Rectifier tubes?

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.

Albert,

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

David

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

I have use both GZ37's and GZ34's in my amp. With the GZ34's the B+ is 425v and the amp has a very taught, muscular robust sound. With the GZ37's the B+ is 400v and the sound is more relaxed with more breath and ease but also slightly softer around the edges.

Not sure what causes the difference in sound. Is it the difference in B+ or is it the different tube? I am guessing its the difference in B+.

I know the topic is very old, but I will respond because it can serve someone for information!
The Airtight ATM300 accepts 5U5GB / 5U4G and 274B, but the ATM300A and ATM300R only accept 5U4GB, according to the manufacturer, any other model will damage the amplifier!
I have an ATM300, I really like the 5U4GB Tung-Sol and the 5U4GB Sylvania, Takatsuki 274B is my preferred rectifier tube (but decreases the maximum amplifier volume) since the Shuguang WE274B is also very good and has the same efficiency as the 5U4GB!