Circuit diagram:

Parts:

P1,P2_________100K Linear Potentiometers
P3____________470K Linear Potentiometer

R1,R2,R3_______12K 1/4W Resistors
R4,R5___________3K9 1/4W Resistors
R6,R7___________1K8 1/4W Resistors
R8,R9__________22K 1/4W Resistors
R10___________560R 1/4W Resistor
R11___________100K 1/4W Resistor
R12___________220R 1/4W Resistor

C1______________1µF 63V Polyester Capacitor
C2_____________47nF 63V Polyester Capacitor
C3,C5___________4n7 63V Polyester Capacitors
C4_____________22nF 63V Polyester Capacitor
C6,C8_________100µF 25V Electrolytic Capacitors
C7______________4µ7 63V Electrolytic Capacitor

IC1___________TL061 Low current BIFET Op-Amp