I'm a relatively new bassist. When I play notes on the E string they are quite loud, but then when I switch to the A string my volume just dies. It's fine on the G and D strings too. What I want to know is, is there a problem with my pickups or something or is it my picking technique? I play with my fingers. Any help would be very welcome. Thanks.

I would look at the strings and the nut first. If the a string sounds dead "open" (unfretted) replace the string and have a tech check out the nut.

What kind of bass are you playing. On a P-Bass you can adjust the pup. Maybe thats the problem.