Circuit Diagram
Description
Here is the circuit diagram of three
input microphone preamplifier. This is a mic mixer preamplifier centered
on the high gain operational amplifier IC LM 348. This IC LM 348 is a
quad operational amplifier IC that is it has four operational amplifiers
embedded in this chip. This IC has also got some advanced features such
as very high gain, class AB output stage and very low input supply
current of 0.6 mA for each op-amp.
The 3 channels of mic input require
three amplifiers. The three op-amps (IC1b, IC1c and IC1d) out of four in
the IC LM 348 are used here as input amplifiers for the corresponding
channels. This three input amplifiers are made in this circuit work as
non-inverting amplifiers. The operational amplifier IC1a is the output
amplifier in this circuit. IC1a is wired as inverting amplifier here.
The output from each input amplifiers are given to the inverting
terminal of output op-amp. IC1a mixes the signals from each channel and
produces the required output.
Notes
Notes
- Use a good quality PCB to assemble this circuit.
- IC LM 348 operates from a dual power supply. A +12/-12V DC dual supply is used here for powering the circuit.
- The gain of individual channels can be adjusted by using potentiometers R5, R6 and R7.
Source -amplifierlab.com
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