Introduction
This is a low-noise preamplifier designed to work with both 2-wire and 3-wire electret microphones. The microphone can be connected through a stereo EP socket. The circuit operates from a dual ±5 V DC power supply. A header connector is provided for power input and audio output. An onboard LED indicates the presence of the power supply.
This 2 or 3-wire microphone pre-amplifier is designed using the low-power, low-noise, and low-distortion OPA1692 audio operational amplifier, making it ideal for high-performance electret microphone applications. The circuit is optimized for electret microphones that use a 2 or 3-wire interface, providing excellent audio quality while maintaining minimal power consumption.
The primary application of this pre-amplifier is in wireless microphone systems, where high audio fidelity and long battery life are essential. A typical wireless microphone consists of an electret microphone element, an analog pre-amplifier stage, and a transmission circuit that may use either analog or digital communication methods.
This board can accommodate 2 wire electret microphone or 3 wire microphones.
- 2 Wire Microphone MK1(3 Pin Header), Short Pin 1 +MK and 2 MKO (Use 3 pin male header and Shunt)
- 3 Wire Microphone R4 = 5.9K 1% SMD size 0805, C6 = 100nF SMD 0805, R5 = 100K 5% SMD size 0805, R2 = 100E, C7 = 100PF, Use 3 pin 3.5MM stereo EP male plug
Features
- Power Supply +/-5V DC
- Current Consumption less than 1.5mA (Without LED)
- Maximum Sound Level Pressure SPL 120dB
- On Board Power LED
- Bandwidth 20Hz to 20Khz
- Gain 11.79 V/V or 21.43 dB
- PCB Dimensions: 25.88 x 13.34 mm
Schematic
Connections
- CN1: Pin 1 = +5V DC, Pin 2 = GND, Pin 3 = -5V DC
- CN2: Pin 1 = Audio Output, Pin 2 = GND
- D1: Power LED
- CN3: 3 Pin Stereo EP 3.5MM Female Socket
- MK1: 3 Pin Male Header for Microphone or as Jumper
Part List
| NO. | QNTY. | REF. | DESC. | MANUFACTURER | SUPPLIER | SUPPLIER PART NO |
|---|---|---|---|---|---|---|
| 1 | 1 | CN1 | 3 PIN MALE HEADER PITCH 2.54MM | WURTH | DIGIKEY | 732-5316-ND |
| 2 | 1 | CN2 | 2 PIN MALE HEADER PITCH 2.54MM | WURTH | DIGIKEY | 732-5315-ND |
| 3 | 1 | CN3 | 3.5MM FEMALE EP STEREO SOCKET | CUI | DIGIKEY | CP1-3525N-ND |
| 4 | 3 | C1,C3,C6 | 100nF/50V CERAMIC SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 5 | 2 | C2,C4 | 10uF/25V CERAMIC SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 6 | 2 | R4,C5 | DNP | |||
| 7 | 1 | C7 | 100PF/50V CERMAIC SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 8 | 1 | C8 | 2.2uF/25V CERAMIC SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 9 | 1 | C9 | 2.2nF/50V CERAMIC SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 10 | 1 | D1 | LED RED SMD SIZE 0805 | LITE ON INC | DIGIKEY | 160-1427-1-ND |
| 11 | 1 | MK1 | 3 PIN MALE HEADER PITCH 2.54MM | WURTH | DIGIKEY | 732-5316-ND |
| 12 | 2 | R1,R2 | 2.2K 5% SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 13 | 1 | R3 | 100E 5% SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 14 | 2 | R5,R7 | 47K 5% SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 15 | 1 | R6 | 0E 5% SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 16 | 1 | R8 | 3.57K 1% SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 17 | 1 | R9 | 150E 5% SMD SIZE 0805 | YAGEO/MURATA | DIGIKEY | |
| 18 | 1 | U1 | OPA1692 SOIC8 | TI | DIGIKEY | 296-51489-1-ND |
PCB View
