Classic active tone control circuit using ICs

A stereo pre amplifiers with active tone control circuit that has been popular for more than 40 years is this circuit which use the RC4739 as main components.

Due to its features that the bass heavy, and treble sound is crystal clear. Due to its features that the bass heavy, and treble sound is crystal clear, still chose this project.

schematic  circuit diagram
Figure 1 the schematic circuit diagram

This pre tone include of 2 main sector are:
– The first, IC1 act as the pre amplifier circuit for the signal amplifier from the Magnetic pickup or microphone and
– The second, IC2 is the low noise pre tone control circuit.

Both transistors Q1,Q2 act as the impedance matching to between the input and the tone control

PCB layout
In Figure 2 show the PCB layout and

the components layout
Figure 3 the components layout

Which is designed to work more convenient and have also the loudness switch on PCB.

How to builds

We assemble the device onto the PCB correctly, The polarity of the electrolytic capacitor must be careful to alternates a pole is strictly prohibited.

The transistor is shown in the picture for the number BC557. If the number MPSA42 to switch the position of the emitter legs and collector into the opposite direction.

What needs to be extremely careful Tools for Beginners soldering points. Requires heating the solder sufficient to ensure that the solder intimacy as well.

But be careful not to heat the solder too much as well. We might device and the plate was peeling off the print line.

Another way to help is going to be a simple soldering pins are clean at all times.

When finished, and then checks the power to the circuit properly. The output of the circuit to the main amplifier circuit. And the signal from the CD player input to input validation to works by adjusting the buttons. To obtain the desired result.

For those who want to The Gramophone player a needle in Magnetic form to input of the pre amplifiers then connect it to output of the pre tone circuit.

Now if you use the pre mic instead should modify the feedback circuit to new as Figure 4

modify  the feedback circuit into the pre microphone system
Figure 4 modify the feedback circuit into the pre microphone system

Parts you will need
IC1_____RC4739N Low Noise Dual Operational Amplifier____________= 2 pcs.
Q1,Q2___BC557 or MPSA42___45V 100mA PNP Transistor___= 2 pcs.
C1,C9,C12,C15,C16___10uF 25V Electrolytic capacitors_____ = 10 pcs.
C20,C21,C22,C23_____10uF 25V Electrolytic capacitors_____ = 10 pcs.
C2__________________4.7uF 16V Electrolytic Capacitors_____ = 2 pcs.
C3__________________0.0022uF 50V Ceramic Capacitors___ = 2 pcs.
C4_________________680pF 50V Ceramic Capacitors______ = 2 pcs.
C5,C6______________0.0047uF 50V Ceramic Capacitors_____ = 4 pcs.
C7_________________0.001uF 50V Ceramic Capacitors_____ = 2 pcs.
C8_________________0.01uF 50V Ceramic Capacitors______ = 2 pcs.
C10,C11___________0.0033uF 50V Ceramic Capacitors______ = 4 pcs.
C13,C14____________0.033uF 50V Ceramic Capacitors______ = 4 pcs.
C17_______________330pF 50V Ceramic Capacitors________ = 2 pcs.
C18_______________100pF 50V Ceramic Capacitors________ = 2 pcs.
C19_______________390pF 50V Ceramic Capacitors________ = 2 pcs.
VR1_______________50KACT____Potentiometer____________ = 1 pcs.
VR2______________100KMN_____Potentiometer____________ = 1 pcs.
VR3,VR4__________ 100KB______Potentiometer____________ = 2 pcs.
R1________________47K__0.25W Resistors________________ = 2 pcs.
R2_________________1.2K__0.25W Resistors_______________ = 2 pcs.

R3_________________1M__0.25W Resistors________________ = 2 pcs.
R4_________________100K__0.25W Resistors______________ = 2 pcs.
R5_________________ 10 ohms__0.25W Resistors___________ = 2 pcs.
R9_________________2.7K__0.25W Resistors_______________ = 2 pcs.
R6,R8______________2.2K__0.25W Resistors_______________ = 4 pcs.
R10________________270K__0.25W Resistors_______________ = 2 pcs.
R7,R11,R12,R13______10K__0.25W Resistors_______________ = 8 pcs.
R14,R17_____________ 10K__0.25W Resistors______________ = 4 pcs.
R19_________________ 470 ohms 0.25W Resistors_________ = 2 pcs.
R10________________270K__0.25W Resistors_______________ = 2 pcs.
R20,R21,R22,R23_____100 ohms__0.25W Resistors___________ = 4 pcs.

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