I just did some work on my car audio system and am having some problems with interference. I added a bluetooth receiver and wired it directly to my stereo cd player input. The receiver is powered from a 12V to 3.7V power supply. The cable from the receiver to my stereo is about 3-4ft long, and since the shielding is in contact with the bare ground, the shield is terminated at both ends, rather than just one. The setup works great with the engine off, but as soon as the engine is started, I get a whine that matches my revs. Any ideas for a solution? Is the problem likely to be with the audio cable, or with noisy power to the 12V to 3.7V supply?