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, no more than 0.0008% (typical value - no more than 0.0006%)
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.
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.
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.
Most audio lovers are quite categorical and are not ready to compromise when choosing equipment, rightly believing that the perceived sound must be clear, strong and impressive. How to achieve this?
Search data for your request:
Schemes, reference books, datasheets:
Price lists, prices:
Discussions, articles, manuals:
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 purchasing, you should pay attention to the following designations, which mark the introduction of high technologies in the production of audio equipment:
Specifications you should pay attention to:
It should be remembered: the manufacture of high-quality amplifiers is a labor-intensive and high-tech process; accordingly, too low a price with decent characteristics should alert you.
Classification
To understand the variety of market offers, it is necessary to distinguish the product according to various criteria. Amplifiers can be classified:
Important: the primary conversion and signal processing takes place in the preamplifiers.
Attention: studying the technical components of the purchase is, of course, necessary, but often the decisive factor is simply listening to the equipment according to the principle of whether it sounds or not.
Application
The choice of amplifier is largely justified by the purposes for which it is purchased. We list the main areas of use of audio amplifiers:
Thus, in order to enjoy clear and high-quality sound for a long time, it is advisable to study in advance all the variety of offers and select the audio equipment option that best suits your needs.
High quality preamplifier NATALY
Schematic diagram, description, printed circuit board
This preamplifier is used for timbre correction and loudness compensation when adjusting the volume. Can be used to connect headphones.
For a high-quality path that includes an UMZCH with nonlinear and intermodulation distortions of the order of 0.001%, the remaining stages become important, which should allow the full potential to be realized. Currently, there are many known options for implementing high parameters, including using op-amps. The reasons for developing our own version of the preamplifier were the following factors:
When assembling a preamplifier on an op-amp, the threshold of its output voltage, and therefore the overload capacity, is entirely determined by the supply voltage of the op-amp, and in the case of power supply from +\-15V it cannot be higher than this voltage.
The results of subjective examinations of preamplifiers based on op-amps in their pure form (without output repeaters) and with those, for example, based on a parallel amplifier, show listeners’ preference for the op-amp + repeater circuit, with almost identical parameters “from the point of view of Kg”, this is explained by the narrowing of the spectrum of op-amp distortion when working with a high-resistance load and operating its output stage without entering the AB mode, which produces switching distortions that are practically below the level of sensitivity of the devices (Kg OU ORA134, for example - 0.00008%), but clearly noticeable when listening. This is why, as well as for a number of other reasons, listeners clearly distinguish a preamplifier with a transistor output stage.
The well-known circuit solution containing an integrated repeater based on the BUF634 parallel amplifier is quite expensive (buffer price is at least 500 rubles), although the internal buffer circuit can be easily implemented in discrete form - for a much more reasonable amount.
Amplifiers in which the op-amp operates in a small-signal mode show high performance, but lose in audition results. In addition, they are very critical to set up and require, at a minimum, a square wave generator and a wideband oscilloscope. And all this with clearly worse subjective results.
The lack of output voltage in the PU circuit (op-amp + buffer) can be eliminated by implementing voltage amplification in the buffer, and deep local feedback eliminates distortion. A sufficiently high initial quiescent current in the output transistors of the buffer guarantees its operation without distortions characteristic of push-pull structures in the AV mode. The presence of only a twofold voltage amplification allows one to achieve an increase in overload capacity by 6 dB, and with a threefold amplification, this figure becomes equal to 9 dB. When the buffer operates from a +\-30V power source, its output voltage range is 58 volts peak to peak. If the buffer is powered from +\-45V, then the output voltage from peak to peak can be about 87V. This margin will be beneficial when listening to vinyl discs that have characteristic features in the form of clicks from dust.
The two-stage implementation of the preamplifier is due to the fact that the timbre block introduces attenuation into the signal up to 10...12 dB. Of course, you can compensate for this by increasing the gain of the second stage, but, as practice shows, it is better to apply as much voltage as possible to the tone block - this increases the signal to noise ratio. In addition, it is quite common to find discs recorded with a high crest factor (loud peaks and rather low average volume). This is not a lack of mixing, rather, on the contrary, because sound engineers often abuse the compressor, trying to fit all levels of sound volume into the CD range. But we cannot pretend that such records do not exist. The listener turns up the volume. Thus, the second stage must have no less overload capacity, in addition, it must have low intrinsic noise, high input impedance and the ability to pass the real signal without distortion after the timbre block, in which the extreme frequencies of the audio range go with the greatest rise. An additional requirement is a linear frequency response when the tone control is turned off, an even response when testing with a meander, and subjective invisibility of the control unit in the path.
Matyushkin’s well-proven tone block 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.
The balance regulator is built into the OOS of the second stage and has no special features.
The low bias voltage of the OPA134 (in the author’s practice, at the output of the second stage is no more than 1 mV) makes it possible to exclude transition capacitors in the path, leaving only one at the input of the control unit, because the level of constant voltage at the output of the signal source is unknown. And, although at the output of the second stage the diagram shows capacitors of 4.7 μF + 2200 pF - with a zero offset level of about a millivolt or less - they can be safely eliminated by short-circuiting them. This will put an end to the debate about the effect of capacitors in the path on sound - the most radical method.
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
The overload capacity in the tone block 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 a pre-amplifier 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.
Setting up a pre-amplifier should begin by checking the DC modes of the output buffer transistors. Based on the voltage drop in the circuits of their emitters, the quiescent current is set - for the first stage it is about 20 mA, for the second - 20..25 mA. When using small heat sinks, which become mandatory at +\-30V, it is possible, depending on the temperature situation, to increase the quiescent current a little more.
It is best to select the quiescent current using resistors in the emitters of the first two buffer transistors. If the current is low, increase the resistance; if the current is high, decrease it. Both resistors need to be changed equally.
With the quiescent current set, we then set the TB regulators to the position corresponding to the flattest frequency response, and, by applying a 1000 Hz signal with a rated voltage of 0.775V to the input, we measure the voltage at the output of the second buffer. Then we turn on the bypass mode and use a trimming resistor to achieve the same amplitude as with the TB.
At the final stage, we connect the stereo balance control, check for the absence of various forms of instability (the author has not encountered such a problem) and conduct a listening session. Setting up Matyushkin's TB is well covered in the author's article and is not discussed here.
To power the preamplifier, a stabilized power supply is recommended, with independent windings for control panel and relay switching. Technically, the power requirements are nothing new. The main thing is the low level of mid-range and high-frequency noise, the suppression of which by power supply is known for the op-amp. About the ripple level - it should not exceed 0.5 - 1 mV.
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.
Double Sided Pre-Amplifier PCB:
INCREASE
Printed circuit board for TB Matyushkin with relay switching:
ENLARGE The circuit is stable. There is no noticeable voltage ripple at the output; measurements were taken on an oscilloscope in the 0.01 division/volt mode (for mine this is the minimum limit).
INCREASE
Measurement results:
On OPA134 (only the first link of two), the power supply is single-stage, +\-15V:
Kni(1kHz)........................ -98dB (about 0.0003%)
Kim(50Hz+7kHz)................less than -98dB (about 0.0003%)
On OPA132 (both links), full version, two-stage power supply:
Kni (1kHz)........................ -100dB (about 0.00025%)
Kim (19kHz+20kHz)................... -96dB (about 0.0003%)
In the case of self-excitation of HF cascades, mica correction capacitors with a capacity of 100 to 470 pF should be soldered in parallel with resistors R28, R88 and their complementary ones in another channel. This was discovered when using transistors BC546\BC556 + 2SA1837\2SC4793.
In the attachments you can download all files of circuits and printed circuit boards in SPlan 6.0 and SL 5.0 formats, respectively,
