From the manual: "Headphones Jack: Accepts the stereo phono plug of headphones. The jack outputs the sound of front speakers only. To listen to the program source only with the headphones, turn off the power amplifiers as the unit does not turn off the line output when the headphone plug is inserted."
Hopefully your amps have volume controls, a mute switch or a standby switch.
Hopefully your amps have volume controls, a mute switch or a standby switch.