To begin with, we cut off the desired piece of textolite, skin it with zero, degrease it with acetone.
He carefully wrapped it, and began to ruthlessly fry the paint so that it would transfer from paper to textolite.
After ironing, give the board time to cool. Next, the case is transferred to the bathroom. We put the board in water in order to let the paper soften. At this time, you can drink tea or coffee - who prefers what.
It's a beautiful photo, isn't it? Let's go further, after we have refreshed ourselves, we can move on to the most, in my opinion, painstaking task - rubbing paper from the textolite. Carefully tear off the paper so as not to tear it off along with our tracks.
All that remains, without fanaticism, rubbed with fingertips.
Then we move on to the important thing - etching. I usually pickle in ferric chloride, as it is faster than pickling in blue vitriol (at first I poisoned them, but was disappointed, because the wait was up to 2 days). Gently place the board in the solution so as not to splatter.
Now you can go for a walk, or do something else. An hour has passed, you can get our payment. Usually it is etched faster, but I found textolite in the store only 2-sided, and the solution is not the first freshness. We take out the board and see our tracks.
The tracks are now under the toner, it needs to be cleaned off. Many people do this with acetone, or another solvent. I do it with the same fine skin.
That's all, the stage of preparing the board for the tone block circuit has been completed. Further it will be more interesting - we drill holes for parts.
There is nothing more to drill than with a drill, it is extremely inconvenient, especially since her cartridge is staggering. So don't scold too much for crooked holes :)
We produce soldering parts of the tone block. We start doing this with a socket (connector) for the TDA1524A chip.
Now we solder all the jumpers and small parts. We insert the microcircuit last, since during soldering it can overheat and fail, which is very sad.
Well, that's basically it! Below is a photo of my tone block.
After soldering, we check the absence of a short circuit, snot between the tracks, if nothing like this is noticed, then you can safely turn it on. Video demonstration of the device:
I always carry out the first start with a serial connection of a 12-volt car light bulb (for current limiting in the event of a short circuit). Tembroblok assembled - everything works fine. The article was written by: Eugene (ZhekaN96).
Most audio enthusiasts are quite categorical and not ready for compromises when choosing equipment, rightly believing that the perceived sound must be clear, strong and impressive. How to achieve this?
Data search for your request:
Passive tone block for amplifier
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Wait until the end of the search in all databases.
Upon completion, a link will appear to access the found materials.
Perhaps the main role in resolving this issue will be played by the choice of amplifier.
Function
The amplifier is responsible for the quality and power of sound reproduction. At the same time, when buying, you should pay attention to the following designations, which mark the introduction of high technologies in the production of audio equipment:
- Hi fi. Provides maximum purity and accuracy of sound, freeing it from extraneous noise and distortion.
- Hi end. The choice of a perfectionist who is ready to pay a lot for the pleasure of distinguishing the smallest nuances of his favorite musical compositions. Often hand-assembled equipment falls into this category.
Specifications to pay attention to:
- input and output power. The nominal value of the output power is decisive, since edge values are often unreliable.
- Frequency range. Varies from 20 to 20000 Hz.
- The coefficient of non-linear distortion. It's simple - the smaller the better. The ideal value, according to experts, is 0.1%.
- Signal-to-noise ratio. Modern technology assumes a value of this indicator in excess of 100 dB, which minimizes extraneous noise when listening.
- dumping factor. Reflects the output impedance of the amplifier in relation to the nominal load impedance. In other words, a sufficient damping factor (more than 100) reduces the occurrence of unnecessary vibrations in equipment, etc.
It should be remembered: the manufacture of high-quality amplifiers is a laborious and high-tech process, therefore, a too low price with decent characteristics should alert you.
Classification
To understand the whole variety of market offers, it is necessary to distinguish the product according to various criteria. Amplifiers can be classified:
- By power. Preliminary - a kind of intermediate link between the sound source and the final power amplifier. The power amplifier, in turn, is responsible for the strength and volume of the signal at the output. Together they form a complete amplifier.
Important: the primary conversion and signal processing takes place precisely in the preamplifiers.
- According to the element base, tube, transistor and integrated PAs are distinguished. The latter arose in order to combine the advantages and minimize the disadvantages of the first two, for example, the sound quality of tube amplifiers and the compactness of transistor ones.
- According to the mode of operation, amplifiers are divided into classes. The main classes are A, B, AB. If class A amplifiers use a lot of power, but produce high quality sound, class B is exactly the opposite, class AB seems to be the best choice, representing a compromise between signal quality and sufficiently high efficiency. There are also classes C, D, H and G, which have arisen with the use of digital technologies. There are also single-cycle and push-pull modes of operation of the output stage.
- By the number of channels, amplifiers can be one-, two- and multi-channel. The latter are actively used in home theaters to form the volume and realism of the sound. Most often there are two-channel, respectively, for the right and left audio systems.
Attention: the study of the technical components of the purchase, of course, is necessary, but often the decisive factor is the elementary listening to the equipment according to the principle of sounds or does not sound.
Application
The choice of amplifier is more justified by the purposes for which it is purchased. We list the main areas of use of audio frequency amplifiers:
- As part of a home audio system. Obviously, the best choice is a tube two-channel single-cycle in class A, also the best choice can be a three-channel class AB, where one channel is defined for a subwoofer, with Hi-fi function.
- For car audio system. The most popular four-channel amplifiers are AB or D class, in accordance with the financial capabilities of the buyer. In cars, the crossover function is also in demand for smooth frequency control, which allows you to cut frequencies in the high or low range as needed.
- in concert equipment. Higher demands are reasonably placed on the quality and capabilities of professional equipment due to the large space for the propagation of sound signals, as well as the high need for intensity and duration of use. Thus, it is recommended to purchase an amplifier with a class not lower than D, capable of operating almost at the limit of its power (70-80% of the declared one), preferably in a case made of high-tech materials that protects against negative weather conditions and mechanical influences.
- in studio equipment. All of the above is true for studio equipment. You can add about the largest frequency reproduction range - from 10 Hz to 100 kHz in comparison with that from 20 Hz to 20 kHz in a domestic amplifier. Also noteworthy is the possibility of separate volume control on different channels.
Thus, in order to enjoy clear and high-quality sound for a long time, it is advisable to study all the variety of offers in advance and choose the option of audio equipment that best suits your needs.
set NK022
Any high-quality amplifier should not only be able to adjust the input signal gain, but also provide frequency response correction for each channel in at least two frequency domains: high and low. This task is successfully handled by electronic devices called timbral blocks.
Circuitry options for building tone blocks are based on the use of RC chains. When they are included in the audio signal path, the effect of filtering a single frequency region in the frequency band of 20 ... 20000 Hz is obtained. This is because the capacitance of RC circuits is frequency dependent. High and low pass filters are built on RC chains, as well as bandpass filters widely used in graphic equalizers.
Some filters allow you to change the frequency response of the amplifier quite effectively. They are capable of introducing not only attenuation, but also amplifying the signal in the process of adjustment. Such filters are called active, since RC circuits are included in the feedback circuits of active radio elements, for example, transistors or operational amplifiers. Their disadvantages include distortion of the input signal caused by the non-linearity of the characteristics of active radio elements.
Another class of filters are passive filters. They consist only of capacitors and resistors. But passive filters have a rather low gain. For example, at medium frequencies (800 ... 1200 Hz) they lower the signal level by 10 ... 12 times! Therefore, when using them, it is necessary to use additional stages of signal amplification. In addition, the limits of regulation of low and high frequencies by a timbre block built on passive filters are the wider, the lower the output impedance of the signal source and the higher the input impedance of the subsequent stage. However, compared to active filters, the non-linear distortion of passive filters is minimal.
The NK022 tone block is built using passive low-frequency (LF) and high-frequency (HF) filters. It is designed for use in high quality low frequency stereo power amplifiers. The tone block allows you to adjust the amplitude-frequency characteristic of the amplifier simultaneously on two channels in accordance with the individual desires of the listener, the characteristics of the acoustic systems and the characteristics of the room, as well as separately adjust the timbres of the high and low frequencies and the volume of each of the two channels. The supply voltage of the device is 9 ... 18 V.
Description of the electrical circuit of the tone block
The appearance of the tone block board with the elements installed on it and the electric circuit of the tone block are shown on Rice. 1 And Rice. 2.
Rice. 1. External view tone block
The device has two separate channels for adjusting the frequency response. Consider the operation of the block on the example of the upper channel. The input signal is fed to an amplifier made on the transistor VT1. Amplification is necessary because passive filters, as mentioned above, significantly attenuate the input signal. The amplified signal is fed to filters for bass (P1) and treble (P2) adjustment.
It is known that the capacitance for low frequency alternating current is a rather high reactance, and for high frequency currents it is low. Therefore, the capacitive chain C5-C6 "shorts" the HF component of the input signal to a common wire, and only the LF component is present at the common connection point of resistors R7 and P1. At the connection point of resistors P1 and R8 LF-co-
Rice. 2. Wiring diagram of the stereo tone block
setting is significantly weakened by this resistive divider. This means that moving the slider of the variable resistor P1 from the upper position according to the scheme to the lower one will lead to a smooth decrease in the spectrum of the low-frequency component at the output of the tone block.
A similar situation takes place on a tunable high-pass filter. At the connection point of C9 and P2 there will be a maximum of the HF component, and at the connection point of P2 and SU - a minimum. By moving the slider of the resistor P2 from top to bottom, we obtain a smooth decrease in the level of the RF component in the output signal spectrum.
The variable resistor P4 forms an adjustable voltage divider relative to the common wire of the circuit, that is, it changes the output voltage of the tone block. It is intended for a frequency-independent change in the volume of the sound of one of the channels of the power amplifier.
Similarly to the first channel, the second channel of the tone block works.
Assembling the tone block
Before assembling the stereo tone unit, carefully read the recommendations for mounting electronic circuits given at the beginning of this book. This will help to avoid damage to the printed circuit board and individual circuit elements. The list of elements of the set is given in Tab. 1.
The locations of the elements on the tone block board and the board with the installed elements are shown on Rice. 3. On Rice. Behind the connection lines of the assembled device are also shown.
Rice. 3. Arrangement of elements on the printed circuit board of the tone block: a - location of the elements on the board; b - board with installed elements
Form the leads of the elements, install the elements on the board and solder their leads; at the same time, first install small-sized, then all other elements. After assembly, check the correct installation, especially carefully check the correct installation of electrolytic capacitors. A properly assembled tone block does not need to be adjusted.
Table 1. List of elements of the set NK022
| Position | Characteristic | Name and/or note | Qty |
| R1, R2, R5, R6. R7, RIO, Rll, R12 | 10 kOhm | Brown, black, orange* | 8 |
| R3.R4 | 100 kOhm | Brown, black, yellow* | 2 |
| R8.R9 | 1 kOhm | Brown, black, red* | 2 |
| Р1…Р4 | 50 kOhm | Variable resistor, dual | 4 |
| С1…С4 | 2.2uF, 50V | 4 | |
| C5, C8 | 0.022uF | Capacitor, 223 - marking | 2 |
| C6, C7 | 0.33uF | Capacitor, 334 - marking | 2 |
| C9, C12 | 1000 pF | Capacitor, 1p0 - marking | 2 |
| SU, SI | 0.01uF | Capacitor, 10p - marking | 2 |
| C13 | 47uF, 25V | electrolytic capacitor | 1 |
| VT1, VT2 | VS238S | Transistor (replacing SC238e or EXDC38) | 2 |
| B110 | 115×38 mm | printed circuit board | 1 |
| * Color coding on resistors. | |||
If you, dear reader, intend to assemble a power amplifier for a home audio center, you will find everything you need for this in the MASTER KIT catalog, which is given in the appendix to this book. This is a stabilized power supply, and a power amplifier, and even a suitable case. Assembling a high-quality low-frequency amplifier is a very real task!
A set for a stereo tone block, as well as other sets that may be needed when assembling the amplifier, can be purchased at radio parts stores or radio markets.
The tone block is used to equalize the Amplitude-Frequency Characteristic (AFC) of low-frequency amplifiers. Since many ULFs have a non-linear characteristic in different frequency ranges: in the low and high frequency range, the gain is much worse than in the mid-frequency range. Therefore, for high-quality sound reproduction, it makes sense to use special modules - "tone blocks", with which you can adjust the audio signal over the entire spectrum of the range.
At their core, these are mid-range filters that control the cutoff depth in a given frequency range without touching the low and high frequencies, and therefore the frequency response of the amplifier is leveled, but the amplitude of the input signal is slightly reduced, and additional amplification may be required. Thus, tone control modules can be divided into two classes: passive (only frequency response adjustment) and active (frequency response adjustment + amplifier stage for compensation)
This design of the tone block attenuates the signal in the midrange by about 10 times, and therefore it is placed between two amplifiers - preliminary and final.
The selection of radio components depends on the resistance of the signal source Rc and the load Rн (input impedance of the next amplifying stage). Let's calculate the ratings of radio elements: Variable resistors always take the same with the condition:
Rc The remaining components are calculated using simplified formulas: R1= R4= 0.1R; R3=0.01R; C3=0.1/R; C1= 22C3; C2=220C3; C4= 15C3 The transistor in the device is used to compensate for signal loss. There are no special requirements for it, you can even take the obsolete KT315. I want to say right away that this tone control can easily compete with those used in modern audio equipment, its circuit was copied from some amateur radio magazine, but now I don’t remember which one. One thing I can say for sure with this design of the tone block is happy as an elephant The appearance of the amateur radio design and the placement of components on the printed circuit board, see the figure at the top of the page Here are the passive tone diagrams of world-famous guitar electronics brands such as Fender, Marshall, and VOX. From the simplest with one control to the more complex three-way. Such a simple design allows only a blockage of high frequencies. It is used in the simplest lamp combos. With the help of the Fender Princeton tone block circuit, you can produce both a boost and a blockage of high frequencies. With this tone block, you can adjust the rise in the low and high frequencies. This tone controls both high and low frequencies. Below are some well-known schemes of timbre blocks - two-poles: Fender "BrownFace" Bandmaster 6G7, Ampeg SVT, Marshall JMC800 Mod.2001 Of this trinity of timbres, each is individual and good in its own way. On which one to stop and make the final choice, there is no definite answer. At this point, experiment yourself, the circuits are not complicated and are easily repeated by surface mounting or on a breadboard. For the purity of the article, I will also give diagrams of three-band timbral blocks. IMHO the most popular among all radio amateurs. These branded guitar designs allow you to adjust low, mid and high frequencies. Marshall gives a heavier sound than the Fender tone block. Below are the ratings of radio components in various variations of these schemes. In this article, readers are offered a number of different tone controls in terms of circuitry and functionality, which can be used by radio amateurs in the development and modernization of sound reproducing equipment. The main disadvantage of the recently popular active tone controls is the use of deep frequency-dependent feedback and large additional distortions that they introduce into the regulated signal. That is why it is desirable to use passive regulators in high-quality equipment. True, they are not without flaws. The largest of them is a significant signal attenuation corresponding to the control range. But since the depth of tone control in modern sound reproducing equipment is small (no more than 8 ... 10 dB), in most cases it is not required to introduce additional amplification stages into the signal path. Another, not so significant drawback of such regulators is the need to use variable resistors with an exponential dependence of resistance on the angle of rotation of the engine (group "B"), which provide smooth control. However, the simplicity of design and high quality indicators still incline designers to use passive tone controls. It should be noted that these regulators require a low output impedance of the stage that precedes them and a high input impedance of the subsequent one. Developed by the English engineer Baksandal back in 1952, the tone control became perhaps the most common frequency corrector in electroacoustics. Its classical version consists of two first-order filter units forming a bridge - a low-frequency R1C1R3C2R2 and a high-frequency C3R5C4R6R7 (Fig. 1a). Approximate logarithmic amplitude-frequency characteristics (LAFC) of such a controller are shown in fig. 1, b. The calculated dependences for determining the time constants of the LAF inflection points are also given there. Theoretically, the maximum achievable frequency response slope for first-order links is 6 dB per octave, but with practically implemented characteristics, due to a slight difference in the inflection frequencies (no more than a decade) and the influence of previous and subsequent cascades, it does not exceed 4 ... 5 dB per octave. When adjusting the tone, the Baksandal filter only changes the slope of the frequency response without changing the inflection frequencies. The attenuation introduced by the regulator at medium frequencies is determined by the ratio n=R1/R3. The frequency response control range in this case depends not only on the attenuation value n, but also on the choice of inflection frequencies of the frequency response, therefore, to increase it, the inflection frequency is set in the mid-frequency region, which, in turn, is fraught with the mutual influence of adjustments. In the traditional version of the considered controller R1/R3=C2/C1= =C4/C3=R5/R6=n, R2=R7=n-R1. In this case, an approximate coincidence of the frequencies of the inflection of the frequency response in the region of its rise and fall is achieved (in the general case, they are different), which ensures a relatively symmetrical regulation of the frequency response (the fall, even in this case, inevitably turns out to be steeper and more extended). With the commonly used n=10 (for this case, the minimum values of the element ratings are shown in Fig. 1, a-3, a) and the choice of crossover frequencies near 1 kHz, the tone control at frequencies of 100 Hz and 10 kHz relative to the frequency of 1 kHz is ±14. ..18dB. As noted above, in order to achieve smooth control, the variable resistors R2, R7 must have an exponential control characteristic (group "B") and, in addition, to obtain a linear frequency response in the middle position of the regulator sliders, the ratio of the resistances of the upper and lower (according to the circuit) sections of the variable resistors should also be equal to n. With the "Hyend" n=2...3, which corresponds to the regulation range of ±4...8 dB, it is quite acceptable to use variable resistors with a linear dependence of resistance on the angle of rotation of the engine (group "A"), but at the same time, the adjustment is somewhat coarsened in the region of the decline in the frequency response and stretched in the region of the rise, and a flat frequency response is obtained by no means in the middle position of the regulator engines. On the other hand, the resistance of the dual variable resistor sections with linear dependence is better matched, which reduces the frequency response mismatch of the channels of the stereo amplifier, so that uneven regulation in this case can be considered acceptable. The presence of the resistor R4 is not important, its purpose is to reduce the mutual influence of the links and bring together the inflection frequencies of the frequency response in the region of higher audio frequencies. As a rule, R4 \u003d (0.3 ... 1.2) "R1. As shown below, in some cases it can be completely abandoned. To reduce the influence of the previous and subsequent stages on the controller, their output Rout and input Rin resistance should be respectively Rout<>R2. The above "basic" version of the regulator is usually used in high-end radio equipment. In household appliances, a somewhat simplified version is used (Fig. 2a). The approximated logarithmic amplitude-frequency characteristics (LAFC) of such a controller are shown in fig. 2.6. The simplification of its high-frequency link led to some vagueness of the regulation in the region of higher frequencies and to a more noticeable influence of the previous and subsequent cascades on the frequency response in this region. A similar corrector for n = 2 (with variable resistors of group "A") was especially popular in simple amateur amplifiers of the late 60s and early 70s (mainly due to low attenuation), but soon the value of n increased to the usual today meaning. Everything said above regarding the range of regulation, matching and choice of regulators is also true for a simplified version of the corrector. If we abandon the requirement of symmetrical regulation of the frequency response in the areas of their rise and fall (by the way, the need for a decline practically does not arise), then the circuit can be further simplified (Fig. 3, a). Shown in fig. Z.b LACHH of the regulator correspond to the extreme positions of the engines of the resistors R2, R4. The advantage of such a regulator is simplicity, but since all its characteristics are interconnected, it is advisable to choose n = 3 ... 10 for the convenience of regulation. As n increases, the steepness of the rise increases, and the slope of the decline decreases. Everything said above about the traditional versions of the Baksandal corrector fully applies to this extremely simplified version. However, the Baksandal tone control circuit and its variants are by no means the only possible implementation of a passive two-band tone control. The second group of regulators is made not on the basis of bridges, but on the basis of a frequency-dependent voltage divider. As an example of an elegant circuitry solution for a regulator, we can cite a tone block, which was once used in various variations in tube electric guitar amplifiers. The "highlight" of this control is the change in the frequencies of the inflection of the frequency response in the process of tone control, which leads to interesting effects in the sound of a "classical" electric guitar. Its basic scheme is shown in Fig. 4a, and the approximated LFCs are shown in Fig. 4.6. The calculated dependences for determining the time constants of the inflection points are also given there. It is easy to see that adjustment in the region of lower audio frequencies changes the inflection frequencies without changing the slope of the frequency response. When the slider of the variable resistor R4 is in the lower (according to the scheme) position, the frequency response at lower frequencies is linear. When the engine is moved upwards, a rise appears on it, and the inflection point in the process of regulation shifts to the region of lower frequencies. With further movement of the slider, the upper (according to the scheme) section of the resistor R4 begins to shunt the resistor R2, which causes a shift in the high-frequency inflection point to higher frequencies. Thus, when adjusting, the rise of low frequencies is complemented by the fall of the middle ones. The higher audio frequency regulator is a simple first-order filter and has no special features. On the basis of this scheme, you can build several options for timbre blocks that allow you to adjust the frequency response in the low and high frequencies. Moreover, in the region of lower frequencies, both an increase and a decrease in the frequency response are possible, and at higher frequencies, only an increase. A variant of the timbre block with frequency response control of the frequency response in the low-frequency region is shown in fig. 5,a, its LACHH - in fig. 5.6. Resistor R2 controls the inflection frequency of the frequency response, and R5 - its slope. The combined action of regulators allows you to get significant limits and greater control flexibility. A diagram of a simplified version of the timbre block is shown in fig. 6a, its LACHH - in fig. 6.6. It is, in essence, a hybrid of the low-frequency link of the timbre block shown in Fig. 3, a, and the high-frequency link of the timbre block shown in Fig. 4, a. By combining the frequency response control functions in the low-frequency and high-frequency regions, you can get a simple combined tone control with one control, very convenient for use in radio and car equipment. Its schematic diagram is shown in fig. 7,a and LACHH - in fig. 7.6. In the lower (according to the scheme) position of the engine of the variable resistor R1, the frequency response is close to linear over the entire frequency range. When moving it upwards, a rise appears at lower frequencies, and the low-frequency inflection point in the process of regulation shifts to lower frequencies. With further movement of the engine, the upper (according to the scheme) section of the resistor R1 turns on the capacitor C1, which leads to a rise in higher frequencies. When replacing the variable resistor R1 with a switch (Fig. 8, a and 8.6), the considered regulator turns into the simplest tone register (position 1 - classic; 2 - jazz; 3 - rock), popular in the 50s and 60s and re-used in the equalizers of radio tape recorders and music centers in the 90s. Despite the fact that it would seem that everything has been said about tone control for a long time, the variety of passive corrective circuits is not limited to the proposed options. Many forgotten circuit solutions are now experiencing a rebirth at a new qualitative level. Very promising, for example, is a volume control with separate loudness control for low and high frequencies [З]. LITERATURE 4.7 kOhm 470 ohm 3.3 kOhm 4.7 kOhm 470 ohm 3.3 kOhm 4.7 kOhm 470 ohm 100 kOhm 10 kOhm 100 kOhm 10 kOhm
Pic.2
Pic.3
Pic.4
Pic.5
Pic.6
Pic.7
Pic.8
1. Shkritek P. Reference guide to audio circuitry (translated from German). - M.: Mir, 1991, p. 151-153.
2. Krylov G. Broadband ULF. - Radio, 1973, N 9, c.56,57.
3. Shikhatov A. Combined frequency response control unit. - Radio, 1993, N 7, p. 16.List of radio elements
Designation
Type
Denomination
Quantity
Note Shop My notepad
Option 1
C1
Capacitor 0.022uF 1
To notepad
C2
Capacitor 0.22uF 1
To notepad
C3
Capacitor 0.015uF 1
To notepad
C4
Capacitor 0.15uF 1
To notepad
R1, R5
Resistor 2
To notepad
R2, R7
Variable resistor 47 kOhm 2
To notepad
R3, R6
Resistor 2
To notepad
R4
Resistor 1
To notepad
Option 2
C1, C4
Capacitor 0.022uF 2
To notepad
C2
Capacitor 0.22uF 1
To notepad
C3
Capacitor 2200 pF 1
To notepad
R1
Resistor 1
To notepad
R2, R5
Variable resistor 47 kOhm 2
To notepad
R3
Resistor 1
To notepad
R4
Resistor 1
To notepad
Option 3
C1
Capacitor 0.22uF 1
To notepad
C2
Capacitor 2200 pF 1
To notepad
R1
Resistor 1
To notepad
R2, R4
Variable resistor 47 kOhm 2
To notepad
R3
Resistor 1
To notepad
Option 4
C1
Capacitor 0.01uF 1
To notepad
C2
Capacitor 270 pF 1
To notepad
R1
Resistor 1
To notepad
R2
Resistor 1
To notepad
R3, R4
Variable resistor 220 kOhm 2
To notepad
Option 5
C1
Capacitor 0.1uF 1
To notepad
C2
Capacitor 270 pF 1
To notepad
R1
Resistor 1
To notepad
R2, R4, R5
Variable resistor 220 kOhm 3
To notepad
R3
Resistor 1
To notepad
Option 6
C1
Capacitor 0.1uF 1
