I would like to use it as a pre to improve the quality of my recording (I am using a Tascam DR-40) but i don't know if it is really worth :)
Are you sure you have the correct product? The Art Phantom II Pro is a 48V power supply and performs no amplification. In principle it adds no noise since the signal passes through it unaltered, but adding a phantom voltage source is never a totally noise-free operation.
uh, no, i do not know that, thanks for telling me :)