They somehow brought me a battered case from the American guitar amp “PEAVEY” and asked me to assemble a guitar amplifier in it.
Assembling the amplifier took a lot of time and lasted more than a year. This was my first combo. There was a lot of experimentation and many preamp circuits were tried. I either threw the whole thing into a corner for a long time, then took up experiments again.
But I gained good experience. And in the spring of this year I finally assembled the finished structure.
The article presents the results of my work. The amp has two channels: “Guitar” and “Bass”, and an honest 50 watts of sound.
The case is pretty shabby, but I didn’t do anything to it, this gives it a vintage look.
Channel "Bass": volume/gain control "Volume". Tone controls common to both channels "Bass", "Middle", "Treble".
Master volume control at preamp output "Master".
According to the scheme, I will only say about the most important things. RC chains C4R4, C5R7, C6R8, C7R10 adjust the frequency response the way we need: emphasizing and shaping the most delicious frequencies of the guitar range. Without them, the sound would be too “flat”, dull and inexpressive.
Diodes serve to limit the amplitude at the peaks, again forming “that same sound.”
The resistance of potentiometer P7 instead of 100K can be set to 470K - 1M, then there will be much more drive in the “Drive” mode and it will be possible to play heavier things.
Resistors R12, R13 with a power of 2-5 Watts.
We install transistor VT7 on the heat sink of one of the output transistors.
The output transistors are installed on heat sinks with an area of at least 400 cm2 each.
Capacitors C6, C7 MBM are sealed in close proximity to the housings of the output transistors, connecting the second terminal to the chassis.
If the amplifier is working well, the quiescent current is about 30-40 mA. At this current, the incandescent lamp, due to the small “cold resistance”, is equivalent to a conductor (short circuit), as if it were not in the circuit. In other words, when the lamp is not on, everything is fine.
If the lamp is on, this indicates a high current consumption and the presence of some kind of malfunction in the circuit. However, a catastrophe will not happen, because... the increased resistance of the heated lamp filament limited the current, which reduced the likelihood of damage to amplifier parts (usually output transistors).
The quiescent current of 30-40 mA is set by trimming resistor R7. If its adjustment is not enough, you need to reduce the resistance of resistor R8.
Experience shows that high quiescent current occurs due to incorrect installation of resistors, defects on the board, poor soldering, high-frequency self-excitation and, much less often, due to bad parts.
Resistors R1, R2 are needed to limit the input voltage of the 7815/7915 stabilizers.
All common wires must be brought together at one point, this is the key to clear sound and stable, uninterrupted operation of the device as a whole.
My capacitors are all Jamicon. C1, C2 must be at least 50 Volts, and C3, C4 - at least 25 Volts.
Good! The freebie is over. If you want files and useful articles, help me!
Having assembled the following perfectly working design. I was recently asked to make an amplifier for an electric guitar. The requirements were not complicated, but it all depended on certain characteristics. The output power should be 400-500 mW, for a load of 32 Ohms - most microcircuits for such a load output 2-3 times less, the power supply needed to be 9 volts - so that it could be connected from a standard Krona battery. I note that the concept of a guitar amplifier is confused with the concept of simply an audio amplifier, the purpose of which is precisely to amplify the sound signal with minimal distortion. However, it is necessary to understand that the final sound of an electric guitar is the result of many factors - the main ones being the properties of the electric guitar itself and the characteristics of the guitar amplifier. Of course, in addition to shaping the character of the sound, the guitar amplifier also affects the volume of the electric guitar. However, enhancing the sound of an electric guitar is only a secondary additional function of the device. The main purpose of a guitar amplifier is to create the sound of an electric guitar. Based on this task, there are many different guitar amplifiers in the world that give a wide variety of colors to the sound of an electric guitar. Here we will not load it with numerous analog effects, such as " Drive, Distortion, Thrash", any smartphone or laptop can handle all this perfectly (with a special program installed), but we’ll simply amplify the sound to an acceptable power.
The printed circuit board was designed for a suitable circuit - the choice fell on the three-transistor version.
Its current, as it turned out, is very small - 15-20 mA in rest mode, and 30-40 mA in operating mode, taking into account the indicator, which is made on an LED and serves as an indication of power on.
The homemade guitar amplifier board is made on PCB. It was machined to a minimum size, since the entire circuit was required to be compact.
The connectors are factory-made - both the connector is for the crown and the connector is of the "female" type, for output to a headphone plug (3.5 mm jack).
Don't skimp on the volume control; Soviet SP-shki are not appropriate here. The rustling and uneven resistance may be too noticeable. But if you don't want to buy new expensive ALPS
- you can simply pull them out of imported non-working equipment.
In ULF transistors, inexpensive domestic ones are used - KT315; they can be used with any letter index, having first checked them, since Soviet transistors have a certain spread in parameters. To reduce noise, it is recommended to use higher quality (imported) ones.
We take resistors and capacitors as small in size as possible, it is possible at all SMD use it, since there is nothing special to warm up here.
In fact, it turned out that the sensitivity of the circuit is good, about 100-150 mV at the input. It works loudly and clearly on 32 Ohm headphones, everyone was pleased with the simplicity, efficiency and small size of the circuit. Of course, over time you can buy more serious guitar equipment, but for starters, this device is quite enough. Author of the project: Redmoon.
Discuss the article GUITAR AMPLIFIER
For some time, having given way first to transistors, and then to microcircuits, radio tubes again returned to the closets of radio amateurs. Currently, these electric vacuum devices have gained great popularity among lovers of good sound. This applies to both musicians and those who listen to their recordings. Numerous companies have responded to the demand and in stores you can now buy a decent amplifier without much hassle, but their cost in some cases is simply astronomical. As a result, many radio amateurs master the basics of building equipment using radio tubes, constructing various amplifiers for their headphones, powerful audio systems and musical instruments. And I didn’t “pass by” when I decided to work on an amplifier for my guitar.
I took a well-proven pre-amplifier circuit as the basis for the future design. Slo Recto Twin designs of Gishyan *AZG* Aznaur, well-known in the circle of tube musical equipment enthusiasts. To the “pre” I added a push-pull power amplifier based on 6P3S beam tetrodes, a delay circuit for the supply of anode voltage and switching with a footswitch.
Schematic diagram
Structurally, the amplifier consists of a pre-amplifier using VL1-VL3 tubes, a push-pull power amplifier (VL4-VL6 tubes) and a common power supply.
The preamplifier, in turn, consists of two channels - clean (clean) and overload ( distortion) with separate tone and volume controls.
The signal from the guitar pickups is fed to the grid of one of the two triodes of the VL1.1 lamp, which is a common amplifier for both channels. In the cathode bias circuit of the triode, using one of the groups of relay contacts, the electrolytic non-polar capacitor C1 is switched, which is included in the circuit in pure sound mode and expands the band of amplified frequencies in the low-frequency region. In overload mode (the relay is activated), it is isolated by the high resistance of resistor R3, so only capacitor C2 remains, which has a relatively small capacity. In this case, the gain of the cascade is noticeably reduced at low frequencies, which prevents the “booming” of the sound.From the anode of the triode, the signal is divided into two channels. The top one operates in the mode of amplifying pure sound, the bottom one is in overdrive. Channelcleanrepresented by three-lane (treble- high, bass- low, middle- medium frequency) with a tone control assembled according to a fender circuit and an amplification stage on a VL1.2 triode.
Overload ( distortion) has already been implemented by a much larger number of lamps and passive elements. Three cascades based on VL2.1 triodes, VL2.2 and VL3.1 have a large overall gain, due to which the sound is greatly distorted. This creates an effect with a characteristic heavy and powerful sound. To coordinate these stages with the tone control, as well as to prevent mutual influence, a cathode follower on the VL3.2 triode is included in the circuit. In pure sound mode, the overdrive channel is blocked by shorting the VL2.2 triode grid.
To separately regulate the signal level of the cascades, each of them is equipped with variable volume resistors R11 and R38. In addition, there is a general volume control R40 master volume. The engines of all volume controls are shunted with fixed resistors with a resistance of 2.2 megaohms. They are necessary to eliminate possible rustling noises caused by wear of the conductive layer. In themselves, they are not terrible, but in this case the mesh is separated from the common wire, as a result of which the volume of the rustling becomes very loud.
The amplified and processed signal from one of the channels is fed to the input of a differential phase inverter assembled on a VL4 lamp. Its task is to additionally amplify and create two identical signals at the output with a phase shift of 180 ° relative to each other for the operation of a push-pull power amplifier using 6P3S lamps.
Switching of the pre-amplifier channels is carried out using two relays, which, in turn, are switched using a footswitch (you can select the desired channel by pressing the foot of a button, like in a lotion) or a switch on the front panel. There are also mode switches bright(S1) and treble shift(S2) to change the sound color of each channel. The indicator LED VD13 in the footswitch is included in the circuit of switching relays and lights up when the S6 button is pressed to turn on the channeldistortion. Capacitor C57 with a relatively large charging current at the moment the button is pressed ensures reliable operation of the relay, since the current flowing through the LED may not be enough for this.
The amplifier is powered by a transformer power supply with passive anode voltage filtering with a delay circuit, and with a 12AX7 lamp filament voltage stabilizer. The anode voltage rectifier uses ultra-fast UF4007 diodes, thanks to which it is possible to almost completely eliminate the switching noise of diode switching. To ensure that power is supplied to the lamps only after their cathodes have warmed up, the amplifier uses a delay circuit assembled on transistors VT3 and VT4. Relay K3 is activated approximately 10-15 seconds after the amplifier is turned on (selected with capacitance C55) and closes contacts K3.1. The filaments of the pre-amplifier lamps are powered by a stabilized voltage of 12.6 volts to reduce background and noise, as well as to increase the service life of these vacuum devices. The voltage at the cathode of the VL3.2 repeater is quite high due to the high resistance of resistor R33, because of this a significant potential difference is created between the cathode and its filament, which greatly reduces the operating time of the lamp. To neutralize this effect, the filament potential “rises” relative to the common wire by approximately 75 volts. The corresponding voltage is supplied from the divider R67 and R68 to the symmetrical filament divider R65 and R66. The same divider is installed in the filament circuit of the output lamps (6.3 volts), but its middle point is connected to the common wire.
The ground decoupling is made according to the “star” scheme, when the wires from the common wire circuits of different stages are connected at one point and have reliable contact with the amplifier body.
Details
All amplifier fixed resistors must be metal film (MF) or metal oxide (MO). They have less noise, unlike carbon CF resistors. Domestic MLT resistors are also suitable.
Film capacitors must be of the MKP series from Wima or Epcos for a voltage of at least 400 volts. These "musical" capacitors are quite common. You can also use good domestic K71 series. Consumer-grade K73 produces slightly worse results. You should beware of old metal paper capacitors such as MB or MBM. As a rule, even the “newest” copies are more than 30 years old and almost all of them have significant leakage currents. Electrolytic capacitors are best used with a maximum operating temperature of 105 degrees due to their proximity to hot lamps. For capacitors in anode circuits, the voltage must be at least 400 volts. The 0.022 μF capacitors shunting them must be of type X2, designed to operate in an alternating voltage circuit of at least 275 volts. Their operating DC voltage is 600-1000 volts, and their low internal resistance to pulse current contributes to good filtering of noise and ripple. Instead of non-polar electrolytes C1 and C10, conventional polar ones can be used. For small-capacity capacitors in tone blocks and in the bass reflex, it is better to take film, mica from the KSO and SGB series or imported high-voltage blue ceramic capacitors.
The preamplifier uses Russian-made 12AX7 tubes from Tung Sol. You can use them instead ECC83 or domestic 6N2P-EV. In this case, the filament voltage should be reduced to 6.3 volts. To do this, you need to replace the VD9 zener diode with another one - with an operating voltage of 3.3 volts. With some deterioration in sound quality, you can use 6N2P, 6N23P and even 6N9S, as well as other double triodes. Common domestic 6P3S tetrodes are used as output lamps.
Transistors in the delay circuit, as well as VT2 in the filament stabilizer of the preliminary lamps, can be any silicon low-power n-p-n structures and with a minimum emitter current transfer coefficient of 100. For example - KT315, KT3102, SS9014 and so on. Powerful transistor VT1 must have a maximum collector current of at least 4 amperes and a maximum voltage of at least 100 volts. If its body is not insulated (TO-220FP), then it should be attached to the radiator through an insulating heat-conducting gasket “Nomakon”, and the tightening screw should be equipped with a plastic washer.
It is advisable to use ultra-fast diodes in the anode rectifier VD1-VD4, such as UF4007, but you can also install regular rectifiers with a maximum reverse voltage of at least 600 volts and a forward current of 1 ampere. In this case, each of them is shunted with a film or ceramic capacitor with a capacity of 0.01 μF to a voltage of at least 630 volts. Diodes VD5-VD8 with a Schottky barrier, they can be replaced with any with a maximum forward current of at least 3 amperes.
I used specialized relays for switching audio signals - 46ND012-P from FUJITSU . But you can use any with an operating voltage of 12 volts, with two switching groups and minimum operating current.
Transformers and chokes are homemade. The first ones are wound on frames and cores from the Russian Corvette computer manufactured in the mid-90s. Their U-shaped tape magnetic cores have a small dispersion field and can be installed without magnetic shields. Any transformer iron with a cross-section of 6 cm 2 is also suitable. Data on windings and voltages are given in the table in the diagram. Between the layers, one layer of varnished cloth or thin capacitor paper should be laid, and between the windings the number of layers should be at least three. Between the halves of the magnetic cores there are insulating pads made of varnished cloth, 0.3 mm thick. The chokes are wound with 0.25mm wire until the frames are filled. Their cores must have a cross-section of at least 2 cm 2 with a dielectric insulator between their halves.
Design
Attention! This amplifier, like most other tube devices, contains high voltage that is dangerous to life and health, so all installation work and adjustments should be carried out in compliance with safety precautions!
Structurally, the amplifier is made on an open duralumin chassis, repeating the design approach to the design of tube audio amplifiers. Variable resistors, almost all connectors and switches are mounted on the front panel, which has an easy-to-use bend at an angle of 45 degrees. The sockets for fuse FA1 and the output of the audio transformer, as well as the power connector, are located on the rear wall.
The footswitch is assembled in a separate durable case, connected to the amplifier with a long cable.
The printed circuit board is quite long, so the thickness of the foil fiberglass laminate must be at least 3 mm to prevent unnecessary deformation. If you cannot find such material, then you can use the common one with a thickness of 1.5 mm, but you must provide holes for attaching the stands in the middle of the board.
Setup
Despite the rather large complexity of the circuit, the amplifier begins to work immediately after switching on, if, of course, all the parts used in it are in working order. However, the operation of the device should be checked step by step. First, the amplifier is turned on without tubes and the operation of the delay circuit is checked. Next, by adjusting the tuning resistor R63, the filament voltage of the pre-amplifier lamps is set to 12.6 volts. Next, with the lamps, you must again adjust this voltage, which will “fall” under load. After this, the voltage on the anode supply capacitors is measured. It should be 330-360 volts. It should be noted that for a working amplifier these figures will be lower.
Next we insert the power amplifier lamps VL4-VL6 into the corresponding sockets. A shielded wire is temporarily soldered to the upper terminal of the variable resistor R40 in the diagram, the second end of which can be connected to any audio source - a player or mobile phone. At the same time, clear, undistorted music should be heard in the speakers. Next, insert the VL1 lamp into the sockets and connect the guitar to the input of the amplifier, which is switched to the “clean” channel. Make sure it works well. Then they insert the remaining lamps and check the channel distortion.
The lamp modes are selected optimal, and they remain so when using resistors with a standard tolerance of ±5%, so no selection of elements is necessary.
Together with this amplifier, I use a cabinet (“speaker” for guitar amplifiers) with a Vintage 30 speaker from Celestion installed in it. It is not recommended to install conventional speakers used in car and household speaker systems, since it is the guitar speaker with its special frequency response shape (mid-frequency rolloff) that creates the special sound of an electric guitar.
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| VL1-VL4 | Lamp | 12AX7 | 4 | ECC83, 6N2P-EV | To notepad | |
| VL5, VL6 | Lamp | 6P3S | 2 | To notepad | ||
| DA1 | Linear regulator | LM7812 | 1 | To notepad | ||
| VT1 | Composite transistor | 2SB1340 | 1 | To notepad | ||
| VT2-VT4 | Bipolar transistor | 2SC945 | 3 | KT315, KT3102, SS9014 | To notepad | |
| VD1-VD4 | Rectifier diode | UF4007 | 4 | To notepad | ||
| VD5-VD8 | Schottky diode | SR306 | 4 | To notepad | ||
| VD9 | Zener diode | BZX55C6V8 | 1 | To notepad | ||
| VD11, VD12 | Rectifier diode | 1N4148 | 2 | To notepad | ||
| VD13 | Light-emitting diode | L-132XHD | 1 | To notepad | ||
| C1, C10, C11 | 22 µF | 3 | To notepad | |||
| C2, C47C50 | Capacitor | 0.47 µF | 5 | To notepad | ||
| C3, C9, C12, C16, C18, C20, C24, C25, C27, C29, C38, C39, C41, C44 | Capacitor | 0.022 µF | 14 | To notepad | ||
| C4, C7, C22 | Capacitor | 220 pF | 3 | To notepad | ||
| C5, C8, C31-C34, C52 | Capacitor | 0.1 µF | 7 | To notepad | ||
| C6 | Capacitor | 0.047 µF | 1 | To notepad | ||
| C13 | Capacitor | 2200 pF | 1 | To notepad | ||
| C14, C17 | Capacitor | 1000 pF | 2 | To notepad | ||
| C15, C21 | Capacitor | 1 µF | 2 | To notepad | ||
| C19, C26, C38, C57 | Electrolytic capacitor | 10 µF | 4 | To notepad | ||
| C23 | Capacitor | 470 pF | 1 | To notepad | ||
| C28, C40, C43 | Capacitor | 3300 pF | 3 | To notepad | ||
| C30, C30 | Capacitor | 100 pF | 2 | To notepad | ||
| C35, C51 | Electrolytic capacitor | 470 µF | 2 | To notepad | ||
| C37, C39, C42, C54 | Electrolytic capacitor | 220 µF | 4 | To notepad | ||
| C46 | Electrolytic capacitor | 10000 µF | 1 | To notepad | ||
| C53, C56 | Electrolytic capacitor | 47 µF | 2 | To notepad | ||
| C55 | Capacitor | 0.33 µF | 1 | To notepad | ||
| R1, R12, R16, R20, R41 | Resistor | 2.2 MOhm | 5 | 0.5 W | To notepad | |
| R2 | Resistor | 68 kOhm | 1 | 0.5 W | To notepad | |
| R3, R60 | Resistor | 100 kOhm | 2 | To notepad | ||
| R4, R24, R32 | Resistor | 1.8 kOhm | 3 | 0.5 W | To notepad | |
| R5, R31 | Resistor | 220 kOhm | 1 | 0.5 W | To notepad | |
| R6, R7, R13, R22, R26, R33, R45 | Resistor | 100 kOhm | 7 | 0.5 W | To notepad | |
| R8, R9, R35 | Variable resistor | 250 kOhm | 3 | B | To notepad | |
| R10 | Variable resistor | 25 kOhm | 1 | B | To notepad | |
| R11, R19, R36, R40 | Variable resistor | 1 MOhm | 4 | A | To notepad | |
| R14 | Resistor | 820 Ohm | 1 | 0.5 W | To notepad | |
| R15, R21, R23< R30, R50, R51 | Resistor | 470 kOhm | 6 | 0.5 W | To notepad | |
| R17, R42, R43 | Resistor | 10 kOhm | 3 | 1 W | To notepad | |
| R18 | Resistor | 680 kOhm | 1 | 0.5 W | To notepad | |
| R25, R47, R49 | Resistor | 1 MOhm | 3 | 0.5 W | To notepad | |
| R27 | Resistor | 39 kOhm | 1 | To notepad | ||
| R28 | Resistor | 330 kOhm | 1 | To notepad | ||
| R34 | Resistor | 47 kOhm | 1 | 0.5 W | To notepad | |
| R37 | Variable resistor | 50 kOhm | 1 | A | To notepad | |
| R38 | Variable resistor | 50 kOhm | 1 | B | To notepad | |
| R39, R48 | Resistor | 22 kOhm | 2 | 0.5 W | To notepad | |
| R44 | Resistor | 82 kOhm | 1 | 0.5 W | To notepad | |
| R46 | Resistor | 470 Ohm | 1 | 0.5 W | To notepad | |
| R52, R53 | Resistor | 4.7 kOhm | 2 | 0.5 W | To notepad | |
| R54 | Resistor |
You can make it if you have the necessary knowledge and experience for this. This publication discusses a device that is not very complex in design, but has a wonderful sound. The circuit presented here is a power amplifier for a bass guitar, in particular, the output stage is made using powerful bipolar transistors, and the preliminary amplification stage is implemented using vacuum tubes.
DIY bass guitar amplifier and its design includes three modules: a triode preamplifier, a final amplifier, and a power supply. Of course, any of these modules can be used separately in other devices if necessary. In the presented version, the amplifier is combined with a combined audio speaker, which made it possible to create a compact and convenient model; therefore, the power amplifier itself does not have a separate housing, but is built into an additional speaker cabinet box located slightly above the speaker. The sound pre-amplification unit is distinctively original, and the final stage and power supply are made according to a standard design. p>
DIY power amplifier for bass guitar has excellent sound, mainly due to the pre-amplifier stage, which is made on electric vacuum triodes, providing clean, transparent sound; in addition, the lamps have significantly less noise than transistors. The elementary design of the device creates conditions for ease of assembly and reduces the cost of all components. Also, one of the important factors is that in circuits made with tubes, there is no negative feedback, and this significantly increases the sound quality. Another indisputable advantage of the tube circuit is the ability to smoothly enter overload, this is especially important for sound amplification devices operating in combination with bass guitars.
In fact, the preamplifier is made using one double tube (VL1). Its first part is a standard circuit with a common cathode, which does not have any special features. Without additional load and with a 12AX7 lamp installed, for example, the gain of this stage will be within 68. Therefore, the input signal does not limit, even if the supply voltage is about 200v and a powerful guitar signal is supplied. When the first stage is loaded with a timbre block, the amplified signal passing through it is slightly reduced, this happens due to the high resistance at the output.
DIY bass guitar amplifier in the original version, a 6N2P-EV lamp was used. It has also been tested with excellent performance, especially with the supply voltage reduced to 140v, the 6N23P double triode; if it becomes necessary to install other lamps, there is no need to change the circuit. To find a specific sound, you can use 12AX7 tubes of various versions. By the way, 12AX7, just like the double triode ECC83, for which in the 6.3v filament channel the voltage is sent to the 9th pin of the lamp panel, and the other wire is supplied to the 4-5 pins connected to each other. In the original circuit, the lamp circuit received power from 150v, and was later improved and the supply voltage became 250v. However, even at 150v the sound was of high quality.
DIY bass guitar amplifier has a standard topology, there is nothing special about it. There are several built-in protections, in particular a circuit to protect the amplifier from exceeding the input voltage. The original design of the device was assembled without the use of a printed circuit board; all powerful output transistors are installed on a cooling radiator, except for the differential stage transistors. VT4 performs the function of a temperature controller, therefore it is installed in close proximity to the output switches, which, by the way, are attached to the heat sink through insulating gaskets using heat-conducting paste KPT-8.
The remaining electronic elements of the input stage are arranged on a solderless breadboard and connected to each other using a surface-mounted method. DIY bass guitar amplifier has a small number of components involved in its circuit, then their installation itself is quite easy. The circuit board itself is mounted on stands to the radiator in the area of the output keys. The principle of setting up an amplifier occurs in this order: - apply supply voltage to the circuit, but without connecting the output transistors. If everything is assembled correctly, the device without load will raise the sound signal without any distortion. Then you need to set, using trimming resistor R14, the minimum bias voltage in the emitter circuit of the pre-output transistors VT5 and VT6 (within 1v), all this needs to be done without a load.
After this, you need to connect the output stage and, again, use trimming resistor R14 to set the quiescent current to 28-30 mA; there is no need to give a high current value for the bass guitar to work. When an acoustic equivalent is connected and the signal is slightly amplified, we look at what the oscilloscope shows - there should be no “step” type distortion on the sine wave; if such distortion is still present, then you need to add a little quiescent current until the “step” disappears. The amplifier presented here can be freely replaced with another one you may have or want to buy in a store.
The non-polar capacitors installed in the circuit are film capacitors designed for a voltage of 100v, and C8 and C12 at 250v are made of ceramics. If you intend to use the device at a power of less than 100 W, then you can reduce the supply voltage to ± 35v, and leave only two powerful complementary transistors in the output path.
It should be borne in mind that this design is made as a built-in amplifier in an audio speaker, and therefore there are no external switching elements for acoustics, as a result there is no short-circuit protection device in the load. When using an additional speaker, you will need to take care of installing a protection module in the amplifier. The principle of supplying the supply voltage is the same as on tube amplifiers, that is, the “Power” key is pressed, and when the tubes are completely warmed up, the load and all the power are connected to the power source using the “Standby” key.
The power transformer used here is a TS-180; naturally, its secondary winding was slightly changed. In the original circuit, to provide voltage to the lamp filament, there is a tap on the secondary winding. Of course, it would be more efficient to wind a special winding for such purposes, but in order for everything to be at a professional level, then you still need to build in a rectifier that provides the filament circuit with direct current. The alternating voltage value in the secondary winding without load should be 34v, and after the rectifier ± 50v. If you need to get an output power within 200 W, then you will need to select a more powerful transformer, for example: TS-250 or a toroidal one with the same power.
The dynamic driver for the cabinet was a 380 mm woofer from CELESTION. In the original version, printed circuit boards were not created for one simple reason - the device had to be assembled in a short time, and even then for personal needs, and developing the boards would have taken more time and money. Although this design may seem quite primitive, the sound made a good impression. By the way, the famous bands “Araks” and “Ex-Smokie” who came on tour played on this device; these are the ones whose guitarist is Allan Silson.
Here in the photo you can see a case with a speaker - this is an amplifier for a bass guitar made with your own hands, and with a guitar in his hands is a bassist from the group “Ex-Smokie”.
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 tubes of different types and manufacturers. The first amplifier I assembled with my own hands was a 2-tube 6p6s and 6n9s. The 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 of the most optimal option for a 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 a classic of 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 actually costs about $100, but can be made from an old 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 fog 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 varnish-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 DIY tube amplifier for 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)
