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.

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: aaroncake.net

Audio Mixer based JFET 2N3819

This is the audio mixer circuit based Junction FET (JFET) of 2N3819.

Audio Mixer based JFET 2N3819 circuit diagram:

Audio Mixer based JFET 2N3819 Parts List:
R1, R3 = 10K Pot
R2, R4 = 100K 1/4 W Resistor
R5 = 6.8K 1/4 W Resistor
C1, C2, C3 = 0.1uF Capacitor
Q1 = 2N3819 Junction FET

Circuit Notes:

• As numerous or as few channels as are needed may be added to the mixer. Do this by just duplicating the input "sections" that are shown on the schematic design.
• A shielded case is perhaps necessary to minimize hum and support to avoid oscillations.
• The Audio Mixer circuit could be powered by a single 9 volt battery.

Original circuit page: go to this page

Low Cost Mixer Circuit

The following circuit is an easy, simple and cheap mixer circuit.

A simple mixer circuit suitable for mixing microphones or effects outputs. The overall gain from input to output is one if the pot related towards the input is full up. You'll be able to generate this a net gain of ten (or any other reasonable gain) by lowering the input resistor towards the second op amp. 10K in this position provides a gain of 10db, or 20db. If you are mixing effects outputs which have an output level control built into them, it is possible to dispense using the input level controls, or make some have level controls, some not. Audio taper pots are most likely better, but linear will be work.

For the op amps, pick a JFET input dual or singles, such as from the National Semi LF3xx series, or something such as the TL072 or TL082.

Download this Low Cost Mixer Circuit in PDF file:
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Mini Audio Mixer circuit

This is simple mini audio mixer. This circuit consume low current due to the simple design. Also featuring three inputs with switchable high/low sensitivity and unusual level-control circuits, providing high overload margins and low-noise figures, proportional to gain-level settings.

Component parts:

P1,P2,P3_________5K  Linear Potentiometers

R1,R11,R15_____180K
R2,R12,R16_______2M2
R3,R13,R17_____750R  (See Notes)
R4,R14,R18_______1K
R5______________15K
R6_____________220R
R7_______________1K5
R8_____________820R
R9_____________150R
R10____________100K

C1,C6,C8_________1µF  63V Polyester or Electrolytic Capacitors
C2,C4,C7,C9____100µF  25V Electrolytic Capacitors
C3,C5__________220µF  25V Electrolytic Capacitors

Q1,Q4,Q5______BC550C  45V 100mA Low noise High gain NPN Transistors
Q2____________BC547   45V 100mA General purpose NPN Transistor
Q3____________BC557   45V 100mA General purpose PNP Transistor

J1,J2,J3________3mm or 6mm Mono Jack sockets
SW1,2,3,4______SPST  Toggle or Slider Switches
B1_______________9V  PP3 Battery
Clip for PP3 Battery

Notes:

• When SW1, SW2 or SW3 are open the input sensitivity is suited to high-output devices like CD players, tuners, tape recorders, iPods, miniDisc players, computer audio outputs etc.
• When SW1, SW2 or SW3 are closed the input sensitivity is suited to low-output, low-impedance moving coil or electret microphones.
• Sometimes, the 750 Ohm value for R3, R13 and R17 resistors could be not easy to find. In this case, two 1K5 resistors wired in parallel can be used to replace each item.
• To make a stereo mixer, all the parts must be doubled excepting R6, C3, C5, SW4 and B1.

Simple Mixer circuit 3 Input

This is the very simple 3 input mixer for your audio system. You can add the number of input by adding some components for mixer input (P=10K R=22K). This circuit is only recommend for low and intermediate audio sound system. You need better mixer circuit for your high class audio system.

Here the Schematic diagram:

This is component layout:

And here the PCB layout: