If the microphone audio signal is weak, you can use this Microphone Preamplifier circuit to boost the weak microphone signal to stronger. This pre amp circuit works on a single C1815 transistor. In this article I’m sharing the 12V microphone pre amp circuit and its additional information’s to build.
What is Microphone Preamplifier?
It is an electronic circuit or device boost the low signals comes from the microphone to stronger signal. This stronger signal is enough to recorder or play through the audio amplifiers, but the weak signals can’t. Actually this type of circuit amplifying the weak audio signal to high like 20dB to 60dB.
12V DC Microphone Preamplifier Circuit Diagram
Components Required
| Component | Value | Quantity |
|---|---|---|
| R1 | 33 kฮฉ | 1 |
| R2 | 220 kฮฉ | 1 |
| R3 | 39 ฮฉ | 1 |
| R4 | 3.9 kฮฉ | 1 |
| R5 | 470 ฮฉ | 1 |
| C1 | 10 ยตF | 1 |
| C2 | 10 ยตF | 1 |
| C3 | 101 pF | 1 |
| C4 | 100 ยตF | 1 |
| Q1 | 2SC1815 | 1 |
| J3 | MIC IN | 1 |
| J1 | OUT | 1 |
| J2, J4 | GND | 2 |
| Supply | 12 V DC | 1 |
Working Principle
This is a very simple circuit designed with 2SC1815 common NPN transistor. The weak AC audio signal from the microphone is enter to the transistor base pin through a 10uf electrolytic capacitor.220K and 33K is the bias and feed back resistor.
If the input signal varies, a large current flow occurs in the collector to emitter. Which created an amplifier signal across the 3.9k resistor. The capacitor C3 filter the high frequency and allow noise free amplified signal to the output.
