Instructables

How, exactly, does a 5AR4 protect against cathode stripping?

I'm in the midst of designing pp 2A3 monoblocks with stand alone power supplys.  I'm thinking more and more about tube life with these triodes being a bit expensive.  Are there other rectifier tubes that will provide the same protection?  I was thinking 5Z3 rectifiers but not sure about potential stripping problems with these.  Can anyone help me out here?

gmoon1 year ago
I think the basic theory is that the 5AR4 filament has a longer warm-up time than other rectifiers, so the B+ doesn't hit the other tubes until they are fully hot.

Maybe just adding a standby switch would do the same thing (cut the B+ to the other tubes until everything is hot)...

As I understand it, cathode stripping isn't a huge problem with audio amps; there are plenty of tube amps that use SS rectifiers with no warmup delay at all.