Quality microphone for computer

AUDIO technique Microphone with narrow. directivity pattern A microphone with a narrow beam pattern can be used for recording and amplifying speech under conditions of large interference, and also for recording the sound of distant sources, for example singing birds. Directivity microphone  Significantly increases the signal-to-noise ratio at the input of the LF amplifier. The schematic of this device is shown in Fig. Its main trifle is an electromagnetic capsule (3), located in a cylindrical case (1). The capsule is poured on both sides with epoxy resin. The side of the capsule facing the open hole of the case has a "sensitive window" of small dimensions, providing access to the membrane for sound vibrations. With the help of three stretches, the capsule is suspended on a wire ring (4), which is located on the back of the case. To reduce reflection from the walls, the inside of the case is covered with a layer of felt or felt (2) approximately 12 mm thick. Schematically the device microphone  . The microphone is connected to the input of the preamplifier, one possible scheme of which is shown in Fig. 2.   Reduction of the intrinsic noise of the first stage is achieved by choosing a low-noise transistor T1 and using it at a small collector current. The second stage, assembled on a T2 transistor in a common-collector circuit, allows the output of the device to be coordinated with a power amplifier. "Practical wireless", 1969, N 7.Res.2. Preliminary amplifier. As a microphone capsule can be used primer DEMSH. For the first cascade ...

For the scheme "Indication of the connection of electrical appliances to the 220 V network"

The display device allows you to monitor when leaving the house: are the electrical appliances switched off from the network? If there is any load in the network\u003e 8 W, both HL1 and HL2 LEDs are on (see figure). ...

For the scheme "The original modulation scheme of the HF generator"

For the scheme "ELECTRONIC ECHO" "

Radio spyElectronic "EAR" C. Sych225876, Brest region, Kobrin district, Orekhovsky settlement, Lenina street, 17 - 1. The proposed one is intended for listening to conversations in the premises at a short distance. There is enough sensitivity for confident perception of weak sound (whisper, quiet conversation) at a distance of 3 ... 4 m from the microphone. The range of the device is approximately 50 m (with the length of the transmitter antenna 30 ... 50 cm). It is desirable to reduce the transmitter scheme to the minimum dimensions (so that it can not be seen). When using VA devices at short distances (up to 15 m), the power can be reduced to 1.5 ... 3 V. It is desirable to feed the transmitter from small items. The current consumption of the device is 3 ... 4 mA. = ELECTRONIC PROTECTION frequency of the transmitter - 66 ... The scheme of a droshod transceiver is 74 MHz. Coil LI - contains 6 turns of PEV-2 wire 0.5 mm and is wound on a frame with a diameter of 4 mm with a winding pitch of 1 ... 1.5 mm. The frequency of the oscillator on VT2 is changed by shifting the coil turns L1. RADIOLYUBITEL 1/98, p.24Since I received many letters with questions on my article "Electronic" ear ", I give additional information on tuning and modification of the circuit and drawing of the printed circuit board (RIS .1). = ELECTRONIC WRONG Set up first, the capacitor ratings C1 and C2 should be selected between 4.7 ... 33 μF to obtain the best signal quality and maximum sensitivity and frequency deviation.Reistors R1 and R2 should be selected within 330 .. .420 kΩ and 4.7 ... 9.1 kΩ corresponding to Twain for the best quality. The transistor VT1 should be elected with the highest current gain. Instead, C4 after setting can be turned on the constant condensation ...

For the "Radio microphone, with improved performance"

Radio broadcasterRadio microphone, with improved characteristics Shatun Alexander Nikolaevich, 312040, Kharkiv region, Dergachi, tel. (8-263) 3-21-18 A variety of descriptions of simple wireless microphones with FM are given in different literature, but, in my opinion, they do not differ in variety . All this, in fact, is the same thing, in different interpretations. I propose a circuit version of a non-quartz microphone, which, in comparison with others, has a higher frequency stability with varying supply voltage and detuning the antenna. In addition, the microphone has a high quality signal, there is also no overmodulation in a loud conversation near the microphone, although the sensitivity is high. At a voltage of 3 volts, the transmitter power is sufficient for reception at a distance of up to 300 meters. works well and at a voltage of 1.5 volts. The range and power consumption are reduced. is shown in Fig.1. All cascades have a direct DC link. The signal from the electret is fed through C2, which with the resistor R2 forms a frequency correction circuit. The transistor VT1 is equipped with a modulating cascade, which is also a stabilizer of the operating point for VT2, VT3, which allows you to equalize the sudden change in power when the supply voltage changes and reduce the frequency drift. The master oscillator is assembled on VT2 by a capacitive three-point circuit. The oscillating circuit of the master oscillator for improving electrical characteristics has two resonances, consecutive L1, C5 and higher in frequency parallel L1, C5, C4, C6. Excitation occurs at the frequency of the parallel resonance.

For the "MODEM FOR PACKAGE"

Nodes of amateur radio technology MODEM FOR PACKAGE My previous article was published a packet modem for operation in the VHF band at a speed of 1200 baud. Somewhat later it was successfully tested and to work in the KB dubase at a speed of 300 baud. which allowed to develop a universal modem 1200/300 Bod. simplicity and reliability. The basic modem is shown in the figure. Compared with [I]. it has not undergone any significant changes except for two moments: switching nodes of the frequency of the 4.43MHz / 2.215 MHz reference oscillator and indication of the modes of operation of the PTT and DCD modems were added. providing additional convenience in work. Economical voltage regulator circuit Switching modes KB and VHF (speed 300/1200 baud) is made by the switch SA 1. Connector X1 is used for the computer's COM port, connector X2 for the KB transceiver. Connector X3 is for the VHF radio station. In addition, I would like to clarify the data in the circuit diagram: the nominal value of resistors R2 and R14-2.2к0м. References 1. Teteryuk V. Modem for the package // Radiolyubitel.- 1997. N 10.   C.37.V. TETERYUK (YL2GL), LV-5402, Latvia. Daugavpils. ul.Valnyu, 31-25 ....

amplifier   The circuit of connecting the intercom device electronics is pu 02 3. Before putting on the coil tubes protect from damage - stick a strip of adhesive tape along the core over the coils. A super-glue pickup is fastened, but not immediately to the surface of the guitar! Suddenly, do you ever decide to change or just remove the pickup? Therefore, first you should stick a tape on the surface of the guitar at the places where the pickup is attached. It should be noted that when the pickup approaches the end of the strings, the signal level at its output is smaller, the sound has a metallic character, and at a distance of 2 ... 5 cm to the end of the strings, the sound is more melodic and "bassy", with a greater amplitude at the output. The level of the pickup signal approximately corresponds to the level of the signal of the dynamic microphone. It will take six heads from the tape recorder, and the heads should be the same. We remove from them the petals intended for the exact extension of the tape, as shown in Fig. 4. ...

For the "Acoustic Guitar Pickups"

I propose two ways of manufacturing a pickup for six-string acoustic guitar. We take five magnets from the kit to assemble the doors of the cabinet. We release them from unnecessary "details" and glue together into one long, one-piece piece of superglue (Figure 1). Then on each side we glue a strip of scotch. The magnetic core of the pickup is ready. Now reel spools, each with 50 turns (wire diameter 0.1 mm or thinner), with a distance between them, so that, under the strings, each respectively was closer to its own. A total of six coils, according to the number of strings (Figure 2). The zvukosnimatel is ready, but it must be "designed" so that it corresponds to the appearance of the guitar. To do this, place it in a rubber tube (from under the rubber water-heater) with a longitudinal (one) slit. To connect to amplifier the pickup is glued (with the same super-glue) by a nest from the headphones (from any player, etc.) to which we glue the leads from the pickup .. The general view of the already prepared pickup is shown in Fig. Schemi forgive homemade transceivers 3. Before putting on the coil tubing protect from damage - stick along the core a strip of scotch over the coils. A pickup superglue, but not immediately on the surface of the guitar! Suddenly, do you ever decide to replace or just remove the pickup? Therefore, first you should stick a tape on the surface of the guitar at the places where the pickup is attached. It should be noted that when the pickup approaches the end of the strings, the signal level at its output is smaller, the sound has a metallic character, and at a distance of 2 ... 5 cm to the end of the strings, the sound is more melodic and "bassy", with a greater amplitude at the output. The level of the pickup signal approximately corresponds to the level of the signal of the dynamic microphone. It will take six heads from the tape recorder, and the heads should be the same. We remove from them the petals intended for the exact extension of the tape, as shown in Fig. 4. ...

For the scheme "MICRO-TRANSMITTERS OF VHF FM WIDTH"

Microwave power transmitters, whose output power ranges from fractions of a few milliwatts, can be used to organize radio communications and data transmission for a distance of several meters. The devices described below operate in the frequency range 66 ... 74 MHz and, if necessary, can be rebuilt for operation in a different frequency range. In all designs, high-efficiency small-size electret microphones of the MKE-332 type are used, which contain a built-in preamplifier on the field-effect transistor. In Fig. 1, we give outline  radiomicrophone, the base bias circuit of which is switched on as a controlled resistor electret microphone. As an antenna, a section of flexible multicore wire with a length of 20 ... 40 cm is used. The current consumed by the device is approximately 1 mA. The device shown in Fig. 2 is a parallel radio telephone adapter and is intended for broadcasting sound signals on the high-frequency channel. An economical voltage regulator circuit The device can be powered directly from a 60-volt telephone line while consuming a current of up to 2 mA; When you remove the handset (reduce the supply voltage), the radio microphone is turned off. The circuit uses cascode switching of transistors, in which, for low frequency signals, the load in the collector circuit of transistor VT2 is a high-frequency generator made on transistor VT1. In turn, for high-frequency currents in the emitter circuit of the transistor VT1, a cascade of amplification on the transistor VT2 is used. When the device is powered from the telephone line, it is not necessary to connect the antenna, since phone line  plays the role of a rather long antenna. Reception of high-frequency signals is possible on a portable FM receiver along the ...

For the "Micro Transmitters"

Radio transmitter Micro transceivers Very simple telephone transmitter. L1 = 6 turns of wire PEV 0,3-0,4 on the mandrel 2,6-3,0 mm turn to the turn. T1 = кт3102, кт315 (А-В) Д1-Д4 = КД510А, КД521ВС1 = 22H, C2 = 33PF, C3 = 33PFR1 = 33KM. Transmitters by non-traditional schemes. Each inessively used circuitry includes an inductive three-point circuit. This transmitter has a narrower range of supply voltages at the same value of resistor R3. Resistor R2 is needed to reduce the effect of capacitance on the master circuit. The L1 coil has 6 turns of PEW 0.45-0.7 on the mandrel 3.4-4.0 mm. The discharge of the emitter T1 is from 3.5-4.5 turns of the total. Consumption current 8-10 mA. T1 = kt3102, kt315 (A-B) R1 = 4.7K, R2 = 4.7K, R3 = 82K * C1 = 33PF, C2 = 4.7MKF, C3 = 22H, C4 = 33PF microphone you can pick up any (small). ...

3.8. MICROPHONES

Microphones are classified on the basis of the conversion of acoustic vibrations into electrical ones and are divided into electrodynamic, electromagnetic, electrostatic (condenser and electret), coal and piezoelectric.

Microphones are characterized by the following parameters:

Microphone sensitivity -  this is the ratio of the voltage at the output of the microphone to the sound pressure acting on it at a given frequency (typically 1000 Hz), expressed in millivolts per pascal (mV / Pa). The higher this value, the higher the sensitivity of the microphone.

Nominal operating frequency range -  The frequency range in which the microphone perceives acoustic vibrations and in which its parameters are normalized.

Uneven frequency response -  The difference between the maximum and minimum sensitivity level of a microphone in the nominal frequency range.

The module of the total electrical resistance -  the normalized value of the output or internal electrical resistance at a frequency of 1 kHz.

Directional characteristic -  dependence of sensitivity   microphone  (in a free field at a certain frequency) from the angle between the axis of the microphone and the direction to the sound source.

The level of the microphone's own noise -  expressed in decibels, is the ratio of the effective value of the voltage due to fluctuations in the ambient pressure and the thermal noise of various resistances in the electrical part of the microphone to the voltage developed by the microphone on the load at a pressure of 1 Pa when the useful signal with an effective pressure of 0.1 Pa is applied to the microphone.

In telephones, basically, electrodynamic, electret and carbon microphones are used. But, as a rule, in 95% of button TA are used electret microphones, which have increased electro-acoustic and technical characteristics:

Wide frequency range;

Small uneven frequency response;

Low nonlinear and transient distortion;

High sensitivity;

Low level of own noise. In Fig. 3.61 is a diagram explaining the operation principle of a condenser microphone. The membrane (1) and the electrode (2) made of the electrically conductive material are separated by an insulating ring (3) and are a capacitor. A rigidly stretched membrane under the influence of sound pressure oscillates with respect to a stationary electrode. The capacitor is connected to the electrical circuit in series with the DC voltage source GB and the active load resistance R. When the membrane vibrates, the capacitance of the capacitor changes with the frequency of the sound pressure acting on the membrane. An alternating current of the same frequency appears in the electrical circuit and an alternating voltage appears on the load resistance, which is the output signal of the microphone.

Electret microphones, by operation principle, are the same capacitor, but the constant voltage in them is provided by an electret charge, a thin layer deposited on the membrane and retaining this charge for a long time (over 30 years).

Since electrostatic microphones have a high output impedance, in order to reduce it, as a rule, a source repeater is built in the microphone housing in a field n-channel transistor with pn junction. This allows you to reduce the output resistance to a value of not more than 3 + 4 kΩ and to reduce the signal loss when connecting to the input of the microphone signal amplifier.

Figure 3.62 shows the internal circuit of an electret microphone with three terminals MKE-3.

In electret microphones with two terminals, the microphone output is made by an amplifier circuit with an open drain.

In Fig. 3.64 shows the internal circuit of an electret microphone with two terminals MKE-389-1. The diagram of connecting such a microphone is shown in Fig. 3.63. Under this scheme, it is possible to connect almost all electret microphones with two terminals, both domestic and imported.

In Fig. 3.67 shows the dimensions and purpose of the outputs of electret microphones. In Table. 3.15 shows their technical characteristics.

The current consumption of the microphone MEK-1 is not more than 0.2 mA, MCE-377-1 and MKE-378 not more than 0.35 mA. The current consumption of the microphones M1-A2, M1-B2 and M-7 is no more than 70 μA.

The difference between the MEK-332 microphone and the MKE-333 is that MEK-332 is unidirectional, and MKE-333 is not directional.

The harmonic coefficient at a frequency of 1000 Hz at a sound pressure of 3 Pa for microphones MKE-377-1 and MKE-389-1 is not more than 4%, MCE-378 is not more than 1%.

The unevenness of the sensitivity frequency response in the nominal frequency range for the MCE-3 microphone is not more than 12 dB, and for M1-A2, M1-B2, IEC-1 and MKE-389-1, not more than ± 2 dB.

Microphones are classified according to the peculiarity of converting acoustic vibrations into electrical ones, and are divided into electrodynamic, electromagnetic, electrostatic (capacitor and electret), coal and piezoelectric.

Types of microphones

Microphones are characterized by the following parameters:

The sensitivity of a microphone is the ratio of the voltage at the output of the microphone to the sound pressure affecting it at a given frequency (usually 1000 Hz), expressed in millivolts per pascal (mV / Pa). The higher this value, the higher the sensitivity of the microphone.

Nominal operating frequency range is the frequency range in which the microphone senses acoustic vibrations and in which its parameters are normalized.

The level of the microphone's own noise is the ratio of the effective value of the voltage, expressed by the fluctuations in the ambient pressure and the thermal noise of various resistances in the electrical part of the microphone, expressed in decibels, to the voltage developed by the microphone on the load at a pressure of 1 Pa when the useful signal with effective pressure 0 , 1 Pa.

The unevenness of the frequency response is the difference between the maximum and minimum sensitivity level of the microphone in the nominal frequency range.

Figure 1. Diagram of switching on a condenser microphone.

In Fig. 1 is a diagram explaining the operation principle of a condenser microphone. The membrane (1) and the electrode (2) made of an electrically conductive material are disconnected by an insulating ring (3) and are a capacitor.

A tightly stretched membrane under the influence of sound pressure produces oscillatory motion relative to a stationary electrode. The capacitor is connected to the electrical circuit in series with the DC voltage source GB and the active load resistance R.

When the membrane vibrates, the capacitance of the capacitor changes with the frequency of the sound pressure acting on the membrane. An alternating current of the same frequency appears in the electrical circuit and an alternating voltage appears on the load resistance, which is the output signal of the microphone.

Electret microphones, by operation principle, are the same capacitor, but the constant voltage in them is provided by the charge of an electret, a thin layer deposited on the membrane and preserving this charge for a long time (over 30 years).

Since electrostatic microphones have a high output impedance, in order to reduce it, as a rule, a source repeater is inserted into the microphone housing on a n-channel transistor with a pn junction.

This allows you to reduce the output resistance to a value of not more than 3 + 4 kOhm and to reduce the loss of signal when connected to the input. In Fig. 2 shows the internal circuit of an electret microphone with three terminals MKE-3.

Fig. 2 Internal circuit of the electret microphone MKE-3.

In electret microphones with two terminals, the microphone output is performed according to the amplifier circuit with open drain.

Fig. 3. Internal circuit of the electret microphone MKE-389-1.

Fig. 4. Scheme of connection of electret microphones with two terminals.

In Fig. 3 shows the internal circuit of an electret microphone with two terminals

MKE-389-1. The diagram of connecting such a microphone is shown in Fig. 4. Under this scheme, it is possible to connect almost all electret microphones with two terminals, both domestic and imported.

The table shows their technical characteristics.

The current consumption of the microphone MEK-1 is not more than 0.2 mA, MCE-377-1 and MKE-378 not more than 0.35 mA. The current consumption of the microphones M1-A2, M1-B2 and M-7 is no more than 70 μA.

The difference between the MEK-332 microphone and the MKE-333 is that the MKE-332 is unidirectional, and the MKE-333 is not directional.