Sherwood AX-4050R amplifier is humming why that?

Sa
- in PlayStation
2

Today I connected my Orbid SO and pluto to listen to music on a Sherwood AX-4050R stereo amplifier. And now I connected the aux cable to my Samsung UE28590D monitor because I'm currently playing 4 games with the Playstation, then I switched on the amplifier and there's a humming sound as soon as I increase the volume but the ingame sound from The Last of us comes. But when I heard music on my computer today there were no problems because I connected the aux cable to my keyboard because it has a speaker output. My dad just said it would be a short to ground because the monitor is not grounded

pr

New cable

Sa

Why should it be the cable if it works perfectly on the cell phone?