I am working on a tremolo guitar pedal circuit. A tremolo pedal basically attenuates the guitar signal using a pattern. Most tremolos use a combination of LEDs and LDRs to do this, but since I do not have any LDRs at the moment I chose to design one using a digital potentiometer. For simplicity I have not included the digital side of the circuit. This only consists of an Arduino Nano, connected to the digital potentiometer using SPI. I have breadboarded the circuit and it works, except it makes a ticking sound. It is very noticeable on the high gain setting on my amplifier. At first I thought it was an issue with the Arduino, but after removing both the Arduino and the digipot -- and replacing the digipot with a resistor -- the issue persists. I have no idea what is going on. Could it be an oscillation of some sort? Should the schematic work and lies the error in my breadboarded implementation?
Thanks in advance!