Ultimate Bass Rig gave you all the bass tones you need for a normal setup. Recently however, after listening to the band CAIN I was impressed by Madison's P-Bass tone, and immediately set out to get that tone from my J-bass. This is the product of that experiment!
The signal chain is very simple: just a compression pedal, an EQ pedal that boosts the lows and low mids, then the preamp, and finally an overdrive pedal. Complete with a volume pedal, this rig gives you lots of space for you to add pedals if you want to. I now primarily use this rig for all my bass tones, and I absolutely love it. It may not sound exactly like a P-Bass, but it's good enough for me. If you have a J-Bass, I think you should definitely get this rig. Bonus point: it's free!
IMPORTANT: You need to make sure that only the neck pickup is on (turn off the bridge pickup) to get the best tone. Also, turn the tone knob down (but not all the way).
Tip: Try turning on the "DIST" (distortion) and palm mute with a pick. Oooh yeahh!!