No, the Q point uses the actual tube plate current, which in a triode is also equal to the tube cathode current,
which is NOT necessarily the same as the cathode resistor current.
In this case, the plate current is the same as the current in the 300k plate resistor, ( 390V - 170V ) / 300k = 0.733mA.
The current in the cathode resistor R4 is the sum of the plate current and the RIAA current,
0.733mA + 0.092mA = 0.825mA.
The currents do not exactly add up to 0.833mA because the DC voltages on the schematic are only approximate.
which is NOT necessarily the same as the cathode resistor current.
In this case, the plate current is the same as the current in the 300k plate resistor, ( 390V - 170V ) / 300k = 0.733mA.
The current in the cathode resistor R4 is the sum of the plate current and the RIAA current,
0.733mA + 0.092mA = 0.825mA.
The currents do not exactly add up to 0.833mA because the DC voltages on the schematic are only approximate.
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