The Input buffer. The input terminal on the left connects to a 0.1 u f capacitor. The other end goes to the grid, pin 2, of a 12AU7. The plate, pin 1, connects to plus 250 volts. The cathode, pin 3, goes to a 3.9 k ohm resistor. The other end goes to a 33 k ohm resistor. The other end of that one goes to ground. The junction of the 3.9 k and 33k connects to one end of a 470 k ohm. The other end goes to the grid, pin 2, of the same tube. The other triode in this 12AU7 is used in the other channel of the amplifier or preamplifier. The cathode, pin 3goes through a 1 uf 200 volt capacitor to the input of the response control circuit.

The response control circuit. The input point goes through a 470 k ohm resistor to ground. It also goes to the junction of a 22 k ohm res and a 680 pf cap. The other end of the cap goes to the clockwise end of a 100 k ohm pot, treble control. The wiper of the pot goes to one end of a 150 k ohm resistor. Meanwhile, the other end of the 22 k ohm resistor goes to the clockwise end of another 100 k ohm pot, bass control. There is a 0.01 u f cap connected from one end of the pot to the other. The wiper of the bass pot goes through a 300 k ohm res then a 150 k ohm res to the wiper of the treble pot. The junction of the 150 k ohm and 300 k ohm resistors goes through a 0.1 u f cap then a 2.2 meg ohm res to ground. The junction of the 0.1 u f and 2.2 meg ohm is the center of the response control circuit and connects to the grid of the feedback amplifier. The counter clockwise end of the treble pot goes to another 680 p f cap. The counter clockwise end of the bass pot goes to another 22 k ohm resistor. The other ends of the cap and res connect together and are the output side of the response control circuit. This point goes through a 470 k ohm resistor to ground. It also connects through a 0.1 uf 630 volt capacitor to the cathode of the 12AU7 in the feedback amplifier. It also goes through a 0.22 uf 200 volt cap to the signal output of the tone control circuit.

The feedback amplifier. The input of the feedback amplifier is the grid, pin 7 of a 12AX7. The cathode, pin 8, goes to ground through the parallel combination of a 3.9 k ohm res and a 100 u f cap. The plate, pin 6, goes through a 750 k ohm resistor to plus 250 volts. The other triode in the 12AX7 is used in the other channel of the amplifier or preamplifier. The plate, pin 6, of the 12AX7 goes to the grid, pin 7, of a different 12AU7. The plate, pin 6, of this 12AU7, goes directly to plus 250 volts. The cathode, pin 8, goes through a 33 k ohm to ground. The other half of this 12AU7 is used in the other channel. As mentioned above pin 8 also goes through a 0.1 uf 630 volt capacitor to the output side of the response control circuit. Also as mentioned above there is a 0.22 uf 200 volt capacitor connected between the output point of the response control circuit and the signal output of the tone control. The signal output goes through a 470 k ohm resistor to ground. End verbal description.
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