Improvements in volume control circuits for thermionic amplifiers

摘要

514,331. Valve circuits for wireless reception. PHILCO RADIO & TELEVISION CORPORATION. May 3, 1938, No. 13154. Convention date, May 8, 1937. [Class 40 (v)] In order to obtain a low minimum volume level with a volume control circuit for a radio receiver of the type employing a degenerative feed-back connection in the audio frequency amplifier, the negative feed-back connection is made to an intermediate tap point on the input volume control. Low frequency signals from the diode load resistance R are fed through the filter C1, Rl, C2, to the volume control potentiometer P, the slider being connected over condenser C3 to the grid of valve V. The output of the amplifier is connected over resistance and condenser R3, C4, which may be arranged to be frequency discriminative, to a point 3 on the volume control. The lower tapped portion of the potentiometer may be shunted by resistance R4 which enables standard volume controls of high and uncertain resistance to be employed. The amount of degeneration is a maximum when the slider is at point 3, and diminishes as the slider is moved in either direction, being zero at the point 2.