line level input to mini plug

Didnt know where else to put this, but I figured someone here would be able to help. My gf has the Athena Ivoice ipod speaker. It has an aux input which is a mini plug mainly for use with other devices which do not dock with the system. I figured I could use the input for her DVD player rather than use the crappy tv speakers, however when I hooked it up it sounded really bad with LOTS of distortion. This was through the L/R outputs of the DVD player to the Aux input using a mini to Rca adapter. Are these line level inputs too strong? (The Aux input does sound fine when used with an ipod.)