If you are looking for a micro mixer circuit that create a simple, affordable, small and compact, and be usable versatile, must be this circuit. We can use to mix up to four input channels such as the microphone signal, FM Tuner, AUX and Other signals, As circuit shown in Figure 1.
How it works.
The input signal Input signal in each channel is entered through R1, R4, R6, R8, respectively, to potentiometer VR1-VR4. which is Adjustment value of Signal in each channel is the right size. Then is entered through a R2, R3, R5, R7 in together, and then pass through C1, R9 to input of IC1.
– The IC1(TA7137) is amplifier a signal that was introduced all together, Until the output signal at pin 8 through C7.
– The R14 and VR5 It is the adjust strength of the total output signal.
– The C3, C2, D1, D2 are feed back circuit for control gain of circuit to has level constant output signal.
– The LED L1 is a signal meter display that it flashes by the signal strength of the input voltage applied to the circuit.
Figure 2 PCB layout and positioning equipment.
The detail parts.
IC1_________________________________TA7137 PRE-AMPLIFIER(RECORDING OR PLAYING-BACK WITH ALC TRANSISTOR FOR TAPE RECORDER)
D1, D2______________________________1N4148___75V 150mA Diodes
L1__________________________________LED 2×5 mm
R1, R4, R6, R8, R12____________________10K____1/4w Resistors
R2, R3, R5, R7, R9, R14________________1K____1/4w Resistors
VR1, VR2, VR3, VR4__________________5K-10K___Potentiometer
C1, C8______________________________4.7uF 16V____Electrolytic Capacitors
C2, C3______________________________0.0033uF 50V___Polyester Capacitor
C4_________________________________30pF 63V___Polyester Capacitor
C5_________________________________47uF 16V___Electrolytic Capacitors
C6_________________________________100uF 16V____Electrolytic Capacitors
C7_________________________________3.3uF 16V____Electrolytic Capacitors
How to builds
We install all the components on the PCB correctly completed. According to circuit in Figure 2. When finishedwe can install it in a box ready, for ease of use.
In installed in the box, should be unloaded VR5 from PCB to hold separate. We can hold PCB to the box, with holding the potentiometer VR1-VR4 to box there.
Then we remove the LED L1 out away, to hold at the box. And then we wiring to the equipment Jack and the PCB orderly.