• Non-symmetrical and 1635 vs 1660 - IslandPink 01:19:26 07/06/04 (5)
  In Reply to: And don't forget... posted by gdahl on July 01, 2004 at 10:30:58:

  I'm more confused now than I was when I built my amp !
  As far as I see it, the LL1676 has 4 connections on one side and 5 on the other, there's no pin 3 . That makes the pin numbering clear, and you just have to follow the wiring as per the numbers on Lynn's/Gary's schematics , yes ?

  My second question (for Gary/Lynn probably) : is there much difference between the 1635 and the 1660 in the ECC99 driver application, I'm using the 1635 .

  Mark
  
  

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  • Re: Non-symmetrical and 1635 vs 1660 - gdahl 06:50:40 07/06/04 (4)
    In Reply to: Non-symmetrical and 1635 vs 1660 posted by IslandPink on July 06, 2004 at 01:19:26:

    When you look at the 1676 data sheet, the diagram for pin numbering looks a lot like the pin side of the transformer. But the diagram is really the top view of the pin "footprint" on a circuit board, as if you could see through the transformer to the pins underneath.

    If you connect the transformer as if the diagram was the underside view, even though it is clear that there are 4 pins on one side and 5 on the other, you will inadvertently use pin 1 for 5, 2 for 4, 6 for 10, and 7 for 9.

    As for the second question, we haven't tried the 1660's. The 1635's are optimized for PP:PP operation, and have the most extended bandwidth, according to the data sheets. The 1660 is capable of greater output, but with less frequency extension. Maybe someone who has heard both can comment. Kevin?

    Gary Dahl
    "So many tubes, so little time..."
    
    

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    • Oops .. - IslandPink 14:34:20 07/06/04 (0)
      In Reply to: Re: Non-symmetrical and 1635 vs 1660 posted by gdahl on July 06, 2004 at 06:50:40:

      Thanks Gary,
      Better look at that then , I connected it up assuming the pins were seen from underneath . What was the conclusion, is this likely to affect anything ?

      Mark
      
      

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    • Re: Non-symmetrical and 1635 vs 1660 - KevinC 07:22:33 07/06/04 (2)
      In Reply to: Re: Non-symmetrical and 1635 vs 1660 posted by gdahl on July 06, 2004 at 06:50:40:

      I haven't done a side-by-side comparison, but some comments are in order. The LL1635 is most appropriate for PP:PP as Gary rightfully concludes and needs to see a pretty low driving impedance to reach its potential. The ECC99 is probably as high as I would go in that regard. The LL1660 is more forgiving in the Rp department and is usable with a wider range of tubes. There is also a special version of the LL1660 called the LL1660S, which has a Faraday shield incorporated into the winding scheme to provide substantially better high frequency performance in SE:PP applications. While the specs indicate wider bandwidth for the LL1635, this property is dependent on the specific implementation.

      I've built excellent sounding amplifiers using both of these transformers.
      
      Kevin Carter
      K&K Audio
      www.kandkaudio.com
      
      

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      • 1635 vs 1660 - IslandPink 14:32:31 07/06/04 (1)
        In Reply to: Re: Non-symmetrical and 1635 vs 1660 posted by KevinC on July 06, 2004 at 07:22:33:

        Thanks Kevin,
        Using the 1635 with ECC99's driving, would you expect any shortcomings (vs the 1660) to be a slight loss of HF bandwidth, or could there be any loss of very-low-level signals ?

        Mark
        
        

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        • Re: 1635 vs 1660 - KevinC 15:24:49 07/06/04 (0)
          In Reply to: 1635 vs 1660 posted by IslandPink on July 06, 2004 at 14:32:31:

          If anything, you will probably get flatter response up through 50KHz with this arrangement than you would with the LL1660, due to the pretty good impedance match between the LL1635 and ECC99.
          
          Kevin Carter
          K&K Audio
          www.kandkaudio.com
          
          

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• Re: And don't forget... - AnandR 09:34:12 07/02/04 (0)
  In Reply to: And don't forget... posted by gdahl on July 01, 2004 at 10:30:58:

  Thanks Gary! I was the one that Gary helped out when I was wondering if I had hooked up the 1676 correctly in 1:1 configuration. My headphone amp now sounds even more glorious at a new operating point! I have the 6C45 set at 10mA, cathode voltage of 3.3V (330 ohm Kiwame resistor) and plate voltage of 200V. I will have new schematics and writeup soon for Lynn Olson. For now...I need to enjoy my July4th weekend with my family...Anand.
  
  

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• does it matter? - arend-jan 03:48:01 07/02/04 (2)
  In Reply to: And don't forget... posted by gdahl on July 01, 2004 at 10:30:58:

  Hi Gary,

  I don't understand why it would make a difference. Seems to me that one can assume that the two coils on each side are to be considered equal, right?

  On the secondary side, the pins that are exchanged are 7 & 9, both hot, and 6 & 10 both cold. On the primary it's 4 & 2 (hot) and 5 & 1 (cold). So in effect you're only exchanging the one coil for the other on each side. This makes me wonder why it would make a difference.

  Ofcourse you should not mix up left and right but that would be kind of hard to do since one has 5 and the other has 4 pins :-)

  Am I missing something here?

  Thanks,
  -- AJ
  
  

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  • In some cases yes; in this case no. - gdahl 09:20:44 07/02/04 (1)
    In Reply to: does it matter? posted by arend-jan on July 02, 2004 at 03:48:01:

    The 1676 is symmetrical, so you are right. I was bringing it up because it is a good thing to be aware of when using the little Lundahl transformers, most of which are not. My start with Lundahl input transformers was with the 1544's. I goofed the orientation at first, which kept them from operating properly.

    The Lundahl data sheets are correct, of course, it just takes a bit of "stop and think" to make sure things are oriented properly, at least for me.

    Gary Dahl
    "So many tubes, so little time..."
    
    

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    • OK, good to know - arend-jan 06:41:12 07/05/04 (0)
      In Reply to: In some cases yes; in this case no. posted by gdahl on July 02, 2004 at 09:20:44:

      Good to know that it does not make a difference for the 1676 indeed. I was afraid I was overlooking something. Those sheets are not all that clear with respect to pin sides, I had them hooked up the 'wrong' way as well :-)

      -- AJ
      
      

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• Thanks for pointing that out! - rwalton 13:40:34 07/01/04 (0)
  In Reply to: And don't forget... posted by gdahl on July 01, 2004 at 10:30:58:

  I am building Kevin's PP KT88 mono amps and I just checked my drawings. I had the 1676's wired wrong (on paper) for the exact reason you mention. The 1676 .pdf says the schematic view is from the "component side", which I assumed was the pin side. That's one problem avoided......

  
  Rick
  
  

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