Yes, that is the DC Restoration mod. It works quite well. Somewhere else on this sight is the blanking mod. It works well also. The only thing I found when I did the mod is to be careful as the diode dies easy. I killed the first one somehow. Once I replaced it the circuit worked great.
Last night I hooked up a speaker and with just a touch up of the ratio detector the sound is great.
Now comes looking for knobs! Remember, this was a true basket case that almost became a parts donor
One other thing, the later 12SN7GTA have higher plate voltage ratings and if I remember correctly have controlled warmup (11 seconds). This may help more stabilization. Since the vertical circuit has all new parts it seems very stable. Horizontal jumps out one time after 15 minutes and once readjusted is fine.