Receiver hum is the most common call I get, and it almost always sorts into one of two families.
Family one: the hum is a ground loop, not bad gear. A steady drone that is there at idle and does not care where the volume knob sits. Suspects, in order: a cable or antenna connection dumping ground noise into the system, a network cable doing the same thing, and gear sharing outlets on different circuits. The diagnostic that costs nothing is unplugging sources one at a time, then trying a different outlet. A cheater plug can tell you that you are on the right track, but treat it as a diagnostic only — a lifted safety ground is how equipment gets hurt.
Family two: the hum is inside the receiver, usually power-supply filter capacitors getting tired after fifty years. That hum often grows with the volume and tends to arrive with softer bass. That is bench work, not forum work.
One test separates the families: unplug every source and leave only the receiver and speakers. Hum gone? Ground loop. Hum stays? Inside the receiver.
Which family is yours? Post when it started and what you have already unplugged — that information alone usually narrows this to an answer fast.