K&K's Trinity system blends the K&K Pure pickup system with an internal gooseneck microphone. It's worth noting two things about this pickup: First, it has the potential to produce absolutely stunning tone. When you listen to some of the recordings available online, you'll likely be blown away by what you hear. However, the combination of a microphone and a soundboard pickup is a recipe for feedback in louder stage situations. So I tend to recommend this pickup for either recording or use in smaller solo settings, perhaps acoustic duos. Not loud stages.
The Trinity Solo 12-String listed here features the same internal guts as the regular Trinity system, but no external preamp. This is the system to get if you already have a way to blend the two signals externally, or if you're considering buying a different blending preamp like the D-TAR Solstice.