ykphuah wrote:If I already have a recording, but I couldn't find a default bass amp modeling in GB that suits my needs, is there a way for me to use that recording and let it goes through Amplitube Ampeg?
You would want to use Inter-App Audio in that case. I am not sure if that is available on an existing track in GarageBand iOS, though.
EDIT: Another option, which may add a couple of steps, but give you the results you're looking for, would be to copy/paste your bass track into AmpliTube iOS (Or AmpliTube CS for iOS). Once imported, you can use the app's 'Bounce' feature to add your choice of tone, then copy/paste your bass track back into your GarageBand session.