recive IR from 1/16" jack

I have a large theater setup with separate amplifiers for each channel. currently I have a very simple program controlling the main amplifiers. when the audio processor is turned on(from 1/16" jack from Harmony RF Wireless Extender) the USB port turns on powering the arduino and starting a simple set of instructions to turn on relays 1 by one with a small gap in-between. my problem comes with my larger Amplifiers. I have a couple 5000W amps running several 18" subs and I down need them on for TV watching. they kick out way to much heat. what I want to do is add a command to my Harmony 1100 to turn on and off the larger amplifiers. I can find a lot of info about adding an IR eye but nothing for adding a 1/16" jack. I would assume I could just put the jack in place of the eye but I am not sure the voltages and don't want to fry the arduino.

I cannot use an IR eye as all equipment is in a rack in another room. commands are sent RF to the Harmony RF Wireless Extender which converts it to IR and sends it over 1/16" plugs to all my equipment. I do have the option to add IR blasters but would like to avoid that if possible. I just need simple discreet on and off commands and will add a movie mode to my remote to turn on or off the big subs. they will be normally off unless I turn movie mode on.