From: ruffrecords@yahoo.com   
      
   GRe wrote:   
   > "GRe"  wrote in message   
   > news:4c9c6247$0$41115$e4fe514c@news.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    36x  typo, should be 72x   
   >> d    3.6% typo, should be 2.6% 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   
   >>   
   >   
   >   
      
      
   Yes, that is identical to the Mullard data sheet I have..   
      
   Cheers   
      
   ian   
      
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