Recently i got a mac and one of the reasons i did so is for garage band. but anyways i recorded one song, did all the parts. it came out great. But now im working on a new song. what im trying to do is plug my 1960's fender amp into my mac so i can get the same distorted sound that the amp produces. the amp has a plug in the back for EXT. Speaker ive tried plugging that into the line in on my mac, doesnt register at all. thats all i usually do is plug my guitar or bass in with and instrument cable to head phone jack adapter to the line in, that works for me fine. but is there any way i can get this to work. 60's fender amps sound so great when the break up.