Aphex IN2 - Manual (Page 7)

You should now see signal on the input and output meters and hear yourself in
the IN2 headphones or speakers.
Logic Pro X
Launch Logic Pro X, select New Project and click on the Empty Project sheet
music icon. In the bottom right corner click on Choose.
Click on the microphone icon for Record using a microphone or line input.
Below, select Input 1 and Output 1+2.
Click the check box for “I want to hear my instrument as I play and record.”
Click the check box for “Prepare new audio tracks for immediate recording.”
Click the arrow to the right of “I hear sound from:”
This brings up the Preferences screen.
Select IN2 as the Input and Output device.
Set the I/O Buffer Size to 64 samples.
Click Apply Changes and exit the Preferences screen.
Back on the previous screen click Create.
The new track should open armed for recording with monitoring on.
You should now be able to hear yourself in the headphones or speakers.
Ableton Live 9
Launch Live and go to File-New Live Set.
Go to Live-Preferences and click the Audio tab.
Set Driver Type to Core Audio.
Under Audio Input Device select IN2 (4 in, 4 out)
Under Audio Output Device select IN2 (4 in, 4 out)
Select sample rate and set Buffer Size to 64 Samples.
Exit the Preferences window.
Open the mixer view.