From: mynamespacedbydots@xs4all.nl   
      
   "Ian Bell"  wrote in message   
   news:i7gi94$pf2$1@localhost.localdomain...   
   >   
   > I just spent some time perusing the 12AX7 data sheets in more detail,   
   > particularly the part about RC coupled amplifiers which gives the maximum   
   > output before the onset of grid current under various conditions. Based on   
   > that data I calculated the cathode voltage and also the peak input voltage   
   > before grid current for several values of Ra, Rk and Va. Subtracting the   
   > two gives the grid bias at the onset of grid current and this seems to be   
   > pretty constant at about -0.6V. It also seems that with the 300V HT I have   
   > there is really only one operating point that will give me the 102V peak   
   > output swing I need without reaching grid current and that is with a 220K   
   > anode load, 2.2K up the cathode leg and a quiescent current of close to   
   > 0.6mA. I will try those values and see what I get.   
      
   That's very close to what the "Muiderkring Electronic Tubes Handbook"   
   (1968/p152) specifies for an ECC83 @ 300Vb and a Vo of 36Veff/102Vpp.   
   Ra   220K   
   R'g1 680K (load)   
   Rk   2K2   
   Ia   0.63mA   
   Vout 36Veff   
   A    44x   
   d    3.6%   
   Rg   1M   
      
   The same page specifies 11 other operating points for the ECC83.   
   Can't find the book online but linked below is an equivalent.   
   http://www.mif.pg.gda.pl/homepages/frank/short/054/2/288.pdf   
      
   Rgds,   
   Gio   
      
   --- SoupGate-Win32 v1.05   
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