Hi first time poster here. I'm wondering if I have blown my stereo?

i just bought a sirius radio unit and had the idea of hard wiring it into my head unit through the rear rca jacks. i pulled the head unit and there were 3 sets of rca jacks on the back. i tried the purple wires which i dimly recalled were the aux ins. nothing happened. then without thinking i tried the other two jacks as well. each time there was a signal from the sirius. after this i notice the head unit is perfectly functional but makes no sound except a tiny tinny sound at max volume on one rear speaker .

fuse seems good. it seems to be well grounded by a bolt on the cage that attaches to a frame. did i blow the amp by sending a signal in though the rca outs?

head unit is a clarion ARX7470. it's an old but nice unit and i have a 12 disc cd player with it so would not want to lose it.