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Originally posted by spinswax changed the wires on my mixer....i figured it out it is the combo of the right tt and the actual socket in the wall that is making the hum. sheesh rock on anyways

That's also another problem. BTW, the power cord for the turntables only have hot and neutral prongs, no ground. The right turntable is missing it's ground wire! (It's actually shoved back inside the turntable.) And the ground wire for the right turntable preamp may be connected to the negative of the signal of both audio signals of the right turntable.

From what I can remember, the left turntable preamp has the negative signal and grounds reversed at the patch bay's phone jacks for both left and right channels. Also the ground wires for both preamps are connected, so it appears that all the negative signals are eventually grounded. And the new ground wires for the mixer will also be grounding the negative signals because of this.

I think that's the main problem. After all that has been corrected the audio from the mixer should not hum.

In some instances, there may be no hum in the mixer audio but there is hum at the next device (mainboard, computer soundcard, etc.). A ground loop isolator connected between the mixer and the next device should reduce the humming considerably, but not necessarily completely.

All these little problems combined are just compunding the problem even more! I guess I'm gonna have to draw out a complete wiring diagram since they don't know WTF they're doing up there.