Help Please - Insane buzzing sound using phono pre-amp

I've been using a 1210 hooked up to an NI S4 for a while now. I decided I wanted to be able to use the turntable as a simple record player without having to fire up my laptop and run it through Traktor. As I'm on a tight budget I thought I could rig up a wee ghetto system easily enough.

I bought a cheap phono pre-amp and a volume control meant for a car subwoofer. Wired the turntable to the pre-amp, then to the volume control, then to my powered KRK speakers. The ground wire is still connected to the S4. I could see no reason why this wouldn't work, but whenever I turn the volume knob up slightly past 0 there's a really loud buzzing, feels like if I was to turn it up even halfway my speakers are going to explode.

Does anyone know what the problem is? Is my whole idea ridiculous and never going to work, or am I just missing something simple? I had thought it might be a problem with the ground wire, but I can't think where else I can run it to.

Any suggestions would be greatly appreciated. Thanks

Connect the turntable ground to the preamp, not the S4. I assume it works fine through the S4?