Well I finished my line out cable -> car stereo project and it works great. For the cable, I just rewired an existing Sandisk cable. The cable provides 5 V for charging, and audio on the green and white USB data wires. On the cable’s circuit board, I cut the traces between the pins and the green and white wires, and re-routed those wires to the audio pins (27 and 28). Also tied pin 7 to pin 22 to enable the audio. I run 5 V into the red wire and use the cable shield as its ground return path, while the black wire is the ground reference for the two audio wires. I found that it is important to keep the audio ground wire separate from the charging ground (although they are tied together in the Fuze), because otherwise a lot of noise shows up in the audio. This works because my car stereo has + and - inputs both isolated from ground, so the black wire is tied to the - inputs for both channels and the green and white wires go to the separate channels’ + inputs.
The cable of course no longer functions as a computer sync cable.
I built a little circuit board with a 5 V regulator and heat sink, and a USB Type A receptacle, which fits right under the stereo.
I like how the latest FW disables the volume control. Now there’s no danger of messing up the headphone audio level accidentally. Sansafix, if you’re listening, I’d like to recommed disabling the equalizer when line out is enabled. Equalization should be the job of the system you’re driving with the Fuze. I’d like one equalizer setting to compensate for headphone deficiencies, and a flat output for line out, without having to manually change the settings when switching back and forth between the two.