George Wright Preamp Hum

My brand new Wright Sound AU-1000 preamp has a very loud hum when i touch the bass tone control.When switched on high gain it is more severe than low gain. This is the only audible hum just on this one knob. The unit is brand new out of the box. As many of you know George has recently passed away so there is no one there to help now and maybe forever. Any suggestions?
Well, when i talked to the secretary she was pretty sure there was no one in the place who knew a thing about tubes except George. I bought the unit without a warranty because of this reason, there would be no one to fix it.
You might ask Joseph Chow at Audio Horizons. He often works on tube gear.