5U4 in place of a GZ34

[sangre azul]

can it be done without harm?

[Old Tele man]

...yes, but might want to "check/adjust" bias to compensate for reduced plate voltage that occurs.

[GenoBluzGtr]

the only real issue is that a 5U4 needs uses 3amps of heater current, where the GZ34 uses 1.9 amps of heater current.

The increased current load could cause some problems, but not likely. Hopefully, some other more knowledgeable experts will chime in.

[Blue Strat]

What Geno said. It depends on whether or not your power transformer is up to it.

[sangre azul]

I have a Classic 45.

I am looking for a replacement GZ34 (probably going with the Sylvania 5AR4 you have Mike)

I read that the 5U4 is interchangeable, and I remember seeing one in a box of old tubes my uncle gave me a few years ago. I just wanted to make sure it wouldn’t harm anything before I try it, for just a few minutes.

[GenoBluzGtr]

sangre azul, I bought a Sylvania 5AR4 from Mike and those rectifiers are awesome. I can tell a difference tonally in my Bassman. I tried a GT and a Ruby tube in there before and both were okay, but I popped in the Sylvania and it made a huge difference.

[Blue Strat]

Instead of using a 5u4, a 5R4 is very similar except that it requires only 2 Amps of heater current which is the same as what a GZ34 requires.

[sangre azul]

I actually have two 5U4 GB tubes, both are GE BUT one bigger than the other. It looks more like a GE 6L6GC in size, and the other one looks like a 5881 in size. Both sounded great in the Germino. The tone was round and softer on the high end and the lows were very warm. The lead tones REALY sing, reminds me of my Clark tweed clone.

Putting the JJ GZ34S back in gave the amp a harder and louder grinding tone. Nice but pretty one dimensional.

Thanks for your help, I think I will go with the 5AR4. What should I expect?

[GenoBluzGtr]

a 5AR4 is the same as a GZ34, but if you go with the Sylvania NOS one, it won't be nearly as harsh as the JJ you tried. I have used both and the NOS is far better for warmth, and organic tone.

[Richard Guy]

I interchange GZ34 and 5Y3s in my Sunset Head (Gerhart Amplification)

When using the GZ34 (5AR4) the amp has killer cleans and mile-high headroom. Swapping in the 5Y3, less headroom, more compression, more sag.

[Blue Strat]

I actually have two 5U4 GB tubes, both are GE BUT one bigger than the other. It looks more like a GE 6L6GC in size, and the other one looks like a 5881 in size. Both sounded great in the Germino. The tone was round and softer on the high end and the lows were very warm. The lead tones REALY sing, reminds me of my Clark tweed clone.

Putting the JJ GZ34S back in gave the amp a harder and louder grinding tone. Nice but pretty one dimensional.

Thanks for your help, I think I will go with the 5AR4. What should I expect?

5AR4= GZ34. Did you mean "what should I expect from a 5R4?"?

http://www.kcanostubes.com/content/newsletter_details.asp?ArticleID=3

[sangre azul]

yes, how will the 5R4 differ from the JJ? also do you think the OT in the Classic 45 can handle running the 5U4 every once and a while?

[Blue Strat]

yes, how will the 5R4 differ from the JJ? also do you think the OT in the Classic 45 can handle running the 5U4 every once and a while?


I think I already explained this above. The 5R4 is similar to the 5U4 that you like so much, but it doesn't require 3 amps of heater current (only requires 2 amps like a GZ34) so it's less dangerous than a 5U4.

[sangre azul]

I think I already explained this above. The 5R4 is similar to the 5U4 that you like so much, but it doesn't require 3 amps of heater current (only requires 2 amps like a GZ34) so it's less dangerous than a 5U4.


Ah, I thought the 5R4 = GZ34. I see now, thanks for your help.

[sangre azul]

a 5AR4 is the same as a GZ34, but if you go with the Sylvania NOS one, it won't be nearly as harsh as the JJ you tried. I have used both and the NOS is far better for warmth, and organic tone.

Thank you, that is wahat I was after.

[Ronsonic]

Ah, I thought the 5R4 = GZ34. I see now, thanks for your help.

That's 5AR4 = GZ34. 5R4 is something else. Much like a 5AR4 but without the slow warmup. I've got some of the crazy potato masher military 5R4 I use in hifi stuff.

http://www.machmat.com/sales/images2/5r4wgy.jpg
Ron

[sangre azul]

Thanks for your help, I went with a 5R4WGA. I will get a Sylvania 5AR4 later.

Oh and while I was at it I got a Mazda 5Y3GB for my Clark.

[sangre azul]

I hope that big 5R4WGB fits in my amp, Is it about the same size as a KT66?