| Hey Gretok, I have read some reviews that unanimously report there to be a little less gain from these. Even though they are passive, the recomendation is to use these with a pre amp( tone circuit ) if your input stage of the power amp you're using does not send enough signal to the output side of your power amp. Or if you wanted more signal. That's about all I can tell you. Do some searching, there are some specific comments and recomendations from users that run that pickup or set.
Good luck | 
Bartolini 9j-l1 
