In Reply to: Interstage Questions posted by HKL on October 22, 2004 at 08:45:23:

I think that the best choice is an LL1660/18mA operated with a 1:1.125 ratio. Of course, the lower the plate impedance, the better your driver stage will perform. I love low impedance driver stages!

Kevin Carter
K&K Audio
www.kandkaudio.com

• Thanks, but more questions ... - HKL 05:19:28 10/31/04 (2)
  In Reply to: Re: Interstage Questions posted by KevinC on October 22, 2004 at 19:36:41:

  Kevin,

  If you don't mind, I have a few more questions regarding the Lundahl 1660/18mA interstage transformer:

  1. Would the transformer still be appropriate if I use a higher quiescent DC current, say, 20mA to 25mA?

  2. The 1660 data sheet shows an 100H in the single-ended mode (Alt. Q) with an 1:4.5 ratio yet you mentioned it could connected with 1:1.25. Did you mean an Alt. S connection?

  3. Would the same 1660/18mA allow different connections of Alt. Q, S, and T? The data sheet seems to suggest that Alt. Q for 1660/18mA and Alt. S for 1660/10mA.

  4. If the 1660/18mA can go with connections of Alt. Q, S, and T, are there other considerations, say frequency response, on the resulting henry rating with the 5k-ohm plate impedance of the driver tube?

  Thanks again for all your help.

  Regards,
  H.K.
  
  

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  • Re: Thanks, but more questions ... - KevinC 13:02:54 11/01/04 (1)
    In Reply to: Thanks, but more questions ... posted by HKL on October 31, 2004 at 05:19:28:

    If you raise the current closer to 25mA, it would be advisable to switch to the 25mA version. Yes, the 1:1.125 connection is Alt. S. The difference in transformer gappings suggested for Alt.S and Alt. Q means nothing as these were simply meant as examples. The gap selected should be judged based on the bias current necessary to properly operate the tube. Yes, the change of ratio and gapping has consequences for the maximum Rp allowable to get adequate frequency response. For example, you need enough inductance for the tube of choice to ensure adequate low frequency response.
    
    Kevin Carter
    K&K Audio
    www.kandkaudio.com
    
    

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    • Re: Thanks for your help (nt) - HKL 19:18:09 11/01/04 (0)
      In Reply to: Re: Thanks, but more questions ... posted by KevinC on November 01, 2004 at 13:02:54:

      
      
      

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