Having looked at the pictures Jerry, this one does have the additional resistance in series with the motor driving the pot so the response to the RC is friendlier than earlier versions which had the pot moving more quickly. It should be fairly easy to set the level you want with this unit.
As someone pointed out 6n6 are not direct substitutes for anything I know of because of pin 9 being a screen. But no matter, the 6n6 is still easy to get & they do sound pretty good.
Two power transformers (1 LT & 1 HT) valve rectifier, L-C-L-C power supply & output transformers. Regulated supply for the 6n6 filament. Nice low gain which is handy given the sensitivity of some power amps and the 2V RMS output of most digital sources.