Paoli High Fidelity Consultants Inc.

Walter W Key

Eugene L Coggins

In a wide-band electronic AC amplifier, the first stage is direct coupled to a split load phase inverter which is RC coupled to a push-pull power output stage and the output is obtained through transformer coupling with a portion being returned to the cathode of the input stage as negative feedback. Instability (e.g., generation of high frequency 'parasitics') is prevented by reduction of the effective impedance of the phase splitter, as seen by the control grids of the output tubes, by greatly lowering the resistance thereof. Since the triode is DC coupled to the pentode, the values of the load resistor and the screen dropping resistor in the pentode section must be reduced in order to increase the high frequency response and keep the current flow in the triode section within the maximum safe limits of the tube design.

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McLean, VA, United States of America

Walter W Key