Help! New Nagaoka MP 500 Cart Makes Hum Ground Noise

I know it is a matter of semantics, but it is probably not the cartridge that is humming, unless you got a defective one.  There is more likely something wrong with the way you connected it. In other words, any system will hum if any cartridge is not correctly connected. Do you hear a very loud hum that seems to be low frequency, around 60 or 120Hz.  If so, that suggests that one channel is not properly grounded in the audio circuit.  Do you hear the hum in both channels or in one? Your post suggests that the amplitude of the hum is volume control dependent.  Is that the case?

It's pretty easy to connect the wires since they are color coded. The hum will increase if I turn the volume up. It will also flux when I touch the cart. It's a pretty simple cart to connect.... you plug it in and twist the outter shell on the arm to tighten it.

The hum is in both channels but much more louder in the right channel. Happens with the turntable power is off (but plugged in)

You need to have subwoofer and turntable plugged into the same circuit otherwise you’re grounding your table to your subwoofer if sub is connected on another circuit and that creates a ground loop. Or disconnect sub ground wire from phono stage. Why do you even ground the sub?

Thanks @audphile1 but it did not help. Good idea, though. 

Update: It has to do with the RCA cables that came with it. I found, with the volume high, if I tap the cables with my fingers I can hear the tap in the speakers!

What do ya'll make of that? These are brand new that came with the turntable!