Sound system gain and equalization circuit

• US 5,717,773 A
• Filed: 03/30/1995
• Issued: 02/10/1998
• Est. Priority Date: 04/28/1993
• Status: Expired due to Fees

• Current Assignee: Night Technologies International
• Original Assignee: Night Technologies International
• Inventors: Parker, Lance, Maag, Clifford
• Primary Examiner(s): TRAN, SINH N
• Application Number:
  US08/413,398
• Time in Patent Office: 1,048 Days
• Field of Search: 381/104, 381/98, 381/71, 381/68.2, 381/68.4, 381/101, 381/103, 333/28 R, 333/28 T
• US Class Current: 381/98
• CPC Class Codes: H03F 3/68 Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602
• CPC Class Codes: H03G 5/025 Equalizers; Volume or gain control in limited frequency bands
• CPC Class Codes: H03G 9/02 in untuned amplifiers
• CPC Class Codes: H04R 3/04 for correcting frequency response
• CPC Class Codes: H04R 5/04 Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments combinations of amplifiers H03F3/68; stereophonic systems H04S

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. The additional operational amplifier includes the same elements as the plurality of operational amplifiers except the feedback circuit which is replaced by a resistor. 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. The summing circuit includes a plurality of variable resistors, each coupled to the output of a different operational amplifier for selectively varying the magnitude of the output signal from the respective operational amplifiers.

Claims

1. A voltage gain and equalization circuit for processing a received audio signal, comprising:

a plurality of at least six operational amplifier means, each for processing and selectively amplifying respective ones of the at least six different bands of the audio signal to produce an output signal with generally no phase shift, where center frequencies of the respective bands are about 10 Hz, 40 Hz, 160 Hz, 640 Hz, 2560 Hz and 10240 Hz, with skirts varying about 11/2 dB at one octave from the respective center frequency, about 6 dB at two octaves, about 10 dB at three octaves and about 131/2 at four octaves, and each operational amplifier means including

an inverting input,

a non-inverting input for receiving the audio signal, wherein a resistance means is coupled between a source of the audio signal and the non-inverting input,

an output,

high pass filter means coupled between the inverting input and ground for determining the lower end of the frequency band processed by said each operational amplifier means, wherein each of said high pass filter means comprises a series connection of a first capacitor and a first resistor coupled between the inverting input and ground, wherein the capacitance of the first capacitor and resistance of the first resistor are selected to roll off the low end of a frequency band different from those of the other operational amplifier means,

low pass filter means coupled between the output and the inverting input for determining the upper end of the frequency band processed by said each operational amplifier means, wherein each of said low pass filter means comprises a parallel connection of a second capacitor and a second resistor, wherein the capacitance of the second capacitor and resistance of the second resistor are selected to roll off the high end of a frequency band different from those of the other operational amplifier means,

at least one additional operational amplifier means for processing and selectively amplifying a frequency band of the audio signal, which is higher than the frequency bands processed by the plurality of operational amplifier means, to produce an output signal, said operational amplifier means including an inverting input, a non-inverting input for receiving the audio signal, an output, high pass filter means coupled between the inverting input and ground, and resistance means coupled between the output and the inverting input, and

summing means coupled to the outputs of each operational amplifier means for combining the output signals, each output signal passing a different frequency band of the audio signal thereof, to produce a resultant signal.

2. A voltage gain and equalization circuit for processing a received audio signal, comprising:

a plurality of at least six operational amplifier means, each for processing and selectively amplifying respective ones of the at least six different bands of the audio signal to produce an output signal with generally no phase shift, where center frequencies of the respective bands are about 10 Hz, 40 Hz, 160 Hz, 640 Hz, 2560 Hz and 10240 Hz, with skirts varying about 11/2 dB at one octave from the respective center frequency, about 6 dB at two octaves, about 10 dB at three octaves and about 131/2 at four octaves, and each operational amplifier means including

an inverting input,

a non-inverting input for receiving the audio signal, wherein a resistance means is coupled between a source of the audio signal and the non-inverting input,

an output,

high pass filter means coupled between the inverting input and ground for determining the lower end of the frequency band processed by said each operational amplifier means, wherein each of said high pass filter means comprises a series connection of a first capacitor and a first resistor coupled between the inverting input and ground, wherein the capacitance of the first capacitor and resistance of the first resistor are selected to roll off the low end of a frequency band different from those of the other operational amplifier means,

low pass filter means coupled between the output and the inverting input for determining the upper end of the frequency band processed by said each operational amplifier means, wherein each of said low pass filter means comprises a parallel connection of a second capacitor and a second resistor, wherein the capacitance of the second capacitor and resistance of the second resistor are selected to roll off the high end of a frequency band different from those of the other operational amplifier means, and

summing means coupled to the outputs of each operational amplifier means for combining the output signals, each output signal passing a different frequency band of the audio signal thereof, to produce a resultant signal.