Thanks for that reminder, TMan. Fortunately, I ended up making a loopback connector that was only inserted when the Empeg wasn't inserted. So that problem didn't affect me, but it's always good to note here just in case someone else comes along reading this thread later.

So far, the project is going well. The loopback connector works well, even when I connect the iginition pin directly to the amp remote pin. No giant amplifier pop noises when I turn the ignition on and off. So that's good.

The real problem, which I hadn't thought of when I started the project, is that the loopback connector idea doesn't benefit from the Empeg's fantastic equalizer. So I get a flat-sounding connection for any device that I plug into the aux when the empeg isn't installed. Ick.

So I've bought a small line-level EQ unit in hopes that I can make it work as part of the loopback connector system. It just came in the mail and I haven't opened the box yet. Not quite sure how I'm going to mount it and such, but I'll come up with something, I've got some options.