I'm pretty sure that something inside the unit near the connector is loose or is scraping the drive tray or something. Today I'll open it and see if I can locate it.

Well, I didn't find any loose wires, but I think I've solved the problem. Here is what I think happened:

The second disk drive's IDE cable was pressing against the differential amplifier sub-board. The board was getting pushed down at a slight angle, and I don't think that's good for it. This alone wasn't enough to cause a problem, but the wires that run from the docking connector to the differential amplifier would move slightly as the unit was plugged and unplugged, exacerbating the problem and causing the noise. This also explains why I couldn't hear the problem through the in-home audio plugs, only the car plugs.

So I adjusted the IDE cable and re-kinked it in a different way so that it didn't rest against the differential amplifier board. The noise problem seems to be gone for now. Hopefully this fix will last in the long term.

To be fair, I'm the one that installed that second drive, so any problems that result from it are entirely my fault.

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Tony Fabris