I have been experiencing a crackling sound after enabling the PulseAudio Equalizer.
(the following answer was provided by OP himself, but was originally included in the question body.)
Searching for a solution I found one within the Arch wiki and I wanted to share it with everyone. This typically affects machines with Intel sound chips.
sudo -i scratch-text-editor /etc/pulse/default.pa
Add line below to end of file, then save
load-module module-udev-detect tsched=0
Then type in terminal:
pulseaudio -k pulseaudio --start
I've added this to the elC - elementary Combobulator project as well.