Posted by Bambadoo (A) on January 13, 2008 at 09:50:28

Is this possible? And if so, what modifications need to be done?

Sincerely

• RE: 5687 instead of 6sh7 in interstage amplifiers? - richardcooper2k 13:37:44 01/15/08 (6)
  In Reply to: RE: 5687 instead of 6sh7 in interstage amplifiers? posted by Bambadoo on January 13, 2008 at 09:50:28

  out of interest.....why do you want to try 5687.....don't you like 6sh7 ?
  
  i have heard the c3g makes a good driver for 300b, anyone tryed this ?
  
  

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  • RE: 5687 instead of 6sh7 in interstage amplifiers? - Bambadoo 14:30:52 01/15/08 (5)
    In Reply to: RE: 5687 instead of 6sh7 in interstage amplifiers? posted by richardcooper2k on January 15, 2008 at 13:37:44

    Because I have a bunch of 5687 laying around, and really like the sound signature of it.
    
    Sincerely
    
    

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    • RE: 5687 instead of 6sh7 in interstage amplifiers? - richardcooper2k 15:47:53 01/15/08 (4)
      In Reply to: RE: 5687 instead of 6sh7 in interstage amplifiers? posted by Bambadoo on January 15, 2008 at 14:30:52

      sounds like a good reason to try it to me !
      
      

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      • RE: 5687 instead of 6sh7 in interstage amplifiers? - GTCharlie 01:28:55 01/16/08 (3)
        In Reply to: RE: 5687 instead of 6sh7 in interstage amplifiers? posted by richardcooper2k on January 15, 2008 at 15:47:53

        you can parallel a 5687 for around 70mA driving current. plus you get a better impedance match.
        
        but check 5687 tube curves to determine your operating points. You may have to have a separate mains transformer.
        
        

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        • RE: 5687 instead of 6sh7 in interstage amplifiers? - GTCharlie 19:39:45 01/16/08 (2)
          In Reply to: RE: 5687 instead of 6sh7 in interstage amplifiers? posted by GTCharlie on January 16, 2008 at 01:28:55

          I forgot. the provided interstage transformer may have been spec'd just for a few mA from the 6SH7, and its very high impedance. So... changing to 5687 requires a different interstage transformer. Or you can resort to capacitor coupling. Or choke load the 5687, and grid choke the 300B, still using a capacitor to couple the driver to the final ...
          
          

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          • RE: 5687 instead of 6sh7 in interstage amplifiers? - Bambadoo 00:14:19 01/17/08 (1)
            In Reply to: RE: 5687 instead of 6sh7 in interstage amplifiers? posted by GTCharlie on January 16, 2008 at 19:39:45

            "Or choke load the 5687, and grid choke the 300B, still using a capacitor to couple the driver to the final ... "
            
            Dear GTCharlie
            I am thinking of the excact same also. Have come across some really good looking schematics I would like to try.
            
            I have a pair of AN silver 0.47uf caps that would fit perfect...
            
            But this is perhaps a bit OT regarding to this AN forum......
            
            Sincerely
            
            
            

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            • RE: 5687 instead of 6sh7 in interstage amplifiers? - GTCharlie 02:14:25 02/27/08 (0)
              In Reply to: RE: 5687 instead of 6sh7 in interstage amplifiers? posted by Bambadoo on January 17, 2008 at 00:14:19

              was revisiting previous topics ... I just found out that it's not easy looking for appropriate "commercial" chokes ... 450 - 600 Hy for your 5687 plate, at around, at least, 35mA or higher. If you're on this path, look for multi-sectioned chokes. A single wind would bring in much stray capacitance and lop off your highs. Cheers
              
              

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