Dennis said that there had been some talk about using a 5W4 rectifier in his amps, and he wanted me to pass along that he loves the 5W4 in his prototype 46 amp...
Untitled by
analog addict, on Flickr
He gave me a voltage chart as measured on the 46 amp on the shop bench, and it is as follows...
5Y3 = 357 VDC
5W4 = 377 VDC
5U4 = 400 VDC
5AR4 = 420 VDC
In this amp, he says the 5Y3 and 5W4 would be the choices as to stay within plate voltage specs for the 46 tube.