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previous: momo Can you direct couple the grid of a... -- 5/28/2000 6:54 PM View Thread

Re: Cathodyne PI

6/2/2000 3:31 PM
Ray Ivers
Re: Cathodyne PI
Ran the numbers - learned a lot.  
I initially planned to suggest the 12DW7 in addition the other tubes you mentioned, but TubeCAD doesn't like those tubes for this application. Apparently the only tube that will work easily in this scenario is the 12AX7 - the others all wanted a PI grid bias voltage that I feel was too low for proper operation of the gain stage (the 12AT7 came close, but was pulling less-than-optimum current). Here's what I came up with:  
Gain stage: 180K plate resistor, 1K cathode  
Split-load PI: 120K plate/cathode  
Bias voltage: @ 116 volts on GS plate/PI grid  
PI signal swing: +60 / -120 volts peak  
These numbers should make a fairly good starting point for you, anyway.