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• Which DHP would you recommend? 47 is great... - Minussss3db 13:02:22 04/09/10 (0)
  In Reply to: RE: Which DHP would you recommend? posted by somejoe on April 09, 2010 at 03:10:39

  actually I apologize SomeJoe, but I cannot say hear what I am using because I find the stock is really variable...however...
  
  I can say I have designed a 47 driving a GM 70....someday...
  
  The 47 would of course also be excellent driving a 45...direct couple it will provide some grid current...so clipping is going to be better with the 47 DC coupled than many of the various triodes cap coupled.
  
  The 47 is easy to work with...it doesn't oscillate...just put a .47uf PIO cap on the power supply cap driving it...regulate the screen with a Zener diode to about 25v lower than the plate, and you will be very happy...
  and of course battery bias the cathode...i can't remember the voltage..
  however the 2.5vAC on the cathode had some hum...I was going to build a DC supply, but went on to battery powered cathode pentodes instead..
  
  i.e. for the 45 175V plate 150v screen and about 20ma is great...I run it straight down into the 45 grid i.e. no decoupling from the 45 plate...I can't remember for the 47, but I think this was a 12k wirewound resistor...
  
  this will be one of the better 45's you have ever heard...
  
  Peace,
  -3db
  
  for the 300B you will have to run the full 250v on the plate
  

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