I just did the hardwire from my Sirius receiver to my Alpine deck via the A1net cable into the aux input and now I have horrible alternator whine, but only when I'm listening to the satellite radio. The CD player and FM radio sound fine and before, when the Sirius receiver was running off the FM modulator, there was no issue either.

Any ideas what this could be or how I could fix it?

Thanks!

 

Try a different grounding point for all of your grounds stereo related.