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5ar4 vs gz37

islanddave

islanddave

Active Member
What are the sonic differences between these two tubes? Can different rectifier tubes really make a big difference? For the record the 5AR4 that I currently have is a cheap china made valve art, and the GZ37 would be a Mullard.


Thanks Dave
 
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If the power supply in the amp i made correctly , and the rectifer tube is good , you should'nt hear any differance by changing one good tube for another .

Now every rectifier tube type drops a diferent voltage across the tube , a 5AR4 , the least and a 5R4 the most .So going from a 5AR4 to a 5R4 the 30 volt drop will put the amp in a different part of the the linearity curve of its tubes operating characteristicts .
 
battradio said:
If the power supply in the amp i made correctly , and the rectifer tube is good , you should'nt hear any differance by changing one good tube for another .

Now every rectifier tube type drops a diferent voltage across the tube , a 5AR4 , the least and a 5R4 the most .So going from a 5AR4 to a 5R4 the 30 volt drop will put the amp in a different part of the the linearity curve of its tubes operating characteristicts .
Click to expand...

What then explains the price difference between a $19.99 5AR4 and say a $100.00 Mullard GZ37?

Dave
 
A GZ37 draws more current than a GZ34(5AR4) tube.
I'm running NOS Mullard GZ33's in my Bob Latino M125 monoblocks and like them a lot.
The solid state Weber Copper Cap Rectifiers that I also have put out more, but the GZ33 is a good comprimise.


Al. Wise
 
I run a big bottle GZ37 by Mullard. Big old thing looks cool and is built for tanks.. Literally!
 
As has been explained already, different rectifiers drop slightly different voltages changing the B+ voltage and they can also draw different current, from 2A to 4A, from the power transformer. So the first thing to do is to establish the specifications on the power transformer. If that's not possible then you can guess from the original equipment. Does the manufacturer specify a GZ34? Then expect that the power transformer supplies 2A. Does the original equipment come with a 5U4? Then you are good to go @ 3A.

The power transformer on my present amps can provide up to 4A of heater current so I did a taste test with a wide range of rectifiers. The results were, in order of preference, IN MY AMPS: 5V3A/5AU4, GZ34, 5U4, GZ37, 5R4, 5V4.

While the 5V3A/5AU4 were clearly the best, there was much more difference between the GZ34 and those that followed. In other words, IN MY AMPS, I preferred the 5V3A/5AU4, and could live with the GZ34, the rest were clearly inferior.

So first determine the specs of the power transformer and then do your own taste test with those rectifiers that are appropriate to the equipment.

BTW: the 5V3A/5AU4 generally are priced about $10 each for NOS. The Mullard GZ34 looks like a toy next to it!
 

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Well I bit the bullet I checked out the specs and the Mullard GZ37 was a go. At the same time I also bought some Gold Lion KT66's

The sound out of the box has been amazing so far, and will get better and better as the hours play on. I would highly suggest the KT 66's. As I have been told the rectifier needs about 10 hours of burn time while these tubes have been reported to need as much as 150 hours. The guy at the tube store said after 12 hours the difference at 150 will be hard if not impossible to quantify.

Thanks Dave
 
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