— I present a device with integrated into one body preamp and an audio power amplifier with perfect sound quality. The lamp has stabilized modes, and in stereo it produces an output power of 350 W per channel. In mono mode, if four 6p45S lamps are installed in the final stage, it will be 700 W. Here is indicated maximum power— was measured before the clipping appeared on the sinusoidal audio signal.
The picture is clickable. You can take the diagram on a large scale → Here
Natural musical power will be slightly less. If two lamps are installed in the output path, then naturally the power will be halved. When assembling a tube sound amplifier, no special selection of lamps is required, since each 6P45S tetrode has an adjustment function. Therefore, everything is simple - take the diagram and start doing it.
Amplifier based on 6P45S tubes
A tube amplifier assembled according to this circuit using 6P45S tetrodes has been tested many times and works great. Two devices were manufactured in a stereo version; if we consider them as mono, then we get four devices. This universal circuit makes it possible, without changing anything in it, to assemble the simplest lamp, such as, for example, a terminal amplifier and work with a remote control. Or make more complex designs, for example: with a built-in tone block, or even more advanced - install additional input modules for connecting electric guitars, microphones or synthesizers.
Tube audio amplifier circuit, also allows you to make the amplifier both monophonic and stereo. In addition, it is possible to install almost any radio amplification tubes without making changes to the circuit. For example: instead of one 6P45S, you can use 2 pieces without any problems. 6P36S or 6P44S. Based on this, it is easy to calculate: if the output stage is mounted on four 6P36S lamps, this will be equivalent in power to two 6P45S.
Output transformer
Also, the output transformer will work stably with a final stage consisting of both two 6P45S and four 6P36S lamps. The output trance from Soviet radio broadcast amplifier U-100U4.2, which has an ideal frequency and excellent quality. If you find such a transformer, it will solve a labor-intensive problem for you - you will not need to wind the output from scratch. In addition to this, the sound power was within 175 W.
In this design, some components recommended by famous radio amateurs were used. In particular, presented here tube audio amplifier circuit contains such output transformers. But you can install those that you have in stock and that are suitable in terms of parameters, everything will work perfectly.
Voltage regulator
A characteristic feature of this modification of the amplifier is the use of the stabilizing mode function. The use of such stabilization eliminates the possibility of a negative impact on the device due to strong changes in mains voltage. Also, this tube sound amplifier is not sensitive to voltage surges in the power circuit, during which all modes of radio tubes operate intermittently.
At the stage of assembling the structure, the device was tested with and without mode stabilization installed - a huge difference between the two options was revealed. The device with a stabilizer was much superior to the second option in terms of reliability and stability in operation, purity of the sound picture, etc. You shouldn't skimp on a pair of transistors. That's why the best solution will be for you if you additionally collect voltage stabilizers. As a result, you will be rewarded with high-quality amplifier performance and excellent sound.
Installation of stabilizer transistors
For ease of installation of transistors in stabilizer circuits, you need to use transistors in plastic case, which are easiest to mount directly directly to the amplifier housing. Thereby providing good thermal stability to transistors. In this circuit I used transistors from the horizontal scan and power supply of branded TVs.
The constant supply voltage in the preliminary stage, supplied to the filament circuit of all lamps installed there, coped perfectly with all kinds of background distortion and noise. It's actually not audible at all. Naturally, I distributed the grounding points, which are laid from one cascade to another. And the last point is output to the common housing at the cathode of the output tetrodes; also at this point the high voltage power wire converges at the “minus”. Pay special attention to correct installation.
The use of the SRPP circuit (in the Russian sense - a cascade with a dynamic load) in pre-amplifier stages is completely justified by its resistance to overloads, excellent quality, and low output resistance.
The presented photos show ready-made complete tube amplifiers: The first is a complete stereo amplifier with a power of 700 W; the second - power 300 W.
I propose a well-developed UHF circuit for 6p45s, with a five-band tone block. The amplifier is made according to a classic single-ended circuit. The circuit of A. Manakov was taken as the basis. The diagram does not need a description of the operation.
Tube bass amplifier
During the assembly and setup process, some resistor values were changed. During the setup process, you will need to select R23, R34 so that the voltage at the 6p14p anodes is 190V. Then, by selecting R45, we set the anode voltage to 6N3P 90-110V. You may have to select the resistance R22, R33; the voltage at pin 9 is set to 90V. The negative voltage on the 6p45s control grid can be from 45 to 70V, it all depends on the lamps used and the degree of wear. For me this value is 54V. This completes the setup. 
Tone block
I used a BA3822LS circuit as a tone block. This microcircuit has good parameters and is available for sale. Our price is 69 rubles. The advantages of such a circuit solution are the absence of a bunch of shielded wires and screens; in the absence of a signal, no background noise or hiss is observed. It is advisable to connect the finished tone block to the ULF input through trimming resistors of 100 kohms, since the microcircuit has sufficient high level gain.
Initially, instead of a microcircuit, I used a similar circuit with two 6n3p lamps, but in the end I abandoned it due to the impossibility of getting rid of interference and background due to weak shielding of the lamps and the entire circuit due to insufficient space in the case. I will note that the control unit on the lamps still sounds warmer, it seems to me. For those who are interested in this option, the diagram is also attached.
Amplifier power supply
Now about the power supply. We took a ready-made TS270 transformer, just wound a few turns on top of the existing windings. The throttles were taken ready-made from... I don’t remember what. Or from a b&w TV or receiver... it is advisable to organize the power supply for each channel separately to reduce interference and distortion between them.
I used one rectifier for both channels. There was no particular desire to wind another winding, just like the wires in particular. Paid more attention to capacitors instead. Nothing like this was noticed; I made do with one step-up winding. The output transformers are homemade, such as ts-20 ts-30, whoever has them, with a horseshoe-shaped core.
We wind it this way: the primary is 94 turns with 0.47 wire, then 900 turns of the primary with 0.18 wire should turn out like this: 94/900/94/900/94/. We connect the primary to the afterbirth and the secondary in parallel; we do not place any paper gaskets between the halves of the iron. We apply supermoment (second glue), assemble and put a bandage on top of the iron if there is one, if not, then we clamp the iron until the glue dries completely.
The advantage of this solution is that it does not make noise during operation (provided the iron is good and the windings are tightly laid), the iron holds securely and, if necessary, can be easily disassembled - just hit it lightly with something heavy at the gluing site. For the body I used 3mm aluminum sheets. The adjustment handles are decorative duralumin handles for furniture doors; the holes are drilled to the required diameter and put on via heat shrink directly onto the alternators.
The body is painted with auto enamel and half is covered with wood-like film. I made the power supply transformer remote in order to reduce its influence on the power supply. The trans was packaged in a case from an old power supply unit, connected to the amplifier with a 6-core cable through a connector on the case of the amplifier. The cable is assembled by hand. There is an inaccuracy in the diagram: R40 AND R29 ARE USUAL MLT-2. BUT R28 R39 must be five-watt!
Comments (28)
Uv. Sam! Can you indicate the output power of this ULF?
Thank you.
yes, of course. this option 12 watts per channel. in triode mode 24 watts per channel. pins 3 and 6 are connected directly to the power supply positive. and select the bias voltage. Set the quiescent current to 100 mA. in triode mode, nonlinear distortions increase. And 12 watts is enough for 100 watt acoustics
12 watts is enough for 100 watt acoustics
You want to say that such an amplifier will only power my S90 by 12 W, something I don’t understand...
If your acoustics are not S-90, then all the others will do just fine. I wish I could demonstrate it. Of course, the main and main condition is correctly wound output trances.
s-90, although they are considered, if not one of better acoustics domestically produced, but their sensitivity is very low
but if there are no other columns, then you can slightly adjust the number of turns of the secondary.
Good day to the author
There are a couple of problems with the diagram
1 The left-right input goes to R52 and R53, are these the central cores, and the common core sits on the ground?
2 there is no information about the 6.3V filament power supply, how many are there for each type of lamp?
3 in the diagram shows where to supply power -70 and +350, and do +70 and -350 go into the circuit or not? some of the pins are unlabeled (end R29 R40)
Good day! I was interested in your article, I want to make the same amplifier, but I didn’t understand how to wind the output signal transformer from lamps (I have no experience in this).
As I understand from the description, the power transformer and the output transformer are combined or what?
I used one rectifier for both channels. There was no particular desire to wind another winding, just like the wires in particular. Paid more attention to capacitors instead. Nothing like this was noticed; I made do with one step-up winding. The output transformers are homemade, such as ts-20 ts-30, whoever has them, with a horseshoe-shaped core.
Quote:
We wind it this way: the primary is 94 turns with 0.47 wire, then 900 turns of the primary with 0.18 wire should turn out like this: 94/900/94/900/94/. We connect the primary to the afterbirth and the secondary in parallel; we do not place any paper gaskets between the halves of the iron.
From the description, I didn’t figure out where the secondary is and where the primary is, since there are two of them in the description. If possible, please write a little more about the output trans or correct where the error is. Thanks a lot!
P.s. Yuri
Where it says 70 and 350 V, conclusions. Pay attention to which of them are grounded, this is not a minus, but the author meant the dash.
I answer for Yuri. first: yes, the braid, aka the common core, sits on the ground. second: the power supply is made on a ready-made transformer from a black and white box of type TS-270. (270 watts). All windings on this transformer can be left. You just need to wind up the secondary winding so that the changes at the output are 300-320V. Those that are on it give 220, this is not enough. For incandescence we use the original winding. It will quite draw 5 amperes. All the filaments of the lamps are connected in parallel. third: 70V winding, plus connects to the ground common wire. -350 is supplied to the ground wire according to the diagram. I didn’t sign, I thought there would be no questions, everything seemed obvious.
in the description above I mentioned the TS 270 and that it was taken from a b&w lamp box. It has all the windings, if there is no 45 volt winding on this trance, we wind it ourselves
70 is served where -70 is on the diagram, this is not a dash
for ALEXEY.. there is only one power transformer; it is not in the photo, it is packed in an old case from a computer power supply, I wrote about this. and two output trances. For the output trance, it is best to take a trance with a horseshoe-shaped core, the same as the ts270, only smaller in size. If there is no such transformer, as I wrote above ts20 or ts30. then you can take any other with an approximate power of 30-40 watt, with W-shaped iron. Why is horseshoe-shaped iron better? Because four ready-made horseshoes have already been assembled and glued together. Sh-shaped is bad because if the plates have burrs, rust, crumpled, then when assembled they will short-circuit with each other, due to the fact that the insulation is broken. such a trance will not work as it should, and will bring nothing but disappointment. required condition such iron, unbroken plates. If there are no vehicle transaxles, then you can take ready-made factory ones like TVK-30. iron is the same. but it will take some time to disassemble them, because they are filled with paint and, in the worst case, epoxy. Now about the winding. First, 94 turns of the secondary winding are wound, the one to which the acoustics will be connected, then a layer of insulation, then 900 turns of the primary winding, then a layer of insulation , in the end you should have three secondary windings independent of each other and two primary windings. You draw conclusions from each winding so that you can then connect them as needed. Connect the secondary windings in parallel, just don’t mix up the beginning and end. beginning with beginning end with end. and you connect the primary windings in series, starting one with the end of the other, in the end you get one primary winding. and one secondary. Well, it seems that it couldn’t be clearer. there is nothing complicated even if you have never done anything like this
hint: if you can’t get rid of the background alternating current in the speakers. Then look at the diagram with the name: entry-level tube amplifier, there is a circuit in the circuit design that completely eliminates this problem. You can easily find this diagram through Yandex.
Really from this lamp high-quality sound 6-7 watts, higher is slag.
for Vlad. most often the slag is obtained from the fact that they use low-quality elements, there is no knowledge, skill, and even more often by hand..
There is a significant flaw in the scheme. The anode load 6P14P is 22 kOhm, which is much more than optimal. This significantly increases the output impedance of the driver, which makes it less pleasant for the output tube. Driver distortion also increases greatly.
The 6P45S lamp has a huge steepness. This means increased distortion.
And indeed, with a power of more than watts, these distortions are both audible and visible even on the oscilloscope screen.
for sound.. everything you wrote was in theory.. here everything was selected manually and it was the 22k anode resistor, try to assemble it yourself first, check and then criticize. for each 6p14p the value of the anode resistor turned out to be different. and everything was set up using an oscilloscope.
Sergey, all the answers to your questions are shown in the following picture (click to enlarge the picture):
Hello, please tell me what the problem is: I assembled such an amplifier, but one channel is louder than the second. It turns out that the channel in which the 4.7k resistor is installed is louder.
Hello. Try swapping the amplifier inputs connected to the 1x250 pass-through capacitors (C1, C26) - if now another channel becomes louder, then the reason must be sought in the signal source, signal wires or preamplifier circuit on a 6N3P lamp.
The circuit diagrams of the LF power amplification channels on 6P14P and 6P45S lamps are completely identical. If they play at different volumes, then there may be faulty or damaged electronic components installed somewhere.
For example, to select R23 and R34, which are 22K each, you can take a variable resistor of 36-56K, set its slider to the position to obtain a resistance of 22K. Then turn on the circuit, measure the voltage at the anodes of the lamps, as indicated in the article, slowly rotating the variable resistor knob to achieve the desired readings from the device. In place of the variable resistor, solder a constant one with the same resistance.
I bring to your attention an amplifier from Yuri Malyshev
The wideband amplifier is designed for vocals or for the mid-high frequency path in a 2-way club system. It can also be used as stage monitors.
Brief characteristics:
1.Frequency range 40-30000Hz (at zero)
2. Output power 2x170W (iron outputs from TS-250 or PL20x40x100) On 6P45S lamps (preferably pairs) or 6P42S. You can use 4P44s, but two per arm and must be matched.
3.Sensitivity -0dB(0.775V)
4.Noise level -80dB
5. Harmonic coefficient - 1.5%, much less is possible with precise balancing of the final stage.
6.Forced airflow of output lamps.
7. Power transmission - twin TS-250 or twin on PL2040100 (preferred)
8. Execution "REK" - new
The circuit has been tested and tested for many years. Several versions of amplifiers have been produced (over 10 years, about a thousand in Kharkov, under different names)
I'll give you the holiday details, then I'll write detailed measurements it is in the operation of the amplifier. And the adjustment from the calculated data is usually no more than 5% of the number of turns in the primary and secondary. Compared to your classics, I still check everything in the “live” product!
So the iron from the TS-250.TS-180, although the same in size, is significantly worse. Two frames are made of fiberglass, although due to poverty (but rather laziness) you can also take a frame made of pressed wood
On each coil of primary wire there are 0.355 - 4 sections of 360 vit. Each section is two layers. On two coils, respectively, 2880 vit.
Secondary 4-ohm 5 sections of 130 volts on each coil 0.45. Total - 10 sections. On top of each coil, home winding on the 8th 55 volt wire 1.06. It is easy to notice that the coefficient of friction on the 4th = 22.15
Insulation is preferably LAVARIL. Of the many hundreds of holidaymakers over 25 years, not a single one has burned out, or at least I have not encountered such breakdowns.
Here I found a very interesting table on detailed measurements of an amplifier with this transformer.
Briefly 28Hz - 182W( output power) at Kg-6%.
28Hz-169W at Kg-3.4%
28Hz-156W already Kg-2.3%
30Hz -182W (4ohm load everywhere) -Kg-3%
40Hz-182W Kg-1.7%
1000Hz 182W Kg-1.3%
10kHz 182W Kg-1.3%
20kHz 182W Kg-1.5%
40kgk 182w Kg-2.0%
60kHz 156W Kg=4.3%
100 kHz about 100 W a blue glow is observed in the lamps and after about 2 minutes. fails.
And in normal operation, it lasts for years with a good Jamikon fan, for example, about 100 mm high. The height of the front panel of the amplifier is 3U - standard. Width is 19″ (482 mm).
The instruments then were a G3-102 generator, a S6-8 distortion meter, an S1-83 oscillator, and a V3-33 output voltmeter.
And here is the diagram of the output transformer. The primary is in red. The sections have two layers of 0.355 wire, 180 volts. in the layer.
Powering the second grids
I present my version of a single-ended amplifier using a 6p45s tube. Based on A.MANAKOV’s scheme
I couldn't find 6e5p, so I decided to try 6p15p and 6p14p. It seemed to me that 6p14p sounds better, and it is also more accessible.
The 6p45s lamp does not behave stable at a fixed bias (the current floats). With auto bias, there is a large power dissipation on the cathode resistor. I chose a compromise option - semi-automatic offset.
The 150 ohm cathode resistor is shunted by a 2200 uF* 35 volt capacitor. The grid is supplied with a negative bias from a separate low-power transformer (you can add an additional winding to the TS-180). I used a 12V trans from a low-power power supply (50-200mA) by connecting the secondary to a 6.3V filament winding.
TS-180 was used as a power source. The best option: use of two TS-180 (two monoblocks) or one TS-270.
Amplifier circuit
As a output, you can use TS-180 without alteration, but it is better to rewind, since without rewind there will be a decline in the tops and bottoms. The primary winding (750 turns on each coil, wire diameter 0.3-0.35 mm) is located between parts of the secondary (120+120 turns on each coil, diameter 0.6-0.7 mm). Two primary windings are connected in series, four secondary windings are connected in parallel (for a load of 8 ohms). It’s better, of course, to buy a branded trans, but it costs a lot of money. You decide. Many people believe that it is impossible to make a good trance out of TS-180 iron. Maybe this is not ideal, but for free...
Nevertheless, this is what happened - Fn-23Hz. Fv-26000Hz at a level of -1db. Measured at a power of 4 watts. Power up to the limit is 8 watts. Maximum - 12W.
I found Klaus’s article “Fixed offset options” and decided to experiment with 6p45s. I was pleased with the result. Option for 6p45s - bias voltage -125 volts is supplied through a 72 volt zener diode. When the mains voltage changes from 160 to 250 volts, the power at the anode remains almost constant.
SETUP. The setup consists of selecting resistor R4 in the circuit of the 2nd grid 6p14p for maximum gain and adjusting the anode current 6p45 with trimming resistor R10 based on the voltage drop of R9-0.165 volts.
Comments on the article:
“Sir, why are they monsters? They are heavy, huge, and very hot.” Let me start by saying that the magazine you are reading is not an audiophile magazine. What is audiophilia? This is a passion for canned (in a good way!) sound. The power switch clicked and... enchanting sounds poured out.
Not from an Edison roller, not from a gramophone, not from a gramophone, but from yours, precisely your acoustic systems. But how to achieve magic, or enchantment with sound? Of course - by using the appropriate components of the sound reproduction system. Let's not talk about turntables and speaker systems, especially about gold-plated cables and silver chassis.
Let's turn our attention to the amplifier circuitry. In the past, in our huge country, all efforts were spent on “defense.” Issues of high-quality sound reproduction were dealt with by individual enthusiasts. There were few publications. The main achievements were obtained not here, but somewhere overseas.
The main sources of information are also located there. Who among us has heard before about Cucing’a triode amplifiers, the famous D.T.N. Williamson’e or that local transformer OOS in the pentode cathode was proposed by Peter I. Walker on f. Acoustical manufacturing, which produces products under the “Quad” brand? Something has appeared in our country in recent years. Although there is still not enough information.
- Firstly, these are lamps.
- Secondly, these are triodes.
- Thirdly, this - (God forbid!) - do not use negative feedback(OOS) and class “B” (only “A”!).
Fourthly, the simpler the scheme, the better it is. “Single stroke” is better than “two stroke”.
Unfortunately, I was not able to hear the real “Ongaku” work. Among my friends there was no owner of this wonderful device from Audio Note. And all kinds of “Priboi” and even one “Luxman” sounded somehow equally “dull” on the tubes, and did not make an impression. But then, one day, an audiophile friend complained that the tube amplifier, which he had assembled with his own hands over the course of a year, did not live up to expectations, did not “sound” and did not even provide the required power.
I helped him adjust the lamp modes, reduce the background and get an output power of 6 W per channel, and also introduced a switchable OOS from the output to the input stage, i.e. covered three stages with it, which is often done in tube amplifiers. In addition, I added an RC circuit at the output (Zobel circuit) to eliminate RF oscillations at idle. Based on the instruments, it turned out to be approximately the same settling time as without OOS, and the same exponential.
And here we are listening to this amplifier. Sounds great! Deep, without being tied to speakers, surround sound is simply mesmerizing! Instead of this tube “monster” we turn on the American “Harman Kardon” (NK-1400) - transistor with OOS (“inexpensive”, only $700). The sound is noticeably worse than that of a homemade one - there is no such volume and depth. We are launching the domestic tube “Priboy 50 UM-204S”. The sound is even drier.
Finally, the most decisive experiment. We turn on OOS in a homemade lamp. At the same time, the bandwidth is expanded from 30 kHz to 100 kHz, the output power increases to 12 W with the same harmonic distortion (about 3%), and the output impedance decreases. Everything seems to be fine, but the effect is amazing! The sound becomes the same. like “Surf”. The charm has disappeared, the sound is “dry”, there is no volume. not to mention the small details.
I don't want to listen. We remove the OOS - and the “magic” is restored! Again, I don’t want to turn off the amplifier. so I would listen and listen... Then we compared its sound with the sound of the Orbita UM-002 Stereo amplifier, copied from the Quad-405, and established that the Orbita is in the same place as the NK-1400, but this place is much lower than the home-made lamp.
It should be noted that the listening was carried out in the same room of 16 m², with the same acoustic systems, with the same CD player, on the same discs (test, jazz, choir, vocals, symphony orchestra).
A homemade amplifier is an I. Morrison amplifier, adapted to our configuration by A. Bokarev. I bring this simple diagram(Fig. 1) with the OOS chain that improved the objective technical specifications, but “ruined” the sound. The amplifier uses a housing and transformers from the Priboi 50UM-204S ultrasonic unit.
The supply voltages turned out to be slightly less than indicated in. The output power was also less. What are the benefits of using triodes instead of pentodes in the output stage? More precisely, 6P45S lamps in triode connection, in class “A” and without environmental protection. In class “A” the output power at the same supply voltage is significantly reduced compared to class “B”.
But for high-quality sound in small rooms (16...18 m²) and with speakers with high output, 6...8 W per channel is quite enough. Triode connection gives a lower harmonic coefficient than pentode connection, by a factor of 2-5% and 10%, respectively (without OOS) at optimal load, and even less with an increase in the load applied to the anodes, but at the cost of a decrease in output power.
The internal resistance of the triode (Rj = ∆Ua/∆Ia) is significantly less than that of the pentode. This can be seen from the given anode characteristics of the GU-50 (P-50, LS-50) pentode (Fig. 2). In triode connection, GU-50 and 6P45S have almost identical output characteristics. For 6P45S in triode connection they are given in.
The use of an output transformer designed for a pentode and having a large inductance of the primary winding makes it possible to greatly expand the frequency response towards low frequencies, because The Ri of a triode is several times smaller than the Ri of a pentode. For the same reason, the current capacitances of the windings are recharged faster, and the frequency band expands towards high frequencies.
The small Ri of the triode gives a low output resistance even without negative feedback, although the low frequencies are somewhat emphasized. And finally, the most important thing. The absence of negative feedback gives a purely aperiodic transient process, without delays and oscillations (tyst = 10 μs to the level of 99% of the steady-state value of Uout). The introduction of resistive feedback with a depth of 20 dB (only resistor R7 is turned on) leads to large fluctuations in the transient response (TC). The oscillation amplitude reaches 60% of the pulse amplitude, and the oscillation period is 6...7 μs.
Turning on capacitance C2 = 1500...2000 pF eliminates oscillations, the process becomes similar to exponential, tyst 5 μs. Oscillations with a period of 6...7 μs indicate the presence of a resonant maximum or dipole on the Bode diagram at a frequency of about 150 kHz, which can cause the PH to tighten and “spoil” the sound. So choose! Either the efficiency is like that of a steam locomotive and great sound, or good performance and the desire to turn off the amplifier as soon as possible. Audiophiles are not afraid of low efficiency. Their slogan: sound quality - at any cost!
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