http://support.fender.com/manuals/ba...nual_rev-A.pdf
NOTE: Both INPUT 1 and 2 can be used simultaneously for
two instruments. In this situation, each input will have a
lower input sensitivity (-6dB).
AUX IN — Plug your CD player or mp3 player in here.
The amp controls do not affect this input. Adjust the
volume or tone of the aux signal at its source.
Also the inputs have different impedances: 1MΩ (Input 1) / 136kΩ (Input 2) / 10kΩ (Aux In)