Sound Modifier

Four shape-controls portable unit

Wide variety of output waveforms

Circuit diagram:

Sound Modifier


P1,P3,P4________22K  Linear Potentiometers
P2_____________220K  Linear Potentiometer

R1,R15_________150K  1/4W Resistors
R2_____________220K  1/4W Resistor
R3______________56K  1/4W Resistor
R4_____________470K  1/4W Resistor
R5,R13,R14______22K  1/4W Resistors
R6______________10K  1/4W Resistor
R7______________33K  1/4W Resistor
R8,R10,R12______47K  1/4W Resistors
R9_______________1K  1/4W Resistor
R11_____________68K  1/4W Resistor
R16____________100K  1/4W Resistor

C1,C3,C5_______220nF  63V Polyester Capacitors
C2______________47nF  63V Polyester Capacitor
C4______________22nF  63V Polyester Capacitor
C6_____________100µF  25V Electrolytic Capacitor
C7_______________4µ7  25V Electrolytic Capacitor

D1,D2_________1N4148  75V 150mA Diodes

IC1____________LM324  Low power Quad Op-Amp IC

J1,J2__________6.3mm. Mono Jack sockets

SW1______________1 pole 3 ways rotary or slider switch
SW2______________SPST Switch

B1_______________9V PP3 Battery

Clip for PP3 Battery


Compared to common Fuzz-box devices, the Sound Modifier circuit allows a choice amongst a wide variety of output waveforms, thanks to its capability of mixing three different modified versions of the input signal.
This stand alone unit, primarily intended for electric guitars, is based on a low power quad op-amp IC and draws a very low current from a common 9V transistor battery.

Circuit description:

IC1A is the linear input amplifier. The input sensitivity of the circuit can be varied from -10dB to +10dB in three fixed steps by means of SW1, in order to cope with almost any pick-up type and model. IC1B forms a rather straightforward fuzz circuit, based on the squaring property of two back-to-back diodes connected across output and inverting input of the op-amp. IC1C and related components convert the squared output signal coming from IC1B into a triangle-shaped waveform. IC1D is wired as a virtual-earth mixer, summing the linear, squared and triangle-shaped signals coming from IC1A, IC1B and IC1C respectively.
A very accurate mixing of these three different signals can be done by means of P1, P3 and P4: the result will be an almost endless choice of different fuzz-effects.