I have a 2003 Boxster with the CDR23 radio and external amplifier mounted in the front trunk. There are two multi-pin connectors, a fiber optic connector and an antenna connector on the rear of the head unit. The display on the head unit in the car seems to be fine as the display appears to be working as it should. The problem is no sound out of any speakers. The problem was intermittent for quite a while as sometimes when I started the car I would have sound from the speakers and other times no sound. Sometimes I would be driving and the sound would suddenly just quit. Now there is no sound at all, but the head unit display still appears to be working ok. Does anyone have any suggestions as to what might be the problem?