There's 2 different output jack available on these basses. The original is a Switchcraft L113 and is wired like this:
(http://club.alembicguitars.net/Images/16271/130211.jpg)
We converted to the Switchcraft 53 jack in 2004 and it's wired like this:
(http://club.alembicguitars.net/Images/16271/130212.jpg)