Posted by Gelatomonster (A) on January 30, 2007 at 23:05:01

In Reply to: Re: 45 Transformer for 26 Preamp posted by mqracing on January 29, 2007 at 22:38:25:

mqracing,
Thank you for the advise. What are your transformers that can be used in Jim DKorts circuit based Preamp 26.
Thank you

• Re:Transformer for 26 Preamp - mqracing 23:12:50 01/30/07 (6)
  In Reply to: Re:Transformer for 26 Preamp posted by Gelatomonster on January 30, 2007 at 23:05:01:

  If you have a url for the schematic I'd be happy to take a look at it and offer a suggestion if I am able to.

  MSL
  
  

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  • Re:Transformer for 26 Preamp - Gelatomonster 23:39:41 01/30/07 (5)
    In Reply to: Re:Transformer for 26 Preamp posted by mqracing on January 30, 2007 at 23:12:50:

    OT ip=20K/20ma is = 2K
    Plate choke 270 henry/20ma

    Thank you
    
    

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    • Re:Transformer for 26 Preamp - Gelatomonster 16:35:26 01/31/07 (1)
      In Reply to: Re:Transformer for 26 Preamp posted by Gelatomonster on January 30, 2007 at 23:39:41:

      I think I need the exact spec as the circuit has been proven to work and solves all the problem related to the 26type tube. I would be needing 4 OT and 4 Plate Choke. Would you pm me the price if you do have them and in what configuration of iron. Thks
      
      

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      • Re:Transformer for 26 Preamp - mqracing 17:49:24 01/31/07 (0)
        In Reply to: Re:Transformer for 26 Preamp posted by Gelatomonster on January 31, 2007 at 16:35:26:

        Our units are not spec'd exactly as the authors choices. If you need exact specs as the author used then it would be best to contact the author and order through his sources.

        MSL
        
        

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    • Re:Transformer for 26 Preamp - mqracing 06:52:20 01/31/07 (2)
      In Reply to: Re:Transformer for 26 Preamp posted by Gelatomonster on January 30, 2007 at 23:39:41:

      Hi GM:

      I found and looked at several of the schematics on the VT52 site which use the 26 in a preamp circuit.

      Several of the circuits look interesting and are simple enough to try out. Two of the circuits used RC coupling off of the 26. The third used
      transformer coupling. All of the 26 circuits were running with 8 milliamps of plate current. which would be about right for a 26.

      Any of the 26 RC coupled circuits could be transformed into a transformer coupled output type circuit--- though you would want to then calculate the resulting gain structure (assuming a step down small signal OT) and make sure it is enough for your needs.

      the plate choke does not need to be rated at 20 mils--- remember a lot of times builders will use parts that they already have--- this 26 tube across the several schematics shown is running at 8 mils--- a good 10 mil plate choke would work fine. We have some 10 madc chokes in the 275 to 300 henry range.

      If you want to transformer couple--- a 15K B7 would provide a sufficient real world load impedance for the 26 to work into very well.

      Starting out--- I would try one of his RC coupled circuits--- and maybe use an input trans with a volume control across the secondary.

      MSL

      
      
      

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      • Re:Transformer for 26 Preamp - Gelatomonster 22:08:56 01/31/07 (1)
        In Reply to: Re:Transformer for 26 Preamp posted by mqracing on January 31, 2007 at 06:52:20:

        mqracing,
        What would be your suggestion/compromised solution that will still be suitable based on my requirement?. (any special material would be highly appreciated)
        Thank you
        
        

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        • Re:Transformer for 26 Preamp - Gelatomonster 04:52:09 02/04/07 (0)
          In Reply to: Re:Transformer for 26 Preamp posted by Gelatomonster on January 31, 2007 at 22:08:56:

          MQRacing,

          Could you email me the price of the choke (275-300mH @ 10mA.
          Thank you
          
          

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