Audio fidelity frequency equalizer system

A method of controlling the frequency outputs of the various major octave bands in a frequency channel of an audio fidelity sound reproducing system, said method comprising buffering the input to an equalization system to reduce transients therefrom, introducing the buffered input into an operational amplifier, creating a resistive feedback path around said operational amplifier from the input to an output of said amplifier, dividing each of the major octave bands in a channel such that a resonant frequency circuit is capable of controlling each of the major octave bands, electronically generating a simulated inductance through an amplifier type element and a capacitor connected thereto in said resonant frequency circuit and introducing the simulated inductance as an input to said operational amplifier through said resistive feedback path, establishing a zero impedance for each selected octave band frequency in a channel and adjusting the frequency of a selected octave band as a function of the generated inductance and thereby achieving a resonant point for each frequency during the generation of the simulated inductance, and generating an output from said amplifier for each selected octave band.

An audio fidelity frequency equalizer system comprising input means, an operational amplifier operatively connected to said input means, a resistive feedback path connected across an output of and an input to said operational amplifier, a plurality of discrete octave band potentiometer elements connected between said feedback circuit and said first named input to said operational amplifier and where said frequency controlling potentiometer elements are connected in parallel relationship with respect to each other and with respect to the output of and the first named input to said operational amplifier, an individual resonant octave band control circuit connected with respect to each said octave band control potentiometer element, each said resonant control circuit comprising an electronically active amplifier type element operating as an electronically active simulated inductor, capacitive means connected in series relationship to said amplifier type element, each said octave band control circuit operating in conjunction with the associated potentiometer element to adjust the frequency of a particular octave band as a function of the inductance generated by the electronically active amplifier type element, and establishing a zero impedance for each selected octave band frequency in a channel thereby achieving a resonant point for such frequency.

An audio fidelity frequency equalizer system comprising input means, an operational amplifier terminal having a pair of inputs and an output terminal, one of said input terminals being operatively connected to said input means, a resistive feedback path connected across an output terminal of and the other of said input terminals to said operational amplifier, a plurality of discrete octave band potentiometer elements connected between said feedback circuit and said first named input to said operational amplifier and where said frequency controlling potentiometer elements are connected in parallel relationship with respect to each other and with respect to the output of and the first named input to said operational amplifier, an individual resonant octave band control circuit connected with respect to each said octave band control potentiometer element, and each said resonant control circuit including an inductive-capacitive circuit therein comprised of a series connected electronically simulated inductor and capacitor.