5Y3 is a full wave rectifier tube
Ah, but there are others, too.
I use a 5Y3 in my little minimalist amp, sometimes. (it actually will use about twenty five different rectifier tubes)
It uses anything similar to an EL84 or an SV83 (there are about nine output tubes that I can use)(input tube must be either one of three known possibilities, though) for an output of just under two watts SET.
It is the most incredibly clean and pure and musical sound I have ever heard. I have heard many amps, too.
... not just a few. In fact, I can only think of seven amplifiers that I have not heard.