Today we have useful homemade for connoisseurs of good sound: a high-quality handmade tube amplifier

Hello!

I decided to assemble a push-pull tube amplifier (my hands itch very much) from what I had accumulated over a long for a long time details: case, lamps, panels to them, transformers and so on.

I must say that I got all this good for nothing (you don’t pay for it) and the cost of my new project will be 0.00 hryvnia, and if something needs to be bought in addition for little things, I’ll buy it for rubles (since I started my project in Ukraine, and I’ll finish already in Russia).

I'll start with the body.

Once upon a time it was, apparently, a good SANYO DCA 411 amplifier.

But I didn’t have a chance to listen to him, because I got it in a terrible dirty and non-working form, it was dug up to the point of being impossible and the burnt 110 V networker (Japanese, probably) smoked all the insides. Instead of native microcircuits of the final stage, some snot from Soviet transistors (this is a photo from the Internet of a good copy). In short, I gutted it all, and began to think. So, I didn’t come up with anything better than to shove a lampovik there (there is quite a lot of space there).

Decision is made. Now we need to decide on the scheme and details. I have enough lamps 6p3s and 6n9s.

Due to the fact that I already assembled a single-cycle 6p3s, I wanted more power and, after rummaging through the Internet, I chose this 6p3s push-pull amplifier circuit.

Diagram of a homemade tube amplifier (ULF)

The scheme is taken from the site heavil.ru

I must say that the scheme is probably not the best, but in view of its relative simplicity and availability of parts, I decided to dwell on it. Output transformer (an important figure in the plot).

It was decided to use the "legendary" TS-180 as output transformers. Do not throw stones right away (save them until the end of the article :)) I myself have deep doubts about such a decision, but given my desire not to spend a penny on this project, I will continue.

I connected the trance conclusions for my case like this.

(8)—(7)(6)—(5)(2)—(1)(1′)—(2′)(5′)—(6′)(7′)—(8′) primary

(10)—(9)(9′)—(10′) secondary

anode voltage is applied to the connection of terminals 1 and 1', 8 and 8' to the anodes of the lamps.

10 and 10′ per speaker. (I did not come up with this myself, I found it on the Internet). To dispel the fog of pessimism, I decided to check frequency response eye transformer. To do this, I assembled such a stand in haste.

In the photo, the GZ-102 generator, the BEAG APT-100 amplifier (100V-100W), the C1-65 oscilloscope, the load equivalent of 4 ohms (100W), and the transformer itself. By the way, the site has.

I set 1000 Hz with a swing of 80 (approximately) volts and fix the voltage on the oscilloscope screen (about 2 V). Then I increase the frequency and wait for the voltage on the secondary of the trance to begin to drop. I do the same in the direction of decreasing the frequency.

The result, I must say, pleased me. The frequency response is almost linear in the range from 30 Hz to 16 kHz, well, I thought it would be much worse. By the way, the BEAG APT-100 amplifier has a step-up transformer at the output and its frequency response may not be ideal either.

Now you can collect everything to the heap in the case with a clear conscience. There is an idea to make the installation and layout inside in the best traditions of the so-called modding (minimum wires in sight) and it would not be bad to make the backlight with LEDs as in industrial copies.

Power supply for a homemade tube amplifier.

I will start the assembly with at the same time I will describe it. The heart of the power supply (and the entire amplifier, probably) will be the TST-143 toroidal transformer, which I at one time (4 years ago) tore with meat from some kind of tube generator right at the time it was being taken to a landfill. Unfortunately, I didn’t manage to do anything more. L, it’s a pity for such a generator, or maybe it was also a worker or it was possible to fix it ... Okay, I digress. Here he is my enforcer.

Of course, I found a diagram for it on the Internet.

The rectifier will be on a diode bridge with a filter on the inductor for anode power. And 12 volts to power the backlight and anode voltage. Throttle I have.

Its inductance was 5 henries (according to the device), which is quite enough for good filtering. And the diode bridge was found like this.

Its name is BR1010. (10 amps 1000 volts). I'm starting to cut out the amplifier. I think it will be something like this.

I mark and cut holes in the textolite for panels for light bulbs.

It turns out not bad :) so far I like everything.

And so, and so. drilling sawing :)

Something began to emerge.

I found a fluoroplastic wire in old stocks and immediately all the alternatives and compromises regarding the wire for installation disappeared without a trace :).

This is how the installation turned out. Everything is as if “kosher” the incandescences are intertwined, the earth is at one, practically, point. Should work.

It's time to fence food. After checking and checking all the output windings of the trance, I soldered all the necessary wires to it, and began to install it according to the accepted plan.

As you know, in our not easy anywhere without materials at hand: the container from the Kinder Surprise came in handy.

And a Nescafe lid and an old CD

I ripped out TV and monitor boards. All capacities are at least 400 volts (I know that I need more, but I don’t want to buy).

I shunt the bridge with containers (which ones were at hand, I’ll probably change them later)

It turns out a bit too much, but oh well, it will sag under load :)

I use the regular power switch from the amplifier (clear and soft).

Done with this. Well done :)

Illumination for the body of the tube amplifier.

To implement the backlight, an LED strip was purchased.

And installed as follows in the case.

Now the glow of the amplifier will be visible in the daytime. To power the backlight, I will make a separate rectifier with a stabilizer on some kind of KRKEN-like microcircuit (which I can find in the trash), from which I plan to power the anode voltage supply delay circuit.

Delay relay.

Digging through the bins of my homeland, I found just such a completely untouched thing.

This is a radio time relay kit for a photo enlarger.

We collect, we check, we try on.

The response time was set to about 40 seconds, and variable resistor replaced with a permanent one. The case is coming to an end. It remains to put everything together, put the muzzle, indicators and regulators.

Regulators (input variables)

They say that the sound quality can greatly depend on them. In short, I put these

Dual 100 kOhm. since I have two of them, I decided to parallelize the conclusions, thereby obtaining 50 kOhm and increased resistance to wheezing :)

Indicators.

I used standard indicators, with standard illumination

The connection diagram was mercilessly bitten by me from the native board and is also involved.

Here's what I ended up with.

When checking the power, the amplifier showed a voltage at the output of 10 volts of an undistorted sinusoid with a frequency of 1000 Hz to a load of 4 ohms (25 watts) equally across the channels, which pleased :)

When listening, the sound was crystal clear without background and dust, as they say, but too monitor, or what? nice but flat.

I naively thought that he would play without timbres, but ...

When using the software equalizer, we managed to get a very beautiful sound that everyone liked. Thank you all very much!!!

The author of the article "do-it-yourself home-made tube amplifier" Vyacheslav Tkachenko.

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I haven't written anything here for a long time... Somehow everything didn't fit.

But finally, something was found that could really be interesting to someone else, besides the author.

Frankly, I thought about this topic for a long time ... I rummaged through everything that could be found on the Internet and only realizing that there was very little really sane and useful on the topic voiced in the title, I decided to crown my efforts with an epistolary report, for which, first all armed with a camera to capture the process in every detail, trying not to miss a single important moment.

So, I'll start, perhaps, from afar ..

It so happened that for more than 30 years of practice of my radio engineering "creativity", I have never had a chance to make a completely tube amplifier.

There were many reasons for this!

I will not list them all. Let me just say that I have dealt with lamps, and quite successfully and productively. But this was due to the pre-amplification cascades and made it possible not to get involved with hemorrhoids, due to the need to mount a bunch of pieces of iron, in the form of chokes, large trances and others like them.

But here I wanted, at least once in my life, to make a classic (moreover, it’s a classic !!!) lampovik, with lamps beautifully glowing in the dark, mounted outside ...

It’s not that I didn’t understand what it would result in for me ... But, to be honest, I didn’t realize that, unlike the design of semiconductor (“stone”) equipment, the manufacture of a tube apparatus should rather be attributed not so much to electronics as to locksmith work.

But I'm getting ahead of myself...

To begin with, as I said above, without further ado, I dug in the search engine line: "do-it-yourself tube amplifier."

However, having reached (no lie!!!) the tenth page of the search engine results, I realized that the main motive of those who had already managed to tell about their experience in creating tube amplifiers with their own hands was not the desire to teach others something, but rather the desire to show off their own achievements without sharing the secret of such "success" with others.

There is very little real information on HOW to do this, and if it is, it is very fragmented and stingy with details.

Actually, at that moment I realized that they favorably left me a place in this clearing. J

So, why, in fact, a lampovik?

I will not rant on the topic of fashion trends, such as Hi-End. It is clear that this is both fashionable and prestigious, and the tube sound, indeed, compares favorably with the transistor one. What? ... - This question is not here! If you only want to "decide for yourself" - raise the brain of your friends who have such devices, or managers in salons, such as the Purple Legion.

And if you decide that you want this, but to spend on this “miracle” of the money that those who sell it usually ask for this kind of equipment are not ready (and who cares, for what reason are you not ready! ..) then this article will probably be useful to you ...

So - where to start?

Perhaps, in this case, you can easily determine the sequence of actions!

In cases with "stone" devices, everything was somewhat different. First, the stuffing was assembled there, and only then did we think about cases for our creations.

In the case of tube amplifiers, everything is exactly the opposite, since for these machines the amplifier housing is, first of all, a structure that carries all the main elements. So, first of all, decide how you would like your amplifier to look as a result, that is, decide on the case!

I must say (I know from my own experience) that this is the most difficult issue in our "fatherland". Alas, in Russia, finding a decent case for radio equipment is an almost impossible task. L

I'm not that lucky ... But at one time I brought a lot of such iron from the "under heaven". Therefore, I was lucky to get past this problem. And I'll even say more! Perhaps I can help some of you deal with this problem! ;) Well, yes, it's all only privately...

In the meantime, having decided on how our creation should look, it is worth solving the second, of the most important tasks - deciding which one to assemble from amplifiers?

Schemes, ideas, not to mention opinions, just an incredible amount!

And it’s incredibly difficult to figure out on the go which of the ideas to grab on to.

In such cases, it is worth starting with the simplest and, at the same time, material that has been worked out not even for years - but for decades ...

But there is a lot of such, as the practice of studying the issue has shown.

And here, perhaps, it is worth starting to share your own experience.

There are a lot of established stereotypes in our minds. So, for example, high-speed car driving inevitably evokes associations with Michael Schumacher, and the racing car itself inevitably evokes the red Ferrari ...

Similarly, in a situation when it comes to tube Hi-End, the first thing that comes to mind for people who have already come into contact, at least to a minimal extent, with this topic is, of course, Audio Note.

For more than a dozen years, the Audionot sound has been almost like a religion among a large part of the “sophisticated high-end players”

At one time, many copies were broken in the field of discussions about what, in fact, is this secret of the sound of the creations of Peter Quartrup (dad and one of the main designers of Audio Note).

I remember that this chest was opened as easily as most of the others.

A relatively small number of experiments made it possible to find out that the main share of colors in the Audinot sound was made by the first cascade, usually built according to the so-called SRPP (cascade) scheme.

I didn’t philosophize either, having determined that it was he who should be at the entrance and nothing else, although something else could be simpler, but not much.

It's even easier with the output stage!

Here it is necessary to proceed from the principle of accessibility. Speaking of accessibility, I mean, first of all, the element base, on the basis of which you can build something quite worthy of sounding.

In this it is worth relying on the "experience of ancestors" that has come down to us in abundance in the form of the remains of old tube TVs and radiograms (Hello garbage dump!!!).

In extreme cases, this junk, in the form of weekend (TVZ-Sh) and power (TS-180) transformers, is usually in abundance at local flea markets, which take place on weekends in all regions and villages of our "immense" ...

And in conclusion, the problem of choosing an output lamp comes down to the understanding that these same TVZ-Sh output transformers were designed to work with almost the only lamp developed in the socialist fatherland, designed specifically to amplify sound. Of course, we are talking about the legendary 6P14P or its more modern counterparts 6P15P or 6P18P.

However, your choice! You can also supply a “branded” analogue in the form of EL 84. How much the result will be worth it is up to you to judge. Here I will only note that these replacements should not entail any structural or schematic changes. Even the modes of these lamps are almost identical and, most likely, you will not have to adjust anything with such a replacement on an already made and working amplifier.

Since we are talking about lamps, it is perhaps worth mentioning the light bulb for the first stage.

I'm not afraid of shields of malicious replicas of "dissenters", but IMHO there is simply no better candidate for the first cascade than 6N23P-EV. However, I will immediately warn you that the number of people who agree with me will be approximately equal to the number of those who objected. Let me just say that if we are striving specifically for the Audionot sound, then this is the very thing! J

Well, in fact, we have almost drawn our own scheme.

To all of the above, it is worth adding, except that speaking about the output stage, I meant precisely and exclusively the 6P14P triode inclusion. It is in this inclusion that this lamp is able to touch the strings of the soul in a way that not many others.

Yes! This will result in a loss in power. But, perhaps, it was worth saying this earlier ... Hi-End is not for dubbing discos. Furthermore! In Hi-End, the quality of the device is usually inversely proportional to the power (read sound volume) at which the amplifier reveals its full potential.

In addition, I will reassure you that the very 1.5 - 2 watts per channel that we can get with 6P14P in a triode connection, in terms of subjective sound volume, will seem adequate to 10 watts per channel, obtained from a typical silicon-transistor mustache.

So, just trust those thousands of people who have already walked this path before you and, believe me, were completely satisfied with the result. ;)

Furthermore! I also have much more “serious” devices, which, of course, are objectively better than this creation. But this simple and, it would seem, completely uncomplicated machine has its own soul, gentle and kind ... Able to touch and warm people's souls with its very warm voice. J (Evan pulled me apart!.. Once again Sorry for the pretentious syllable.)

The only question of the circuitry of our wuxia, perhaps, was the question of "correct and healthy eating". And this, it must be said, is a matter of paramount importance when it comes to sound! For, the sound that we hear as a result, in fact, is nothing more than the power of your amplifier modulated by the input signal.

Hence the conclusion - the power supply of the tube amplifier must also be tube! So this is a kenotron! And if you absolutely remain adherents of the classics, then the throttle ...

And if everything is simple with a kenotron (by summing the anode currents of all the lamps, we get the total consumption, based on which the desired kenotron is selected), then with a choke, a problem can really arise ...

However, I was lucky. In my bins there was a real choke from some old tube TV. But even if not, then the simplest and most effective solution to this problem would be to buy a banal 18-watt choke for old fluorescent lamps at the nearest construction market for 120 wooden ones. Their 2 henry inductance (usually something like that...) is enough for our purposes.

How long - how short, but on the Runet spaces I managed to find two whole schemes that almost completely correspond to all the aspects voiced above. The first of them is built exactly according to the idea that was described by me above. The second one differs only in that it has a pair of output lamps in parallel at the output, but it has a beautifully painted power supply that fully meets all my requirements.

Here are the diagrams:

In fact, strange as it may seem, the essence of my article is not directly related to the amplifier circuit ... In any case, this is not the main thing for me in this case. The main thing is to tell about how to collect all this?

It is worth noting that the classic approach to building a tube amplifier, in contrast to transistor devices, usually assembled on printed circuit boards, is the assembly of the so-called surface mounting.

Frankly, for me this has always been the most repulsive factor in the issue of assembling tube circuits. For me, who is accustomed to making a separate printed circuit board even for a stand-alone volume changer, so that everything is correct and tidy, the very thought of parts freely dangling in the amplifier case, fastened together only by soldering and, sorry, hanging on snot, was frightening ... And , starting to build this machine, I had to overcome some internal barrier and practically invent on the go how to fix everything so that in the future I would not worry about that, and not that .... is there anything there at one fine moment ?. ..

Well, yes, everything is in order.

We take the case of our amplifier.

First, it is worth carefully diluting those commutations that we will need later. With your permission, I will omit this stage, since it is specific and does not imply many solutions.

I will just present the result as a given. In my case, it was the wiring of the input switch, ALPS for the volume control, and the actual input, output and power connectors themselves.

Characteristically, at this stage we remove the top and bottom panels of the case. The bottom panel just interferes with us, and we need the top panel as the basis of our design.

Here is what we have at this stage:

It seems that I missed one important point ... The fact is that before proceeding with the assembly of the amplifier, you must first select at least the main elements of the future machine. They are necessary in order to determine the design of your device.

This is primarily about light bulbs, sockets for them, output and power transformers and chokes. About the very elements that are attached directly to the body.

And only after fully picking up everything you need, we can arrange it the way you like it, determine the places for these elements and mark out the top panel.

Here is how I decided to arrange the elements of my amplifier:

I admit, I had an idea to plagiarize the topology of the arrangement of elements from one of the most popular Audio Note amplifiers, but, having overcome this temptation, I decided to arrange the elements according to the classical scheme. The idea of ​​this topology, in this case, is not fundamental. The fact itself is important as a stage. This must be done very carefully, thinking about how convenient the chosen location will be for subsequent internal installation and about the mutual influence of the elements on each other.

This, of course, is about the magnetic fields of transformers and their orientation.

I suppose there is no need to present a short school physics course .. Just remember this. ;)

First of all, we place the panels for our lamps and determine the size of the holes for them:

Here we are in for another ambush and a silent question in our eyes: “And how to drill such HOLES in a sheet of iron?!”… In my case, it was exactly like that. And the answer to this question in the articles of "colleagues" who joyfully reported to me about how wonderful they assembled tube amplifiers with their own hands, I could not find.

I had to go to the nearest construction market and retrain from an electronics engineer to a locksmith.

I took the data with an ordinary caliper before going to the market. It turned out that the diameter of the holes for the sockets for finger lamps is 18 mm, and the diameter of the hole for the socket for the octal lamp (kenotron) is already 28 mm!

The study of the issue showed that for drilling holes with a diameter of 18 mm. you can find a classic drill, but for larger holes you will have to use a "crown" from "Bimetal".

Here's what it looks like:

Fortunately, I easily bought both of them on the construction market at 350 wooden ones per unit of goods. J

You need to drill holes very carefully, and always from the other side. top panel, which will later be turned inside the case. I affirm this based on my own experience. Actually, an inquisitive eye will be able to see the consequences of my flaws in the photographs with which I accompany my story ...

Drill revolutions are the most minimal. In this case, if possible, it is worth using the auxiliary handle of the drill in order to stabilize the beating of the crown as much as possible.

Naturally, the edges of the holes obtained must be processed in order to remove the burrs that will inevitably remain after drilling the holes.

It turns out something like this:

To be continued…

As you know, in the circles of radio amateurs, amplifier layouts often remain layouts. It is easy to quickly assemble a layout “on plywood”, but to build beautiful body often lack of time! Difficult, expensive, lazy...

With this article I want to contribute to the "enclosure" of amateur designs. So, the case of a tube headphone amplifier from scratch in a day or two! The basis was taken, published on the portal. It doesn't matter. So you can assemble a case for any design.
We take an aluminum corner as a basis (I used a corner with a section of 20 × 20 mm). It is better that its thickness be at least one and a half millimeters. And carefully cut the blanks for the future case.

Carefully cut corners at 45 degrees:

Slowly we begin to assemble the structure:

This is the resulting frame:

I note that this is still an intermediate assembly, then all screw connections will be flush.

We take a sheet of duralumin and cut blanks for the top and bottom covers of the future case:

Important! We cut with an allowance of 1-2 mm.

We press the cut sheet to the body with clamps (sorry, I forgot to take such a photo) and drill holes for fastening immediately in the lid / bottom and corners of the frame. The fact is that the holes are first made with a drill of a smaller diameter - for threading, and only then a larger one - for screws, separately in the housing covers. If you drill separately, then nothing good will come of it. The holes just don't line up!
Take over general rule drill all through connecting holes immediately in the "package".

The covers should protrude slightly from the body. Excess in place can be easily removed with a file or grinder.

This is an image of another case, but the essence is clear.

We cut wooden slats for the "sides" of the amplifier. Wooden flashings (they are also door trims) are perfect as a material.

This is where the right tool is a big advantage. I use the following kit: a precise disc miter box and a very high-quality hacksaw for trimming Kataba Speed ​​Saw 265. The cut starts very accurately, the blade does not “walk”, the angle is maintained very well with slow sawing.

In addition to a hacksaw and a miter box, the set includes a square and a test hacksaw blade without teeth for zeroing.

Made In Japan. The cunning wiring is clearly visible - the teeth are sharpened inward.

Although, with some experience, you can manage with conventional tools.
Advice! Cut blanks "addressally". Those. they attached the rail to the facade of the case, marked the exact line of the cut, cut it and attached it. Exactly. After that, they attached a rail, for example, to the left “side” of the hull, marked the cut line, cut it off and attached it precisely. This is the only way to avoid or minimize the appearance of gaps between the slats.
Small gaps after assembly can be easily closed with wood putty.

The amplifier itself was assembled on a small duralumin chassis, connected to the top cover with screws and 5-7 mm racks. This is done in order to hide the lamp panels. Naturally, all the holes in the chassis and the top cover were pre-drilled in the "package". I wrote about this above.

Assembly process:

The parts of the rectifier and the anode voltage doubler are attached to the bottom cover. The incandescence of the lamps is powered by separate windings. AC voltage and "rested" into the ground with a pair of 150 ohm resistors.

Test run:

Then everything is as usual. Sanding, painting, varnishing. It is convenient to solder the casing for the transformer from textolite. In my case, it is sheet metal. Open on a sweep.

— the majority of connoisseurs of quality music, who know how to handle soldering equipment and those who have some experience in repairing radio equipment can try to assemble a high-end tube amplifier, which is usually called Hi-End, on their own. Tube devices of this type belong in all respects to a special class of household radio-electronic equipment. Basically, they have an attractive design, while nothing is covered by a casing - everything is in sight.

After all, it is clear the more you can see mounted on the chassis electronic components, the more authority the device has. Naturally, the parametric values ​​of the tube amplifier are significantly superior to models made on integral or transistor elements. In addition to this, when analyzing the sound of a tube device, all attention is given to a personal assessment of the sound, rather than the image on the oscilloscope screen. In addition, it differs in a small set of used parts.

How to choose a tube amplifier circuit

If the scheme is chosen preamplifier there are no special problems, then when choosing a suitable circuit for the final stage, difficulties may arise. Tube Audio Power Amplifier may have several options. For example, there are single-stroke and two-stroke type devices, and they also have various modes operation of the output path, in particular "A" or "AB". The output stage of the single-ended amplification is by and large a model, because it is in the "A" mode.

This mode of operation is characterized by the lowest values ​​of non-linear distortion, but its efficiency is not high. Also, the output power of such a cascade is not very large. Therefore, if necessary, voicing inner space medium-sized, you will need a push-pull amplifier, with the "AB" mode of operation. But when a single-cycle device can be made with only two stages, one of which is preliminary and the other is amplifying, then a driver is needed for a push-pull circuit and its correct operation.

But if single tube audio power amplifier may consist of only two stages - a pre-amplifier and a power amplifier, then a push-pull circuit for normal operation requires a driver or a stage that generates two voltages of identical amplitude, shifted in phase by 180. The output stages, regardless of whether it is single-ended or push-pull, assume the presence in the circuit output transformer. Which acts as a matching device for the interelectrode resistance of a radio tube with low acoustic resistance.

True fans of "tube" sound argue that the amplifier circuit should not have any semiconductor devices. Therefore, the power supply rectifier must be implemented on a vacuum diode, which is specially designed for high-voltage rectifiers. If you intend to repeat a working, proven tube amplifier circuit, then you do not need to immediately assemble a difficult push-pull device. To sound a small room and get the perfect sound picture, a single-ended tube amplifier is fully enough. In addition, it is easier to manufacture and configure.

The principle of assembly of tube amplifiers

There are certain rules for the installation of radio-electronic structures, in our case it is tube audio power amplifier. Therefore, before starting the manufacture of the device, it would be desirable to thoroughly study the paramount principles for assembling such systems. The main rule when assembling structures on vacuum radio tubes is the wiring of connecting conductors along the shortest possible path. The most effective method is to refrain from using wires in places where you can do without them. Fixed resistors and capacitors must be installed directly on the lamp sockets. At the same time, special “petals” should be used as auxiliary points. This method of assembling a radio-electronic device is called "hinged mounting".

In practice, when creating tube amplifiers printed circuit boards do not apply. Also, one of the rules says - avoid laying conductors parallel to each other. However, such, at first glance, chaotic wiring is considered the norm and is fully justified. In many cases, when the amplifier is already assembled, a low-frequency background is heard in the speakers, it must be removed. Performs the primary task right choice ground points. There are two ways to organize grounding:

• The connection of all wires going to the "ground" at one point - called "asterisk"
• Installing an energy-efficient electrical copper bus around the perimeter of the board, and solder the conductors to it.

It is necessary to verify the place for the ground point by experiment, listening for the presence of a background. To determine where the low-frequency background comes from, you need to do this: You need to use the method of sequential experiment, starting with the double triode of the pre-amplifier, to short the lamp grids to the “ground”. In the case of a noticeable decrease in the background, it will become clear which circuit of which lamp is “phoning”. And then, also empirically, you need to try to eliminate this problem. There are auxiliary methods that are mandatory for use:

Pre stage lamps

• Vacuum lamps of the preliminary stage must be closed with caps, and they, in turn, must be grounded
• Cases of trimmer resistors are also subject to grounding
• Lamp wires need to be twisted

Tube Audio Power Amplifier, or rather, the filament circuit of the pre-amplifier lamp can be powered direct current. But in this case, you will have to add another rectifier assembled on diodes to the power supply. And the use of rectifier diodes in itself is undesirable, as it breaks the constructive principle of manufacturing a tube Hi-End amplifier without the use of semiconductors.

By pairing the output and mains transformers in a lamp device, it is enough important point. These components must be installed strictly vertically, thereby reducing the background level from the network. One of them effective ways installation of transformers is their placement in a casing made of metal and grounded. The magnetic circuits of transformers must also be grounded.

retro components

Radio tubes are devices from distant times, but again come into fashion. Therefore, it is necessary to complete tube audio power amplifier the same retro elements that were installed in the original lamp designs. If it concerns fixed resistors, then carbon resistors with high parameter stability or wire ones can be used. However, these elements have a large spread - up to 10%. Therefore, for a tube amplifier the best choice there will be the use of small-sized precision resistors with a metal-dielectric conductive layer - C2-14 or C2-29. But the price of such elements is significantly high, then MLTs are quite suitable for them.

Particularly zealous adherents of the retro style get the "audiophile's dream" for their projects. These are BC carbon resistors, developed in the Soviet Union specifically for use in tube amplifiers. If desired, they can be found in tube radios of the 50-60s. If, according to the scheme, the resistor should have a power of more than 5 W, then PEV wire resistors coated with vitreous heat-resistant enamel are suitable.

Capacitors used in tube amplifiers are basically not critical to one or another dielectric, as well as to the element design itself. Any type of capacitor can be used in the tone control paths. Also in the rectifier circuits of the power supply, you can install any type of capacitors as a filter. When designing high quality low frequency amplifiers, great importance have isolation capacitors installed in the circuit.

It is they who have a special influence on the reproduction of a natural, not distorted sound signal. Actually thanks to them we get an exceptional "tube sound". When choosing isolation capacitors to be installed in tube audio power amplifier, special care must be taken to keep the leakage current as low as possible. Because the correct operation of the lamp, in particular its operating point, directly depends on this parameter.

In addition, we must not forget that the decoupling capacitor is connected to the anode circuit of the lamp, hence it follows that it is under great tension. So, such capacitors must have an operating voltage of at least 400v. One of the best capacitors working as a transition capacitor are JENSEN capacitors. It is these capacitances that are used in top-end HI-END class amplifiers. But their price is very high, reaching up to 7500 rubles for one capacitor. If you use domestic components, then the most suitable would be, for example: K73-16 or K40U-9, however, they are significantly inferior in quality to branded ones.

Single Ended Tube Audio Power Amplifier

The presented tube amplifier circuit has three separate modules:

• Pre-amplifier with tone control
• The output stage, that is, the power amplifier itself
• Source of power

The preamplifier is made according to a simple scheme with the ability to adjust the signal gain. It also has a pair of separate bass and treble tone controls. To increase the efficiency of the device, an equalizer for several bands can be introduced into the design of the pre-amplifier.

Preamp Electronics

The preamplifier circuit presented here is made on one half of a 6N3P double triode. Structurally, the preamplifier can be made on a common frame with an output stage. In the case of the stereo version, then naturally two identical channels are formed, therefore, the triode will be fully involved. Practice shows that when starting to create any design, it is best to first use the circuit board. And after adjusting, already assemble in the main body. Provided that the preamplifier is assembled correctly, it starts to work synchronously with the supply voltage without any problems. However, at the setup stage, you need to set the voltage of the anode of the radio tube.

The capacitor in the output circuit C7 can be used K73-16 with rated voltage 400v, but preferably from JENSEN, which will provide best quality sound. Tube Audio Power Amplifier not particularly critical to electrolytic capacitors, so any type can be used, but with a voltage margin. At the stage of tuning work, we connect a low-frequency generator to the input circuit of the pre-amplifier and apply a signal. An oscilloscope must be connected to the output.

Initially, the input signal range is set within 10 mv. Then we determine the value of the voltage at the output and calculate the amplifying factor. Sound signal in the range of 20 Hz - 20000 Hz at the input can be calculated throughput amplifying path and depict its frequency response. By selecting the capacitive value of the capacitors, it is possible to determine an acceptable proportion of high and low frequencies.

Setting up a tube amp

Tube Audio Power Amplifier implemented on two octal tubes. In the input circuit, a double triode with separate 6N9S cathodes is installed, connected in parallel, and the final stage is made on a rather powerful output beam tetrode 6P13S, connected as a triode. Actually, it is the triode installed in the final path that creates the exceptional sound quality.

To perform a simple adjustment of the amplifier, an ordinary multimeter will be enough, and in order to perform accurate and correct adjustment, you must have an oscilloscope and a generator audio frequencies. You need to start by setting the voltage on the cathodes of the 6H9C double triode, which should be within 1.3v - 1.5v. This voltage is set by selecting a constant resistor R3. The current at the output of the beam tetrode 6P13S should be in the range from 60 to 65 mA. If a powerful constant resistor 500 Ohm - 4 W (R8) is not available, then it can be assembled from a pair of two-watt MLTs with a nominal value of 1 kOhm and connected in parallel. All other resistors indicated in the diagram can be installed of any type, but preference is still C2-14 is given.

Just like in the preamplifier, an important component is the decoupling capacitor C3. As mentioned above, the ideal option would be to install this element from JENSEN. Again, if there are none at hand, then Soviet film capacitors K73-16 or K40U-9 can also be used, although they are worse than overseas ones. For the correct operation of the circuit, these components are selected with the lowest leakage current. If it is impossible to perform such a selection, it is still advisable to buy elements from foreign manufacturers.

Amplifier power supply

The power supply is assembled using a 5Ts3S direct-heated kenotron, which provides rectification alternating current, which fully complies with the design standards for HI-END class tube power amplifiers. If it is not possible to purchase such a kenotron, then two rectifier diodes can be installed instead.

The power supply unit installed in the amplifier does not require any adjustment - it turned on and that's it. The topology of the circuit makes it possible to use any chokes with an inductance of at least 5 Gn. As an option: the use of such devices from outdated TVs. The power transformer can also be borrowed from old Soviet-made lamp equipment. If you have the skills, you can make it yourself. The transformer must consist of two windings with a voltage of 6.3v each, providing power to the radio tubes of the amplifier. Another winding should be with an operating voltage of 5v, which are fed into the kenotron filament circuit and the secondary one, which has a midpoint. This winding guarantees two voltages of 300v and a current of 200mA.

Power amplifier assembly sequence

The assembly procedure for a tube sound amplifier is as follows: first, a power source and the power amplifier itself are made. After the settings are made and the necessary parameters are set, the preamplifier is connected. All parametric measurements measuring instruments must be done not on the "live" acoustic system, but on its equivalent. This is in order to avoid the possibility of removing expensive acoustics from standing. The equivalent load can be made from powerful resistors or from thick nichrome wire.

Next, you need to deal with the case for the tube sound amplifier. The design can be developed independently, or borrowed from someone. The most affordable material for the manufacture of the case is plywood. Lamps for the output and preliminary stages and transformers are installed on the upper part of the housing. On the front panel there are devices for adjusting the timbre, sound and an indicator for supplying voltage. In the end, you may end up with devices like the models shown here.

Especially for the competition from Aka Kasyan and the site site.

Once again I congratulate Ak Kasyan's channel on his birthday :)

In this article, I would like to talk about tube sound and my crafts from tube radios.

We live in the 21st century and we all know that tubes are dying out and they are not used anywhere except in tube amplifiers, but this luxury (I mean factory production) can only be afforded by "elite" people. But there are such wonderful people as radio amateurs, well, or lovers of tube sound, because as they say - "It is worth hearing the tube sound once and you won’t pull it off after", but only those who are deep in their youth, when they first appeared, are fond of this delicate work. transistors remained on the side of the tubes, or, in our time, they fell in love with the tube sound. But after all, they still think that only people of the older generation are fond of the direction of tube amplifiers, and indeed radio engineering in general. In fact, this is by no means true, and in this article I will try to dispel this judgment. And so, it's time to introduce myself, I'm a beginner radio amateur, my name is Danil, I'm 14 years old, and I'm from the city of Voronezh. Usually, after I say this phrase, everyone immediately stops taking me and my hobby seriously. But there were people who could support me. When I shot my first video, Aka Kasyan commented on it, which I was infinitely happy about, I was also happy about Mikhail's support. And then I realized that since Aka responded positively, then I need to continue.

It was summer and I decided to take on something more difficult for me, and it was a tube amplifier. At first I went deep into studying the theory of tube sound, read a lot, watched videos and studied. When I already had "basic knowledge" I started looking for what kind of amplifier I would assemble, it took a lot of time, but I decided to start with a simple single ended amplifier on 3 lamps (two 6P14P and 6N2P).

It seems like I decided what I would do, but ... It was difficult to find the details, and then I realized that I needed to find the old tube TV. It also took a long time to find him. But after several weeks of searching, I found a TV that was perfect for the amplifier. Record B312.

When they said that the black-and-white record was not working, it was not a pity to remove the lamps. I took off the lamps, capacitors (they were in good condition), a couple of resistors and three transformers - power, TVK and TV-ZSh (See Fig. 3.1, 3.2).

I bought the missing elements, and again there was a problem. Everything was enough for the first channel, but the second one needed a couple more trances - TVK and TV-ZSh, where TVK played the role of a power choke, and TV-ZSh was an output transformer. Well, I coped with this problem and have already gone to extremes by buying a transformer. In the meantime, the second month of summer is coming, yes, I have been searching for so long. Well, then it was necessary to deal with the amplifier case, I found the power supply case from the Soviet logic and decided to be creative, of course it didn’t work out very well, but I think it will do for the first time. This frame from BP served as the basis (See Fig. 1). The bottom base is made from a laminate board, and top cover also from it, for the sidewalls I also made lining from a laminate, but already lighter.

Now for the assembly: I installed the power transformer at the back, blocking it with a flap from the iron cover of the PSU (it turned out to be a kind of screen). Inside I installed a diode bridge of her407 diodes, two chokes on the anode and audio transformers(See Fig. 4.1, 4.2). Next, the upper board of the laminate was adjusted to the body and the fresco was removed, including for the panels of lamps with conders that I installed on this board (See Fig. 2). Now he began to assemble and solder the elements, spread the ground. I soldered shielded Soviet wires to the input. Incandescence, by the way, is also from Soviet wires (See the remaining pictures at the bottom of the article).