HK 3390 and HK AVR 120 to one sub

Dan2036

Because my receiver has no pre outs i'm going to be forced to switch the wire in the back of my speakers to switch between HT and Stereo, i was just wondering if i could, instead of having to switch the sub input as well, have one line in from the stereo connecting to the L (White) input on the rear of the sub and the HT connected to the R (red) input ???