rockem said:
My problem is , that my bass sounds really thin
and I need in fat and large
That's usually an issue that involves four main things:
1) The bass itself, the quality of the model (American-made Precision, Jazz Bass, Musicman, etc. all = good. Ibanez, Epiphone, Court, JC Penny = bad), and the pickups. You're Yammy, by the way, is pretty respectable as a beginner's bass. It's nice to learn on, but I'm not sure I'd want it around for any serious recording sessions.
2) The type and condition of strings you're using (fresh=good. old, warn=bad. Light top, heavy bottom are nice if you want fat).
3) Maintanance; how long has it been since you've had it set up? If you play it regularly, then you should have it done
at least twice a year.
4) Technique. You'll get a fatter tone using your fingers instead of a pick (sorry if I'm stating the obvious). I've also noticed that
where you pick in relation to the pickups has a lot to do with the heft of the tone; picking directly over the pickups=bad, and is a good recipe for "thin." If you learn to play closer towards the
bottom pickup, it
will sound fatter. Those are just some examples of the role your technique plays.
Good news is that, overall, you're talking about an instrument that isn't very high-maintanace, here.

A lot of people get perfectly good, fat, round tone just plugging them directly in to the mixer, God love 'em. I think us bass players just get complacent because we have it so easy (we don't have to lug around drum kits or heavy guitar amps, we only have 4 strings to worry about instead of 6, etc.).
Again, though, it starts with the bass itself and the player. If you can get a fat tone out of your bass when you practice, then you should be able to get a similar fat tone to tape or disk without much difficulty. The trick, obviously, is to get that fat tone to begin with. -- Funny how that seems to be a recurring theme with recording in general and not just with the bass.
If you are indeed getting just that, and it's merely a case of that mamoth, girthy tone getting lost in a busy mix, then you probably just need to brush up on your mixing skills.