Andy comments:
When I was in high school, I did exactly what you are suggesting to generate the high voltage to power four 811A s in parallel, running around 500 watts input. I used 866 mercury vapor rectifiers....
The transformer was a 5 kva pole pig that I bought from the power company, taken out of service, for around $10 ( in 1960 )...
I drained the transformer oil out.....since I wasn't running it at anywhere max ratings, it didn't need the cooling.
I "think" the secondary was two 220 windings and the primary was somewhere around a couple thousand volts..... I most likely ran the primary from 110 and ended up with around 1200 volts for the
811A s .... I don't remember the voltages accurately anymore, but it was very straighforward..... The idling current is not very high, no more than an amp or so maximum, so don't worry about blowing out fuses since your 220 is probably at least a 20 amp circuit. Those pole pigs are well made, and very efficient, since the power company doesn't want to waste power on magnetizing current any more than you do...Andy in Eureka, Texas W4OAH since 1960