Almost every novice radio amateur, and not only, had a desire collect color music prefix or a running fire to diversify listening to music in the evening or on holidays. In this article, we will focus on a simple color music set-top box, assembled on LEDs, which even a novice radio amateur can collect.
1. The principle of operation of color music consoles.
The work of color music consoles ( CMP, CMU or SDU) is based on frequency division of the spectrum of an audio signal with its subsequent transmission through separate channels low, middle and high frequencies, where each of the channels controls its own light source, the brightness of which is determined by the oscillations of the sound signal. The end result of the work of the set-top box is to obtain a color scheme corresponding to the music being played.
To obtain the full gamut of colors and the maximum number of color shades, at least three colors are used in color-music consoles:
The division of the frequency spectrum of the audio signal occurs using LC- and RC filters, where each filter is tuned to its own relatively narrow frequency band and only passes through itself the vibrations of this section of the audio range:
1
. Low pass filter(LPF) transmits oscillations with a frequency of up to 300 Hz and the color of its light source is selected in red;
2
. Mid Pass Filter(FSF) transmits 250 - 2500 Hz and the color of its light source is selected green or yellow;
3
. High pass filter(HPF) transmits from 2500 Hz and above, and the color of its light source is selected blue.
There are no fundamental rules for choosing the bandwidth or the color of the glow of the lamps, so every radio amateur can use colors based on the characteristics of his perception of color, and also change the number of channels and bandwidth at his own discretion.
2. Schematic diagram of a color music set-top box.
The figure below shows a diagram of a simple four-channel color music set-top box, assembled on LEDs. The set-top box consists of an input signal amplifier, four channels and a power supply unit that provides power to the set-top box from the AC mains.
An audio signal is applied to the contacts PC, OK and General connector X1, and through resistors R1 and R2 falls on a variable resistor R3, which is the input level control. From the middle terminal of the variable resistor R3 beep through the capacitor C1 and resistor R4 enters the input of a pre-amplifier assembled on transistors VT1 and VT2... The use of an amplifier made it possible to use the set-top box with almost any audio signal source.
From the output of the amplifier, the audio signal is fed to the upper terminals of the trimming resistors R7,R10, R14, R18, which are the load of the amplifier and perform the function of adjusting (tuning) the input signal separately for each channel, and also set the desired brightness of the channel LEDs. From the middle terminals of the trimming resistors, the audio signal is fed to the inputs of four channels, each of which operates in its own band of the audio range. Schematically, all channels are made the same and differ only in RC filters.
Per channel higher R7.
Channel bandpass filter formed by a capacitor C2 and only passes the high-frequency spectrum of the audio signal. Low and middle frequencies do not pass through the filter, since the resistance of the capacitor for these frequencies is high.
Passing the capacitor, the high frequency signal is detected by the diode VD1 and fed to the base of the transistor VT3... The negative voltage appearing at the base of the transistor opens it, and a group of blue LEDs HL1 — HL6 included in its collector circuit are ignited. And the greater the amplitude of the input signal, the more the transistor opens, the brighter the LEDs light up. To limit the maximum current through the LEDs, resistors are connected in series with them R8 and R9... If these resistors are missing, the LEDs may be damaged.
Per channel middle frequency signal is supplied from the middle terminal of the resistor R10.
The channel bandpass filter is formed by the contour С3R11С4, which for low and high frequencies has significant resistance, therefore, on the base of the transistor VT4 only mid-frequency vibrations are received. LEDs are included in the collector circuit of the transistor HL7 – HL12 Green colour.
Per channel low frequency signal is fed from the middle terminal of the resistor R18.
The channel filter is formed by a contour С6R19С7, which attenuates the signals of medium and high frequencies and therefore to the base of the transistor VT6 only low frequency vibrations are received. The channel is loaded by LEDs HL19 – HL24 of red color.
For a variety of colors, a channel has been added to the color music prefix yellow colors. The channel filter is formed by a contour R15C5 and operates in the frequency range closer to low frequencies. The input signal to the filter comes from a resistor R14.
The color music console is powered by constant voltage 9B... The set-top box power supply consists of a transformer T1, diode bridge made on diodes VD5 – VD8, microcircuit voltage stabilizer DA1 type KREN5, resistor R22 and two oxide capacitors C8 and C9.
AC voltage rectified by a diode bridge is smoothed by an oxide capacitor C8 and goes to the voltage stabilizer KREN5. From the conclusion 3 of the microcircuit, a stabilized voltage of 9V is supplied to the set-top box circuit.
To obtain an output voltage of 9V between the negative bus of the power supply and the terminal 2 microcircuit included resistor R22... By changing the value of the resistance of this resistor, they achieve the desired output voltage at the output 3 microcircuits.
3. Details.
Any fixed resistors with a power of 0.25 - 0.125 W can be used in the set-top box. The figure below shows the values of resistors in which colored stripes are used to indicate the value of resistance:
Variable resistor R3 and trimmer resistors R7, R10, R14, R18 of any type, if only they fit the size of the printed circuit board. In the author's version of the design, a domestic variable resistor of the SP3-4VM type was used, and trimming resistors were imported.
Fixed capacitors can be of any type, and are designed for an operating voltage of at least 16 V. If you have difficulty acquiring a 0.3 μF capacitor C7, it can be made up of two 0.22 μF and 0.1 μF capacitors connected in parallel.
Oxide capacitors C1 and C6 must have an operating voltage of at least 10 V, capacitor C9 at least 16 V, and capacitor C8 at least 25 V.
Oxide capacitors C1, C6, C8 and C9 have polarity, therefore, when mounting on a breadboard or printed circuit board, this must be taken into account: for Soviet-made capacitors, a positive terminal is indicated on the case, for modern domestic and imported capacitors, a negative terminal is indicated.
Diodes VD1 - VD4 any of the D9 series. A colored strip is applied to the diode body from the anode side, defining the letter of the diode.
As a rectifier, assembled on VD5 - VD8 diodes, a ready-made miniature diode bridge is used, designed for a voltage of 50V and a current of at least 200 mA.
If you use rectifier diodes instead of a ready-made bridge, you will have to slightly correct the printed circuit board, or the diode bridge should be taken out of the main board of the set-top box and assembled on a separate small board.
For self-assembly of the bridge, the diodes are taken with the same parameters as the factory bridge. Any rectifier diodes from the KD105, KD106, KD208, KD209, KD221, D229, KD204, KD205, 1N4001 - 1N4007 series are also suitable. If you use diodes from the KD209 or 1N4001 - 1N4007 series, the bridge can be assembled directly from the printed wiring side directly on the contact pads of the board.
LEDs are conventional with yellow, red, blue and green glow colors. Each channel uses 6 pieces:
Transistors VT1 and VT2 from the KT361 series with any letter index.
Transistors VT3, VT4, VT5, VT6 from the KT502 series with any letter index.
Voltage stabilizer type KREN5A with any letter index (imported analogue 7805). If you use nine-volt KREN8A or KREN8G (imported analogue 7809), then the resistor R22 is not installed. Instead of a resistor, a jumper is installed on the board, which connects the middle terminal of the microcircuit with the negative bus, or this resistor is not provided at all in the manufacture of the board.
To connect the set-top box with a sound signal source, a jack-type connector for three contacts is used. The cable is taken from a computer mouse.
Power transformer - ready-made or home-made with a power of at least 5 W with a voltage on the secondary winding of 12 - 15 V at a load current of 200 mA.
In addition to the article, watch the first part of the video, which shows the initial stage of assembling a color music set-top box.
This concludes the first part.
If you are tempted to make color music on LEDs, then select parts and be sure to check the health of diodes and transistors, for example,. And then we will make the final assembly and adjustment of the color music console.
Good luck!
Literature:
1. I. Andrianov "Prefixes for radio receivers".
2. Radio 1990 №8, B. Sergeev "Simple color music prefixes".
3. Operation manual for the radio designer "Start".
In this article we will talk about color music. Probably, every novice radio amateur, and not only, at one time had a desire to collect color music. What it is, I think, is known to everyone - to put it simply, it is the creation of visual effects that change in time to the music.
That part of color music that emits light can be performed on powerful lamps, for example, in a concert installation, if color music is needed for home discos, it can be done on ordinary 220-volt incandescent lamps, and if color music is planned, for example, as computer modding, for everyday use, it can be done on LEDs.
Recently, with the advent of LED strips on the market, color music consoles using such LED strips are increasingly used. In any case, for the assembly of Color Musical Installations (CMU for short), a signal source is required, which can be a microphone with assembled several amplifier stages.
Also, the signal can be taken from the line output of the device, the sound card of the computer, from the output of the mp3 player, etc., in this case, you will also need an amplifier, for example, two stages on transistors, for this purpose I used the KT3102 transistors. The preamplifier circuit is shown in the following figure:
Preamplifier - schematic
Below is a diagram of a single-channel color music with a filter, working in conjunction with a preamplifier (above). In this circuit, the LED blinks under the bass (bass). To match the signal level in the color music scheme, a variable resistor R6 is provided.
There are also simpler color music schemes that any beginner can assemble on 1 transistor, moreover, they do not need a preamplifier, one of these schemes is shown in the picture below:
Color music on a transistor
The pinout diagram of the Jack 3.5 plug is shown in the following figure:
If for some reason it is not possible to assemble a preamplifier on transistors, you can replace it with a transformer included as a step-up. Such a transformer should produce voltages on the windings of 220/5 Volts. The transformer winding with fewer turns is connected in a sound source, for example, a radio tape recorder, parallel to the speaker, while the amplifier must deliver at least 3-5 watts of power. A winding with a large number of turns is connected to the color music input.
Of course, color music is not only single-channel, it can be 3, 5 or more multichannel, when each LED or incandescent lamp blinks while reproducing the frequencies of its range. In this case, the frequency range is set by using filters. In the following diagram, three-channel color music (which he himself recently collected), capacitors are used as filters:
If we wanted to use not separate LEDs in the last circuit, but an LED strip, then the current-limiting resistors R1, R2, R3 should be removed in the circuit. If RGB tape or LED is used, then it must be done with a common anode. If you plan to connect long LED strips, then powerful transistors installed on radiators should be used to control the strip.
Since the LED strips are designed for a 12 Volt power supply, respectively, we should raise the power supply in the circuit to 12 Volts, and the power supply must be stabilized.
Thyristors in color music
So far, the article has only talked about color-music devices based on LEDs. If there is a need to assemble a CMU on incandescent lamps, then thyristors will need to be used to control the brightness of the lamps. What is a thyristor in general? It is a three-electrode semiconductor device, which accordingly has Anode, Cathode and Control electrode.
KU202 Thyristor
The figure above shows the Soviet thyristor KU202. Thyristors, if you plan to use it with a powerful load, must also be mounted on a heat sink (radiator). As we can see in the figure, the thyristor has a thread with a nut and is attached similarly to powerful diodes. Modern imported ones are simply equipped with a flange with a hole.
One of these thyristor circuits is shown above. This is a three-channel color music circuit with a step-up transformer at the input. In the case of the selection of thyristor analogs, one should look at the maximum permissible thyristor voltage, in our case for KU202N it is 400 volts.
The figure shows a similar color music scheme given above, the main difference in the lower scheme is that there is no diode bridge. Also, color music on LEDs can be built into the system unit. I have assembled such a three-channel color music with a preamplifier in the case from a sidirom. In this case, the signal was taken from the sound card of the computer using a signal divider, into the outputs of which active acoustics and color music were connected. There is an adjustment of the signal level, both general and separately for the channels. The preamplifier and color music were powered from the 12 Volt Molex connector (yellow and black wires). The preamplifier and three-channel color music schemes for which they were assembled are given above. There are other LED color music schemes, for example, this one, also three-channel:
Color music on 3 LEDs - diagram
In this circuit, in contrast to the one that I collected, inductance is used in the medium-frequency channel. For those who want to first collect something simpler, I give the following diagram for 2 channels:
If you collect color music on lamps, you will have to use light filters, which can be, in turn, both homemade and purchased. The picture below shows the available light filters:
Some fans of color music effects collect devices based on microcontrollers. Below is a diagram of a four-channel color music on the MC AVR tiny 15:
The microcontroller Tiny 15 in this circuit can be replaced with tiny 13V, tiny 25V. And at the end of the review on my own behalf, I want to say that the color music on lamps loses in terms of entertainment to the color music on LED, since the lamps are more inertial than LEDs. And for self-repetition, you can recommend this
Homemade color music
Self-made color music in the salon of your own car will be of interest to all lovers of beautiful disco music. Making it with your own hands is completely easy.
Color music at home can be quickly and easily assembled if you know some of the nuances of the scheme and its correct installation.
Color music schemes in cars
A large number of homemade color music schemes are published on the forums of radio amateurs. Some of them are intended only for experienced, others - for beginners.
In principle, all circuits are built according to the same principle, which is recommended to be understood so that the assembly is no longer something impracticable and very complicated.
Simple circuit
Even a schoolboy is able to assemble color music according to this scheme, because it consists of only one transistor. Its name is KT815G.
This color music can be assembled on diodes borrowed from a simple pocket flashlight.
Everything is done as follows:
- We split the LEDs that we removed from the flashlight in half;
- We find a suitable box in which we will assemble our circuit. In this case, instead of a box, a rectangular plastic box from used shoe cream is ideal;
- We take out the switch. He will change the light-music mode to simple lighting.
Note. The LEDs will flash under the bass and the louder the volume, the brighter they glow. As for the channels, two are enough that are not connected to the speaker.
- The power source in our case will be three finger batteries;
- All that remains is to put the homemade color music in the trunk and enjoy the effect.
Complex schemes
They will allow you to create more professional schemes from the user's point of view.
The first variant of the scheme
It is assembled on five diodes. All of them are 5 mm and 3 V, have clear lenses. KT815 or KT972 is taken as a transistor. Its task is to strengthen and fulfill the role of the key.
Everything is done like this:
- Powered by 2 one and a half volt batteries;
- There are two inputs for music, respectively: X1 and X2;
- Replace LED3 with a red diode, the rest of the remaining pairs will be blue and green;
Note. As a result, we get a very successful color-music scheme. The LEDs glow very effectively to the beat of the music, the circuit consumes little current, and the low frequencies are reproduced just super. You just need to be on the lookout: from loud music, the LEDs may not stand up and burn out.
The second variant of the scheme
We find the KT817 transistor, wires, a headphone plug and an LED tape.
Started:
- We solder the transistor according to the following scheme;
- Then the LED tape is added and everything is moved to the luggage compartment of the car.
Light music from garlands
Quite a good solution, which will require the use of bulbs from New Year's garlands:
- Garlands (see) must be assembled together several pieces and fixed with electrical tape;
- Make an adapter to connect to the head unit and connect the wire.
Note. The circuit in this case will imply eight twisted pair conductors that transmit the signal from the PG contacts to the color music control unit.
LED color music
An original scheme for making beautiful color music. In this case, you need a body made of plexiglass.
Let's get started:
- We select two plates measuring 5x15 cm and two square plates 5x5 cm;
- A pair of holes is made in one of the parts (for power and headphones);
- We matte and skin all the plates;
- We find LEDs, which we also matte for a better effect;
- We assemble the body with a thermal gun, which is ideal for working with plexiglass;
- We are now assembling an electrical circuit for color music according to this scheme:
- We connect the wire from the headphones with the corresponding connector to the car radio and enjoy the effect.
The plexiglass body can be installed in the car, anywhere. Everything will depend on individual preferences, wire length, etc.
In the process of work, the following must be taken into account:
- The adapter's output voltage and the rated voltage of each diode must be related. In other words, the total number of diodes used in the circuit must equal the ratio of the adapter's output voltage.
Note. As an example, if the adapter is 12V, and the voltage for each diode is 3V, then the total number of LEDs should be 4.
- It is advisable to use a 3-core wire, one of the cores of which must be left unused.
Circuit with signal from speaker
Another popular scheme for creating color music.
We do the following:
- We take the signal from the speakers (see).
Note. In this case, it is very important not to short-circuit the SPD output *. For this purpose, we solder only one wire.
SPD * - Sound card amplifier
- Arranges the switch so that it turns on the LEDs by music;
- We select the resistance according to the diagram below, where the rating for switching on one diode is indicated;
Note. If the color music will be assembled from 4 LEDs, then the R value should be equal to 820 ohms.
Popular multi-colored scheme
Another common scheme involves the possibility of increasing the power supply. This will be especially true if a chain of many LEDs is used.
The scheme is as follows:
- There should be two frequency filters. They pass HF and LF at the input;
- The signal is then fed to the amplifier stages, and then to the LEDs;
- It is recommended to connect inputs 1 and 2 to the source speaker.
Advice. If there is a desire to make the color music brighter, then you just need to reduce the resistor values to a couple of hundred, and change the transistors to KT817.
This scheme has one advantage that no other has: the ability to use LEDs of any color.
So, when playing LF bass, the red LED will blink, while playing MF and HF - green. As for the brightness setting, it is regulated by the sound volume rotator: the higher the sound, the brighter the glow.
Car ceiling in LEDs
If there is a desire, then you can not only arrange something like a disco in the car, but also build a backlight that would either turn on separately or be associated with music playback. This operation also involves the use of LEDs.
"Starry sky" on the ceiling of the car will look wonderful. This type of lighting, it turns out, has been practiced for a long time, and even not only in cars, but also in their own apartments.
You can use this scheme in different ways:
- Place the LEDs evenly, in any shape or like a certain shape;
- Use light bulbs of different power that simulate the glow of stars (bright / not bright);
- Use a different ceiling background. For example, you can drag it to black.
Instructions for creating:
- We drag the ceiling of the car;
- We collect or acquire a current stabilizer.
Note. It is very important at this stage to do everything right. Otherwise, you will have to dismantle the assembled ceiling if the diodes burn out. To avoid this situation, it is necessary to check the circuit after assembly (find out how many volts and what current the circuit has). An old power supply unit from a computer is suitable as a test block.
- We use a large capacitor to make the LED dimming smoothly. Suitable, for example, KT470;
- We place the circuit in a matchbox;
- We check the work by connecting three LEDs in series and one resistor;
- On the ceiling, we insert LEDs into the holes, which are fixed on the back with glue;
- We also attach the switch and the stabilizer.
Note. LEDs can be grouped by 3 and connected to a resistor, and then the groups can be conducted to the stabilizer in parallel.
That's all there is to it. We hope that the reader will be able to choose something for himself from the given schemes. Just do not forget to take care not to turn on the beautiful color music while the car is moving. This greatly distracts from the road and can provoke an accident.
In the process of doing it yourself, a video review on the topic, photo materials, diagrams, etc. will be useful. Instructions similar to the above can be found in other articles on our site. The price of self-creation and installation of color music is considered the lowest in the world of auto-tuning, because consumables can also be made by hand.
It is difficult to find such a person who would not like to listen to music. To satisfy this desire, high-quality music centers, speakers and other devices are purchased. For even more pleasure, many are thinking about creating special color effects that can decorate any sound and create a romantic atmosphere on a date or a fun mood in the process of organizing a holiday party. Color music, as well as music centers, can be purchased, or you can do it yourself. The best option is to make color music on LEDs according to one of the proposed schemes.
Benefits of LED products
The modern electronics market presents a wide variety of LED strips that have a wide variety of color effects. With their help, you can create high-quality point lighting, it is possible to make color music with blinking or blurry effects.
Unlike conventional light bulbs, LEDs are characterized by a large number of positive characteristics. Among the main advantages of LED strips are:
- wide and varied colors;
- transfer of saturated colors;
- different design options - rulers, modules, discrete elements, RGB tapes;
- high response speed;
- the minimum amount of energy consumed.
The ribbons can be used at home, in clubs and cafes, and showcases can be effectively illuminated. This article will describe in more detail the version of LED color music for ordinary home use.
Simple circuit with one luminaire
To begin with, it is worth studying a simple color music scheme. It is a device that runs on a single LED, transistor and resistor. Power for such color music can be supplied from a constant current source with a voltage of 6-12 volts. The device operates on the principle of a common emitter amplifier stage. The impact in the form of a signal and amplitude varying in frequency comes to the main base. As soon as the oscillation frequency exceeds a certain threshold value, the transistor opens and the LED immediately flashes.
This circuit has one drawback - the rate of blinking of the LED depends entirely on the level of the sound signal produced. In other words, the light effect will be activated only at a certain level of the volume produced by the musical center. With a decrease in the intensity of the sound, the glow will be constant with occasional winks.
Single color ribbon scheme
This transistor-based color music is assembled using an LED strip in the load. To organize such color music, you will need to increase the power supply to 12 V, find and install a transistor with a maximum collector current that exceeds the load current, and you will also need to recalculate the total value of the resistor. Such color music is quite simple, made on one single-color LED strip and is ideal for novice radio amateurs. You can assemble it without any problems at home.
Simple three-channel circuit
To get color music, devoid of all the disadvantages listed above, it is worth using a special three-channel sound transducer. Such a circuit is powered by a constant voltage of 9 V and is able to effectively illuminate one or two LEDs in each channel. Among the main structural elements that characterize such a color-musical scheme, one can note:
- three independent amplifying stages, which are assembled on transistors of the KT315 (KT3102) category;
- LEDs of different colors are included in the load of transistors;
- for the pre-amplification element, a small mains transformer of a step-down character can be used.
The input signal is fed to the secondary winding of the transformer, which, in turn, performs two main functions - it decouples two devices at a galvanic level, and also amplifies the sound from the main line output. After that, the signal goes to three parallel-located and connected filters, assembled on the basis of RC-circuits. They operate on an individual frequency band, which directly depends on the value of the capacitor and resistor.
Color music with RGB tape
This set-top box circuit operates from 12 volts and is ideal for installation on a car. Such color music optimally combines the main functions of the previously considered schemes and is able to work both in the lamp mode and in color music. The second mode is achieved due to the special contactless control of RGB tape by means of a microphone. As for the luminaire mode, it is based on the simultaneous activation of the green, red and blue LEDs at full power. The choice of the mode can be carried out by means of a special switch, which is located on a special board.
To understand how this set-top box works, it is worth studying its sequence of actions. The main signal source here is a microphone, which converts sound vibrations emanating from a phonogram. The received signal is insignificant, therefore it requires amplification. This can be achieved by using a transistor or a special operational amplifier. After that, the automatic AGC level controller is started. It effectively keeps the vibrations of the sound within reasonable limits and prepares it for further processing. Built-in filters divide the signal into three parts, each of which operates in one specific frequency range. In the end, you just need to amplify the previously prepared current signal. For this purpose, special transistors are used that operate in a key mode.
Purchase of a ready-made CMU
If you do not want to make a color music for use at home, you can purchase a CMU, that is, a color music installation. This is a ready-made functional solution, which includes a controller. It will process the sound, transforming it into a light and music visual presentation. In the process of light reproduction, its intensity and color scheme will change, thereby creating the effect of a real disco. Also, the CMU device includes a panel with built-in diodes.
These devices can be based on spectral frequency decomposition, where each of them will correspond to a certain color scheme or predefined adjustments with a variety of effects and their alternation. You can configure them using the supplied remote control.
Important! Modern CMUs are very easy to install and configure. It is the perfect solution for organizing a home party or disco.
Conclusion
There are a lot of schemes for self-implementation of color music installations. You can pick up a fairly simple option, where the color of the RGB tape will simply change, to quite complex ones, which in the process of work will create a large number of various effects, overflows and fading. In direct dependence on the skills, you can choose and execute the appropriate option. It is enough to work a little and create something truly unique, it will be lighting equipment, delighting with overflows of various color shades. Also, do not forget that there is always an opportunity to buy a ready-made color music solution and fill your home with color shades and joy.
Almost all color music devices of sufficient power are designed for the use of conventional incandescent lamps. There are CMU circuits on the Internet and on LEDs, but they are usually under low-power LEDs. How to connect 50-100 watt LEDs to such a device? You can take as a basis one very good color music scheme (besides, with control from sound through a microphone) and slightly modifying the output part - to get the desired result.
CMU circuit for high-power LEDs
Schematic diagram of the CMU for 220V 
Schematic diagram of the CMU for 12V 
The power supply of the input part of the frequency processing is done on a piece of the universal board. The transformer is filmed from some kind of radio. It is ideal because it is symmetrical and has 10 V windings. BT151 / 600 thyristors were used as powerful switches, with a margin so that they would not burn out from high currents.
The circuit can be made completely isolated from the network, if you use the executive part on triacs and optocouplers.
When testing, temporarily install resistors of rated resistance and power from 10 W instead of LEDs.
CMU with LED strips 12 V
If you want to use 12 V DC LED strips in the CMU, then you can power the entire circuit with the same 12 volts from a pulsed network driver, and assemble the output part on power field-effect transistors.
A variant of the scheme is shown above. Here the resistor R2 sets the current limitation of the LED strip (or a powerful single LED).
By the way, when installing individual high-power LEDs, for example, at 100 watts (32 V at 3 A) - supply the supply voltage from the driver through the LED to the drain of the field-effect transistor (making sure from the datasheet that it can withstand such U / I parameters), and the specified set the required current level above the resistor.
The body is made of wood (easier to find material and easier to handle). The holes for the lamps are drilled with large cutters. Naturally, in front there are all the necessary knobs for adjusting the signal levels and HF-MF-LF channels and a power button.
