The other thing you can't not have is some way to get the sounds together on one cable and out to an amp or your computer. That's exactly what this module is for, with a little added extra: built in overdrive! 4 channels that are summed together and stepped down to line-level so you don't blow anything up & smooth, but gritty overdrive for when you want to get aggressive. Very nice when you have pulsing ambient drones going on.
In the article we cover op-amps as inverting amplifiers (and summing amplifiers), using op-amps on a single-rail power supply as well as decibels and how diodes in an op-amp's feedback loop create clipping.