What can a microphone be made from? Two ways to make a microphone from regular headphones. Is it possible to make a microphone with your own hands?
It's been in my head for a long time. Having gathered my strength, I began to search for amplifier circuits. Most of the schemes I looked at I didn't like. I wanted to assemble it easier, better and smaller (for a laptop, because the built-in one was apparently made just for show - the quality is poor). And after a short search, a microphone signal amplifier circuit with phantom power was found and tested. Phantom power (this is when power supply and information transmission are carried out over one wire) is a huge advantage of this circuit, because it saves us from third party sources nutrition and related problems. For example: if we power the amplifier from a simple battery, it will sooner or later run out, which will lead to the inoperability of the circuit at the moment; if we power it from a battery, then sooner or later it will have to be charged, which will also lead to some difficulties and unnecessary movements; If we power it from a power supply, then there are two disadvantages that, in my opinion, exclude the option of using it - these are wires (for powering our PA) and interference. You can get rid of interference in many ways (install a stabilizer, all sorts of filters, etc.), but getting rid of wires is not so easy (you can, however, transfer energy at a distance, but why fence off a whole complex of devices to power some a microphone amplifier?) In addition, this reduces the practicality of the device. Let's move on to the diagram:
Amplifier circuit option for a dynamic microphone
The circuit is distinguished by its super-simplicity and mega-repeatability; the circuit contains two resistors (R1, 2), two capacitors (C2, 3), a 3.5 plug (J1), one electret microphone and a transistor. Capacitor C3 works as a microphone filter. Capacity C2 should not be neglected, that is, it is not necessary to set it neither more nor less than the nominal value indicated in the diagram, otherwise this will entail a lot of interference. We install domestic transistor T1 kt3102
. To reduce the size of the device, I used an SMD transistor marked “1Ks”. If you don’t know how to solder at all, go to the forum.
When replacing T1 there were no significant changes in quality. All other parts are also in SMD cases, including capacitor C3. The entire board turned out to be quite small, although it can be made even smaller using the LUT printed circuit board manufacturing technology. But I made do with a simple half-millimeter permanent marker. I etched the board in ferric chloride in 5 minutes. The result is a microphone amplifier board that is attached to a 3.5 plug.
All this fits well inside the plug casing. If you do this too, I advise you to make the board as small as possible, since for me it deformed the casing and changed its shape. It is advisable to wash the board with solvent or acetone. The result was a useful device with good sensitivity:
Before connecting the microphone to the computer, check all the contacts and whether there is +5v power at the microphone input (and there should be), in order to avoid comments like: “I assembled it exactly as in the diagram, but it doesn’t work!” This can be done this way: connect a new plug to the microphone connector and measure the voltage with a voltmeter between ground (large tap) and two short solder taps. Just in case, try not to short-circuit the plug leads together when you measure the voltage. I don’t know what will happen then and I don’t want to check. I have microphone amplifier It has been working for 3 months, I am completely satisfied with the quality and sensitivity. Collect and post on the forum about your results, questions, and maybe even about modifications to the case, circuits and methods of their manufacture. I was with you BFG5000, Good luck!
Discuss the article ELECTRIC MICROPHONE AMPLIFIER
It’s very difficult to get by without a computer microphone these days; you can’t use it without it. voice search, you won’t be able to chat with a friend via video call. However, not all computers have built-in microphones, and moreover, they often do not have very good sensitivity. You can solve this problem quite simply - assemble the microphone yourself.
Scheme
The circuit is extremely simple, containing only two resistors, two capacitors, a transistor and an electret microphone capsule. Almost any low-power transistor can be used n-p-n structures, for example, KT3102, BC547, BC337. An electret microphone can be obtained, for example, from a broken headset, handset, or purchased at a radio parts store. The sensitivity of the microphone will greatly depend on this element, so it is advisable to take several and check which one is best suited. The advantage of this circuit is that it uses phantom power. Those. The sound signal is transmitted through the same wires as the power supply. If you take a voltmeter and measure the voltage at the microphone input of your computer, it will be about 3-4 volts. When connecting the microphone circuit, this voltage should drop to a level of 0.6-0.7 volts, thus, an external power source will not be needed and there will be no extra wires at the workplace.Circuit assembly
The circuit contains a minimum of parts, so it can be assembled by hanging installation. But, sticking to tradition, I etched a miniature printed circuit board. You can even draw paths with a marker or nail polish. A few photos of the process:Download the board:
(downloads: 206)
A microphone capsule is soldered on one end of the board, and a shielded wire on the other. Please note that the wire must have a shield, otherwise the microphone will produce terrible noise. The braid of the wire is soldered to the negative, and the two inner cores are connected and soldered to the output of the circuit. It is imperative to maintain the polarity of the microphone capsule, otherwise the circuit will not work. One of its outputs goes to minus, and the second to plus. Determining the polarity is very simple - you need to ring the terminals with the metal body of the capsule. The terminal that connects to the housing is negative.
Microphone assembly
For ease of use, a board with soldered parts must be placed in a suitable housing. Because Since the board has a narrow, elongated shape, you can use an ordinary ballpoint pen as a body. To do this, you need to remove the writing rod from it and check whether the board is the right width. If the circuit is assembled by hanging installation, then it can be given any shape and there will be no problems with capacity. In addition to a pen, any elongated object will work well, be it a marker or a simple plastic tube.Almost all home devices, from telephones to laptops, are equipped with their own microphone for communication. Particularly zealous fans of programs such as Skype or Mail Agent even buy themselves stationary microphones to improve communication with subscribers. Free-standing devices wireless headsets, mechanisms built into the body - today a microphone can take on the most bizarre shapes. However, like all devices, it can break unexpectedly, which is why it will be useful for everyone to learn how to make a microphone from headphones.
In most cases, owners simply dispose of the failed electrical appliance and go shopping for a new one. But there is no need to rush in this matter, because anyone can assemble a microphone from ordinary headphones. To turn your phone headphones into a high-quality microphone for your computer, you will need to prepare suitable materials, namely:
- headphones from any brand, the simplest included headphones from your phone will do;
- 3.5 mm plug, better known as “jack”;
- high-quality wires for connections (carefully examine their integrity, do not damage the insulating material);
- soldering iron of sufficient power;
- sufficient amount of solder, rosin.
You can choose one of two options. You can use the headphones directly, or you can turn them into a full-fledged headset. The procedure will not take you much time and will not cause difficulties.
First way
Making a microphone out of old headphones is the most economical way out of the situation. Upon completion of the work, you will be able to receive not only a new device, but also breathe life into “junk” that no one needs. First you will have to do some soldering work.
If you strictly followed the instructions and did not overdo it with solder, which could cause a short circuit at the soldering points, then when you connect the headset to the laptop, you will hear light clicks. This means that the microphone is working normally.
Second way
This is a much less effort and resource-intensive way to create a microphone at home. To do this you will need a telephone, computerBluetooth adapter and headphones included.
Connect mobile device with a computer via Bluetooth connection. Connect the headset to the phone jack and you will get a working microphone. This method will allow you to quickly restore a lost connection, but it is not recommended to use it on an ongoing basis.
This scheme is used as a temporary replacement when there is no time or money to purchase a good microphone.
Such a system is characterized by instability, because the Bluetooth connection can be interrupted at the most unexpected moment. Added to this is the need to constantly monitor the battery charge in your phone. Connecting it to an outlet will add more wires, which may make it difficult to use.
As you can see, from ordinary telephone headphones, which are included with most models, you can make an excellent headset for communication. Of course, it will never replace a real microphone. DIY devices can significantly inferior in quality transmitted sound to factory analogues. However, with quality parts on hand, you can try to build a real microphone.
It’s very difficult to get by without a computer microphone these days; without it you can’t use voice search, and you won’t be able to chat with a friend via video call. However, not all computers have built-in microphones, and moreover, they often do not have very good sensitivity. You can solve this problem quite simply - assemble the microphone yourself.
Scheme
The circuit is extremely simple, containing only two resistors, two capacitors, a transistor and an electret microphone capsule. The transistor can be used in almost any low-power n-p-n structure, for example, KT3102, BC547, BC337. An electret microphone can be obtained, for example, from a broken headset, handset, or purchased at a radio parts store. The sensitivity of the microphone will greatly depend on this element, so it is advisable to take several and check which one is best suited. The advantage of this circuit is that it uses phantom power. Those. The sound signal is transmitted through the same wires as the power supply. If you take a voltmeter and measure the voltage at the microphone input of your computer, it will be about 3-4 volts. When connecting the microphone circuit, this voltage should drop to a level of 0.6-0.7 volts, thus, an external power source will not be needed and there will be no extra wires at the workplace.
Circuit assembly
The circuit contains a minimum of parts, so it can be assembled by hanging installation. But, sticking to tradition, I etched a miniature printed circuit board. You can even draw paths with a marker or nail polish. A few photos of the process:
Download the board:
A microphone capsule is soldered on one end of the board, and a shielded wire on the other. Please note that the wire must have a shield, otherwise the microphone will produce terrible noise. The braid of the wire is soldered to the negative, and the two inner cores are connected and soldered to the output of the circuit. It is imperative to maintain the polarity of the microphone capsule, otherwise the circuit will not work. One of its outputs goes to minus, and the second to plus. Determining the polarity is very simple - you need to ring the terminals with the metal body of the capsule. The terminal that connects to the housing is negative.
Microphone assembly
For ease of use, a board with soldered parts must be placed in a suitable housing. Because Since the board has a narrow, elongated shape, you can use an ordinary ballpoint pen as a body. To do this, you need to remove the writing rod from it and check whether the board is the right width. If the circuit is assembled by hanging installation, then it can be given any shape and there will be no problems with capacity. In addition to a pen, any elongated object will work well, be it a marker or a simple plastic tube.
The board is placed inside, the microphone should stick out slightly from the case. The wire comes out from the other side. For reliability, the board along with the wire can be sealed inside the case. The tip of the handle needs to be cut down so that the hole becomes wider and the sound waves can easily reach the microphone capsule.
We solder a 3.5 jack plug to the other end of the wire to connect to the microphone input of the computer. At this point, the assembly of the computer microphone is completed, you can turn it on and check the sound quality.
DIY microphone amplifiers.
Amplifier for computer microphone with phantom power.
I installed a program like Skype on my computer. But here’s one problem: you need to keep the microphone close to your mouth so that the interlocutor can hear you well. I decided that the microphone sensitivity was not enough. And I decided to make an amplifier amplifier.
An Internet search yielded dozens of amplifier circuits. But they all required a separate power source. I wanted to make an amplifier without an additional source, with power from the sound card itself. So that there is no need to change batteries or pull additional wires.
Before you fight the enemy, you need to know him by sight. Therefore, I dug up information on the Internet about the microphone design: https://oldoctober.com/ru/microphone. The article tells how to make a computer microphone with your own hands. At the same time, I borrowed the idea itself: there is no need to break a ready-made device for my experiments if you can do it yourself. A brief retelling of the article comes down to the fact that a computer microphone is an electret capsule. An electret capsule is, from an electrical point of view, field effect transistor open source. This transistor is powered from the sound card through a resistor, which is also a signal current-to-voltage converter. Two clarifications to the article. Firstly, there is no resistor in the capsule in the drain circuit, I saw it myself when I took it apart. Secondly, the connection between the resistor and capacitor is made in the cable, not in the sound card. That is, one pin is used to power the microphone, and the second is used to receive a signal. That is, it turns out something like this:
Here left side of the picture is an electret capsule (microphone), the right one is a computer sound card.
Many sources write that the microphone is powered from a voltage of 5V. This is not true. In my sound card this voltage was 2.65V. When the microphone power output was shorted to ground, the current was about 1.5 mA. That is, the resistor has a resistance of about 1.7 kOhm. It was from such a source that the amplifier was required to be powered.
As a result of experiments with microcap, this scheme was born.
The capsule is powered through resistors R1 and R2. To prevent negative feedback At signal frequencies, capacitor C1 is used. The capsule is supplied with a supply voltage equal to the voltage drop across p-n junction. The signal from the capsule is isolated at resistor R1 and fed to the base of transistor VT1 for amplification. The transistor is connected according to the circuit with common emitter with a load on resistors R2 and a resistor in the sound card. Negative feedback DC through R1, R2 ensures a relative constant current through the transistor.
The entire structure was assembled by surface mounting directly on the microphone capsule. Compared to a microphone without an amplifier, the signal increased approximately 10 times (22 dB).
The entire structure was first wrapped with paper for insulation, and then with foil for shielding. The foil has contact with the capsule body.
Single-wire powered microphone amplifier.
A microphone with a preamplifier housed in the housing requires power wires (in addition to the shielded signal wire) to connect to the device. From a constructive point of view, this is not very convenient. The number of connecting wires can be reduced by supplying the supply voltage through the same wire through which the signal is transmitted, i.e., the center conductor of the cable. It is this method of power supply that is used in the amplifier brought to the attention of readers. His circuit diagram shown in the figure.
The amplifier is designed to operate from any type of electret microphone (for example, MKE-3). Power is supplied to the microphone through resistor R1. The sound signal from the microphone is supplied to the base of the transistor VT1 through the isolation capacitor C1. The required bias at the base of this transistor (about 0.5 V) is set by the voltage divider R2R3. Increased voltage audio frequency is allocated to the load resistor R5 and then goes to the base of transistor VT2, which is part of a composite emitter follower assembled on transistors VT2 and VT3. The emitter of the latter is connected to the upper contact of the XP1 connector (amplifier output), to which is connected the central conductor of the connecting shielded cable, the braid of which is connected to the common wire. Note that the presence of an emitter follower at the output of the preamplifier significantly reduces the level of interference to the microphone input.
Near the input connector of the device to which the microphone is connected, two more parts are mounted: load resistor R6, through which power is supplied, and separating capacitor SZ, which serves to separate the sound signal from the constant component of the supply voltage.
The circuit design used in this amplifier provides automatic installation and stabilization of its operating mode. Let's look at how this happens. After turning on the power, the voltage at the upper terminal of the XP1 connector increases to approximately 6 V. At the same time, the voltage at the base of the transistor VT1 reaches its opening threshold of 0.5 V and current begins to flow through the transistor. The voltage drop that occurs in this case across resistor R5 causes the transistor of the composite emitter follower to open. As a result, the total current of the amplifier increases, and along with it the voltage drop across resistor R6 increases, after which the mode stabilizes.
Since the current gain of the composite emitter follower (it is equal to the product of the current gain of transistors VT2 and VT3) can reach several thousand, mode stabilization is very strict. The amplifier as a whole operates like a zener diode, fixing the output voltage at 6 V regardless of the supply voltage. However, when using a power source with a different voltage, it is necessary to select the resistors of the divider R2R3 so that the voltage at the upper contact of the XP1 connector is equal to half the supply voltage. It is curious that the mode practically cannot be changed by adjusting the resistance of the load resistor R5. The voltage drop across it is always equal to the total opening voltage of the transistors of the composite emitter follower (about 1 V), and changes in its resistance only lead to a change in the current through transistor VT1. The same applies to resistor R6.
Even more interesting is the operation of the amplifier in boost mode AC. The audio frequency voltage from the lower terminal of resistor R5 is transmitted by the emitter follower with very little attenuation to the upper terminal - the output of the amplifier. In this case, the current through the resistor is constant and is almost not subject to vibrations at audio frequencies. In other words, the only amplifier stage is loaded onto the current generator, i.e. to very high resistance. The input impedance of the repeater is also very high, and as a result the gain is very large. During a quiet conversation in front of a microphone, the amplitude of the output voltage can reach several volts. The R4C2 chain does not allow the alternating component of the audio frequency signal to pass to the power circuit of the microphone and voltage divider.
A single-stage amplifier is not at all prone to self-excitation, therefore the location of the parts on the board is not particularly important; it is only advisable to place the input and output at different ends of the board.
The setup comes down to selecting resistors of the divider R2R3 until half the supply voltage is obtained at the output. It is also useful to select resistor R1, focusing on the best sound of the signal recorded from the microphone. If the input impedance of the radio device with which this amplifier is used is less than 100 kOhm, the capacitance of the capacitor SZ should be increased accordingly.
Connecting a dynamic microphone to the microphone input of a computer sound card.
The microphone input of the sound card is intended for connecting an electret microphone. The pin assignments of the microphone input connector are shown in Fig. 1. The sound signal is supplied to the sound card input through the TIP contact. Power for the electret microphone is supplied through resistor R to the RING pin. The TIP and RING pins are connected together in the microphone cable.
Rice. 1
Almost all multimedia microphones costing $2-4 are only suitable for speech recognition, telephony, etc. Although these microphones usually have high sensitivity, they have high level nonlinear distortions, insufficient overload capacity, as well as a circular radiation pattern (that is, they perceive signals equally well from any side). Therefore, to record vocals at home, it is necessary to use a highly directional dynamic microphone, which allows you to minimize extraneous noise from the fan system unit and other sources.
A dynamic microphone can be connected directly to the microphone input of the sound card. The signal wire of the microphone cable must be soldered to the TIP pin, the shield to the GND pin, and the RING pin must be left free. If the microphone has two signal contacts - HOT and COLD, then connect the HOT contact to the TIP contact, and connect the COLD contact to GND. Since the sensitivity of a dynamic microphone is low compared to an electret microphone, a sufficient recording level is obtained only when the microphone is positioned at a distance of 3-5 centimeters from the performer’s lips. This is not always acceptable, since some types of microphones will spit despite the built-in wind protection. Such microphones must be placed further from the performer, and to obtain a sufficient recording level, use a preamplifier. The circuit of a simple preamplifier powered by a microphone input connector is shown in Fig. 2.
Rice. 2
This circuit works well for me at the following ratings: R1, R3 - 100 kOhm, R2 - 470 kOhm, C1, C2 - 47 uF, VT1 - kt3102am (can be replaced with kt368, kt312, kt315).
The circuit is based on a classic transistor cascade with a common emitter. The load of the cascade is the resistor R of the sound card (Fig. 1). The gain depends on the parameters of transistor VT1, the value of feedback resistor R2 and the value of resistor R of the sound card. Capacitor C1 is required for DC decoupling. Resistor R1 is used to eliminate clicks when connecting a microphone on the fly; if desired, you can exclude it.
Upon closer examination, it turned out that on the TIP pin of the microphone input of my SB LIVE 5.1 there is constant voltage about 2 V. It was not possible to investigate the reason and whether this is typical only for my copy of the sound card or for all. But it is absolutely certain that the performance of the circuit practically does not change when elements C2 and R3 are excluded.
The advantage of this scheme is its simplicity. The disadvantages include large nonlinear distortions - about 1% (1 kHz) at 1 mV at the input. Nonlinear distortion can be reduced to 0.1% using an additional 100 Ohm resistor connected between the emitter of transistor VT1 and the GND bus, while the gain is reduced from 40 dB to 30 dB. The changes are shown in Fig. 3.
Rice. 3
Higher parameters can be achieved by using an external microphone amplifier with self-powered, connected to the line input of the sound card. For example - assembled according to a circuit with a symmetrical input.
DIY microphone amplifier.
Probably, many of you have had the need to record sound on a computer, for example, when scoring videos or creating clips. The use of Chinese inexpensive consumer goods is absolutely undesirable, firstly, due to the rather low sensitivity, and secondly, the quality of sound recording
it turns out *dirty*, sometimes even your own voice becomes unrecognizable.
High frequencies have a significant and unjustified rollover, and their durability leaves much to be desired.
A high-quality microphone, alas, is beyond our means!
But there is a way out! Many have old, still Soviet dynamic microphones, for example MD-52 or similar ones. And even in their absence, these copies can be bought for *mere pennies*. Do not try to connect such microphones directly to the sound card directly - the AF voltage at the output is too low. Therefore, we will use the simplest microphone amplifier, based on the widely used K538UN3 microcircuit, its cost is less than 50 rubles. But we used an old microcircuit soldered from an ancient cassette recorder. Directly, the microcircuit itself is connected according to a standard, common switching circuit, with a maximum gain. The amplifier is powered directly from the computer, the supply voltage is 12 V, although operation remains at - 5 V, in this case, power can be taken from the USB connector.
Microphone amplifier. Scheme.
Electrolytic capacitors - any, for a voltage of 16V. The capacitance value of the capacitors can be changed within small limits. The device can be assembled using a simple, hinged installation.
The amplifier does not require any adjustment and does not require shielding. But, the use of shielded cables is desirable and not too long. Tests of the samples showed a relatively low level of self-noise, fairly high sensitivity and very decent sound quality, even on built-in computers. sound cards, type AC97. Dynamic range– about 40 dB. To record sound on a computer, we used the Sound Forge program.
Well, and a few more diagrams for the articles in addition.
Clean sound to you!!!