Amplifier characteristics:
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 coefficient, no more than 0.002% (typical value less than 0.0015%)
The UMZCH scheme contains:
balanced input
clip limiter on optocoupler AOP124
protection system against current overloads and short circuits in the load
The nodes that are not needed for the truncated version are circled in red. In brackets are the ratings for power supply +\- 45V.
The protection includes:
speaker connection delay
protection against constant output, against short circuit
airflow control and turning off the speakers when the radiators overheat
Protection circuit
Recommendations for assembling and configuring the UMZCH:
Before you begin assembling the printed circuit board, you should perform relatively simple operations on the board, namely, look in the light to see if there are any short circuits between the tracks that are barely noticeable under normal lighting. Factory production does not exclude manufacturing defects, unfortunately. Soldering is recommended to be done with POS-61 solder or similar with a melting point of no higher than 200* C.
First you need to decide on the op amp used. 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, and an excessively high speed can lead to irreparable self-excitation of the amplifier. Replacing OPA134 with OPA132, OPA627 is welcome, because they have less distortion at HF. The same applies to 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. The UMZCH will work with KR544UD1, KR574UD1, but the level of zero offset at the output will increase and the harmonics will increase. The sound... I think no comments are needed.
From the very beginning of installation, it is recommended to select transistors in pairs. This is not a necessary measure, because the amplifier will work even with a spread of 20-30%, but if your goal is to get maximum quality, then pay attention to this. Particular attention should be paid to 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 the gain as close as possible. For latch transistors, selection is optional. Output transistors - if they are from the same batch, you don’t have to select them, because The production culture in the West is slightly higher than what we are used to and the spread is within 5-10%.
Next, instead of the terminals of 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 quiescent current of approximately 20..25 mA, but statistically it turned out to be from 75 to 100 Ohms, this greatly depends on the specific transistors.
As already noted in the topic on the amplifier, you should not use transistor optocouplers. Therefore, you should focus on AOD101A-G. Imported diode optocouplers were not tested due to unavailability, this is temporary. The best results are obtained on the AOD101A of one batch for both channels.
In addition to transistors, it is worth choosing complementary UNA resistors in pairs. The spread should not exceed 1%. Particular care must be taken to select R36=R39, R34=R35, R40=R41. As a guide, 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 inability to obtain precise details that at one time stopped the author’s experiments in the non-OOS direction. 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 you want to more accurately adjust the current shunt, then it is better to do the same as with R30, R31 - solder in the wiring for soldering.
As it turned out during the repetition of the circuit, under certain circumstances it is possible to excite an EA in the tracking circuit. 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 the collectors T15, T18.
The necessary adjustments were initially 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 radiator with “Moment” type glue or similar.
Before turning it on for the first time, you must thoroughly wash the board from traces of flux, check for any short circuits in the tracks with solder, and make sure that the common wires are connected to the midpoint of the power supply capacitors. It is also strongly recommended to use a Zobel circuit and a coil at the output of the UMZCH; they are not shown in the diagram, because the author considers their use to be a rule of good form. The ratings of this circuit are common - these are a series-connected 10 Ohm 2 W resistor and a K73-17 capacitor or similar with a capacity of 0.1 μF. The coil is wound with varnished wire with a diameter of 1 mm on an MLT-2 resistor, the number of turns is 12...15 (until filling). On the protection PP this circuit is completely separated.
All transistors VK and T9, T10 in UN are mounted on the radiator. Powerful VK transistors are installed through mica spacers and a paste of the KPT-8 type is used to improve thermal contact. It is not recommended to use computer pastes - there is a high probability of counterfeiting, and tests confirm that KPT-8 is often the best choice, and also very inexpensive. To avoid getting caught by a fake, use KPT-8 in metal tubes, like toothpaste. We haven't gotten to that point yet, fortunately.
For transistors in an insulated housing, the use of a mica spacer is not necessary 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-circuit the D2 optocoupler LED leads (1 and 2) and turn on. If everything is assembled correctly, 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 output of the UMZCH should not exceed 10 mV. Unwrap 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 ones by about 10-20 V. In the case when this deviation is less than 5 V, and the quiescent current is too high, 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 fall within 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 would have to significantly increase R57, R58 - until the resulting current mirrors are fully adjusted. In this case, the newly introduced transistors must be in thermal contact with the radiator, as well as the diodes in their place.
Next you need to set the quiescent current UNA. Leave the amplifier turned on and after 20-30 minutes check the voltage drop across resistors R42, R43. 200...250 mV should drop 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 it is less, then increase it accordingly. It may happen that the quiescent current of the UNA will be asymmetrical - 5-6mA in one arm, 50mA in the other. 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 replacing transistors. In general, there is no point in using transistors with large H21e in the latch. A gain of 50 is enough.
After setting up the UN, we again check the quiescent current of the VK. 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-final stage and up to 10 mA can be spent on controlling the optocoupler, so in the case when, for example, 33 mV drops across these resistors, the quiescent current will be 70...75 mA. It can be clarified 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 completely preserved.
Based on the results of voltage measurements 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 ratings of R51, R56 by about one and a half times and re-measure. The situation with voltages should change, but the quiescent current should remain the same. The optimal case is when the voltages on the collectors T15, T18 are equal to approximately half of the supply voltages, but a deviation from the supply of 10-15V is quite sufficient; this is a 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 severe 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.
The actuation of the latch 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 as follows: around 2008, then the little-known waso (Vadim Mogilny) posted his project - an amplifier circuit of his own design - on the amateur radio forums Vegolab and Soldering Iron for discussion. 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. Natalie's first ULF models were assembled using domestic parts, due to the fact that imports were difficult in Novokuznetsk in the mid-90s. Even with the domestic configuration, the ULF sounded quite good; the noise was barely noticeable 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 mercilessly at discos and dubbing various events.
In the discussion of the project, incl. Many forum members participated in expressing critical remarks. 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 huge amount of work was done: adjustment of modes was done on the mock-ups, measurements, selection of the element base, then wiretapping, rejection... and all over again.
The result of this work was Natalie EA's ULF. The operating mode of the output stage is SuperA (economical A) with 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 coefficient, no more than 0.002% (typical value less than 0.0015%)
For the home version, a one-sided PCB was installed; for compact installation, diodes VD18, 19 are attached on the solder side.
ULF Nataly EA installation on a radiator
Mounting the output stage in one row on a radiator is not widespread, but it was tested in a prototype:
We have assembled the 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). Everything should be perfect in ULF: sound, details, housing... Try making a similar housing at home.
In the photo: Natalie preamplifier in the housing of a satellite receiver
This project became another long-term construction project on my list and beat all deadlines for completion. The fact is that the idea of assembling 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 drawer.
And, as often happens, all the enthusiasm suddenly evaporated somewhere, so we had to stop everything we started for an indefinite period of time. Although why is it indefinite... very definite - before the onset of autumn cold, when all the summer tasks, of which there were a lot this year, will be completed and there will be free time for soldering.
Then I paid attention to the circuit of the famous Solntsev preamplifier, and already while searching for information on Solntsev’s PU I came across a circuit reminiscent of Solntsev’s in conjunction with Matyushkin’s passive RT. It was . This was exactly what I needed!
Having slightly simplified the preamplifier circuit and modified it to suit myself, I got this result. The transition to a single-story power supply and the removal of “extra” parts made it possible to somewhat simplify the board layout, 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 of bypassing the tone control, balance and loudness compensation unit that I didn’t need.
To the tone control circuit I didn’t contribute anything of my own, but I still needed to reset the board because... I couldn’t find a ready-made single-sided seal of the size I needed on the Internet. Switching of the tone block modes is done using domestic relays RES-47.
In order to make the control I needed for the tone control and preamplifier, I immersed myself for several days in the theory of the principles of operation of counters and triggers of domestic microcircuits. For the preamplifier, I chose a case from an outdated satellite receiver, which had a rather large window, and it needed to be filled with something beautiful and useful. So, I wanted to make sure 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 diagram of three MSs was drawn.
K561LE5 sets pulses that arrive at the inputs of K174IE4 and K561IE9A. The counter on IE9 controls 4 keys that switch relays on Matyushkin’s RT. At the same time, the counter on IE4 changes the readings on the seven-segment indicator ALS335B1, indicating what mode the tone control is in at the moment. The number “0” corresponds to the mode with the minimum level of low frequencies, the number “3” – to the maximum. Another simple electronic switch is made on the MS K155TM2. One half of the microcircuit controls the switch that switches the modes of the signal level indicator, 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 unit made on the basis of the TP-30 transformer, of course with the secondary winding rewound to the required voltages.
All voltages are stabilized:
+/- 15V - on / LM337 to power the preamp board
+9V at 7805 to power the relay and control unit
+5V is again on to power the USB sound card
The recommended quiescent current for this control unit is 20-22 mA, and it is calculated by 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 resistors R9, R10, R30, R31 (in the original circuit, 51 Ohms). A higher quiescent current corresponds to a higher resistance of the resistor and vice versa. In my version, instead of constant 51 Ohm resistors, I soldered in multi-turn trimmers with a nominal value of 100 Ohms, which made it possible to set the required quiescent current without any extra effort and with high accuracy.
Two troubles that a person who decides to repeat this preamplifier may encounter is excitement, and a constant output. Moreover, as a rule, the first problem gives rise to the second. First you need to make sure that there is a DC component at the output of each buffer and each op-amp. A small amount of constant is allowed, but just a small one, roughly speaking no more than a few mV.
If there is no permanent residence, I congratulate you! If there is, we look for the reason, but there are not so many reasons. This is either an installation error, or the “wrong” part, or there is an excitment somewhere. The first thing you need to do is to carefully inspect the board for missing connections or, on the contrary, stuck together tracks, double-check whether you are using all the parts of the required value, and if everything is correct, the third option remains, i.e. excited To find it you will need an oscilloscope.
I myself encountered this problem. All four buffers had a constant output of 100-150 mV. And the reason for its occurrence turned out to be precisely the “wrong” detail. The fact is that instead of OPA134 operational amplifiers, I installed NE5534, which are not entirely suitable for use in this circuit. I struggled with this problem for a long time and unsuccessfully, and the problem disappeared by itself after replacing the op-amp with OPA134.
The buildings used to be good, big ones! It was precisely because of its size and large window that I chose this building. There was nothing superfluous on the front panel except for the inscriptions. Of course, there are 3 unused buttons left, but that’s not a big deal. I painted over the inscriptions with matte paint from a spray can purchased at a car dealership. The paint matched 98 percent of the color with the one the body was originally painted with. The difference can only be noticed if you look closely.
The scheme undoubtedly deserves attention and to be repeated. I liked the sound of the finished device; it adds some color to the music. Despite only 4 steps in the Matyushkin tone control, I can’t say that there are not enough low-frequency adjustments. Four positions of the bass control are enough to select the desired level of low frequencies for a specific style of music and your preferences.
Do you like explosive bass? Switch the tone block to the fourth position and let the speakers explode! The range of adjustments for highs is also more than enough when the knob is positioned as far to the right as possible, the amount of highs begins to hurt the ear.
What I have at the moment:
1. The amplifier itself:
2. Naturally, the power supply of the final amplifier:
When setting up the PA, I use a device that ensures a safe connection of the PA transformer to the network (via 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 contacts for closure, one momentary button (S2), one latching button or switch (S1). When S1 is closed, the transformer is connected to the network through the lamp, if all modes of the PA are normal, when you press the S2 button, 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 remains in this state until S1 opens, or the voltage decreases below the holding voltage of the relay contacts (including short circuit). The next time you turn on S1, the transformer is again connected to the network through the lamp, and so on...
Noise immunity of various methods of shielding signal wires
3. We also have assembled AC protection against DC voltage:
The protection includes:
speaker connection delay
protection against constant output, against short circuit
airflow control and turning off the speakers when the radiators overheat
Setting up:
Let's assume that everything is assembled from serviceable transistors and diodes tested by a tester. Initially, place the trimmer engines 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. The protection board contains Zobel circuits, which are necessary for the stability of the amplifier; if they are already present 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, on 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 provided for it on the board. After winding, I recommend impregnating the wire with varnish or glue, for example, epoxy or BFom - for rigidity.
For now, connect the wires going from the protection to the amplifier outputs to the common wire, disconnecting them from its outputs, of course. It is necessary to connect the earth protection polygon, marked on the PCB with the mark “Main GND”, to the “Mecca” UMZCH, otherwise the protection will not work correctly. And, of course, 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. After unscrewing the trimmer one or two more turns, we turn off the network protection, connect two speakers in parallel on any of the channels and check whether the relays 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 “Protection” indication if you connect a chain of a red LED and a 10 kOhm resistor between ground and the VT6 collector. This LED will indicate a fault.
Next, we set up thermal 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 the thermistors indicated on the diagram. Two identical ones from those available will do, with a resistance of 4.7 kOhm, but in this case the resistance of R15 should be equal to twice the resistance of the thermistors connected in series. Thermistors must have a negative coefficient of resistance (reduce it with heating), posistors work the other way around and have no place here. Boil a glass of water. Let it cool for 10-15 minutes in calm air and lower the thermistors into it. Turn R13 until the “Overheat” LED goes out, which should have been lit initially.
When the water cools down to 50 degrees (this can be accelerated, exactly how is a big secret) - turn R12 so that the “Blowing” or FAN On LED goes out.
We solder the VD7 zener diode into place.
If no glitches are detected from the sealing of this zener diode, then everything is fine, but it happened 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 10 V. The reason is a zener diode leak.
When the thermistors heat up to 90*C, the “Overheat” LED should light up - Overheating and the relay will disconnect the speakers from the amplifier. When the radiators cool down a bit, everything will be connected back, but this mode of operation of the device should at least alert the owner. If the fan is working properly and the tunnel is not clogged with dust, thermal activation should not be observed at all.
If everything is fine, solder the wires to the amplifier outputs and enjoy.
The airflow (its intensity) is adjusted by selecting resistors R24 and R25. The first determines the cooler's performance when the fan is turned on (maximum), the second - 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 24V windings, then they must be connected in parallel, but if they have 12V windings, then they must be connected in series.
Replacement of parts. As an op-amp, you can use almost any dual cheap op-amp in SOIK8 (from 4558 to OPA2132, although, I hope, it will not come to the latter), for example, TL072, NE5532, NJM4580, etc.
Transistors - 2n5551 are replaced with BC546-BC548, or with our KT3102. We can replace BD139 with 2SC4793, 2SC2383, or with a similar current and voltage, it is possible to install even KT815.
The polevik is replaced with one similar to the one used, the choice is huge. A radiator is not required for the field worker.
Diodes 1N4148 are replaced with 1N4004 - 1N4007 or with KD522. In the rectifier, you can put 1N4004 - 1N4007 or use a diode bridge with a current of 1 A.
If blowing control and protection against overheating of the UMZCH are not needed, then the right side of the circuit is not soldered - the op-amp, thermistors, field switch, etc., except for the diode bridge and filter capacitor. If you already have a 22..25V power source 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 the UMZCH:
Before you begin assembling the printed circuit board, you should perform relatively simple operations on the board, namely, look in the light to see if there are any short circuits between the tracks that are barely noticeable under normal lighting. Factory production does not exclude manufacturing defects, unfortunately. Soldering is recommended to be done with POS-61 solder or similar with a melting point of no higher than 200* C.
First you need to decide on the op amp used. 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, and an excessively high speed can lead to irreparable self-excitation of the amplifier. Replacing OPA134 with OPA132, OPA627 is welcome, because they have less distortion at HF. The same applies to 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. The UMZCH will work with KR544UD1, KR574UD1, but the level of zero offset at the output will increase and the harmonics will increase. The sound... I think no comments are needed.
From the very beginning of installation, it is recommended to select transistors in pairs. This is not a necessary measure, because the amplifier will work even with a spread of 20-30%, but if your goal is to get maximum quality, then pay attention to this. Particular attention should be paid to 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 the gain as close as possible. For latch transistors, selection is optional. Output transistors - if they are from the same batch, you don’t have to select them, because The production culture in the West is slightly higher than what we are used to and the spread is within 5-10%.
Next, instead of the terminals of 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 quiescent current of approximately 20..25 mA, but statistically it turned out to be from 75 to 100 Ohms, this greatly depends on the specific transistors.
As already noted in the topic on the amplifier, you should not use transistor optocouplers. Therefore, you should focus on AOD101A-G. Imported diode optocouplers were not tested due to unavailability, this is temporary. The best results are obtained on the AOD101A of one batch for both channels.
In addition to transistors, it is worth choosing complementary UNA resistors in pairs. The spread should not exceed 1%. Particular care must be taken to select R36=R39, R34=R35, R40=R41. As a guide, 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 inability to obtain precise details that at one time stopped the author’s experiments in the non-OOS direction. 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 you want to more accurately adjust the current shunt, then it is better to do the same as with R30, R31 - solder in the wiring for soldering.
As it turned out during the repetition of the circuit, under certain circumstances it is possible to excite an EA in the tracking circuit. 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 the collectors T15, T18.
The necessary adjustments were initially 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 radiator with “Moment” type glue or similar.
Before turning it on for the first time, you must thoroughly wash the board from traces of flux, check for any short circuits in the tracks with solder, and make sure that the common wires are connected to the midpoint of the power supply capacitors. It is also strongly recommended to use a Zobel circuit and a coil at the output of the UMZCH; they are not shown in the diagram, because the author considers their use to be a rule of good form. The ratings of this circuit are common - these are a series-connected 10 Ohm 2 W resistor and a K73-17 capacitor or similar with a capacity of 0.1 μF. The coil is wound with varnished wire with a diameter of 1 mm on an MLT-2 resistor, the number of turns is 12...15 (until filling). On the protection PP this circuit is completely separated.
All transistors VK and T9, T10 in UN are mounted on the radiator. Powerful VK transistors are installed through mica spacers and a paste of the KPT-8 type is used to improve thermal contact. It is not recommended to use computer pastes - there is a high probability of counterfeiting, and tests confirm that KPT-8 is often the best choice, and also very inexpensive. To avoid getting caught by a fake, use KPT-8 in metal tubes, like toothpaste. We haven't gotten to that point yet, fortunately.
For transistors in an insulated housing, the use of a mica spacer is not necessary 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-circuit the D2 optocoupler LED leads (1 and 2) and turn on. If everything is assembled correctly, 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 output of the UMZCH should not exceed 10 mV. Unwrap 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 ones by about 10-20 V. In the case when this deviation is less than 5 V, and the quiescent current is too high, 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 fall within 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 would have to significantly increase R57, R58 - until the resulting current mirrors are fully adjusted. In this case, the newly introduced transistors must be in thermal contact with the radiator, as well as the diodes in their place.
Next you need to set the quiescent current UNA. Leave the amplifier turned on and after 20-30 minutes check the voltage drop across resistors R42, R43. 200...250 mV should drop 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 it is less, then increase it accordingly. It may happen that the quiescent current of the UNA will be asymmetrical - 5-6mA in one arm, 50mA in the other. 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 replacing transistors. In general, there is no point in using transistors with large H21e in the latch. A gain of 50 is enough.
After setting up the UN, we again check the quiescent current of the VK. 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-final stage and up to 10 mA can be spent on controlling the optocoupler, so in the case when, for example, 33 mV drops across these resistors, the quiescent current will be 70...75 mA. It can be clarified 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 completely preserved.
Based on the results of voltage measurements 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 ratings of R51, R56 by about one and a half times and re-measure. The situation with voltages should change, but the quiescent current should remain the same. The optimal case is when the voltages on the collectors T15, T18 are equal to approximately half of the supply voltages, but a deviation from the supply of 10-15V is quite sufficient; this is a 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 severe 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.
The actuation of the latch 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. Pre-amplifier and its power supply
Serves for timbre correction and loudness compensation when adjusting the volume. Can be used to connect headphones.
The well-proven Matyushkin TB was used as a tone block. It has a 4-stage low-frequency adjustment and smooth high-frequency adjustment, and its frequency response corresponds well 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 disable any frequency correction in the path; the output signal level is adjusted by a trimming resistor to equalize the gain at a frequency of 1000 Hz in the TB mode and when bypassing.
Design characteristics:
Kg in the frequency range from 20 Hz to 20 kHz - less than 0.001% (typical value about 0.0005%)
Rated input voltage, V 0.775
Overload capacity in TB bypass mode is at least 20 dB.
The minimum load resistance at which operation of the output stage is guaranteed in mode A is with a maximum peak-to-peak output voltage swing of 58V 1.5 kOhm.
When using the control unit only with CD players, it is permissible to reduce the buffer supply voltage to +\-15V because the output voltage range of such signal sources is obviously limited from above, this will not affect the parameters.
A complete set of boards consists of two PU channels, Matyushkin RT (one board for both channels) and a power supply. Printed circuit boards were designed by Vladimir Lepekhin.
Measurement results:
The amplifier does not have the usual thermal transistor, like other ULFs with EA from waso. You won't be able to twist the multiturn to set the quiescent current; it simply isn't there. Setting up EA requires a certain level of understanding of “what and how to do” and even with good theoretical preparation, it is mandatory to read the FAQ (see bottom of the page) on setting up before enlightenment. Then the number of repetitive questions in the topic will be significantly reduced.
While EA-2012 was being made into EA-2014, elements were added or removed from the circuit, and they did not pay special attention to the serial numbers. To restore order - bringing the circuit marking to a standard and eliminating in some places the inconsistency between the serial numbers of elements on the boards and the circuit from the first post, the topic “EA-2014 Continuation” was opened.
Boards for this scheme are made:
In addition to updating the markings, to reduce the possibility of the formation of ground loops when assembling the ULF, I made changes to the GND wiring. GND1 near the output terminal is connected to GND1 (input ground) with a loop of wires.
Because There is a Zobel circuit on the AC protection board, so I didn’t duplicate the ULF on the board. Please note that when setting up Necessarily hang a chain over a canopy, for example, like in the picture.
A little about the configuration. The most budget pair of transistors in the output stage (hereinafter referred to as VC) manufactured by TOSHIBA 2SA1943 / 2SC5200. Transistors from SANKEN or ONS (Motorola) will cost more, but to compensate for the costs they are noted as more musical in comparison with TOSHIBA. Expensive, and therefore not so often used, LM318H / LM118H microcircuits from Thomson or NSC in a metal case, assembled by V2014EA, are put in first place. Very good reviews about m/s LT318AN (Linear), the structure of the LT is the same as the LM, but the Linear company is remembered (they were bought by TI) for high-quality products, particularly for amplifiers. It would seem that m/s with the same name, but from different manufacturers, should work the same or at least closely, the internal structure is the same. But practice has shown that in V2014EA, and other ULFs, it is not recommended to use LM318 from TI, the sound is dull, but from UTC it is not worth it at all, there is no sound and excitement is difficult to “treat”. The LME49710NA NSC (TI) in a plastic case and especially the LME49710HA in a metal TO-99 performed well. A metal case is more expensive, sometimes several times more, but those who had previously assembled with “plastic”, confident “well, it’s even better in sound, that’s all, the limit,” noted “they just didn’t expect such an increase in transparency, airiness, transmission of nuances” with m/ s in metal. We tried the LME49990MA, it is available only in the SO8 package, apparently who and how lucky were from the m/s batch. Someone wrote “I set the modes and am enjoying it”, while others wrote “I’m tired of choosing the correction.” In general, m/s showed itself to be somewhat “capricious”; it was not ready to work with any set of transistors in the UN-e.
One thing can be said about the use of electrolytes: everything is as “pocketable” as possible. For a budget option, Samwha is quite suitable
High-voltage ceramics are used in the correction. High-voltage ceramics have thick plates, which guarantees the avoidance of the piezoelectric effect. I recommend trying domestic ceramics K10-43A. Let's start listing the advantages: they consist of two chips, one with positive, the other with negative TKE (change in capacitance with temperature change), i.e. The change in capacitance in one chip is compensated by the other. All K10-43A NP0 1% and OS (especially stable), while the body is made of plastic, i.e. vibration-resistant. K10-47A also has good parameters; all peak capacitors are rated at a voltage of 250 - 500V, i.e. The ceramic plates are thick, the piezoelectric effect is eliminated.
Some technical points on assembly using the example of the use of LM318N and OPA134-x microcircuits:
I would like to draw your attention to two points: 1. LM318N has correction C5, and OPA134 has Rcor - C5. Therefore, on the board it is provided, depending on the type of m/s, to set C or RC; in cases where only C is in the correction, then set R to jumper 1206-0. See picture:
2. This is balancing the microcircuit, setting “0” at the ULF output using a multi-turn trimmer. In the pictures we see that the LM318 is balanced on legs 1 and 5, the middle leg of the joint venture goes to the plus power supply, and the OPA134s is balanced on legs 1 and 8, the middle leg also goes to the plus power supply. Depending on the type of m/s, it is possible to switch on SP balancing at the choice of 1 and 5 or 1 and 8; for this, it is enough to short-circuit the required pads with a drop of tin. See picture:
I didn’t think that there would be problems with the installation of R66, R67. The values recommended by the author for installation are in the range 0R3 - 0R43. To reduce the size of the PCB, I used 2512 chip resistors mounted on the bottom side. Usually 2512-1R is soldered in 3 pieces. in parallel 1R/3= approximately 0R333. And here’s an unexpected question: “why are there four seats for 2512 chips?” And if 2512-1R is not available, we’ve run out on planet Earth..., then we take it in the range 2512-1R2 - 2512-1R6 and solder four pieces in parallel. Now it is clear)?
Installation of the top layer:
Installation of the bottom layer:
Archive of diagrams, montages and drilling. There are “conflicts” between the printer and the PDF - this is about a file in the “drill” archive, it does not print 1:1. Control with a ruler or place the board on the printed sheet. The size of the PP is 198.12 x 66.55 mm (“curved” dimensions, because the wiring grid is inch). The PP was specially made narrow, the minimum width at the extreme points of the installed VK transistors is 85 mm - this allows the ULF to be placed in Amphiton-type cases (100 mm high).
Archive of descriptions of the operation and settings of the ULF EA line from waso.
Assembly to order:
If debugging this ULF is difficult for someone, but you really want to listen, then regarding assembly, you can contact Spiridonov(Vyacheslav).
ULF V2014EA boards assembled:
Power supply board for dual mono, electrolytes d=30mm:
Power supply board for those wishing to increase the capacity in the filter with separate power supply of the UN-a and the output stage (VC), electrolytes d up to 25mm:
With a two-level power supply, for those who want VT27/28 to be powered through a filter, see “cut/connect” using the example of the positive arm, the same manipulations with the negative arm:
For single-level power supply, connect with a jumper (drop solder). But in order for VT27/28 to be powered through a filter, see the recommendations above:
In the second revisions of PP V2014EA corrected wiring inaccuracies, eliminating the need to cut tracks. As planned earlier, the ULF power supply can be one or two-level. With single-level power supply, you need to drip tin onto the contact pads (see arrows), i.e. restore the conductors in the +/-U power supply arms; with a two-level supply, this is not necessary. In both options, the power supply to the UN goes strictly through the RC filter.
