Hi. I'm recording a song in GarageBand and all is going well with the amp mods and in built stop boxes. However, I want to use my Digitech Whammy to get a decent octave down sound (non of the in built effects have this as far as I can see) but when I try and plug in I don't get a signal at all. Is there a way to get this working? I'm simply using a jack to mini jack converter (like this) and don't have the cash to buy an audio interface. Id this doable or is there any decent pitch shifter plug ins available? Thans for any help anyone can offer.