Rectifier tubes?

I cannot speak from experience with this exact product but in general, NOS tubes are far superior to new stocks.

My luck with NOS 5U4GB has obviously been better than yours. My first choice would be Sylvania Gold Brand with old Tung Sol running a close second. My tests and reliability results were (as I remember) with Tube Research GT 400 and Mike Elliott's EASE Magnum.

Here is a link to BWS tube who has them in stock.

http://www.bws-tube.com/htm/tubes.html

Does GZ34 and GZ37 are the same?

According to the Tube Substitution Handbook the following tubes can be substituted for each other.

GZ34, 5AR4, 52KU, U54, GZ37, and U54.

5AR4 shows the following are also compatible, U77, 5U4GB, 5AS4, 5AU4 and 5V3A

There is also an antique tube, the CV378 (British) which is excellent. I have a couple of them myself.

Last, if you want something cheap but decent there is a Chinese rectifier called 5C3PJ that subs perfectly. I bought some on line for $3.00 each a couple of years ago.

Have fun experimenting, you never know what will sound best until you experiment.

I just did search on the 5C3PJ and came up empty. Do you have a link to where you bought them? Thanks!

Correction, number is 5Z3PJ, keyboard fumble. Ebay has them at high price, maybe worth it to try one out and if you need quantity go elsewhere.

Most websites in English language look high, the one site that was close in price I have no experience with. Exercise common sense, post results if you test.

Chinese 5Z3PJ