Abstract: A multi-band digital gain and equalizer system for receiving and processing an audio signal includes an analog-to-digital converter for converting the audio signal to a digital signal X, a plurality of digital filters, each for processing and selectively amplifying/attenuating a different frequency band of the signal X, to produce an output signal Y.sub.n, in which the waveform of the frequency response is concave downward for the central frequencies of the band and concave upward for the frequencies above and below the central frequencies, a summing circuit for summing the output signals Y.sub.n to produce a resultant digital signal, and a digital-to-analog converter for converting the resultant digital signal to a resultant analog audio signal. The center frequencies of each band processed by a digital filter is separated from adjacent center frequencies of bands processed by other digital filters, by about two octaves.

Abstract: A multi-band equalizer for receiving and processing an audio signal includes a plurality of operational amplifiers, each for processing a different frequency band of the audio signal to produce an output signal. Each operational amplifier includes an inverting input, a non-inverting input, a resistor means coupled to the non-inverting input for receiving the audio signal and supplying it to the non-inverting input, an output, a feedback circuit coupled between the output and the inverting input for determining the upper limits of the frequency band processed by that particular operational amplifier, and an input circuit coupled between the inverting input and ground potential for determining the lower limits of the frequency band processed by that operational amplifier. An additional operational amplifier is provided for processing a higher frequency band of the audio signal than those processed by the plurality of operational amplifiers, for producing an output signal.

Abstract: A multi-band equalizer for receiving and processing an audio signal includes a plurality of operational amplifiers; each for processing a different frequency band of the audio signal to produce an output signal. Each operational amplifier includes an inverting input, a non-inverting input, a resistor means coupled to the non-inverting input for receiving the audio signal and supplying it to the non-inverting input, an output, a feedback circuit coupled between the output and the inverting input for determining the upper limits of the frequency band processed by that particular operational amplifier, and an input circuit coupled between the inverting input and ground potential for determining the lower limits of the frequency band processed by that operational amplifier. A summing circuit is coupled to the outputs of all of the operational amplifiers for combining the output signals thereof to produce a resultant signal.

Abstract: A multi-band equalizer for receiving and processing an audio signal includes a plurality of operational amplifiers, each for processing a different frequency band of the audio signal to produce an output signal. Each operational amplifier includes an inverting input, a non-inverting input, a resistor means coupled to the non-inverting input for receiving the audio signal and supplying it to the non-inverting input, an output, a feedback circuit coupled between the output and the inverting input for determining the upper limits of the frequency band processed by that particular operational amplifier, and an input circuit coupled between the inverting input and ground potential for determining the lower limits of the frequency band processed by that operational amplifier. An additional operational amplifier is provided for processing a higher frequency band of the audio signal than those processed by the plurality of operational amplifiers, for producing an output signal.

Abstract: A preamplifier for processing an audio signal includes an equalizing and amplifying circuit comprised of parallel operational amplifiers, each with a feedback impedance circuit and an adjustable source impedance circuit. The adjustable source impedance circuit provides the preamplifier with a super-gain region in the high audio and supersonic frequency range. A summer adds the output of the parallel operational amplifiers to produce a single output signal. The parallel operational amplifiers, with the summer, gives the preamplifier unique low noise characteristic with an improved signal to noise ratio over a single operational amplifier with the same gain. The preamplifier may include an optional second stage for further equalizing and amplifying of the output signal.