Figure 4. Diagram Showing HK tone solution showing some wiring capacitances. The top input terminal of the H-K tone circuit goes to one end of a 270 k ohm resistor. The other end goes to the grid of one triode in a 12 A X 7. There is a 47 p f capacitor connected in parallel with the 270 k ohm resistor. This is a real capacitor. The other input terminal is grounded. The cathode of the triode goes to ground through the parallel combination of a 1.8 k ohm resistor and a 47 u f capacitor. The plate of the triode goes through another 270 k ohm resistor to B plus. The plate also connects to one end of a 0.1 u f capacitor. The other end goes to a 3.3 meg ohm resistor. The other end of this resistor goes to the grid of the tube. There is a 2.5 p f capacitor drawn in red connected across the 3.3 meg. This capacitor simulates the parasitic capacitance of the resistor. The frequency response shows a rise at the high end without it. The real Harmon Kardon circuit shows no such rise. The junction of the 0.1 u f capacitor and 3.3 meg ohm resistor goes to the input of the tone circuit. Now describing the tone circuit. Its input goes through a third 270 k ohm resistor to the top end, CW, of the bass pot. The other end, CCW, goes through a 27 k ohm resistor to ground. The bass pot is labeled 500 k ohm audio taper. There is a 0.0015 u f capacitor connected from the top of the bass pot to its wiper. There is a 0.015 u f capacitor connected from the bottom of the bass pot to its wiper. Now we return to the input of the tone circuit. It goes through a 270 p f capacitor to the top, CW, end of the treble pot. The bottom, CCW, end of the treble pot goes through a 0.0027 u f capacitor then a 4.7 k ohm resistor to ground. The treble pot is labeled 500 k ohm audio taper. The wiper of the treble pot connects to the wiper of the bass pot and this is the output point of the tone circuit. There is a 50 p f capacitor drawn in red connected from the output of the tone circuit to ground. The output of the tone circuit also goes to one end of a 120 k ohm resistor. The other end goes to the top of the balance control pot, 250 k ohm linear taper. The other end of the pot goes through another 120 k ohm resistor to ground. The wiper of the pot is the top output terminal. The bottom output terminal is grounded. The balance control is a dual pot with the section that is in the right channel having its CW end at the top. In the left hand channel the CCW end is at the top so they work in opposite directions as they should.
End verbal description.