noise problem with audio research ls-1 pre-amp

I have a noise problem with my AR pre. When you turn the volume control knob I have crackling static type noise. It also has a hum, but that can stop when the knob is turned. Could it be a bad tube or maybe dirt in the volume control? thanks for any help. norm
Dirty volume pot. Local tech should be able to correct.No need to send to audio research, (Hopefully)