Monday, June 20, 2011

Mic Audio Mixer Circuit

The following design is the circuit diagram of microphone audio mixer with 3 input channels. It use 741 op-amp to amplify the input signal. This circuit can be used for dynamic microphone.
Mic Audio Mixer Circuit diagram

Components Part:
R1, R2, R3 = 1K
R4, R5, R6 = 10K Logarithmic Pot
R7 = 1M
R8, R10 = 10K
R9, R11 = 100K Linear Potensiometer
C1, C2, C5, C6 = 100nF
C3, C4 = 22nF
U1, U2 = IC 741 Op-Amp
J1, J2, J3 = Input Mic Jacks
MISC = Board, Wire, Knobs, IC Sockets

Mic Audio Mixer Circuit Notes:
  • R1-R3 are volume level control on each input. R9 and R11 will control bass and treble for all input.
  • The circuit only need low current to run, two 9V batteries which connected in parallel can be used for a power supply.
  • The placement of the mixer in a metal case and connected the ground to the case will cut down on noise.

Circuit Source:

About Audio Amplifier
An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.

The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio amplifiers require these low-level inputs to adhere to line levels.

While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts. More explanation about power audio amplifier can be found at

This is a video tutorial about how to a very simple audio amplifier based on the LM386 amplifier chip. It can be built for less than $20 (or might be less than $8 in some countries) and used to amplify any low level audio signal including a guitar, bass or mp3 player.

Watch the video:

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