Volume control device for electric musical instruments

Claim 1

A VOLUME CONTROLLED AMPLIFIER STAGE FOR ELECTRONIC MUSICAL INSTRUMENTS WHEREIN TONES ARE GENERATED BY APPROPRIATE OSCILLATOR AND FILTER CIRCUITS, SAID AMPLIFIER STAGE COMPRISING AND ELECTRONIC VALVE HAVING A CONTROL ELECTRODE AND A FIRST AND A SECOND CONDUCTIVE ELECTRODE, AN INPUT TERMINAL FOR APPLYING A GENERATED TONE TO SAID CONTROL ELECTRODE, AN OUTPUT TERMINAL, MEANS FOR CONNECTING A LOAD IMPEDANCE ACROSS SAID FIRST AND SECOND CONDUCTIVE ELECTRODES AND TO SAID OUTPUT TERMINAL, A FIRST RESISTOR CONNECTED BETWEEN SAID INPUT TERMINAL AND SAID CONTROL ELECTRODE AND ADAPTED TO APPLY SAID INPUT SIGNALS TO SAID CONTROL ELECTRODE, A SECOND RESISTOR CONNECTED BETWEEN SAID OUTPUT TERMINAL AND SAID CONTROL ELECTRODE TO FEED OUTPUT SIGNALS BACK TO SAID CONTROL ELECTRODE, ONE END OF EACH OF SAID FIRST AND SECOND RESISTORS BEING CONNECTED TOGETHER AND TO SAID CONTROL ELECTRODE, A THIRD RESISTOR CONNECTED AT ONE END TO THE JUNCTION OF SAID FIRST AND SECOND RESISTORS AND SAID CONTROL ELECTRODE AND AT THE OTHER END TO SAID SECOND CONDUCTIVE ELECTRODE AND PROVIDING MEANS IN WHICH THE INPUT SIGNAL AND THE FEEDBACK SIGNAL COMBINE ALGEBRAICALLY, SAID FEEDBACK SIGNAL BEING IN PHASE OPPOSITION TO SAID INPUT SIGNAL ACROSS SAID THIRD RESISTOR, A FIRST CAPACITOR CONNECTED ACROSS SAID FIRST RESISTOR, A SECOND CAPACITOR CONNECTED ACROSS SAID SECOND RESISTOR, AND MEANS FOR SIMULTANEOUSLY VARYING THE CAPACITANCES OF SAID FIRST AND SECOND CAPACITORS IN OPPOSITE DIRECTIONS TO MODIFY THE RELATIVE IMPEDANCES OF THE FIRST AND SECOND RESISTOR-CAPACITOR COMBINATIONS TO MODIFY THE AMOUNT OF FEEDBACK SIGNAL APPLIED TO SAID THIRD RESISTOR IN RELATION TO THE AMOUNT OF SAID INPUT SIGNAL APPLIED TO SAID THIRD RESISTOR TO DETERMINE THE AMOUNT OF CANCELLATION OF SAID INPUT SIGNAL AND THE AMPLITUDE OF SAID OUTPUT SIGNAL AT SAID OUPUT TERMINAL.