Ah. Problem solved, just some shielding worries.
However after case testing in the car, I realize that a lot of inteference is introduced by my PDA charger, which heart is essentially a MC34063. I believe that this is due to grounding issues, something about mixing power ground and audio ground?
My PDA has both audio ground and power ground. Currently, the audio ground is wired to the preamp(s) ground, which is also wired to the car ground (aka bare metal). Although this would constitute mixing of grounds, there is no choice. However, there is zero noise with this setup.
The moment my PDA charger is plugged in, which 5v and power ground is wired to the previous ground, ground looping comes into play.
What methods can I use to isolate the audio ground away from the power ground? i'm not sure how to do that (in the sense of wiring the input ground, which i guess is the best solution)