I have just tried 3.5mm mini jack x 2 RCA lead from an iPhone 5 into my G61. It was dreadful. To get any sound level at all, I needed to put the iPhone volume at max and then virtually the same on the G61. That was with the iPhone volume limiter (that we have in EU countries) switched off. The quality was dreadful though.

I think better results can be obtained by using a specialist lead from the lightning connector, or an Apple TV or Airport Express into an optical digital input, but I haven't tried it as I was only experimenting.

.