I noticed that Gary suggests to use the PA2V2 "In a vehicle between a portable player and the AUX input jack"... so I had to try it. Wow, this little thing instantly turns my Elantra's crappy stock stereo into a rather decent system! Night and day. Easily, the best bang-for-the-buck upgrade anyone can make to their car audio.
Great suggestion, have to give that a try this week on planned trip!