Audio Limiter
Based on the NJM2761 chip, this adjustable audio limiter provides effective speaker protection by maintaining a low-noise output with a user-definable limit range of 0.2V to 1V across a wide DC power supply.
This simple project is an audio limiter based on the NJM2761 chip. It provides effective protection for speakers by limiting the audio signal level. The limit level is adjustable through an external trimmer potentiometer (PR1).
Screw terminals allow easy connection of the audio input and output signals, while header connectors are provided for powering the board. The project operates over a wide supply voltage range of 2.7 V to 13 V DC. The output is low-noise, and the variable limit level can be adjusted from 0.2 V to 1 V using the PR1 trimmer potentiometer.
Calculations
RSENSE=4000/Vlim[Ohm]
Vlim: Limit level (Vrms)
Limit range: 200mVrms to 1Vrms (20k to 4kOhm)
Features
- Supply 2.7V to 13V DC
- Stereo Input and Output
- Screw terminals for Audio Input and Output
- On Board Power LED
- Header Connector for Power Input
- PCB Dimensions 45.72 x 20.96 mm
Connections
- CN1: Pin 1,2 = VDD 2.7V to 13V DC, Pin 3,4 = GND, Pin 5 = Limit ON/OFF
- CN2: Pin 1 = Audio Output Channel A, Pin 2 = GND
- CN3: Pin 1 = Audio Output Channel B, Pin 2 = GND
- CN4: Pin 1 = Audio Signal Input Channel A, Pin 2 = GND
- CN5: Pin 1 = Audio Signal Input Channel B, Pin 2 = GND
- PR1: Audio Limit Adjust
- D1: Power LED
Schematic
Parts List
| NO. | QNTY. | REF. | DESC. | MANUFACTURER | SUPPLIER | SUPPLIER PART |
|---|---|---|---|---|---|---|
| 1 | 1 | CN1 | 5 PIN MALE HEADER PITCH 2.54MM | WURTH | DIGIKEY | 732-5318-ND |
| 2 | 4 | CN2,CN3,CN4,CN5 | 2 PIN SCREW TERMINAL PITCH 5.08MM | PHOENIX | DIGIKEY | 277-1247-ND |
| 3 | 3 | C1,C5,C6 | 220nF/63V THT 2.5x7MMM FILM CAPACITOR | DIGIKEY | ||
| 4 | 1 | C2 | 10uF/50V THT ELECTROLYTIC 5X11MM | DIGIKEY | ||
| 5 | 2 | C3,C4 | 1uF/63V ELECTROLYTIC THT 5X11MM | DIGIKEY | ||
| 6 | 1 | C7 | 0.022uF/100V THT 2.5X7MM FILM CAPACITOR | DIGIKEY | ||
| 7 | 1 | C8 | 0.22uF/50 ELECTROLYTIC 5MMX11MM | DIGIKEY | ||
| 8 | 1 | D1 | LED SMD SIZE 0805 | OSRAM | DIGIKEY | 475-1278-1-ND |
| 9 | 1 | PR1 | 20K TRIMMER POTENTIOMETER | NIDEC | DIGIKEY | 563-CT-6EP203-ND |
| 10 | 2 | R1,R2 | 1K 5% SMD SIZE 0805 | DIGIKEY | ||
| 11 | 1 | U1 | NJM2761 | NISSINBHO MICRO | DIGIKEY | 2129-NJM2761RB2-TE1CT-ND |
| 12 | 1 | R4 | 4K 1% SMD SIZE 0805 | DIGIKEY |
Connections
Simplified Schematic
Block Diagram
Gerber View
Photos
