RCA Tube Manual Circuit. There are two input terminals on the left. The lower one is grounded. The upper one connects through a 0.047 uf 630 volt capacitor to the grid, pin 2, of a 12AX7. The cathode, pin 3, goes through a 1.5 k ohm then a 15 k ohm resistor to ground. The junction of the 1.5 k and 15 k goes through a 470 k ohm resistor to the grid, pin 1. The plate goes to a point that for our convenience we will call B plus 3. There is no such label on the visible schematic. The cathode also goes through a 0.1 uf 200 volt cap to one end of a 100 k ohm resistor. The other end goes to the top of a 1 meg ohm audio taper pot which is labeled bass. The bottom of the bass pot goes through a 10 k ohm resistor to ground. The wiper of the bass pot goes through a 0.0022 uf cap to the top of the same pot. The wiper also goes through a 0.022 uf cap to the bottom of the bass pot. The wiper of the bass pot also goes through a 100 k ohm resistor to the wiper of the treble pot, also a 1 meg audio taper. The top of the treble pot goes through a 220 pf cap to the junction of the 0.1 uf cap and 100 k ohm res. The bottom of the treble pot goes through a 0.0022 uf cap to ground. The wiper of the treble pot also goes to the grid, pin 7, of the second triode in the 12AX7. The cathode, pin 8, goes through a 1 k ohm res to ground. The plate, pin 6, goes through a 0.22 uf 630 volt cap to the upper output terminal. The lower output terminal is grounded. The plate also goes through a 100 k ohm res to B plus 2. B plus 2 goes through a 15 k ohm res to plus 250 volts. B plus 2 also goes to ground through a 22 mike 450 volt cap. B plus 2 also goes through a 22 k ohm res to B plus 3. B plus 3 goes through another 22 uf 450 volt cap to ground. End verbal description.
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