dnpainting
Super Member
1.0 volt is the maximum output from the iPhone headphone jack. This is low and will not hurt your receiver. Many CD players and tuners put out about 2 volts and get plugged directly into the RCA input of receivers or amps. Don't believe me (or anyone on the internet) check the output specs on your phone and the input specs on your receiver.
My apologies for giving the incorrect information. I had read an article, in which I now can't find, that stated it can be dangerous because of voltage levels being too high and you should always use a dock for line level input into stereo. After Reynolds531 information, I did find this article:
http://beavishifi.com/articles/headphonejack/
Again, my apologies!