I have a passive Carvin B50 with two volumes and a tone control. It has their quieter H50A pickups. I would like to add a preamp to boost the signal a bit. What I need are suggestions about which preamp to consider that won't require major surgery to the bass. I like the EMG BTC but have been told that it can only be used with EMG pickups. Sounds like marketing to me, is there any truth to it? My plan is to keep the three control knobs with two volumes, but add a stacked bass/treble boost. Guidance would be appreciated. Thanks.