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Posted by Hujo (A) on May 27, 2009 at 17:24:07

I recently changed from GZ37s to GZ34s as the rectifiers in my Cary SLA-70B amp. I appreciate everyone's help in selecting the GZ34's. I got a pair of used Mullards with thick black bases and double "D" getters. The results were amazing! It is not just that the highs are clearer and the base is tighter, everything is better and more true. I use Amperex long plates with "D getters as phono tubes. They used to sound a little thin. Now they have a rich mellow sound, without any loss of detail. The GZ37 is definitly not an exact substitute for the GZ34. In some applications it works better, but in my system changing to the GZ34s was an unqualified upgrade.

Hujo

• Just went from GZ34 to GZ33 - Maxamillion 22:12:33 05/29/09 (4)
  In Reply to: RE: GZ34 vs GZ37 posted by Hujo on May 27, 2009 at 17:24:07

  GZ33 sounds much better to me in my Supratek Chenin preamp. More soundstage, more sparkle - and a whole lot better looking. And it's designed to handle much higher currents than the GZ37. By the way, the voltages to the output tubes remained exactly the same when switching from GZ34 to GZ33, not even 1 volt difference.
  
  

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  • GZ37 and GZ33 current capabilities are essentially equal... - Steve O 11:00:42 05/30/09 (3)
    In Reply to: RE: Just went from GZ34 to GZ33 posted by Maxamillion on May 29, 2009 at 22:12:33

    ...Actually, the GZ37 will handle a bit more current with L input filter. PIV capability is higher in all cases.
    
    

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    • RE: GZ37 and GZ33 current capabilities are essentially equal... - Maxamillion 21:29:00 05/30/09 (2)
      In Reply to: RE: GZ37 and GZ33 current capabilities are essentially equal... posted by Steve O on May 30, 2009 at 11:00:42

      GZ33 high current:
      
      
      

      • http://www.r-type.org/exhib/aad0148.htm   (Open in New Window)

      
      

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      • RE: GZ37 and GZ33 current capabilities are essentially equal... - Maxamillion 21:33:43 05/30/09 (1)
        In Reply to: RE: GZ37 and GZ33 current capabilities are essentially equal... posted by Maxamillion on May 30, 2009 at 21:29:00

        Hmmm, my text was cut off - GZ33 can handle a much larger first input cap (200uF vs 16uF) thus much higher peak current handling.
        
        

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        • Check This Out.... - Steve O 18:30:07 05/31/09 (0)
          In Reply to: RE: GZ37 and GZ33 current capabilities are essentially equal... posted by Maxamillion on May 30, 2009 at 21:33:43

          

          Based on the Mullard data sheets, I'd say that the GZ37 is equal to the GZ33 WRT peak current capability. The 37 is also equal to the 33 WRT max continuous current with cap input filter and exceeds the 33 when using a choke input filter.

          Not sure where your max cap values come from. The Mullard data sheet indicates 60uF max for the 33 under the specific conditions of PT RMS voltage AND effective sec impedance. I've never seen a max cap value for the 37 although 4uF is shown as typical . Actually, the max cap spec is a very fuzzy thing because it's influenced by both the voltage of the PT secondary and the effective impedance of the secondary. If one wanted, one could use a 1F input cap with sufficient series impedance.

          Overall, in light of the fact that the peak current capabilities of the 33 and 37 are equal, it's safe to conclude that max cap capabilities are essentially equal too. Morgan Jones covers this in a bit more detail and comes to the same conclusion.
          
          

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          Edits: 05/31/09   05/31/09   05/31/09
• RE: GZ34 vs GZ37 - Steve O 17:38:22 05/27/09 (1)
  In Reply to: RE: GZ34 vs GZ37 posted by Hujo on May 27, 2009 at 17:24:07

  Under equivalent conditions, GZ37 has a much higher voltage drop than does the GZ34. The GZ37 is more-or-less an indirectly heated 5U4 in many respects. Not surprised you find differences between them.
  
  

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  • RE: GZ34 vs GZ37 - PakProtector 16:58:48 05/28/09 (0)
    In Reply to: RE: GZ34 vs GZ37 posted by Steve O on May 27, 2009 at 17:38:22

    hey-Hey!!!,
    If you liked that change, you'll go totally nuts for a really low drop rectifier; try a pair of 866's. They'll need 4-pin socets, and 10A of 2.5V between them...but they're able to deliver 4x the current of a GZ34 at lower drop...:)
    cheers,
    Douglas
    
    ps...you'll also need a means to pre-heat the cathodes before turning on the HV too. And more space...and top caps...
    
    
    Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
    
    

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