Something is not well-grounded like a cable, or you are using multiple AC circuits for all of the components. They should all be powered from the same AC outlet preferably. Try that.
Hum from devices.
Hi my setup denon dcd-510ae to musical fidelity v-90 dac to musical fidelity v-can to headphones. There is hum in the left ear headphones when everything is on but nothing is playing a song. Now when I either touch without letting go of my hand my dac or v-can, the hum goes away. But when I let go of my hamd the hum comes back. What can I do ?