No, you don't have to have output coming from the UX1. I have the output coming from the computer speakers/headphones from the computer.

Thanks for your reply though.

I had a techspert help me out last night and have resolved the issue.

I thought I'd post it for anyone else who has the same problem.

On the Mac, in the main System Preferences under the Apple icon you can access the Line6 driver, called "Line 6 Audio-Midi devices" down at the bottom of the panel under "Other".

If you click on this it will tell you it has to reopen the System preferences to access this driver. Just click OK and it will reopen and bring up a control panel for the Line 6 driver.

Click on the "Inputs and Recording" tab.

This will show a panel with a drop-down selection menu headed "Input Select". These allow you to choose which Inputs the UX1 will have activated.

You can choose from      - Mic 1

                                     - Line 1

                                     - Line 2

                                     - Line Stereo

                                     - Line 1 & 2

                                     - Instrument

                                     - Inst. & Mic 1

For some reason it's default setup is to have "Instrument" selected so therefore it is only accepting a signal from the UX1's Instrument port.

I was trying to get a signal through the UX1's microphone jack, and hence was getting no signal at all in garageband.

You still have to select the UX1 as the Input device in both the System preferences and Garageband preferences.

Hope this helps someone