Sorry to revive an older thread, but I was hoping to use the preamp outs on my Blaupunkt MP68. When I look in the installation manual, however, it only lists:

Line Out LR
Line Out RR
Line Out / Ground
Line Out LF
Line Out RF
12V Amp

My concern is that it doesn't list the polarity (+/-) for each line out. If it helps for reference, the manual is here: http://www.driscocity.com/MP68.pdf. The wiring images are the last four or so pages.

Has anyone use preamp outputs on a Blaupunkt receiver?