How to make a tube guitar amplifier with your own hands. Review of Hi-End Guitar Amplifiers

Many people, and especially musicians, are familiar with phrases such as “warm tube sound", "tube sound". It is clear that tube amplifiers have this sound. Let's look at tube guitar amplifiers together. Let's look at different manufacturers and their models, and also listen to examples. Those who are not familiar with tube amplifiers will learn this topic in detail, and more experienced musicians will hopefully find interesting information for themselves.

The structure of guitar tube amplifiers

To begin with, let me remind you that a guitar amplifier consists of the following parts: a preamplifier (or preamp), a power amplifier and a cabinet (the speaker for sound reproduction and its housing). In classic guitar combo amplifiers, the preamp and the amplifier itself are assembled using tubes. The most common lamps are the 12AX7 model.

12AX7 lamp

And this is what a guitar combo amplifier looks like, assembled using tubes from the inside. Actually, four lamps can be seen with the naked eye. This example is from 1956 Fender.

For those interested in amateur radio, I will give an example of one of the circuits of a tube guitar amplifier.

Fender Guitar Amplifier Circuit

Since the first guitar amplifiers were tube amplifiers, they are considered to be the standard. Models produced in the 50s or 60s of the twentieth century are a great rarity, and are also highly valued by serious musicians and, if sold, sell for very large sums of money. In general, probably every guitarist dreams of owning a tube amp. Modern devices from famous brands also try to make them similar to the old, standard ones. They are used in lamp construction, but they are also used modern technologies. The names of such models most often contain the names of their predecessors as a tribute to memory, as well as for more successful marketing.

Legendary tube amplifiers for electric guitar

Fender was one of the first to produce guitar amplifiers. This was in the late 40s of the twentieth century. All amplifiers of that time were tube amplifiers. And in general, electronics were based on tubes. One of the legendary Fender amps was the Bassman model. Initially, this amplifier was created for bass guitars, but the musicians experimented with the sound and it turned out that the Fender Bassman is perfect for electric guitars.

Fender Bassman

You can also note such companies as Marshall and Vox, which began their journey in the mid-twentieth century. Their Marshall JTM45 and VOX AC30 models can rightfully be called legendary.

Marshall JTM45

1966 Marshall JTM45 amplifier

The VOX AC30 was released in 1959.

VOX AC30

1964 VOX AC30 combo amp

You can also give an example of the legendary Hiwatt DR103 amplifier, which was played by the famous David Gilmour from the band Pink Floyd.

Hiwatt DR103

So, sound examples different manufacturers and we heard models. Now we need to move on to listing the pros and cons that are common to most guitar tube amplifiers.

Pros of tube guitar amps:

• Dynamics, pronounced attack;
• Volumetricity of sound;
• Volume and sensitivity have a wide range;
• The beauty of overdriven sound.

Cons of tube guitar amps:

• Large dimensions and considerable weight;
• Fragility of lamps (it is necessary to change them quite often);
• There is a “microphone effect”;
• Yours directly high-quality sound reach at high volume;
• Amplifiers get hot and often require additional cooling.

By the way, as I mentioned above, there are many modern tube combo amplifiers that represent an excellent combination of new technologies in electronics and the design basis of classic tube models.

An electric guitar requires an amplifier for its sound. It consists of an acoustic system and an electronic unit that converts a previously assembled electrical signal c This device is sold in specialized stores separately from the electric guitar. You can also assemble it yourself, but you can only use such an amplifier at home.

What categories are amplifiers divided into?

According to its design, a guitar amplifier can be of two types:

• combo;
• stack.

The former are a single box that houses both the audio system and, as a rule, combo amplifiers have low power. However, among them there are a large number of options capable of producing high-quality sound. Stacks are professional equipment: in them, the speakers are located separately from the amplifier itself.

If you purchase equipment for rehearsals at home, then just buy a combo. Stacks are more suitable for performances and recording studios. They are much more expensive, but they give out high quality sound. There is no point in buying them for your home, since they only show their capabilities at a volume level of half the nominal volume. For example, if it is stated that a guitar amplifier is capable of delivering a power of 100 W, then you will be able to see all its positive qualities at a volume of 50 W.

Differences between guitar amplifiers by circuit

The electronic unit consists of a preamplifier (it is responsible for collecting the incoming sound) and an end unit (it amplifies the collected sound vibrations). The guitar amplifier circuit can be one of the following types:

1. Fully tube. They are considered elite and best suited for training. With the help of such an amplifier, you can notice any mistake made during the game.
2. With transistor terminal and tube amplifier. The most common option, as it belongs to the middle price category and produces good sound quality.
3. Fully transistorized. These are lightweight and inexpensive models that beginners can afford. This guitar is not that difficult to assemble, as the parts can be purchased at almost any radio parts store. You can also find ready-made kits for sale for those who want to try themselves as a designer.

You should choose an amplifier according to its circuit based on your tastes and budget. They all differ in sound quality. Another point to consider when purchasing is that repairing tube-type guitar amplifiers is much more expensive than other options.

What effects can you create?

Many amplifiers are capable of creating sound effects, which are necessary for studio recording or home rehearsals. Most often there are two of them: clean sound (similar to and overdrive (gives the instrument a rocky sound with overdrive).

The switch from one effect to another is most often located very inconveniently, so it is best to purchase an additional guitar processor. It is a pedal with which you can change sound settings while playing. With its help you can get even more effects.

Basic Control Panel Functions

A modern guitar amplifier has a fairly complex control panel with a large number of controls. There are three main ones:

• volume level;
• degree of overload (if this effect is built-in);
• sound frequencies (there may be several of them: bass, treble, middle).

Using the controls, you can adjust the sound to your liking: make it softer, change the timbre of the instrument, or set a significant degree of overdrive. It is best to choose amplifiers that provide all of the above configuration options.

Is it possible to assemble an amplifier yourself?

If you want to save money and assemble a guitar amplifier with your own hands, then you need to have a large number of tools on hand: drills, an oscilloscope, a tester, a soldering iron and a drill on a tripod. In addition, prepare radio components (based on the selected circuit), material for the board and housing. Be prepared for the amplifier to cost you more in the end.

Most schemes suggest assembling tube amplifiers. This is fair, because they are of better quality than transistor ones. However, if you want to assemble a high-quality model, you will have to spend a long time searching for materials that are not commercially available. It is best to first assemble the transistor version for testing.

Best Guitar Amplifier

A music store will have many types and brands of amplifiers to choose from. Each musician chooses a suitable guitar amplifier for himself, based on his tastes. Rating best brands and models includes:

1. The Blackstar ID:Core Stereo 10 combo features stereo sound, three power settings, multiple effects, and a built-in tuner. This is a fairly budget model, which is comparable in quality to more expensive analogues.
2. Peavey Vypyr VIP 3 is a semi-professional combo amplifier that is suitable for implementing any ideas. They are manufactured using the latest digital technology and have received high marks not only from musicians, but also from sound specialists.
3. Tube Marshall C5-01, which, despite its low power, produces high-quality and loud sound.
4. The Fender Mustang III V2 is a mobile option suitable for use in small spaces and home rehearsals.
5. Roland CUBE Lite with the ability to play at home with headphones, which is very important if you live in the city and do not have a soundproof room.

All amplifiers in this rating are of the combo type and are suitable for beginners and amateurs. Among the assortment of stores you can find other worthy options. Modern amplifiers have come a long way in sound quality and have a large number of useful features.

November 17th, 2010

So. As I already wrote, I have been struggling for about 3 months to find the best circuit and the most interesting sounding tube amplifier. The goal is to make a tube amplifier with your own hands with the least loss, both financial and in sound quality. I tried several lamps different types and manufacturers, my first amplifier, actually assembled with my own hands, was a 2-tube 6p6s and 6n9s. 6p6s lamp (but it would be more correct to assemble an 18-watt marshal on lamps such as 6p14p, 6p14p-ev, 6p43p, and what about the original EL84) I really liked the sound best option for guitar. 6n9s is a double triode, so in order to save space we are replacing it with a 6n2p more modern brother. After playing for a month on a single-ended amplifier, I still realized that it was not. NOT ENOUGH! You need to stir up something more and louder. I read several dozen articles from forums, I understood the principle by which they work. I first tried a circuit with 3 lamps and then finally returned to a 4-lamp Marshall 18 Watt circuit.

Marshall 18 Watt Circuit

on Yandex.Photos

The circuits differ only in tone blocks, I personally did the same as on the bottom one, but I leave the choice up to you.

(to view in a large size, follow the link to the photo and select "in another size > original")

The presented schemes are Lite versions

In general, the scheme is as old as time, let’s say it’s a classic musical sound. One of the most common schemes of the famous company. This amplifier even has its own website with hundreds of replica options. And so, the process of purchasing and selecting parts began. At that time I had a couple of 6p6s lamps and a couple of 6n2p lamps before I bought the pads. Then I started looking for transformers. You can order the output transformer in the online store from Erasov, or try to find something similar on the breakers. I found a transformer on the radio market in Tsaritsino. I used TPP 245-127/220-50, the primary windings were just right for splitting into
half-cycles from the lamps, and the secondary ones are 15-16 and 17-18, that is, 10+10 volt
windings

To reduce noise, it is recommended to install a small choke immediately after the diode bridge. I used D22, although it has a small current, nothing fatal happened to it. Lamps can be ordered either in the same Erasov or in the online store http://www.istok2.com/. We either buy all the related parts where we can buy them, or we assemble them ourselves.

Next we make the chassis. The chassis is the basis on which all installation is done. You can buy it, which is actually about $100, but you can make it from an old one computer case. Which is exactly what I did. The old AT case has a top cover and both walls are a single bent sheet. We measure out how much we need and saw off.

" " on Yandex.Photos

" " on Yandex.Photos

I made the power board on a PCB.

Don't forget about currents! So 6.3 volts would be enough for all the lamps. I had to buy a 4*6.3 transformer separately in order to power all 4 lamps. Also, don’t forget to shunt 6.3 volts to common “-”. Another recommendation for power supply I can only say is that, if possible, try to split the heat and 300V into different toggle switches. Since it is better to supply voltage to a warm lamp.

on Yandex.Photos

At first I was lazy and soldered it basically haphazardly. Everything is completely scary, the noise is buzzing, in short, chaos. So it’s better to do it right away and honestly. But at this stage it is recommended to decide where you will have what. And for purely practical reasons, I can advise placing the lamps on the opposite side from the front panel. AND DON'T AT ANY TIME!!! case, do not paint if you are not sure. I'll have to disassemble everything and repaint the chassis!

The board can be made from anything, the main thing is that everything is clean and neat. and with the shortest distance of wires through which the signal flows. And just try to concentrate the power in one place and run all the wires along one bundle.

If we have collected everything and everything works for us, then it should look something like this.

(the article is not finished and will be added to, painting is ahead, assembling the head housing and cabinet, fine tuning and samples!)

Again, a recommendation: before drilling holes, think carefully or try on your knees what configuration you will end up with. To attach the chassis to the body, 2 boards were screwed to the side walls. DIY amplifier he actually assumes that you will do and redo everything 150 times if you don’t think everything through from the beginning.

Now a little about routing the wires. From my recommendations... immediately after the sockets, place a resistor on the common (-) 1 Mohm, mount it directly on the lamp legs, the wire from the sockets is strictly shielded.

The 6.3 volt filament wires must be woven into a tight braid (twisted pair).

We bring all common wires (ground) to one point, this installation is called a star. We take the wire from any old choke with a cross-section of 0.75; if you find it, the insulating wire should be made of lacquer-kini, but in principle you can use any cambric without any problems.

Well, as I said, the chassis will have to be repainted.

In the end, I left only the master volume, and simply threw away all the other tinsel.

To prevent current from getting into playful hands, I installed a grid. Regular garden mesh, bought at any construction market. For aesthetics it is painted black.

The side crossbars are screwed to the walls and the mesh is attached to them.

I remind you for those who have already lost their minds, we have been doing this for several months Tube amplifier DIY guitar.

Thanks to all my friends for your help and information. I give a few more links to articles from. At http://rumapucm.ya.ru the scheme was completely redesigned by me and from Light it was made even lighter.

Really awesome amplifier Marshall 18 watt Unfortunately, I did not assemble the original circuit, but replaced the output lamps with actual ones. Of course, this radically changes the sound, it’s still real Marshal 18 the amplifier is considered to be 6p14p (EL84)

Guitar amplifiers, along with electric guitars themselves, have always been of interest to many beginners and not only musicians. Timbre, gain and overload characteristics are very individual, and the ideal combination varies from one guitar to another. There is no amplifier that completely satisfies all requirements, and this circuit proposal will not be an exception. But it is universal, powerful (about 100 watts) and has all the necessary adjustments. Unlike a store-bought amplifier, if you build a VLF yourself, you can change many things to suit your own needs. The opportunity to experiment is presented in full. And it’s much more honorable to play on your own equipment, because our individuality is manifested primarily through creativity. The proposed guitar amplifier is designed for 100 W of power into a 4 Ohm load. This is the usual power for guitarists, which is enough for both home and concerts.

We solder the guitar pre-amp on a separate board, later placed in an interference shield. A photo of the preamp board is shown below. It is based on two operational amplifiers with a tone and gain control unit.

This is a simple but proven circuit design that provides excellent tonality throughout the entire range. The design is ideal for those guitarists who would like to get great sound. The tone controls have enough range to cover almost anything, from violin to bass guitar.

The preamp uses dual operational amplifier for strengthening. The transistor is connected according to the emitter follower circuit and has a low output impedance, after the master volume control. As shown in the diagram, there is a typical guitar input from which you can get a very fat overdrive and then adjust it to a suitable level. Please note that when using the TL072 op amp, noise with a lot of high frequencies is possible. We highly recommend using the OPA2134 op amp from Texas Instruments, then you will truly have the quietest guitar amp you've ever heard!

The module's power is connected directly to the main +/-35 V bus of the power amplifier. You need to use 1 W zener diodes (D5 and D6), and 680 Ohm resistors R18 and R19 should also be 1 W each.

For greater gain, we recommend reducing R11 to at least 2.2 kOhm. If the bright switch makes the sound too bright (too much high frequency), you need to increase the resistor R5. The output diodes are designed to allow the preamp to create "soft" clipping as the volume increases.

Make sure the input connectors are isolated from the chassis. This helps prevent noise, especially when the guitar amp is connected to a different power source.

Amplifier

The photo below shows the fully assembled printed circuit board UMZCH. The TIP35 and TIP36 output stage transistors ensure reliability in the harshest stage conditions. Other features of the circuit include short circuit protection - bias components of diodes D2 and D3.

Short circuit protection limits output current to relatively safe level. The protection will limit the peak output current to approximately 8 amps. The bias current is adjustable and should be set at about 25 mA at rest. Transistors TIP3055/2966 or MJE3055/2955 can also be used for UMZCH. The circuit allows you to connect up to two 8-Ohm acoustic speakers(4 ohms each). Do not use speakers less than 4 ohms into this amplifier - it is not designed for such low impedance!

ULF power supply

The power transformer should be toroidal for best performance and minimum interference. The amplifier is designed for a maximum supply of +/-35V and this value should not be exceeded. The transformer should be rated for 25-0-25 volts, and no more. Less is fine if you don't need the full 100 watts. The transformer power should be 150VA (3 A secondary current). More than 250VA is overkill. Use good quality PSU filter electrolytes, since they will be subject to current and temperature loads. The current of the diode bridge rectifier should be 35 A. Mounting type - on a chassis with thermal paste.

All fuses must be as specified in the diagram - do not be tempted to use larger ones. The input and output connections are shown in the figure.

Nests Preamp out And power amp in allow you to insert effects into the audio path, such as compression, reverb, digital effects and others. Exit preamplifier connected so that the signal preamplifier can be removed without turning off the power amplifier, so it can be used for direct audio supply. This is especially useful for bass. The preamp output can also be used for .

Setting up a guitar amp

1. Before the power is turned on for the first time, temporarily install 22 ohm 5 W resistors instead of fuses. Do not immediately connect the load (AC)! When applying power, check that the voltage direct current the output is less than 1 V. Check all transistors for heating - if any element is hot, turn off the power immediately, then look for the error.
2. If everything is good, connect sound system and the signal source and make sure that the sound is not distorted (for example, connect music from the player).
3. If the VLF passes all these tests, remove the 22 ohm resistors and reinstall the fuses. Disconnect the load speaker cable and turn the unit back on. Make sure that the DC voltage at the AC terminals does not exceed 100 mV, and again check the heating on all transistors and resistors.
4. Once you are sure everything is good, set the bias current. Connect a multimeter between the collectors of Q10 and Q11 - you are measuring the voltage drop across two 0.22 ohm resistors R20 and R21. The required quiescent current is 25 mA, so the voltage across the resistors should be set to 11 mV. The value setting is not too critical, but lower currents will result in less dissipation in the output transistors.
5. After this, it remains to adjust the offset when the temperature of the body and all parts of the guitar amplifier stabilizes. Often temperature and current are slightly interdependent. That's it - the design is ready!

I made this small low-power tube guitar amp a long time ago, probably about 15 years ago. This was my first design assembled using vacuum tubes. Since at that time I was not involved in lamp technology, I did not have stocks of more or less high-quality components for such a design. And in general, for me it was an experiment. The housing for this small-sized combo amplifier was made by my friend, carpenter and guitar maker Oleg Gnilitsky. Electronic components were literally found "in the landfill" and in my electronic trash. I unscrewed the output transformer from some old tube TV, and the lamp sockets were also from some old tube equipment. I used the power transformer type TAN 16-220-50. This excellent transformer happened to be available in my "electronic supplies". After rummaging through my cabinets and drawers for an hour, I scraped to the surface of this world several old lamps of type 6N2P and 6P14P of unknown origin. I speculated that some of these Soviet-made lamps might still be in working order. And so it turned out. And by the way, we must give them credit, these lamps still work in the combi.

This low-power amp was used for several years for home rehearsals and then, when other equipment appeared, it was pushed into the far corner of the electronic junk warehouse and undeservedly forgotten. Recently I was clearing out this electronic trash and found this miracle device. I cleaned it of dust, turned it on and it turned out that it works great to this day. I just had to clean and lubricate the rustling and creaking potentiometers and the little amp was like new again. So I decided to publish this article on my website. I think it will be useful to those who are starting to study tube technology and want to make a cheap small tube amplifier.

Looking ahead, I will say that instead of 6N2P and 6P14P in this combo you can use the more common 12AX7 and EL84 lamps today. The EL84 output lamp is a complete analogue of the 6P14P, and when using a 12AX7, you need to change the connection diagram of its filament circuits, which will be discussed in this article.

Pinout of lamps EL84 and 6P14P

Lamp pinout 6N2P

Lamp pinout 12AX7

The filament circuit of the 6N2P double triode is designed for a voltage of 6.3 volts. The filament voltage must be supplied to lamp legs 4 and 5. The 12AX7 lamp heater is also connected to legs 4 and 5, but is designed for a voltage of 12.6 V. However, the filament circuit of the 12AX7 lamp can also be powered from a voltage of 6.3 V since the connection point of the lamp halves heaters is connected to leg 9. Since each of the lamp halves heaters 12.6 V is designed for the same 6.3 V, we can connect them in parallel and use this lamp instead of 6N2P. To do this, legs 4 and 5 of the 12AX7 lamp must be connected together, and the filament voltage must be applied to pin 9 and to legs 4 and 5 connected together.

Schematic diagram of a small-sized tube guitar amp. Click on the diagram to enlarge it

The guitar is connected to jack J1. At the amplifier input, the level control on potentiometer R1 is turned on. From the potentiometer slide, through resistor R2, the signal is supplied to the grid of the first triode of the lamp VL1. Resistor R2 serves to prevent the lamp from operating with an unconnected grid in the event of an open circuit in the R1 potentiometer motor circuit (malfunctions in potentiometers occur frequently).

From the output of the cascade (anode of the triode VL1-a), the amplified signal is supplied to a three-band tone control, which provides adjustment for high, mid and low frequencies. From the output of the tone control (potentiometer R6) the signal is fed to the “Master” level control. A slight loudness compensation of this regulator is achieved by connecting a capacitor with a capacity of 680 picofarads between the engine and the top terminal of the potentiometer in the circuit. As a result, as the volume decreases, the proportion of high frequencies in the output signal slightly increases. Next, the signal goes to the second voltage amplification stage, assembled on the second half of the lamp - triode VL1-b. From the anode of this triode, through the coupling capacitor C9, the signal is supplied to the output stage of the amplifier.

The output stage is assembled using a single-cycle circuit using two 6P14P (EL84) lamps VL2 and VL3, connected in parallel. Connecting two lamps in parallel allows you to slightly increase the output power of the amplifier. You can use only one lamp, leaving the second socket empty. This is exactly how I use the combo, since at home its output power and sound volume are more than enough for me. With one tube, the output power of the amplifier is 2..3 watts. If you install a second lamp, the power will be around 5 watts. Due to the fact that the tube output stage has a signal clipping characteristic that differs from transistor circuits, we can (subjectively) say that three watts of “tube” is much louder than “transistor” three watts. Although this statement sounds unscientific at first glance, in reality it all comes down to the nature of the distortions introduced by tube circuits into the signal when overloaded. The distortion of a tube circuit is not as sharp as in a transistor one, and therefore a tube amplifier can operate in the saturation region, producing a rather pleasant sound, while transistor circuits, when overloaded, limit the signal very sharply, immediately turning it into a kind of rectangular pulses, which causes a very unpleasant sound. distortions. For this reason transistor amplifier should have a much larger gain headroom than a tube one. As we see, there is no mysticism here and everything fits into the laws of physics.

The speaker of the amp has a coil resistance of 8 ohms. It is connected via an output transformer. The output transformer is a very important and most expensive part of a tube amplifier. The sound of such an amplifier and its frequency range greatly depend on the quality and design of the output transformer. Tube amplifiers designed for listening to music often use expensive and difficult to wind ultra-linear transformers. Since a guitar amp does not require as wide a frequency range as an amplifier designed for listening to music, a guitar amp does not have as high a requirement for the output transformer. You could even say that too wide a frequency range is even harmful for a guitar amplifier. A large amount of high frequencies leads to the appearance of "sand" in the guitar sound. Therefore, loudspeakers intended for use in guitar amps are made with an upper limit of reproduced frequencies in the region of 7 - 8 kilohertz. Frequencies above this limit should be cut, as this is the "sand" area. It must be noted that in amplifiers and amps for classical (acoustic) guitars everything is exactly the opposite. Their frequency characteristics are very close to “musical” amplifiers. So we are talking only about amplifiers for electric guitars. For the same reason, “guitar” amplifiers are not suitable for listening to music.

In my mini-combo, I used an output transformer from an old tube TV. Such a transformer is quite suitable for a small guitar amplifier and fits well with the output tube, since the TV used exactly the same 6P14P tubes. The loudspeaker is connected to the secondary winding of the transformer through a regular telephone jack. This is a common solution in guitar amps. You can turn off the internal speaker and connect an external speaker to this jack. There is also a jack for connecting headphones. The headphones are turned on through a voltage divider across resistors R22 and R23. The divider is connected to the amplifier output automatically when the speaker plug is removed from the socket.

Schematic diagram of the power supply for a tube guitar amp

The weak point of my combo is the loudspeaker. Strictly speaking, the dynamic head used is not a “guitar” one; I didn’t have guitar loudspeakers at that time and I installed a Japanese 3 W speaker, torn out of some old Japanese radio. Although the speaker is not bad, it is not a “guitar” speaker, that is, it is quite broadband and reproduces frequencies that are not needed for the guitar signal, lying in the “sand” area. To some extent, this is compensated by the not very broadband output transformer and the presence of a tone control. But still, in acoustics for an electric guitar, it is better to use special “guitar” dynamic heads.

Switch Sw2 "Tone" turns on capacitor C14, which bypasses resistor R19 in the cathode circuit of the output lamina. At the same time, the sound becomes brighter and the output power of the amplifier increases slightly. Chain C11 R22 eliminates possible self-excitation of the amplifier.

The power supply unit of the combi is assembled on the basis of a unified Soviet transformer TAN16-220-50 (Anode-Nakalny Transformer). This transformer is very convenient for use in homemade lamp designs, as it has all the necessary voltages to power both the filament and anode circuits of lamps. however, you can use any transformer, for example from an old tube TV or a homemade one. The transformer must contain at least 2 secondary windings. Incandescent, for a voltage of 6.3 V (and a current sufficient to power the incandescent lamps) and a high-voltage winding with a voltage of 250 - 270 volts. In the case of the TAN16-220-50 transformer, I connected several of its secondary windings in series to obtain a voltage of about 210 volts. This transformer has 2 filament windings of 6.3 V. So I “bossed” and powered each lamp from its own winding. No one bothers you to connect the heaters of both lamps to one filament winding in parallel, if your transformer has only one such winding. The filament circuit of the first lamp includes a construction resistor R26 with a resistance of 470 Ohms. Its engine is connected to the ground. When setting up the amplifier, turn the R26 knob to achieve a minimum background alternating current in dynamics. the adjustment must be made with the R1 regulator set to the minimum volume position.

I used the winding of a 15-16 24 volt transformer to connect a power-on LED to it. Switch SW2 turns on or off the anode voltage. This is done in order to extend the life of the lamps. As is known, the service life of electronic tubes is reduced if the anode voltage is applied immediately at the moment the amplifier is turned on, while the filaments have not yet warmed up. Therefore, first we turn on the amplifier to the network, wait for the lamps to warm up (2-3 minutes) and then turn on the anode voltage with switch Sw2.

Mr. Shanti. June 2018

Chassis and mounting of a tube guitar amp amplifier. View from above