary measure as the amplifier will work with a spread of 20-30%, but if you set a goal to get the maximum quality, then pay attention to this. Of particular note is the selection of T5, T6 - they are best used with maximum H21e - this will reduce the load on the op-amp and improve its output spectrum. T9, T10 should also have as close gain as possible. For latch transistors selection is optional. Output transistors - if they are from the same batch, you can not select them, because. the culture of production in the West is somewhat higher than we are used to, and the spread is within 5-10%.

Further, instead of the terminals of the resistors R30, R31, it is recommended to solder pieces of wire a couple of centimeters long, since it will be necessary to select their resistances. An initial value of 82 ohms will give a UN quiescent current of about 20..25 mA, but statistically it turned out from 75 to 100 ohms, this strongly depends on the specific transistors.
As already noted in the topic on the amplifier, you should not use transistor optocouplers. Therefore, it is worth focusing on AOD101A-G. Imported diode optocouplers were not tested due to unavailability, this is temporary. The best results are obtained on AOD101A of one batch for both channels.

In addition to transistors, it is worth picking up UNA complementary resistors in pairs. The spread should not exceed 1%. You need to carefully select R36=R39, R34=R35, R40=R41. For reference, I note that with a spread of more than 0.5%, it is better not to switch to the option without environmental protection, because. there will be an increase in even harmonics. It was the impossibility to get the exact details that stopped the author's experiments in the non-OOS direction at the time. The introduction of balancing into the current feedback circuit does not completely solve the problem.

Resistors R46, R47 can be soldered at 1 kOhm, but if there is a desire to more accurately adjust the current shunt, then it is better to do the same as with R30, R31 - solder the wires for soldering.
As it turned out in the course of repeating the circuit, under some set of circumstances, excitation in the EA tracking circuit is possible. This manifested itself in the form of an uncontrolled drift of the quiescent current, and especially in the form of oscillations with a frequency of about 500 kHz on collectors T15, T18.
The necessary adjustments were originally included in this version, but it's still worth checking with an oscilloscope.

Diodes VD14, VD15 are placed on the radiator for temperature compensation of the quiescent current. This can be done by soldering the wires to the leads of the diodes and gluing them to the heatsink with Moment glue or similar.

Before turning it on for the first time, it is necessary to thoroughly wash the board from traces of flux, look for the absence of short circuits with solder, make sure that the common wires are connected to the midpoint of the power supply capacitors. It is also strongly recommended to use the Zobel circuit and the coil at the output of the UMZCH, they are not shown in the diagram, because. the author considers their application as a rule of good form. The ratings of this circuit are common - these are a 10 Ohm 2 W resistor connected in series and a K73-17 capacitor or similar with a capacity of 0.1 μF. The coil is wound with a varnished wire with a diameter of 1 mm on an MLT-2 resistor, the number of turns is 12 ... 15 (before filling). On the protection board, this circuit is completely wired.

All transistors VK and T9, T10 in UN are mounted on a radiator. Powerful VK transistors are installed through mica spacers and KPT-8 type paste is used to improve thermal contact. It is not recommended to use near-computer pastes - there is a high probability of a fake, and tests confirm that KPT-8 is often the best choice, and also very inexpensive. In order not to fly into a fake, use KPT-8 in metal tubes, like toothpaste. We haven't gotten there yet, fortunately.

For transistors in an insulated package, the use of a mica gasket is optional and even undesirable, because. worsens the conditions of thermal contact.
Be sure to turn on a 100-150W light bulb in series with the primary winding of the network transformer - this will save you from many troubles.

Short the D2 optocoupler LED pins (1 and 2) and turn on. If everything is assembled correctly, then the current consumed by the amplifier should not exceed 40 mA (the output stage will operate in mode B). The DC bias voltage at the UMZCH output should not exceed 10 mV. Turn on the LED. The current consumed by the amplifier should increase to 140 ... 180 mA. If it increases more, then check (it is recommended to do this with a pointer voltmeter) collectors T15, T18. If everything works correctly, there should be voltages that differ from the supply voltages by about 10-20 V. In the case when this deviation is less than 5 V, and the quiescent current is too large, try changing the diodes VD14, VD15 to others, it is very desirable that they were from the same party. The UMZCH quiescent current, if it does not fit in the range from 70 to 150 mA, can also be set by selecting resistors R57, R58. Possible replacement for diodes VD14, VD15: 1N4148, 1N4001-1N4007, KD522. Or, reduce the current flowing through them by simultaneously increasing R57, R58. In my thoughts there was the possibility of implementing a bias of such a plan: instead of VD14, VD15, use transitions of BE transistors from the same batches as T15, T18, but then you will have to significantly increase R57, R58 - until the resulting current mirrors are fully tuned. In this case, the newly introduced transistors must be in thermal contact with the radiator, as well as the diodes, instead of which they are placed.

Next, you need to set the quiescent current UNA. Leave the amplifier on and after 20-30 minutes check the voltage drop across resistors R42, R43. 200 ... 250 mV should fall there, which means a quiescent current of 20-25 mA. If it is greater, then it is necessary to reduce the resistances R30, R31, if less, then increase accordingly. It may happen that the quiescent current of the UNA will be asymmetrical - in one arm 5-6mA, in the other 50mA. In this case, unsolder the transistors from the latch and continue without them for now. The effect did not find a logical explanation, but disappeared when the transistors were replaced. In general, it makes no sense to use transistors with a large H21e in a latch. A gain of 50 is enough.

After setting the UNA, we again check the quiescent current of the VC. It should be measured by the voltage drop across resistors R79, R82. A current of 100 mA corresponds to a voltage drop of 33 mV. Of these 100 mA, about 20 mA is consumed by the pre-terminal stage and up to 10 mA can go to control the optocoupler, therefore, in the case when, for example, 33 mV drops across these resistors, the quiescent current will be 70 ... 75 mA. You can refine it by measuring the voltage drop across the resistors in the emitters of the output transistors and subsequent summation. The quiescent current of the output transistors from 80 to 130 mA can be considered normal, while the declared parameters are fully preserved.

Based on the results of measuring the voltages on the collectors T15, T18, we can conclude that the control current through the optocoupler is sufficient. If T15, T18 are almost saturated (the voltages on their collectors differ from the supply voltages by less than 10 V), then you need to reduce the values ​​\u200b\u200bof R51, R56 by about one and a half times and re-measure. The voltage situation should change, and the quiescent current should remain the same. The optimal case is when the voltages on the collectors T15, T18 are equal to about half of the supply voltages, but a deviation from the supply by 10-15V is quite enough, this is the reserve that is needed to control the optocoupler on a music signal and a real load. Resistors R51, R56 can heat up to 40-50 * C, this is normal.

Instantaneous power in the most difficult case - with an output voltage close to zero - does not exceed 125-130 W per transistor (according to technical conditions, up to 150 W is allowed) and it acts almost instantly, which should not lead to any consequences.

Latch actuation can be determined subjectively by a sharp decrease in output power and a characteristic “dirty” sound, in other words, there will be a highly distorted sound in the speakers.

4. Preamplifier and its PSU

High quality PU material:

Serves for tone correction and loudness when adjusting the volume. Can be used to connect headphones.

The well-proven TB Matyushkina was used as a timbre block. It has 4-stage bass control and smooth treble control, and its frequency response is well suited to auditory perception, in any case, the classic bridge TB (which can also be used) is rated lower by listeners. The relay allows, if necessary, to turn off any frequency correction in the path, the output signal level is adjusted by a tuning resistor according to gain equality at a frequency of 1000 Hz in the TB mode and when bypassed.

Design characteristics:

Kg in the frequency range from 20 Hz to 20 kHz - less than 0.001% (typical value is about 0.0005%)

Most audio enthusiasts are quite categorical and not ready for compromises when choosing equipment, rightly believing that the perceived sound must be clear, strong and impressive. How to achieve this?

Data search for your request:

Natalie amplifier home version

Schemes, reference books, datasheets:

Price lists, prices:

Discussions, articles, manuals:

Wait until the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Perhaps the main role in resolving this issue will be played by the choice of amplifier.
Function
The amplifier is responsible for the quality and power of sound reproduction. At the same time, when buying, you should pay attention to the following designations, marking the implementation high technology in the production of audio - equipment:


  • Hi fi. Provides maximum purity and accuracy of sound, freeing it from extraneous noise and distortion.
  • Hi end. The choice of a perfectionist who is ready to pay a lot for the pleasure of distinguishing the smallest nuances of his favorite musical compositions. Often hand-assembled equipment falls into this category.

Specifications to pay attention to:

  • input and output power. The nominal value of the output power is decisive, since edge values ​​are often unreliable.
  • Frequency range. Varies from 20 to 20000 Hz.
  • The coefficient of non-linear distortion. It's simple - the smaller the better. The ideal value, according to experts, is 0.1%.
  • Signal-to-noise ratio. Modern technology assumes a value of this indicator above 100 dB, which minimizes extraneous noise when listening.
  • dumping factor. Reflects the output impedance of the amplifier in relation to the nominal load impedance. In other words, a sufficient damping factor (more than 100) reduces the occurrence of unnecessary vibrations in equipment, etc.

It should be remembered: the manufacture of high-quality amplifiers is a laborious and high-tech process, respectively, too low price with worthy characteristics should alert you.

Classification

To understand all the variety of market offers, it is necessary to distinguish the product according to various criteria. Amplifiers can be classified:

  • By power. Preliminary - a kind of intermediate link between the sound source and the final power amplifier. The power amplifier, in turn, is responsible for the strength and volume of the signal at the output. Together they form a complete amplifier.

Important: the primary conversion and signal processing takes place precisely in the preamplifiers.

  • According to the element base, tube, transistor and integrated PAs are distinguished. The latter arose in order to combine the advantages and minimize the disadvantages of the first two, for example, the sound quality of tube amplifiers and the compactness of transistor ones.
  • According to the mode of operation, amplifiers are divided into classes. The main classes are A, B, AB. If class A amplifiers use a lot of power, but produce high quality sound, class B is exactly the opposite, class AB seems to be the best choice, representing a compromise between signal quality and sufficiently high efficiency. There are also classes C, D, H and G, which have arisen with the use of digital technologies. There are also single-cycle and push-pull modes of operation of the output stage.
  • By the number of channels, amplifiers can be one-, two- and multi-channel. The latter are actively used in home theaters to form the volume and realism of the sound. Most often there are two-channel, respectively, for the right and left audio systems.

Attention: the study of the technical components of the purchase, of course, is necessary, but often the decisive factor is the elementary listening to the equipment according to the principle of sounds or does not sound.

Application

The choice of amplifier is more justified by the purposes for which it is purchased. We list the main areas of use of audio frequency amplifiers:

  1. As part of a home audio system. It's obvious that the best choice is a tube two-channel single cycle in class A, also the best choice can be a three-channel class AB, where one channel is defined for a subwoofer, with a Hi-fi function.
  2. For speaker system in the car. The most popular four-channel amplifiers are AB or D class, in accordance with the financial capabilities of the buyer. In cars, the crossover function is also in demand for smooth frequency control, which allows you to cut frequencies in the high or low range as needed.
  3. in concert equipment. Higher demands are reasonably placed on the quality and capabilities of professional equipment due to the large distribution space. sound signals, as well as a high need for intensity and duration of use. Thus, it is recommended to purchase an amplifier with a class not lower than D, capable of operating almost at the limit of its power (70-80% of the declared one), preferably in a case made of high-tech materials that protects against negative weather conditions and mechanical influences.
  4. in studio equipment. All of the above is true for studio equipment. You can add about the largest frequency reproduction range - from 10 Hz to 100 kHz in comparison with that from 20 Hz to 20 kHz in a domestic amplifier. Also noteworthy is the possibility of separate volume control on different channels.

So that for a long time to enjoy clear and high-quality sound, it is advisable to study all the variety of offers in advance and choose the option of audio equipment that best meets your needs.

In the photo: Natalie preamplifier in the case satellite receiver


The article will focus on my build option preamplifier"Natalie" with a successful solution to the hull problem.

This project has become another long-term construction project on my list and has beaten all deadlines. The fact is that the idea of ​​\u200b\u200bassembling a preamplifier appeared more than a year ago, and along with the idea, almost all the components necessary for this circuit settled in my parts box.

And, as is often the case, all the enthusiasm suddenly evaporated somewhere, so that everything that had been started had to be curtailed for an indefinite time. Although why is uncertain ... very definite - before the onset of autumn cold, when all the summer affairs, which were very many this year, will be completed and there will be free time for soldering.

About the scheme and details


The scheme was chosen for a long time, a very long time! The path to this pre-amplifier began with the use of specialized microcircuits like the LM1036 or TDA1524 as a control panel with a tone control, but local forum users successfully dissuaded me from this sin. Then there was a circuit taken from some foreign site on three TL072 type op-amps with treble and bass adjustment. Even etched PP and collected, and listened to this before for a while, but the soul did not lie down to him.

Then he drew attention to the circuit of the famous Solntsev preamplifier, and already while searching for information on the Solntsev PU, I came across a circuit resembling Solntsev's in conjunction with Matyushkin's passive RT. It was . It was just what I needed!

Having slightly simplified the preamplifier circuit and, having finalized it for myself, I got this result. The transition to a single-storey power supply and the removal of "extra" parts made it possible to somewhat simplify the layout of the board, make it one-sided and, most importantly, slightly reduce the size of the PCB. I didn’t change anything significant in the circuit that could worsen the sound quality, I just removed the functions that I didn’t need bypassing the tone control, balance and loudness block.

To the tone control circuit I didn’t contribute anything of my own, but I still had to redistribute the board, tk. I did not find on the Internet a ready-made one-sided signet of the size I needed. Switching modes of the tone block is made on domestic relays RES-47.

In order to make the control of the tone control and preamplifier I needed, I plunged into the theory of the principles of operation of counters and triggers of domestic microcircuits for several days. For the preamplifier, I chose a case from an obsolete satellite receiver, in which there was a rather large window, and it needed to be filled with something beautiful and useful. So, I wanted to make it so that there was visual information about the modes of the tone control, and it would be better if these were not LEDs, but numbers familiar to the eye and brain. As a result, such a scheme of three MS was drawn.

K561LE5 sets the pulses that are fed to the inputs K174IE4 and K561IE9A. The counter on IE9 controls 4 keys that switch relays on the Matyushkin RT. At the same time, the counter on IE4 changes the readings on the ALS335B1 seven-segment indicator, indicating what mode the tone control is in at the moment. The number "0" corresponds to the mode with the minimum level low frequencies, the number "3" - the maximum. Another simple one electronic switch made on MS K155TM2. One half of the microcircuit controls a relay that switches the signal level indicator modes, the second half is responsible for the input selector relay. Well, and a typical circuit of the signal level indicator on the LM3915 MS separately for each channel.

Power Supply made on the basis of the TP-30 transformer, of course, with the secondary winding rewound to the required voltage.

All voltages stabilized:
+/- 15V - on / LM337 to power the preamp board
+9V at 7805 to power the relay and control unit
+5V again for USB power supply sound card

About setup and possible problems

Despite all the apparent complexity of the circuit and a lot of details, with proper assembly and the use of known-good and recommended components for this circuit, you can most likely fence yourself off from unpleasant surprises that may arise when assembling this PU. The only part of this whole circuit that needs tweaking is the preamp board itself. It is necessary to set the quiescent current, check the level of the constant at the output, and the waveform.

The recommended quiescent current for this PU is 20-22 mA, and it is calculated from the voltage drop across 15 ohm resistors R20, R21, R40, R42. For a current of 20-22 mA, 300-350 mV should drop across these resistors (300:15=20, 350:15=22). The voltage drop, and, accordingly, the current can be adjusted in one direction or another by changing the value of the resistors R9, R10, R30, R31 (51 Ohm in the original circuit). A greater quiescent current corresponds to a greater resistance of the resistor and vice versa. In my version, instead of fixed 51 Ohm resistors, I soldered multi-turn trimmers with a nominal value of 100 Ohm, which made it possible to set without any extra effort and with high accuracy desired current rest.

two troubles that a person who decides to repeat this preamplifier may encounter is an excitation, and a constant at the output. And, as a rule, the first problem gives rise to the second. First you need to make sure the presence or absence of a constant component at the output of each buffer and each op-amp. A small amount of constant is allowed, but just a small amount, roughly speaking no more than a few mV.

If there is no constant, I congratulate you! If there is, we are looking for the reason, but there are not so many reasons. This is either an installation error, or a “wrong” part, or somewhere there is an excitation. First of all, you need to carefully examine the board for non-soldering or, vice versa, sticky tracks, double-check whether you are using all the details of the required denomination, and if everything is correct, the third option remains, i.e. excit. You will need an oscilloscope to find it.

I myself have encountered this problem. All four buffers had a constant output of 100-150 mV. And the reason for its occurrence turned out to be just the “wrong” detail. The fact is that instead of the OPA134 operational amplifiers, I had NE5534 installed, which are not quite suitable for use in this circuit. For a long time and unsuccessfully, I struggled with this problem, and the problem disappeared by itself after replacing the op-amp with an OPA134.

About location and connection


Due to the fact that the existing case was not very large, I had to draw all the boards again in order to make them even a couple of centimeters more compact. The placement of boards in the case turned out to be very tight, but fortunately everything fit. Everything is a preamplifier board, a tone control board, a dual board of a control and indication unit, USB sound card, a power supply transformer and a rectifier-stabilizer board, and two small boards for an input selector and a volume and treble control.


I connected all the common wires at one point, on the volume and treble control board. This got rid of the frightening problem of hum and background, which is possible with improperly ground.


Again, due to cramped conditions, the control and indication board had to be made composite, consisting of one large and one small board. They are connected to each other through a pin connector.


I attached all the boards to the chassis of the case through such plastic insulating spacers. This made it possible to completely isolate the boards from contact, as with metal case, and from each other, in places where this is not needed.

Comfortable housing

Let me tell you a little about the body itself. As I already mentioned, the case from a satellite receiver is used as a case for the preamplifier. The old man faithfully served for many years, was repaired several times, and after another trip to the workshop was sent to me with a diagnosis of "corpse".

The hulls used to be good, big ones! It was because of its size and large window that I chose this case. On the front panel, apart from the inscriptions, there was nothing superfluous. There were, of course, 3 unused buttons, but it's not scary. I painted over the inscriptions with matte paint from a spray can bought at a car dealership. The paint matched 98 percent in color with the one that the body was originally painted with. The difference can only be seen if you look closely.


I installed them as handles for these regulators, which by the way. They perfectly (in my opinion) fit into the overall design of the preamp, which is designed in silver and black.

About sound and impressions

And it's time to talk about the most interesting, about what happened in the end. And in the end, I got another good toy in my collection of sound reproducing equipment.

The scheme certainly deserves attention and to be repeated. I liked the sound of the finished device, it brings some color to the music. Despite only 4 steps in the Matyushkin tone control, I can’t say that there are not enough bass controls. Four positions of the bass control are enough to find the right level of low frequencies for a particular style of music and your preferences.
Love explosive bass? We switch the tone block to the fourth position and let the speakers break! The range of adjustments for highs is also more than enough when the knob is positioned as far as possible to the right, the number of highs starts to cut the ear.