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Oct 21, 2021
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How to make a stereo computer microphone with decent sound quality

How to make a stereo computer microphone with decent sound quality

Any computer user may need a microphone, whether for recording a voice message in a messenger, making calls or video calls, recording a voice or a musical instrument. Low-end microphones are sold at every corner, but they often do not meet the most basic requirements – they are easily overloaded, have a low signal amplitude at the output, or even fade.

Buying an expensive microphone for simple home use is not always justified, but you can easily make it yourself using inexpensive components. The general concept of the microphone is quite standard: the sound is picked up by electret capsules, amplified by an operational amplifier and fed to the line-in of the computer. To power the amplifier in the microphone, a 5 volt power supply is required, it can be taken from the nearby USB output of the computer.

Description of the circuit

The general scheme is presented below.

How to make a stereo computer microphone with decent sound quality

It can be conditionally divided into 4 blocks. The first of them is a power converter (upper left corner), which creates a bipolar voltage of 5 volts in each arm from a unipolar voltage of 5 volts supplied to the input from the USB connector, so the total swing will be already 10 volts. A bipolar voltage, firstly, is necessary for the operation of an operational amplifier (OA) with a variable audio signal, and secondly, the amplitude of 5 volts is simply not enough for the op-amp microcircuit. The converter contains a minimum of parts, the diode being especially important – it must be Schottky, and an inductance of 1000 μH, any one on a ferrite core will do. The converter works on the MC33063 microcircuit, which is quite often used to create various pulse converters and is sold in any radio store.

The second part is a two-tier CLC filter (upper right corner), which cleans the microphone power supply from various noise, which literally teems with the voltage received from the USB output, and which is additionally created by a pulse converter. Both supply arms are filtered, and for the highest quality filtering, two links are required for each arm, respectively, 4 inductors of 2000-3000 μH and 6 capacitors are required. Each electrolytic capacitor is shunted with tantalum (you can take a ceramic one) for additional filtering of high-frequency interference. If desired, the circuit can be powered from any 9-12 volt source, creating an artificial midpoint with a resistor divider instead of a bipolar power supply, in this case neither a converter nor a CLC filter is needed, however, USB power is very convenient for a computer microphone.

Parts 3 and 4 are amplifiers themselves, identical for the right and left channels, so the sound from the microphone will be in stereo. A low-noise operational amplifier NE5532 is used, instead of it, you can also use the TL072 or TL082, all of them are dual, only one microcircuit is required to amplify the two channels. With the help of trimming resistors PR1, PR2, you can adjust the gain separately for each of the channels. After assembling the microphone, they will need to be adjusted so that the signal amplitude in both channels is the same, and the signal level does not overload the computer input. As the pickups themselves, electret microphone capsules are used, exactly the same as those used in cell phones or headsets.

Assembling the microphone

In order for the microphone electronics not to take up much space and easily fit into any suitable housing, SMD components are used for assembly. Of the output capacitors, only electrolytic capacitors in the CLC filter and blocking capacitors in amplifiers are used, since they are preferable to take film ones. You can also use the output inductors in the filter if there is no SMD at hand, as I did. The printed circuit board itself is made by the LUT method, you can find the pattern of the tracks for printing and the layout of the elements in the archive.

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How to make a stereo computer microphone with decent sound quality

Electret capsules are soldered directly onto the board from the end. On the other side of the board there are terminals for connecting outputs (right, left) and supplying 5 volts. Power minus and signal ground are the same pin. After soldering, the board should definitely be washed from the flux (the assembly process is shown in the photo).

How to make a stereo computer microphone with decent sound quality
How to make a stereo computer microphone with decent sound quality
How to make a stereo computer microphone with decent sound quality

Installation in the case

The board is installed in a housing that will not only allow you to conveniently use the microphone, but also protect the electronics from electromagnetic interference. The case can be of any shape, the main thing is that it is metal – it will need to be connected to the ground of the circuit. A good option would be an unnecessary housing from a cheap microphone, which can be bought literally for 100-200 rubles. A rectangular board fits perfectly into it, you can use the standard XLR connector to connect the output, or simply bring out a one-piece shielded wire with cores for the right and left channels and the 5 volt line, soldering 3.5 mm and USB plugs to its end.

How to make a stereo computer microphone with decent sound quality
How to make a stereo computer microphone with decent sound quality
How to make a stereo computer microphone with decent sound quality

Microphone tests

A properly assembled microphone with an adjusted gain level produces ample signal with natural, clear sound. The video below shows an example of an acoustic guitar recording made with an assembled microphone.

A simple microphone for a computer with your own hands – https://sdelaysam-svoimirukami.ru/4420-mikrofon-dlya-kompyutera-svoimi-rukami.html

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