After a tedious and long lasting process (>1 year) I have finally diagnosed and corrected the ground loop noise (ignition whine) in my Miata installation.

What I did, as a matter of a lucky guess, was run a ground wire from the sled (jamming it between the player and the sled) to the cigarette lighter socket.

To my surprise and gratitude the whine went away.

I had tried to ground the sled earlier in the process but sent the ground wire to the grouding point of the player....and that is what was wrong. I can't elexplain the reason why this didnt work, but to a different grounding point it certainely did work!

Also, upon fixing that issue I installed my old Sony cd mp3 player..and grounded that the the same point as the sled AND installed a noise choke between the line outputs of the Sony and the AUX input of the Rio...absolute silence.

The player now sound better as well for there isnt any drain of current that would have gone directly to the amps.

So, lesson learned: perserverance and creativity!

I was on the verge of scrapping the whole rio installation..but now tooling around town very happily!

Thanks again to all who contributed to this install!

Ed