Dumb tube question: GZ34 vs. 5AR4 - are they the same thing?

[lincolnic]

I was looking at my Pro Reverb today to get an idea of what repairs/mods need to be done (finally preparing to do the AA165 conversion), and while I was removing the tubes I noticed that the rectifier (an old Mullard) says "GZ34/5AR4" on one side, and "5AR4" on the other side. It also has "Great Britain" written on it.

I can't seem to Google up a solid answer on this, so I'm turning to the knowledgeable crowd here: are GZ34 and 5AR4 the same tube? All I could find were people referring to them seemingly interchangeably. Was 5AR4 just the European designation, or are they actually two different tubes?

[Morgan]

Yep, they are the same. GZ34 is the English designation and 5AR4 is the American designation for the same tube.

The Mullard GZ34 is widely regarded as the best of those tubes. No need to replace it unless you are getting low B+ readings or other symptoms. Rectifier tubes mostly work until they don't.  They aren't like power tubes that put out less and less power over time.

[lincolnic]

Oh, I'm not replacing any of the tubes - I was just removing them from the sockets so I'd have an easier time taking the chassis out to look at the circuit.

Thanks for the clarification! I'm aware that the Mullards are usually considered the best, and I feel very lucky that the amp came with one.