What you did should work. As Marty suggests, you might not have had the volume on the iPod set properly. It's also possible that there was an impedance problem with your preamp. Try before you buy (as always), but in general feeding iPods into a system is no big deal.
How Can I Use MY IPOD For a Music Source?
I was wondering if anyone could tell me what the best avenue is for putting together a high-end system (speakers, amp, etc...) but running my music data off an IPOD? Is there a converter to take the info from the IPOD to the amp? I tried using a monster RCA connector from my IPOD into my Classe' CP-45 preamp and it was limited on the output. I've recently sold all of my equipment and looking to put a new system together and would like to use my IPOD as the main data base for my music. Thanks for any suggestions you might have.