I wonder, did Jason ever use an Alembic with Flotsam & Jetsam (his pre-Metallica band)? I have seen a couple of pics of him with the Exploiter looking bass pictured above, and indeed he is wearing a F&J shirt in the pic. The pics looked either pre-Metallica or very early on his Metallica career. It seems unlikely he would've been able to afford an Alembic before Metallica, but who knows...He did have some good gear with F&J, and he was probably putting all of his money back into the band at that point, gear before food even, I'd guess. haha.
Also, I wonder why, when he joined Metallica in late '86, he chose (or was he forced?) to play the very plain looking Warmoth P/J bass when in F&J he was playing some very interesting basses such as a BC Rich, an old G&L SB and possibly the Exploiter above?
I can definitely see Lars and James telling him hey, you can't be playing a flashy bass like that - just get a Fender. Don't try and hog the spotlight if he had tried to play the BC Rich or Exploiter. Of course, soon he would be playing higher end stuff like ESP (no surprise given the band's relationship with them), Wal, and Alembic. There was that period from '87-88 or so, where he kind of rotated between those before settling on the Alembics through the Black album tour.
As for his Sadowskys, they're OK but I prefer the look and sound of pretty much all of his other basses (especially the Wal and Alembics). The Spector era (like '94-'95) was shortlived, due to electronics cutting out because of his profuse sweating, I believe, hence the infamous bass-in-the-bathtub-filled-with-salt-water-tests.
