As Poor tom says, the Jazz growl is much about the location of the pickup - the bridge pickup to be more precise. The famous Jaco growl is often achieved on a Jazz by rolling off the neck pickup completely, rolling off some treble on the bridge pickup and picking the strings very close to the bridge pickup.
The pickup on a Precision is really more like the neck pickup on a Jazz, so you can't expect a Jazz bridge pickup sound from a Precision. Another famous Jazz bass sound is with both pickups on full. This gives a slightly mid scooped/out of phase sound which cannot be achieved on a bass with just a single pickup.
However, there are differences in the construction of a Jazz and Precision pickup, for one thing the coil in a Jazz pickup is much taller. This gives the pickup a different frequency response and overall output.
I had a pickup special made for me that essentially was a Jazz pickup in a Precision pickup clothing. I was very happy with the result, even though it didn't make my Precision bass sound exactly like a Jazz. It was built by a fellow Swede that runs a firm called 'Urban Pickups'. He is registered here under this name and can also be reached on
grafstrompickups@hotmail.com. He's not very expensive and he has also made other pickups for me and people I know who are all satisfied customers. I don't know of any production pickup from the major brands that incorporates this "Jazz in a P box" concept.
Of course if you want the whole Jazz bass deal in a Precision package you need to shop for an instrument with two pickups like the Special with a Precision neck pickup and a Jazz bridge pickup.
/Mats D
