Just a word of warning to those of you who may be thinking of using this filter with the Harman Kardon drive+play iPod interface.

It indeed does remove the whine sound from the audio system, but it also removes all lower frequency bass sounds. I had to remove it because I felt that I would rather keep the noise and still maintain the bass.

It worked just fine with my XM satellite receiver, though.

If anyone has a suggestion for a different filter that might work with the HK drive+play, please let me know!