12AX7/ECC83

       Rp = 0.047 MOhm                Rg = 0.15 MOhm

  Ebb (V)     Rk (Ohm)       Ip(mA)      Eo (Veff)[6]  Gain   % Distortion[7]

    200         l500          0.86           18         34        8.5
    250         1200          1.18           23        37.5       7.0
    300         1000          1.55           26         40        5.0
    350          820          1.98           33        42.5       4.4
    400          680          2.45           37         44        3.6






       Rp = 0.1   MOhm                Rg = 0.33 MOhm


  Ebb (V)     Rk (Ohm)       Ip(mA)      Eo (Veff)[6]  Gain   % Distortion[7]

    200          1800         0.65           20          50       4.8
    250          1500         0.86           26         54.5      3.9
    300          1200         1.11           30          57       2.7
    350          1000         1.40           36          61       2.2
    4Q0           820         1.72           38          63       1.7






       Rp = 0.22  MOhm                Rg = 0.68 MOhm


  Ebb (V)     Rk (Ohm)       Ip(mA)      Eo (Veff)[6]  Gain   % Distortion[7]

    200         3300          0.36           24          56       4.6
    250         2700          0.48           28         66.5      3.4
    300         2200          0.63           36          72       2.6
    350         1S00          0.85           37         75.5      1.6
    400         1200          1.02           38         76.5      1.1

[6] Eo at grid current starting point.
[7] The total harmonic distortlon is approximately proportional to the output
voltage