Just get an AC/DC converter, hook the amp to the converter, plug the converter into the wall, and turn the radio on. No need to jumper anything, or risk frying something. You can get the converter at Radio Shack.
<span style='color:green'>Nobody likes you.</span><img src='http://www.bmw-forums.com/forum/html/emoticons/ph34r.gif' border='0' alt='user posted image' />
<span style='color:green'>Are you experienced, little girl? I want to know what goes on in your little girl world.</span>
<span style='color:green'>I'm the man! I'm bad, I'm so bad I should be in detention. I'm the man!!!</span>