Mysterious Turntable buzz/hum

Record Hog

2013-03-13 8:23 pm
Just finished setting up my equipment. This is what I have:

Technics 1200 w/ shure m447 needle
Rane TT 56S DJ 2-ch mixer
Furman sound conditioner

I am only using headphones for now, and I am noticing a slight buzz/hum when I exceed mid level on the headphone volume and/or the channel volume when using the turntable (grounded to the mixer). It is most audible when the record is actually NOT playing and most noticeable when my hand touches the headshell.

Thoughts? I changed up the needles, used a different turntable, and it is still there. Could it be somehow related to the sound conditioner? That is the only thing I can think of.
Since nobody answered, let me give my dumb advice: check continuity of the headshell, arm tube and GND with a DMM. Usually there is an independent ground wire for grounding the chassis, arm, and other metal parts to the chassis of the preamplifier. That should be separated from the GND of the RCA connectors coming from the turntable (and ideally the L GND and R GND should also be separated). Don't measure continuity of the cartridge itself! It might kill the delicate internal coil.