Preamplifier for Dynamic Microphones UA739

Introduction

To record the vocals, dynamic microphones are extensively used. Since the condenser microphones are also used to boost the input audio. But, they need some supply and don’t have an impressive output to the big booming sound. Therefore, dynamic microphones are now considered practically tremendous. However, to boost the audio signal, the dynamic microphone circuits need a preamplifier. Thus, in this article, we will learn to make a preamplifier for dynamic microphones. But before making the circuit we must understand what are the preamplifiers.

An Overview of the Preamplifiers

When we talk about amplifiers, we know that it’s a circuit that increases the amplitude of the input signal at the output. Further, there are two types of amplifiers, the preamplifier, and the power amplifier. Preamplifiers are the circuits that raise the volume of an audio signal. But, raising the amplitude, makes the signal free from noise and distortion. Most importantly, it provided a voltage gain but no substantial current gain.

Specifications about Circuit

• The circuit uses a dual audio operational amplifier uA739 IC
• The circuit uses the power supply of 18V
• The input impedance of the circuit is about 50K
• The circuit can handle the signal range from 20Hz to 20KHz

Hardware Required

S.no	Component	Value	Qty
1.	PCB Board	–	1
2.	Mic	–	1
3.	Resistor	10 ohms, 1K, 47K, 10K, 100K, 1M	1, 1, 1, 1, 2, 1
4.	Ceramic Capacitor	0.1uF, 0.0082uF, 0.001uF	1, 1, 1
5.	Electrolyte Capacitor	100uF, 10uF	1, 2
6.	IC	UA739	1
7.	Power supply	18V DC	1

Circuit Diagram

Working Explanation

The circuit Preamplifier for Dynamic microphones uses the IC having two op-amps. However, the circuit needs only one op-amp. Capacitor C1 decouples the input signal. Resistor R1 and Capacitor C2 make the network bypass the undesirable high frequencies. For better stability, a bit of output is fed back to the input. As a result, we get the high amplitude audio signal at the output

Application and Uses

• It is used in recording vocals
• In seminars, concerts, live sessions