I just wanted to let people know about this since this helped me with a very annoying problem. I have an ELE fm transmitter which is a real cheap POS (don't buy these). As a result, I had this really annoying 60 Hz buzz in the audio when it was connected to my computer. Other transmitters I've used on the same desktop haven't had this problem.
Anyway, I was able to solve it with a $20 ground loop isolator from radio shack. You can also get them online (like Amazon) for around 10 bucks. This fixed the problem completely. During periods of silence I now really do have silence on the other end.
The best part it is doesn't affect the music or audio quality. All audio frequencies go through just like they did before. I can even play a 60 Hz test tone and it still goes through loud and clear.
So is the RS unit basically a 1:1 audio transformer? If so I had to use something very similar for my AM unit.
I never realized how annoying problems like that could get until I had them myself. It becomes really bad when going from balanced audio to unbalaced and vice versa.
Sometimes a few wraps of the audio cable around a toroidal core can help in this situation also.