The first preamp I installed in Marcus' bass was made by Stars Guitars in San Francisco. It was a treble and bass boost circuit. About a year later they went out of business. They recommended I use the Bartolini TCT from that point on, which was a very similar circuit. At some point, the Stars preamp failed in Marcus' bass and I replaced it with the TCT. That is the circuit he has had ever since. In 1990 I began making my own circuit and that is what Marcus has in all of his other Sadowsky basses.
Roger
Thanks a lot for the info Roger.
I love Macus' slap tone as everybody else, but IMO there is nothing as sweet as the bass boost that your preamp gives.