Tube DIY Asylum

• RE: Dynaco ST70 modification to use KT66 - 6bq5 21:59:44 05/30/24 (1)
  In Reply to: RE: Dynaco ST70 modification to use KT66 posted by tudo99@yahoo.com on May 29, 2024 at 18:29:43

  please remember that the KT 66 is a VERY different tube from an EL-34
  Yes, they are both Octal based Pentodes, Power tubes -
  but electrically there are some important differences:
  1: the KT 66/6L6GC has the G3 tied to the Cathode on pin 8. Not so in the EL-34
  2: yes the rest of the pinouts are the same
  3: the max plate voltage is different:[Class A amp PP] KT-66/6L6GC= 270; ERL-34= 800
  While the two tubes both fit and will operate, for a while, the ST-70 was designed for EL-34 output tubes and has voltages, bias, grid settings to reflect that - considerably above the design specs for the KT-66/6L6GC...
  Happy Listening
  
  

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  • RE: Dynaco ST70 modification to use KT66 - Triode_Kingdom 08:47:25 05/31/24 (0)
    In Reply to: RE: Dynaco ST70 modification to use KT66 posted by 6bq5 on May 30, 2024 at 21:59:44

    "please remember that the KT 66 is a VERY different tube from an EL-34"
    
    And in addition to everything you noted, the optimum loading and gain are substantially different. Not a good swap.
    
    

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