Sound system gain and equalization circuit

DETAILED DESCRIPTION It is an object of the invention to provide a new and improved equalizer circuit for processing and performing equalization on audio signals.
It is a further object of the invention to provide such a circuit which is capable of selectively providing gain as well as equalization to an audio input signal.
It is another object of the invention to provide such a circuit for effectively reducing distortion, thereby improving clarity in currently available sound systems.
It is still another object of the invention to provide an analog equalizer which is simple in design, relatively inexpensive and yet effective in performing equalization without significant phase shift.
It is an additional object of the invention to provide such a circuit capable of accurately reproducing an audio square wave.
It is also an object of the invention to provide such a circuit which may be implemented as part of an audio preamplifier and in other environments requiring equalization.
It is a further object of the invention to provide a gain and equalization circuit having a substantially undistorted (flat) frequency response.
The above and other objects of the invention are realized in a specific illustrative embodiment of a gain and equalization circuit for processing received audio signal and including a plurality of operational amplifiers, each for processing and selectively amplifying a different band of frequencies of the audio signal to produce an output signal.
Each operational amplifier includes an inverting input, a non-inverting input for receiving the audio signal, an output, a high pass filter network coupled between the inverting input and ground potential for determining the lower end of the frequency band processed by the operational amplifier, and a low pass filter network coupled between the output and the inverting input for determining the upper end of the frequency band processed by the operational amplifier.
The gain and equalization circuit further includes a summing circuit coupled to the outputs of the operational amplifiers for selectively attenuating selected output signals and for combining the signals to produce a resultant combined signal covering the audio spectrum or desired portion thereof