GZ33 as a replacement for GZ34?

[Jef]

Could I pop in a GZ33 in place of a GZ34? I have some very nice NOS Mullard GZ33s lying around but my amp ask for a GZ34...

Here's some information I found on the net:
"The GZ33 shares base pin layout with the GZ32 and the GZ34. All are full wave rectifiers with a rating of 500 Volts for the anodes. The GZ34 is an upgrade to the GZ32 and both are rated at 125 mA rectifier current. The GZ33, however, is a high current version and is rated at 250 mA rectified current, and unlike its lower rated counterparts is not given a maximum reservoir current rating, but 200 µF would seem a maximum value that would be used in practice. The cathode is tied to one side of the heater as heater-cathode insulation would not be sufficient to withstand the full voltage."

Oh yes, I have a Fender Bandmaster Reverb with GZ34 and a project on my bench based on the 18watt and AC15, with a 5V winding on the PT.
Could I substitute a GZ33 for a GZ34 and would I have to change other components? (input filter cap?)

thanks!

Jef

[Dai]

The specific info for the site you quoted sounds off. For one thing, GZ34 max. current should be higher than the GZ32 (which should be more like a 5V4), and 200uF of input capacitance seems way too high (unless it was a choke input). When subbing rectifiers, I think you need to look at the filament draw difference, the max. current you can draw, any differences in max. input capacitance, and if the new rectifier will give higher B+, what effects that could have on the amp in question (in an amp already "pushing things" with the ratings, you may not want to push any more). I would say that if your amp can handle a 5U4 (which requires higher heater current than 5AR4/GZ34), then you can probably sub since apparently the 33 will give less voltage at the output than the 34. I would check the bias too just to be sure.
Also it looks like a big bottle (like the GZ37), so you would want to make sure it fits in the space too. I don't have any 33s, but I do have some 37s (which appear similar), and they are very beautiful looking tubes.

http://frank.pocnet.net/sheets/129/g/GZ33.pdf

[Jef]

Thank you Dai,

they are very beautiful looking tubes.

Yes, they are really beautiful big bottles indeed and that's why I would like to use them.

Jef