[Al (astral highway)]

I think there might be a distinction between low power valves of the type you mention and eg high power valves like 811, 572 transmitting / modulator tubes where the cathode is the filament. These aren’t supposed to be run under temperature/ filament voltage.

Variacs. Looks to me that those who have them use them and those who don’t, don’t! Simples. I think they and lamp limiter do entirely different things. The visual with a lamp limiter is brilliant and enough protection for firing up loft finds and restoration projects.

I do have a variac which is specifically used on a homemade high power inverter where I need more volts in than mains but not doubled mains. So I wind it up to 270V and that’s it. I acquired it from a scrap yard when that kind of thing was negotiable. I don’t think they’re essential bits of kit at all but nicely engineered, the old lab grade ones at least.