Phono Stage Hum

I have been experiencing hum on the input from my phono preamp. In the past, any problem like this has typically resulted from a ground issue, but the ground seems to be well grounded. The hum/noise starts somewhere around the 25% mark on the volume.

The system:

KAB modded Technics 1200 w/ Audio Technica 150 MLX Cart.
Zu Xaus cable
Jolida JD 9A phono stage (high output line out)
(I have it set to no gain, but to the impedance to match the cart.)
Zu Gede
Jolida JD 102B Integrated

I have a second system that I can run my turntable through to trouble shoot. I don't get any noise over the line from my DAC (fed by my cdp and my digital library).

Any thoughts as I start the troubleshooting process?