The amp is going draw to much amperage for the transformer. It might work at low volume but will start to starve for DC voltage as you crank it up.
Call these guys talk to tech department
http://www.casmfg.com/Accessories.htm They sell the transformer/Voltage Booster/Power Inverters.(check link)
The audio input would work from the I-tunes, the problem is not enough DC juice to drive amp.
Check this post for diagrams and links.
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=853440#Post853440 If you need more info let me know.