While surfing the internets, I found this list of drummer jokes that someone has maliciously edited into bass player jokes. These are the worst ones. This is not funny at all. This is the sort of thing that gives guitarists a bad name.
Q: How many bass players does it take to change a light bulb? A: Only one - but the guitarist has to show him first.
This is a selectable onboard passive distortion circuit using clipping diodes wired to ground. All solid-state 'artificial' distortion circuits, no matter how expensive, have something like this at their core. Instead of requiring power, this circuit uses the output of the pickups themselves and therefore should work better with higher output pickups. It uses a 2-pole 4-position rotary switch to select various combinations of diodes for different degrees of distortion, or none. You could also select one of the diode combinations and wire it to a push-pull switch for a single level of distortion, or even wire it to a separate 'volume' control to control the resistance to ground and therefore the amount of distortion. The diodes cost pennies. I have yet to actually try this one, but when I get back to building six-strings, I definitely want to.