FWIW when a hum increases when you turn up the volume it is unlikely that it really is a ground loop and I would doubt that a ground loop exterminator, whether a cheater plug or a more 'sophisticated' one would help. But you might try identifying which source is generating a hum itself and attaching a cheater plug to its power cord. That might help, or not, but the cheater plug only costs a couple of bucks. Disconnect and unplug all of your sources and see if there is any hum. Then reconnect each component PC and IC one at a time and see when the hum appears. Then put a cheater plug on the PC going to that source.
FWIW.
FWIW.