Guess I should have read the manual
Among the features that make AXE I/O the definitive guitarist interface is the Re-Amplification feature. The “AMP OUT” is a fifth physical output which is independent from main Output 1-2 and 3-4. With this output, you can feed a DI recorded guitar to external analogue stomps or a real amplifier, still being able to monitor the session from main Output (1-2). The external stomps (or the miked amplifier) will be connected back to Input to return into the DAW on a newly recorded track.
The AMP OUT is a floating unbalanced output topology specifically designed to properly interface with guitar or bass amplifiers of any kind for maximum signal fidelity and integrity. This ensures the immunity from noises caused by ground loops with the Amps, so actually allowing reamping without the typical associated noise/hum issues.
please close - very cool feature