Microphone Conferencing System

For more effective online meetings

For meetings that do not involve too many people the microphone built into the webcam or laptop is usually sufficient for conferencing, but for larger groups or in acoustically less than ideal rooms (with a lot of reverberation, for example) the degree of intelligibility at the other end of the line is often very low. To solve this problem we designed a simple circuit.

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Materials

100465-PCB.pdf

Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

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PCB

Download Gerber file: 100465-1-V10

Extra info / Update

- Can be used with any PC or laptop with Line or Mic input.
- Simple to operate
- Two units are easily connected
- Pickup pattern of the microphones is easily adapted to suit the situation
- Easy to build using standard components

Component list

Resistors
R1 = 10kOhm
R2 = 22kOhm
R3,R4 = 33kOhm
R5 = 220kOhm
R6 = 330kOhm
R7 = 220Ohm
P1 = 22kOhm trimpot, horizontal
P2 = 250kOhm trimpot, horizontal
P3 = 2.2kOhm logarithmic potentiometer
Capacitors
C1 = 10µF
C2 = 100nF
C3 = 22µF
C4 = 100pF
C5,C6 = 1µF
Semiconductors
IC1 = TL071
Miscellaneous
K1,K2 = 3.5mm jack socket, PCB mount
K3–K6 = 2-pin pinheader
K7 = 3-pin pinheader
Mating headers for K3–K7
S1 = pushbutton, 1 make contact
S2 = on/off switch
Electret microphone capsule, e.g Panasonic MCE-2020U or WM-61A
PCB # 100465-1