Are you using steel strings or Nylon ? My buddy had steel string and was using a P-bass PuP mounted on a piece of Plexiglas at the bottom the fretboard. (I think he got that Idea from Lee Rocker?) Then he switched to Nylon strings he had to start using a piezo system. I'm not sure what he did.
But I know took it around the block to his neighbor Jess Oliver (who plays Dbl Bass BTW) Not sure what Jess did? But it is nice having the Leo Fender/Jim Marshall of Bass amplification as your neighbor .
Its for my friends double bass, shes using steel strings but she wants to change to gut strings...
Can you suggest a website or brand that has a way of amplifying the sound.
Check out Fishman's website, they make excellent pickups for double bass. Don't forget where you are as well, Duncan also has the same pickup system for double bass.