• RE: 300B Push Pull - Stigla 13:21:33 08/18/11 (5)
  In Reply to: RE: 300B Push Pull posted by KevinC on August 14, 2011 at 09:49:57

  Hey Kevin,
  
  Could you perhaps write a few words about your impression and experience of the 6BX7 tube in general, as a driver? Is it difficult to find good matched pairs of this tube with good performance?
  
  - Stigla
  

  ---

  • RE: 300B Push Pull - KevinC 14:07:30 08/18/11 (4)
    In Reply to: RE: 300B Push Pull posted by Stigla on August 18, 2011 at 13:21:33

    The 6BX7GT is a really nice driver tube, but matching triodes is a challenge, particularly if you demand them in the same glass envelope! However, if you are not too picky about matched manufacturers and vintages, it should be possible to get matched triodes without too many samples. I'd say that you'd need 10 pieces to find a good match between triodes in different bottles.
    
    As good as the 6BX7GT is though, it doesn't stand up to my new (non-DHT) favorite, which is the TungSol KT-120. It sounds a bit silly, I admit, but an Australian builder convinced us to try it and he was right. And you can buy matched pairs that are typically good enough without sorting.
    
    Kevin Carter
    K&K Audio
    www.kandkaudio.com
    
    

    ---

    • RE: 300B Push Pull - tannat 12:56:24 08/19/11 (1)
      In Reply to: RE: 300B Push Pull posted by KevinC on August 18, 2011 at 14:07:30

      Kevin,

      So you are using KT120s as drivers? I guess they then are better as drivers for the PPP KT120 output stage also? Six KT 120s per channel...

      You talk very well about the KT120s as both drivers and in the output. The KT120s have very high max plate dissipation, have you tried them with higher plate voltages than what you use for the 6550s?

      The KT120s have unusually large plate area, just like most old DHT designs. Maybe that's not a coincidence sound-wise.
      /Jonas
      
      

      ---

      Edits: 08/19/11

      • RE: 300B Push Pull - KevinC 18:31:50 08/21/11 (0)
        In Reply to: RE: 300B Push Pull posted by tannat on August 19, 2011 at 12:56:24

        If memory serves, the highest voltage has been about 560VDC (with the cathodes standing on CCSs at about 50VDC) as output tubes and they worked fine.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
        
        

        ---
    • Thanks Kevin and I am using ... - fiacono 03:53:56 08/19/11 (1)
      In Reply to: RE: 300B Push Pull posted by KevinC on August 18, 2011 at 14:07:30

      the 6H30P for the input tube, extra 50 volts on the plates and about 13ma per side. BTW which IT are you using for the KT-120's.
      Regards Frank
      

      ---

      • RE: Thanks Kevin and I am using ... - KevinC 04:52:16 08/19/11 (0)
        In Reply to: RE: Thanks Kevin and I am using ... posted by fiacono on August 19, 2011 at 03:53:56

        For the KT-120s we use the LL1671/PP or AM version of same, typically stepping the driver output 2+2:1+1 to get even better control of output tube grids.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
        
        

        ---
• RE: 300B Push Pull - Max Dissipation 12:51:56 08/15/11 (0)
  In Reply to: RE: 300B Push Pull posted by KevinC on August 14, 2011 at 09:49:57

  I'll send you an email, thank you very much :-)
  

  ---

Post a Followup:

This post is made possible by the generous support of people like you and our sponsors:

DIY Hifi Supply

[ DIY HiFi Forum ]

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2013, Audio Asylum, all rights reserved ] [ Take5 ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---