First, this is not speaker hum but a ground loop hum in the electronics.
Second, there are devices that will stop the hum but not cure it. In other words, the ground imbalance remains, so it would be better to cure it than put on a band-aid.
From your description, it is coming on the signal with each IC and that suggests the hum is being generated in the preamp. What happens if you remove each of the input ICs to the preamp? That should isolate the input device that is causing the ground loop. Are all your input devices on the same AC line?
Kal
Second, there are devices that will stop the hum but not cure it. In other words, the ground imbalance remains, so it would be better to cure it than put on a band-aid.
From your description, it is coming on the signal with each IC and that suggests the hum is being generated in the preamp. What happens if you remove each of the input ICs to the preamp? That should isolate the input device that is causing the ground loop. Are all your input devices on the same AC line?
Kal