Benjroush

I recently hardwired an aux cord into the wiring harness behind the cd changer in my 2000 RX300. I used an RCA to aux cable, cut the rca plugs off and wired it into the harness. This required me to remove all the CDs or else the six input and cd would play over each other. This installation worked well, but if I turn off the CD player, I get a very loud, constant bass buzz from my aftermarket subwoofer. If I turn the headunit back on, the sound stops. Any thoughts on why or ideas to fix it? Thanks!