I recently bought a Carvin B4f that I really like, however I just plugged it in and no sound is coming out through active output. I have passive, so I fugred the battery was dead. After fresh batteries it still wasnt making sound, so I called Carvin and they are sending out a new active/passive module. I asked Carvin if they knew of any replacement active/preamp modules to put in instead, however they said that there was not as there are 5 posts, etc. My question is has anyone replaced the preamp with another third party replacement? How did it sound? I heard that Sadowsky doesnt make a replacement, maybe Aguilar? Thanks.