I suspect that control signal is digital and not likely a source of hum, but you might check out the condition of the satellite cable(s) just to be sure. But you won't know if you don't try.Edit: There is one more connection here: the right-side satellite probably has an on/off volume/balance control that somehow has to communicate with the amplifier. Some might not be possible, or be worth your time. Some of these are easier to diagnose and fix than others. Could be as simple as a loose ground wire, or a shot filter cap, or a cold solder joint that finally gave way. If the former, (1) how good are you with a screwdriver, soldering iron, and multimeter and (2) how badly did you need new speakers anyway? - View image here: -If you do dig into it, keep in mind it may be more of an educational field trip than a successful repair. First off, if the PSU has a three-prong plug, is it plugged into a properly polarized and grounded mains outlet? If so, is the power supply integrated into the sub-woofer, or is it an external brick? If the latter, you might be able to find another similar unit to test it against.
