Essentially, the circuit consists of an IC 741 whose gain at various freguencies is determined by corresponding potentiometer setting.
power supply for the circuit can be derived from the amplifier / preamplifier itself. The wide rangeof supply voltage (6V-20V) makes the circuit very versatile. Power consumption is negligible.
R1,R2,R3,R4,R5,R6 : 27kΩ C1: 100n C6: 300pF
R7: 470kΩ C2: 33n C7: 100uF/16V
R8: 330kΩ C3: 10n C8: 4.7uF/16V
R9: 100kΩ C4: 3.3n C9: 47uF/16V
R10: 4.7kΩ C5: 1n IC1: 741 Op amp
VR1,VR2,VR3,VR4,VR5,VR6: 100kΩ Linear Potentiometers