Yes, there is a separate fuse in the fuse panel for the audio system.
From '03+, Porsche used the MOST (fiber optic) loop system daisy chaining the head unit, amp, and any accessories (NAV, CD changer, etc) together. Thus, there aren't any traditional line level outputs or amplified outputs from the rear of the head unit.
See this thread for more help/info...
renntech.org/forums/index.php/topic/25829-becker-cdr-23-pinout-or-connector-wiring-diagram/
Congrats on your new to you Boxster
