Adding a cathode resistor in parallel. The grid of one half of a 12AU7 goes to ground through a 470 k ohm resistor. The cathode goes to ground through a 1.8 k ohm resistor. The cathode also goes to the positive end of a 10 microfarad capacitor. The negative side goes through a 2.4 k ohm resistor to ground. The plate goes through a 100 k ohm resistor to plus 250 volts. The plate also goes through a 0.1 mike cap then a 470 k ohm res to ground. A legend at the bottom says quote gain = 12. AC PARALLEL. End quote. End verbal description.
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