You might ask Joseph Chow at Audio Horizons. He often works on tube gear.
http://www.audio-horizons.com/
http://www.audio-horizons.com/
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?