Improvements in or relating to thermionic valve amplifiers for sound reproduction

摘要

447,346. Valve amplifying circuits. AIGNER, F., 13, Karlspatz, Vienna. Dec. 29, 1934, No. 37288. Convention date, Dec. 30, 1933. [Class 40 (v)] The volume range fed to a reproducer is increased by controlling the gain of an amplifier through which the signals pass as a modulation on a carrier frequency. The Figure shows a supersonic heterodyne receiver in which energy from the first intermediate frequency amplifier ZF1 is applied to a rectifier which is used to supply anti-fading control to the preceding valves. The output from the rectifier is also amplified and the low frequency applied to a further rectifier G2 which controls the bias of the second intermediate frequency amplifier ZF2 to increase the volume range. The rectification and amplification may be effected in a single diode-triode valve and in wireless reception the arrangement gives suppression of weak signals. In gramophone reproduction the signal is modulated on a local oscillation and the control effected at this frequency.