I found the seven page Audio Refinement Complete Alpha manual, and this is what is says regarding the "IR Sensor and Pre Out Indicator" which is on the front panel at the center bottom. I quote directly, bad grammer, typos, and all.
"IR SENSOR AND PRE OUT INDICATOR: This sensor receives a signal from the remote handset, it also used for the function of indicating pre-out is enabled, as you press the "AMP" button on the remote control and then press "STOP" button, a light blue LED behind the acrylic under the panel will lit up, indicating that the per-out function is enabled. Pressing "STOP" button one more time will turn off the LED and return to the original state without pre-out."
"PRE-OUT: Pressing the remote control of "AMP" button, then press the "STOP" Button, after 3 minutes the pre out function will be enabled, the signal will through volume control and could supply to subwoofer or power amplifier."
"IR SENSOR AND PRE OUT INDICATOR: This sensor receives a signal from the remote handset, it also used for the function of indicating pre-out is enabled, as you press the "AMP" button on the remote control and then press "STOP" button, a light blue LED behind the acrylic under the panel will lit up, indicating that the per-out function is enabled. Pressing "STOP" button one more time will turn off the LED and return to the original state without pre-out."
"PRE-OUT: Pressing the remote control of "AMP" button, then press the "STOP" Button, after 3 minutes the pre out function will be enabled, the signal will through volume control and could supply to subwoofer or power amplifier."