Microphone Preamplifier – Sound Sensor

Rajkumar Sharma
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SKU: EL110607
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This is an easy to construct dual-stage microphone pre-amplifier. The project can be used as a sound sensor or microphone pre-amplifier. The 1^st op-amp pre-amplify the very low-level signal coming from the condenser microphone and 2^nd op-amp provides more boost to the audio signal. The pre-amplifier is an important building block for many audio communication systems and sound sensors. The circuit has been built around OPAMP LM358. The output signal level is dependent on the input sound level. The maximum peak to peak output is 2V_pp.

Connections: CN1 Pin1 = VCC, Pin 2 = Low level audio signal, Pin 3 = NC, Pin 4= High level Audio Signal (it can be used for microcontroller interface)

Features

Power supply: 5V DC @ 10 mA
On-Board electret condenser microphone
Dual Stage Amplification using OPAMP LM358
PCB dimensions: 47.31 x 14.76 mm

Schematic

Parts List

NO.	QNTY.	REF.	DESC.	MANUFACTURER	SUPPLIER	SUPPLIER PART NO
1	1	CN2	5 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5318-ND
2	2	C2,C4	4.7uF/25V	NICHICON	DIGIKEY	493-11353-3-ND
3	3	C3,C6,C7,C1	0.1uF/50V SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
4	1	C5	10uF/25V SMD SIZE 1206	MURATA/YAGEO	DIGIKEY
5	7	D1,U2,D2,R7,C8,R9,R10	DNP
6	1	MK1	MIC	SOBERTON INC	DIGIKEY	433-1088-ND
7	2	R1,R5	100K 5% SMD SIZE 0805	MURATA/YAGEO
8	2	R2,R8	10K 5% SMD SIZE 0805	MURATA/YAGEO
9	2	R3,R4	1K 5% SMD SIZE 0805	MURATA/YAGEO
10	1	R6	24K 1% SMD SIZE 0805	MURATA/YAGEO
11	1	U1	LM358 SOIC8	TI	DIGIKEY	LM358MX/NOPBCT-ND